Caliper Spray

[n/a]

Just wondering if the DIY caliper spray jobs that everyones been doing would hinder the caliper from releasing heat which could lead to cracking.

[panda[cRx]]

^ what he said. i don't think i've ever heard of a caliper on a street car (modified or not) cracking

[omgzilla]

The heat from the brakes gets dissipated from the pads and discs themselves. The calipers job isn't to release heat.

Painting the calipers is perfectly fine!

If it mattered even in the slightest you would see Brembo, Alcon, AP Racing etc calipers left unpainted!

Tip: Make sure you get the specified Brake Caliper Paint and not just a generic heatproof/fireproof paint - usually the generic heat/flameproof ones are very matte colour. The actual Brake Caliper Paint has gloss in it - which is far more resistant to brake dust ;)

Make sure you clean the caliper extremely well, get rid of any trace of brake fluid and tape up all your piston seals and fluid line and bleeder fittings before you paint ;)

[Boban]

^^what all of the above said, and also make sure you tape up your brake pad before you paint the caliper, looks really dodgy if you spray over the brake pad and the caliper. I removed mine when i did it, but that's just me. Also do a couple of coats, don't be stingy, good quality paint won't set you back more than $20 for a can, i did my brakes and 2 Rocker/tappets covers with one can

[n/a]

no worries, thanks for the info.

[JohnL]

On the road it's probably not a real issue, but if I were racing the car I wouldn't do it. The problem is that while most of the heat is dissipated by the disc, some heat (quite a lot really) does get into the caliper and then into the fluid. If the fluid gets hot enough it will boil, even new fluid with no water in it. Heat will be radiated and convected (to air) through the caliper itself, and really you do want to do all you can to encourage this.

If you paint the caliper the paint will act as an insulating layer, and in some degree (no pun intended) reduce the ability for heat to dissipate. It would be a bit less of a problem if you painted them black (and a bit less still if matt black), but the paint is still an insulator. If you paint air cooled kart engines I know there is a tendency for them to run slightly hotter, even with black paint.

Most coloured calipers I've seen (though I haven't paid that much attention to that many coloured calipers) have been anodised, which won't act as an insulating layer. Best would be black anodised.

[EuroDude]

Painting Calipers is perfectly fine. The calipers dont reach extreme temperatures anyway, unlike an engine rocker cover which gets much hotter, and that is painted from the factory.

Put it this way; Brembo, Porsche, and other performance brakes are all painted! No reason why you cant do the same on stock calipers ;)
They wouldn't paint performance calipers if there was a heat problem.

http://www.zeckhausen.com/images/brake_install/BMW/E39/Movit/front/12t_Install_Caliper.jpg

[JohnL]

OK, but I did say it's probably no real deal on a road car, and it's probably not a big deal on a racer either, most of the time. I't's just something I wouldn't do myself because a heat retentive affect does exist, even if it's relatively slight. I do think calipers get significantly hot (burned my hand on at least one), just not nearly as hot as the disc.

[Feverpitched]

You'd burn your hand on most things in your car that have reached optimum operating temperature. I don't think caliper paint makes a difference worthy of consideration.

[EuroDude]

^ yes its different for V8 supercars and F1 cars since they reach 300km/h+ and brake like crazy, but for road cars and most performance cars (bar Ferraris enzo's perhaps) it not really an issue, a few degrees difference wont hurt.

Ive touched my euro's calipers after braking considerably, they were only warm to the touch.

[DreadAngel]

James is superman XD

[EuroDude]

btw if you have painted calipers, is there a problem using Wheel Cleaner?

Wheel cleaner is high in Alkaline and probably not good for paint I imagine. Has anyones paint peeled off or bubbled or anything?

[ek4-guy]

lol ive got a friend that races v8supercars and he despises paint especially on brakes because is extra weight and retains heat

check with ur local racer he'll tell you all about paint


lol v8supercars dont even paint their blocks when they had iron blocks they were orange from rust

[ek4-guy]

^ yes its different for V8 supercars and F1 cars since they reach 300km/h+ and brake like crazy, but for road cars and most performance cars (bar Ferraris enzo's perhaps) it not really an issue, a few degrees difference wont hurt.

Ive touched my euro's calipers after braking considerably, they were only warm to the touch.

lol and those brakes you pictured are normal road going brakes are they


they are actually similar to the harrop brakes the supercars use

[ek4-guy]

The heat from the brakes gets dissipated from the pads and discs themselves. The calipers job isn't to release heat.

Painting the calipers is perfectly fine!

If it mattered even in the slightest you would see Brembo, Alcon, AP Racing etc calipers left unpainted!

Tip: Make sure you get the specified Brake Caliper Paint and not just a generic heatproof/fireproof paint - usually the generic heat/flameproof ones are very matte colour. The actual Brake Caliper Paint has gloss in it - which is far more resistant to brake dust ;)

Make sure you clean the caliper extremely well, get rid of any trace of brake fluid and tape up all your piston seals and fluid line and bleeder fittings before you paint ;)


damn wtf is wrong with people is that why on my v8 i have finned calipers go and look why anything is finned in sutch a way its to give more surface for heat to escape

[EuroDude]

lol and those brakes you pictured are normal road going brakes are they


they are actually similar to the harrop brakes the supercars use


True, they are 8 piston brakes, but the car itself doesnt perform like an F1 car or V8 supercar and brake from 300km to 20km in 5 seconds, so I doubt they will get red hot. Basically they wouldnt be factory painted if the paint was going to cause problems.

[DreadAngel]

Why is this an issue anyway? =|

[FAT VTI]

I understand the calipers do not generate extreme heat.
However, I'd still reccomend you paying the extra $5 for the hi-temp spray can instead of the just normal temp spray paint.

The difference in price is not that much ,however few pointers, CLEAR THE FKN RUST!!!!!!!!!!!!!!, and also after doing this, use some mineral turps, then paint.
The result of paint onto an unclean surface will look ugly, plain and simple.


Sean

[JohnL]

True, they are 8 piston brakes, but the car itself doesnt perform like an F1 car or V8 supercar and brake from 300km to 20km in 5 seconds, so I doubt they will get red hot. Basically they wouldnt be factory painted if the paint was going to cause problems.

The calipers won't have to get anywhere near red hot to cause a problem. If you are racing and hitting the brakes hard time after time from high speeds on a hot day then you want all the reserve capacity you can get, especially if the brakes are NOT purpose designed racing units. Having said this you might get away with it time after time, but it only takes one time to wreck your day, and the difference between not boiling and boiling will be a sudden threshold.

If it's a road car (even a high performance one) it's probably not an issue because the brakes just don't see really extreme usage. The only caveat I might place on this is that a lot of road cars never have the brake fluid changed, and water rich boiling brake fluid on say that downhill run to Wollongong or a similar hill could easily kill you, and others.

I do have to say that a serious objection based on the weight of the paint is a little, um , anal, even for a racer.

[FAT VTI]

pfft

Weight of paint, I agree it is very anal.

For the extra 400grams of weight, get on a fkn diet, or dont eat a packet of chips 1 day and you'll be right.

Sean

[n/a]

I understand the calipers do not generate extreme heat.
However, I'd still reccomend you paying the extra $5 for the hi-temp spray can instead of the just normal temp spray paint.

come on sean thats a given!

always a little sceptical when it comes to modifying OEM parts.

[dc2sparks]

nah man it wont crack or anything, mines still perfect :)

[JohnL]

pfft

Weight of paint, I agree it is very anal.

For the extra 400grams of weight, get on a fkn diet, or dont eat a packet of chips 1 day and you'll be right.

Sean

Still, someone said he had a racer freind who stated this as a real objection to painted calipers. I can't see even close to 400gms of dry paint even on all four calipers put together. Of course if this racer knows his stuff his objection is less to do with weight added to the total mass of the car, but to unsprung weight and the affect on handling...but even so!

[ek4-guy]

it might be anal but when you race in a class with weight restrictions it counts a lot more because you can use this weight as balast insted

bassically saying that it holds heat and adds weight as just being simple

can anyone name one performance gain from painting your calipers that will outweigh the above

As for going on a diet well thats a joke the people who race these cars are superfit. IMO they would have worked it out long ago that they perform better with that 400grams on their body.

[JohnL]

it might be anal but when you race in a class with weight restrictions it counts a lot more because you can use this weight as balast insted
bassically saying that it holds heat and adds weight as just being simple
can anyone name one performance gain from painting your calipers that will outweigh the above
As for going on a diet well thats a joke the people who race these cars are superfit. IMO they would have worked it out long ago that they perform better with that 400grams on their body.

Of course to save weight racing drivers should make sure that their hair is short, fingernails cut, not wear underwear, and that the long ends of their racing boot laces are cut off...

No-one can identify a performance gain from painting the calipers because of course there are only downsides, apart from bling value. My objection is that there is a not great but potentially significant heat retension increase in the caliper because of using paint, and while I don't deny some weight is added it's just miniscule, whether in terms of total mass or just in terms of unsprung weight. The affect is real, but only barely measurable in terms of actual weight and not measurable in terms of lap times.

In any case I'll bet that most top end racing sedans are comfortably below the class weight limits, and have to actually add weight to make the cut. This might seem silly at first glance, but the benefit is that whatever weight you need to add can be placed where it will do the most good for CG location, both in the vertical and horizontal planes.

I remember rumours that Dick Johnson used to push this idea to it's limit, having access (reportedly) to a huge acid bath at Palmer Tube Mills, and used it to dip his car bodies in order to thin down the panels to reduce weight. This allowed greater freedom in the location of ballast to improve CG height and general CG location within the wheelbase / track width. It didn't much affect the chassis strength because most of the structural rigidity comes from the roll cage.

Just in case I get a letter from some lawyer, I'm not saying that Dick Johnson or Palmer Tube Mills actually did this, but that a rumour was circulating at one time.

[ek4-guy]

Of course to save weight racing drivers should make sure that their hair is short, fingernails cut, not wear underwear, and that the long ends of their racing boot laces are cut off...

No-one can identify a performance gain from painting the calipers because of course there are only downsides, apart from bling value. My objection is that there is a not great but potentially significant heat retension increase in the caliper because of using paint, and while I don't deny some weight is added it's just miniscule, whether in terms of total mass or just in terms of unsprung weight. The affect is real, but only barely measurable in terms of actual weight and not measurable in terms of lap times.

In any case I'll bet that most top end racing sedans are comfortably below the class weight limits, and have to actually add weight to make the cut. This might seem silly at first glance, but the benefit is that whatever weight you need to add can be placed where it will do the most good for CG location, both in the vertical and horizontal planes.

I remember rumours that Dick Johnson used to push this idea to it's limit, having access (reportedly) to a huge acid bath at Palmer Tube Mills, and used it to dip his car bodies in order to thin down the panels to reduce weight. This allowed greater freedom in the location of ballast to improve CG height and general CG location within the wheelbase / track width. It didn't much affect the chassis strength because most of the structural rigidity comes from the roll cage.

Just in case I get a letter from some lawyer, I'm not saying that Dick Johnson or Palmer Tube Mills actually did this, but that a rumour was circulating at one time.

this is why i also highlighted that not even the engine block is painted so as to give an example just how bare these are

and in the end things like caliper, disc, block, tailshaft, diff being unpainted aswell as having 2 insted of 6 coats of paint on the rollcage, underbody and interior all adds up

and as for these cars being on weight its how you build it i know my friend bought his last shell from HRT and its only compliance was a plate under the left headlight saying HRT003

and it was far from your average road going model it was far lighter and features like access to the rear struts from inside the car

[ek4-guy]

although none of this is relevent to the thread starter

to the thread starter

no you should not build up enough heat in painted OEM calipers to crack them unless you use them for purposes they are not designed for

[FAT VTI]

hey ,
Som1 said its a given to buy high temp paint.

Well, if this person wanting to do this went to bunnings right now, they would find probably 4different colours of paint for high temp spray paint, out of the 200-300cans bunnings stock.
So, it isnt a given ;), haha im jst justifying something stupid.

And, I am not saying typical things to reduce weight shouldnt be taken aboard by hardcore racers, I am saying for just about all members on ozhonda, painting your calipers will make next to no difference in the lap time of your car!.
I understand weight reduction is needed, but there are so many more things you would be able to take from your car toogive you massive weight reductions, much more than half-3/4 of a 400gram spray can.

The "hardcore" racers, probably have high class brakes anyways, And they are probably manufactured and painted, or powdercoated.
So to put this discussion to rest, the weight reduction of not spraying your calipers is next to minimal.
However, painting your calipers is not a performance mod, obviously.
People do all kinds of physical alterations to make their cars look better to them or the general public who view there cars.
If your going to sit there typing how "ppl on this forum" should justify why they want to spray their calipers, you have just opened up a whole new topic of why anybody gets anything done to their car which is not a performance mod.
In conclusion, you cannot tell/ask ppl to justify visual mods which do not add anything performance wise.

Sean

[JohnL]

no you should not build up enough heat in painted OEM calipers to crack them unless you use them for purposes they are not designed for

I forgot that the original question asked whether the heat could crack the caliper if it were painted. This is a complete non-issue, the chances of cracking a caliper painted or not is less than miniscule. If it did happen it would be 99.99% certain that the caliper casting had a pre-existing crack that got worse.

[JohnL]

[QUOTE=FAT VTI;1490814]I understand weight reduction is needed, but there are so many more things you would be able to take from your car toogive you massive weight reductions, much more than half-3/4 of a 400gram spray can.

Less weight than that when most of the thinners have dried out...

The "hardcore" racers, probably have high class brakes anyways, And they are probably manufactured and painted, or powdercoated.

I'd be very surprised if they were painted or powdercoated. I've seen some very prety racing calipers that were anodised, but then anodising doesn't create a thermal barrier.

So to put this discussion to rest, the weight reduction of not spraying your calipers is next to minimal.
However, painting your calipers is not a performance mod, obviously.

So other than bling value there is no reason to do it, and at least one credible reason not to.

[FAT VTI]

LOL dude

Ur saying that a general street car shouldnt paint their calipers because it doesnt have a performance gain and the only con to doing this is because of the added weight?

Come on mate, are u hearing the same thing i am?

Also, once again, how can you ask me or any1 else to justify spraying calipers, as opposed to any other mod which is not a performace mod.

And, the 1 credible reason not to do it, is debatable unless your driving a high performance car...
I dont think the weight reduction is credible at all in my opinion
I think the only con to doing it, is that spray paint can look ugly if its done wrong, and from personal opinion, unless you take your brake caliper off and do it right, your bound to fk up, but i am very picky when it comes to paint.

U could even powdercoat it, would look that much better.


Sean

[Vinnie]

painting calipers is purely for bling factor.
there is no added weight.
heat retention would be minimal if any.

basically for a road car if you want to paint your calipers there will be no detrimental effects to your braking, just make sure you do it properly.

[JohnL]

[QUOTE=FAT VTI;1490948
LOL dude
Ur saying that a general street car shouldnt paint their calipers because it doesnt have a performance gain and the only con to doing this is because of the added weight?
Come on mate, are u hearing the same thing i am?


Sean,
I'm trying to say (obviously not very clearly) that the weight thing is really a non issue, won't make a jot of difference either way.

Also, once again, how can you ask me or any1 else to justify spraying calipers, as opposed to any other mod which is not a performace mod.

You don't need to justify it. If you think it will make the car look pretty then do it, so long as you're certain it won't create a problem in the context in which you use your car.

And, the 1 credible reason not to do it, is debatable unless your driving a high performance car...

This is a bit of a storm in a teacup! I'm simply saying that there is a real theoretical reason to avoid doing it (heat retention), but if you do then in most instances it won't be a problem, but in others it potentially could be. Just be aware of whether it won't or might be. Hypothetically, if somone is unaware of the issue, then he/she might decide to blast down Con-Rod Staight at 150mph and potentially have a tad of trouble when they hit the brakes.

It could also be an issue for some fool who paints calipers that are still filled with ten year old brake fluid, and it might make the difference between boiling and not boiling the fluid on a hot day going down a long steep hill.

I dont think the weight reduction is credible at all in my opinion

Agreed! Even though weight is added it's so slight as to be inconsequential, even for a racing car.

I think the only con to doing it, is that spray paint can look ugly if its done wrong, and from personal opinion, unless you take your brake caliper off and do it right, your bound to fk up, but i am very picky when it comes to paint.

Nothing looks worse than a bodge job, so if you feel the need to do it do it right, or leave it alone. Personally I prefer the no-frills functional / purposeful look, but that's just me I'm wierd that way!

U could even powdercoat it, would look that much better.

Would powder coat like the heat? Suppose it depends on whether the brakes are used really harde, like on a race track. But if we're talking heat retention, powder coat would be worse than paint...

[EUR003act]

[QUOTE=FAT VTI;1490814]I understand weight reduction is needed, but there are so many more things you would be able to take from your car toogive you massive weight reductions, much more than half-3/4 of a 400gram spray can.

Less weight than that when most of the thinners have dried out...

The "hardcore" racers, probably have high class brakes anyways, And they are probably manufactured and painted, or powdercoated.

I'd be very surprised if they were painted or powdercoated. I've seen some very prety racing calipers that were anodised, but then anodising doesn't create a thermal barrier.

So to put this discussion to rest, the weight reduction of not spraying your calipers is next to minimal.
However, painting your calipers is not a performance mod, obviously.

So other than bling value there is no reason to do it, and at least one credible reason not to.

what the f*ck are you talking about? painted calipers would be the difference between whether you had taken a shit before going for a drive or not.. seriously, the weight difference would be so so so minimal!

and think of all the performance brakes, Brembo, AP racing, wilwood, etc, they all are enamel coated.... it adds not heat restriction at all... if anything, the enamel absorbs the heat from the caliper...

painting calipers is purely cosmetic, it looks sexy, makes your brakes stand out, and thats about it, no performance gain!

and as for the paint cracking? caliper paint is normally rate dto 1400 degrees celcius, i would love to see your calipers get hotter than that!

[Limbo]

let the fools be EUR003act. If they wanna drive around in their unpainted calipers its their loss.

I've painted quite a few sets when i've upgraded to larger calipers never had any issues, so i'll keep going.


[quote=JohnL;1490942]

what the f*ck are you talking about? painted calipers would be the difference between whether you had taken a shit before going for a drive or not.. seriously, the weight difference would be so so so minimal!

and think of all the performance brakes, Brembo, AP racing, wilwood, etc, they all are enamel coated.... it adds not heat restriction at all... if anything, the enamel absorbs the heat from the caliper...

painting calipers is purely cosmetic, it looks sexy, makes your brakes stand out, and thats about it, no performance gain!

and as for the paint cracking? caliper paint is normally rate dto 1400 degrees celcius, i would love to see your calipers get hotter than that!

[JohnL]

what the f*ck are you talking about? painted calipers would be the difference between whether you had taken a shit before going for a drive or not.. seriously, the weight difference would be so so so minimal!

If you read my earlier post you'll note that I did say more or less the same thing, i.e. "I'm trying to say (obviously not very clearly) that the weight thing is really a non issue, won't make a jot of difference either way".

When I said; "Less weight than that when most of the thinners have dried out", I was merely pointing out a fact.

When I said; "Of course to save weight racing drivers should make sure that their hair is short, fingernails cut, not wear underwear, and that the long ends of their racing boot laces are cut off", I was being facetious.



and think of all the performance brakes, Brembo, AP racing, wilwood, etc, they all are enamel coated....

The paint is there just to get you to buy them (or the car to which they're fitted), such brakes are typically so far above what a sane road user will ever really need it makes no practical difference.


it adds not heat restriction at all...

I'd be interested to hear you back that up with the relevant physics...


if anything, the enamel absorbs the heat from the caliper...

The paint will of course absorb some heat, but the quantity it can absorb is infintesimally small because the paint just doesn't have the mass to absorb more. The issue is whether or not the paint is a thermal barrier, slowing or not slowing the rate at which heat can be dissipated by the caliper.



painting calipers is purely cosmetic, it looks sexy, makes your brakes stand out, and thats about it,

As I said previously, it's purely for bling value, so we agree.



no performance gain!

I never said there was, the opposite in fact.



and as for the paint cracking? caliper paint is normally rate dto 1400 degrees celcius, i would love to see your calipers get hotter than that!

The concern of the original poster was not the paint cracking, but the caliper itself, which is of course a non issue.

Please read more carefully before start saying things like; "what the f*ck are you talking about", and peppering us with aggressive exclamation marks.

[EUR003act]

If you read my earlier post you'll note that I did say more or less the same thing, i.e. "I'm trying to say (obviously not very clearly) that the weight thing is really a non issue, won't make a jot of difference either way"
i must have missed that post, sorry...


The paint is there just to get you to buy them (or the car to which they're fitted), such brakes are typically so far above what a sane road user will ever really need it makes no practical difference.
funny enough, everyone that buys a brembo kit for their car dont just do it for looks... if they just wanted looks they could paint their stock calipers... id say the majority spend thousands of $$$ because they are tracking/dragging/racing and need to be able to pull up...




I'd be interested to hear you back that up with the relevant physics...
ok, there may be the slightest bit of heat retention ever, but i dont think, ferrari, aston martin, maseratti, jaguar, audi, hsv, fpv, nissan, mercedes, bmw, and every other company that use painted calipers on their vehicles would do so if there was going to be any problem with heat retention? i mean, theyre only worth billions and billions of dollars together...


The paint will of course absorb some heat, but the quantity it can absorb is infintesimally small because the paint just doesn't have the mass to absorb more.
i agree totally with that


The issue is whether or not the paint is a thermal barrier, slowing or not slowing the rate at which heat can be dissipated by the caliper.
correct me if im wrong, a darker colour will dissipate heat quicker and more effectively than a lighter colour? so painting light coloured calipers dark red, should increase their effectiveness?


I never said there was, the opposite in fact.
i shouldve said, "no performance gain or loss"


Please read more carefully before start saying things like; "what the f*ck are you talking about", and peppering us with aggressive exclamation marks.
i wasnt directing it straight at you, i was talking to everyone in this thread who thought tht painting calipers is bad for performance! all it does is ruin it for the noobs that wanted to paint the brakes, but now wont because they think itll slow them down, or cause their brakes to crack...

[JohnL]

funny enough, everyone that buys a brembo kit for their car dont just do it for looks... if they just wanted looks they could paint their stock calipers... id say the majority spend thousands of $$$ because they are tracking/dragging/racing and need to be able to pull up...

I'm sure that plenty of people use Brembos et al and etc purely because they know they are superior components and have real practical need for such quality parts. But my best guess (and that's all it is) is that most aftermarket trick parts never see real competition or even the odd track day. They get fitted to show cars (or wannabe show cars) and boulevard cruisers, they are fitted for bling value and because of fetishistic obsession. I could be wrong.

I'ts not just about looks or purpose, it's also about image amd status and 'cache', e.g. Brembos are the real deal and fitted to all sorts of racers and other exotica, so, I (hypothetical 'I') want Brembos because if I just painted my brakes to look like them then I'd just be a wanker, or I think I might at least run the risk of being seen as one.

If we have had the choice of a brightly coloured bit of bling kit that could also do it's job well, and a nondescript drab component that also did it's job well, which would you choose, all else apparently being equal? Most will go the bling, which is understandable.


ok, there may be the slightest bit of heat retention ever, but i dont think, ferrari, aston martin, maseratti, jaguar, audi, hsv, fpv, nissan, mercedes, bmw, and every other company that use painted calipers on their vehicles would do so if there was going to be any problem with heat retention? i mean, theyre only worth billions and billions of dollars together...

Keeping in ind that even though these are high performance cars they are still road cars, and it's not ever likely to be a problem for their customers because even fast road use just doesn't see the same relentless pounding seen in competition (not even on the autobahn, unless you're insane). On the other hand their cars MUST look sexy as, or they just won't sell no matter how good they are. IMO it's marketing, but there's so much spare capacity designed in that (for road use) it's not detrimental to add a bit of bling.

On the other hand, if I take my sedan and mod it to death with turbo's and semi slicks etc etc. And then paint my stock calipers (which are not likely to have anywhere near the spare capacity of the stock brakes on exotics as above), then do some hard laps on the track on a hot day, then I think there's a chance I'll be approaching the extreme edge of the performace envelope of the calipers ability to dissipate heat. People do boil the brake fluid on the track, it's not common but not that uncommon.


correct me if im wrong, a darker colour will dissipate heat quicker and more effectively than a lighter colour? so painting light coloured calipers dark red, should increase their effectiveness?

You're not wrong, you're absolutely correct, but darker or lighter colour is only part of it. If we have two identical metal objects one painted light and one dark and both are at an identical higher than ambient temp then the darker painted object will lose heat faster.

This is comparing an apple to an apple, but if one of the objects is painted and the other is not, then regardless of the colours we are now comparing an apple with an orange. The paint is a thermal barrier, and may cause the object to cool more slowly even if the unpainted obect is light coloured and the painted one dark. Air cooled motors are generally not painted for this reason and it can adversely affect performance, slightly. I once painted the head on my kart motor black, my engine builder made me sandblast it off!


i wasnt directing it straight at you, i was talking to everyone in this thread who thought tht painting calipers is bad for performance! all it does is ruin it for the noobs that wanted to paint the brakes, but now wont because they think itll slow them down, or cause their brakes to crack...

As I more or less said before it's no big deal except right on the extreme edge of the high performance envelope, not a real issue for road cars unless maybe their brakes are neglected or are used way outside their design parameters, and possibly not even for a lot of competition cars. I just wouldn't do it myself...

[AzKik-R]

IF, and I cant stress the IF enough, but If it were a heating problem, then obviously the type of rotars would weigh in heavily, if you have slotted or drilled rotars, then this would help with the heat dispersing, and therefore reduce the amt of heat transfered to the calipers.

[dsp26]

what is this thread about... the answer was stated in Post#2-5

[JohnL]

I'd think so.

[JohnL]

It's about being stubborn!

[dsp26]

IF, and I cant stress the IF enough, but If it were a heating problem, then obviously the type of rotars would weigh in heavily, if you have slotted or drilled rotars, then this would help with the heat dispersing, and therefore reduce the amt of heat transfered to the calipers.

the cooling of the area is shared by the whole system from pads/rotors to:

- Hub --> wheels
- Caliper

Heat transfer to calipers is normal hence why theres different gradings of brake fluid as it boils.. this is also another reason why theres SS braided brake lines sleeved in teflon.

Type of rotors don't matter too much.. it's size and pad efficiency that counts.
Slots - clean the surface and shave off any glazing
CrossDrills - dissipate SOME heat, if the quality of the rotor is poor then it will crack between crosdrills under heavy brake pressure

[FAT VTI]

LOL,

Mate, when you tell people to read the threads/posts more carefully, i think you need to have a go at reading over yours before posting, because I couldnt tell if we were agreeing or disagreeing.

I cant be bothered going on about this,

All i wanted to know is why you said this
So other than bling value there is no reason to do it, and at least one credible reason not to.

If you do not believe the weight reduction is a REAL issue, and you also think that the heat produced by the calipers is not enough to be an issue.
What was the credible reason?
haha, im not about winning an arguement by any means, I just didnt understand why you posted that, when you were disagreeing that the problems would cause an issue.

Sean

[dsp26]

LOL,

Mate, when you tell people to read the threads/posts more carefully, i think you need to have a go at reading over yours before posting, because I couldnt tell if we were agreeing or disagreeing.

I cant be bothered going on about this,

All i wanted to know is why you said this
So other than bling value there is no reason to do it, and at least one credible reason not to.

If you do not believe the weight reduction is a REAL issue, and you also think that the heat produced by the calipers is not enough to be an issue.
What was the credible reason?
haha, im not about winning an arguement by any means, I just didnt understand why you posted that, when you were disagreeing that the problems would cause an issue.

Sean
was that reply to me? coz i don't understand the relevance of your post to my last 2...

Original post is:

Just wondering if the DIY caliper spray jobs that everyones been doing would hinder the caliper from releasing heat which could lead to cracking.

As per Post#2, answer is NO.

As per my last post, it stands... the whole system shares the cooling/heat load.... The caliper will not crack, it is cast.... they are manufactured to withstand higher temps beyond any brake fluid available.

If you mistook my comment about ROTORS cracking to the above question about CALIPERS... then??? wtf?? The only instances of rotors cracking wether standard or crossdrilled is in motorsport where they have full braided lines, good fluids, etc... the rotors would glow red hot, and udner pressure from caliper piston/hydraulics would lead to cracking and disastrous shattering.... this still has nothing to do with calipers heating up....

[FAT VTI]

john L mate, not you.
sorry, should of said LOL
Sean

[dsp26]

john L mate, not you.
sorry, should of said LOL
Sean

LOL:thumbsup: was thinking wtf... someones been watching my posts waiting to flame me.....

[EUR003act]

LOL:thumbsup: was thinking wtf... someones been watching my posts waiting to flame me.....

hahaha i just like debates...

i think we've both made our points... :thumbsup:

[JohnL]

LOL,

Mate, when you tell people to read the threads/posts more carefully, i think you need to have a go at reading over yours before posting, because I couldnt tell if we were agreeing or disagreeing.

I cant be bothered going on about this,

All i wanted to know is why you said this
So other than bling value there is no reason to do it, and at least one credible reason not to.

If you do not believe the weight reduction is a REAL issue, and you also think that the heat produced by the calipers is not enough to be an issue.
What was the credible reason?
haha, im not about winning an arguement by any means, I just didnt understand why you posted that, when you were disagreeing that the problems would cause an issue.

Sean

Sean,
The confusion arises because as I see it there are two real issues with varying degrees of practical import. One issue is the weight issue that while being real, is inconsequential in practice. I'm not going to agree that it isn't real, but at the same time I'm not going to agree that it's in any way important because the affect of it is so slight in any application.

More confusion is obviously arising from my use of the terrm 'non credible', by which I mean the weight issue is not a rationally convincing reason to not paint the calipers if you want to. By 'non-credible' I don't mean untrue.

The other issue is the heat retension issue, which is more complex insofar as it is generally of no importance in most applications but potentially is of importance in other applications. When I say this is a 'credible' reason I mean that in particular applications it is a rationally convincing reason not to paint the calipers.

Sorry if it ends up sounding like I'm arguing both sides of the argument, but I'm not really arguing a black and white case. Hope I've cleared up any confusion as to where I stand on this topic (sort of half on and half off the fence!).

[JohnL]

the cooling of the area is shared by the whole system from pads/rotors to:

- Hub --> wheels
- Caliper

Heat transfer to calipers is normal hence why theres different gradings of brake fluid as it boils.. this is also another reason why theres SS braided brake lines sleeved in teflon.

Yes, the whole system shares in heat dissipation, but, if you have a well vented rotor that dissipates heat well to air (as opposed to a poorly or non vented rotor that doesn't), then more heat will dissipate through the rotor and take some of the thermal pressure off the rest of the system.

The pads generate their own heat, but also pick up heat from the rotor, so if rotor temp is lower then less heat conducts to the pads from the rotor and then less heat from the pads into the caliper and fluid (if the rotors are really good then the pads will be able to conduct some of their generated heat to the rotor, taking even more thermal load off the pads and caliper). The calipers also pick up radiant heat from the rotor, so less heat in the rotor means less radiant heat into the caliper as well.


Type of rotors don't matter too much.. it's size and pad efficiency that counts.
Slots - clean the surface and shave off any glazing
CrossDrills - dissipate SOME heat, if the quality of the rotor is poor then it will crack between crosdrills under heavy brake pressure

Both slots and drilled holes also vent gas generated by the pads. As the pads get very hot they start to give off invisible gasses and smoke (which is also gas), and this gas can build to very high pressure between the rotor and the pads, enough to physically lift the pad off the surface of the rotor. When this happens the effective co-efficient of friction between pad and rotor drops to zero (kind of like the pads are 'aquaplaning' on high pressure gas). The gas is being produced at such a rate it simply cannot ecape fast enough from between the two surfaces.

I've heard this phenomenon called 'pad fade' or 'gassing up the pads', and is at least one reason why high performance and racing pads work better at higher temperatures than 'road' pads do, i.e. they don't start giving off gasses until they reach higher temperatures than road pads.

Both slots and holes provide an escape route for the excess gas, allowing the pads and rotor to remain in meaningful contact. This is why the slots ought to extend past the edge of the pad, typically toward the inside of the rotor, because if they extended to the outer edge the rotor is likely to crack at this point. Holes allow the gas to escape to the venting cavities inside the rotor.

There is also some marginal increase in rotor surface area with slots and holes, and this also assists in some small degree to dissipate more heat (more rotor surface area, either internal or external = more radiating area). With holes though you have to be careful with the size of the holes, too small and not enough gas can escape, too large and you'll actually reduce the radiating surface area of the rotor because the walls of each hole has to have more surface area than twice the circular area of the hole (or the hole will cause a lessening of surface area), so thickness of rotor wall also has an affect on this.

[dsp26]

Yes, the whole system shares in heat dissipation, but, if you have a well vented rotor that dissipates heat well to air (as opposed to a poorly or non vented rotor that doesn't), then more heat will dissipate through the rotor and take some of the thermal pressure off the rest of the system.

The pads generate their own heat, but also pick up heat from the rotor, so if rotor temp is lower then less heat conducts to the pads from the rotor and then less heat from the pads into the caliper and fluid (if the rotors are really good then the pads will be able to conduct some of their generated heat to the rotor, taking even more thermal load off the pads and caliper). The calipers also pick up radiant heat from the rotor, so less heat in the rotor means less radiant heat into the caliper as well.



Both slots and drilled holes also vent gas generated by the pads. As the pads get very hot they start to give off invisible gasses and smoke (which is also gas), and this gas can build to very high pressure between the rotor and the pads, enough to physically lift the pad off the surface of the rotor. When this happens the effective co-efficient of friction between pad and rotor drops to zero (kind of like the pads are 'aquaplaning' on high pressure gas). The gas is being produced at such a rate it simply cannot ecape fast enough from between the two surfaces.

I've heard this phenomenon called 'pad fade' or 'gassing up the pads', and is at least one reason why high performance and racing pads work better at higher temperatures than 'road' pads do, i.e. they don't start giving off gasses until they reach higher temperatures than road pads.

Both slots and holes provide an escape route for the excess gas, allowing the pads and rotor to remain in meaningful contact. This is why the slots ought to extend past the edge of the pad, typically toward the inside of the rotor, because if they extended to the outer edge the rotor is likely to crack at this point. Holes allow the gas to escape to the venting cavities inside the rotor.

There is also some marginal increase in rotor surface area with slots and holes, and this also assists in some small degree to dissipate more heat (more rotor surface area, either internal or external = more radiating area). With holes though you have to be careful with the size of the holes, too small and not enough gas can escape, too large and you'll actually reduce the radiating surface area of the rotor because the walls of each hole has to have more surface area than twice the circular area of the hole (or the hole will cause a lessening of surface area), so thickness of rotor wall also has an affect on this.
^^^
I agree with your first paragraph

2nd paragraph.. dunno if i can agree... i'm quite confident the rotors will never have lower temps than the pads as it is the pads that define heat range and and how much it can resist as a result of friction against the rotor... metal will be metal and will will glow when hot, you can only make rotors out of varying grades of steel but pads are made differently with different materials to suit application. But yes the calipers can pickup radiant heat but not as much as the transfer through the hub.

I agree with your 3rd paragraph

I agree with your 4th paragraph, if you have never experienced it yourself, in summer after changing your pads.. goto a safe area where you would normally bed in your brakes, but instead... do about 60-80km/h and hard brake on first run... your car will not stop and it will smoke up.... this happened to me because i forgot to bed in the Bendix Ultimates I had installed.

5th paragraph, got it backwards... if you look at slotted rotor design it's actually extended outwards than inwards or not at all... this is why slots are directional for each side of the car. If you look at the passenger side of the car (front to the left and rear to the right), slot design curves from inwards on the left to outwards to the right for this gas dissipation you speak of. It will not work efficiently backwards. but when we both mention extended, no slots are ever extended all the way to the edge or inside, i have never seen one and it would be foolish for the exact danger you mentioned.
But rotors will RARELY crack as a result of slots, the effect on rigidity and integrity is no where near detrimental compared to improper sizing,pattern,placement of cross-drills. It is the crossdrills that make a rotor weak as it actually removes solid surface area, cracking is known to happen between holes because of this. Slots on the other hand are regulated to a certain depth % of the surface so as to not effect strength.

Your 6th paragraph... can you please elaborate on this point:
- Increase in rotor surface area from slots+crossdrills

[dsp26]

also... what is being debated in this thread as i cannot understand the issue between FatVti & JohnL? seems to be way off-topic from first page.

i thought off-topic debate was about:
- increased heat retention as a result of caliper painting
- caliper overheating?
- some brake component cracking??

Also, JohnL.. are you by any chance a law student or work in the profession? :p you and tinkerbell should have a debate about something lol.

[FAT VTI]

hahaha

Who u calling tinkerbell bitch.

Yeah i am over this thread. I got my own car problems LOL

Sean

[dsp26]

hahaha

Who u calling tinkerbell bitch.

Yeah i am over this thread. I got my own car problems LOL

Sean

lol.. no... as in the member tinkerbell... i've read a few of his past posts... quite structured in debates hehehe

[FAT VTI]

LOL, my bad

Sean

[JohnL]

^^^
I agree with your first paragraph

2nd paragraph.. dunno if i can agree... i'm quite confident the rotors will never have lower temps than the pads as it is the pads that define heat range and and how much it can resist as a result of friction against the rotor... metal will be metal and will will glow when hot, you can only make rotors out of varying grades of steel but pads are made differently with different materials to suit application. But yes the calipers can pickup radiant heat but not as much as the transfer through the hub.

After I posted and on the way to bed I realised I didn't have this quite correct. The rotor must typically run at lower temp than the pads (even with relatively poor rotors), and the pads must lose most of their heat to the cooler rotor. The rotor is designed to lose heat and has a huge surface area from which to do it (both radiate and conduct to air), the pads are relatively tiny and have little surface area from which to lose heat, i.e. the sides of the pads and the rear and front faces.

However, the pad contact faces cannot lose heat if the rotor is as hot or hotter than the pad is, and even the ability of the pad to lose heat through the sides and rear of the pad is limited due to the friction material itself being a relatively good insulator (compared to metal). The surface temp of the pad's friction material at the contact face is going to be significantly hotter than the temp of friction material at the back of the pad where it's adhered to the backing plate, simply because the friction material won't relatively be a very good conductor of heat.

If the contact face of the pad can't lose heat to a cooler rotor then the temp of the pad's contact face would probably rise exponentially quickly relative to the rotor's temp, and 'gas up' quite quickly unless very resistant to this.

The pads do of course come in different grades, and this does define the fade reistance of the pads, but I don't see why this means ipso facto that the rotor must run hotter than the pads do. It just means that if the disc is poorer at dissipating heat then a 'harder' pad will be required for heavy duty applications.

How much heat makes it's way into the caliper itself will be cumulative, from radiant heat from the disc, from heat conducted from the pads (and their backing plates), and conducted through the caliper attachment points. I would expect the least of these to be from the attachment points because for substantial heat to pass from the rotor to the caliper through this pathway it needs to pass through the 'top hat' part of the disc, through the hub, through the bearings, through the stub axle into the 'upright', through the attachment lugs (which are relatively small so represent a 'resistance'). It's a long pathway with plenty of opportunity for substantial heat to be lost along the way, i.e radiated and just absorbed by the mass (of the upright in particular, being a large mass).



I agree with your 4th paragraph, if you have never experienced it yourself, in summer after changing your pads.. goto a safe area where you would normally bed in your brakes, but instead... do about 60-80km/h and hard brake on first run... your car will not stop and it will smoke up.... this happened to me because i forgot to bed in the Bendix Ultimates I had installed.

New pads have an effectively smaller friction area because of the new flat pad surface not mating exactly with any slight imperfections in the rotor surface (there will be minute gaps between the rotor and pads). On the first few applications before the pad has bedded in to the rotor only part of the pad is in significant contact with the rotor, and thus a lot more heat is going into a much smaller area of pad material and that material that is actually working will heat up very fast and very high (not effectively conducting this heat into the rest of the friction material due to the poor conductive quality of the friction material). In this case it's that the pad is gassing up but also simply because less friction area tends to mean less friction.


5th paragraph, got it backwards... if you look at slotted rotor design it's actually extended outwards than inwards or not at all... this is why slots are directional for each side of the car. If you look at the passenger side of the car (front to the left and rear to the right), slot design curves from inwards on the left to outwards to the right for this gas dissipation you speak of. It will not work efficiently backwards. but when we both mention extended, no slots are ever extended all the way to the edge or inside, i have never seen one and it would be foolish for the exact danger you mentioned.

If I read you correctly, then you're correct, the slots should never be allowed to run out of the rotor faces as this creates a severe stress riser (the slots themselves are unavoidably stress risers, but no need to make this worse than necessary), they should always end gradually within the machined face or the risk of cracking is much increased (perhaps inevitable). For improved ventilation of the pad / rotor interface, the pads can be arranged so they don't extend quite all the way to the inner ending of the slots, but it's not entirely necessary because the slots are not purely radial but 'slanted' across the rotor face. This means that as the slot is 'entering' and 'exiting' the pad it can vent the pad quite effectively to the front and rear of the pad.

I suspect that the venting properties of the slots will be more or less equal regardless of the directionality of the slots. The rotors will typically be 'sided' because of the angularity of the venting tubes inside the disc, these should be arranged so that a 'fan' effect causes air to pass from the inner part of the rotor to the outer edge, not the other way around. The slots are 'sided' more for reasons to do with matching the direction of the internal vents because the arrangemnet of the slots relative to the vent tubes will probably have some affect on resistance to cracking. I also suspect an aesthetic consideration, i.e. it looks nicer for the slot direction to match side to side.

On some karting discs I've seen the 'slot' is actually a machined groove in the form of a never ending circle machined into the rotor, but offset from the rotor centre (some rotors have two such circular grooves). The 'slot' never touches either the inner or outer edges of the rotor, and as the rotor spins the 'slot' 'oscillates' in and out across the pad faces due to the slot circle being non concentric. In this case the venting gasses pass from under the pad to the front and rear of the pad.

You may have also noticed many pads come with slots machined into the actual friction material, this is also for reasons of venting pad gasses from the centre of the pad (which is where you would typically see the highest pad gas pressure because from the centre of the pad the gas has further to travel before it can escape).


But rotors will RARELY crack as a result of slots, the effect on rigidity and integrity is no where near detrimental compared to improper sizing,pattern,placement of cross-drills. It is the crossdrills that make a rotor weak as it actually removes solid surface area, cracking is known to happen between holes because of this. Slots on the other hand are regulated to a certain depth % of the surface so as to not effect strength.

Another reason to be careful with drilled holes, too small and or too closely spaced or too close to the edge of the rotor and the chance of cracking increases. The thicker the rotor walls the less problem this will tend to be, so rotors with thin walls should propbably be left alone. Small holes are more risky because the smaller hole is more of a stress riser than a larger hole, simply because the larger hole will have a greater radius around it's circumference. If the holes are too close to each other or too close the edges of the rotor, then there is increased risk of cracking between the holes or the holes and the edge of the rotor.

My understanding is that the reason well designed rotor slots are curved has only to do with increased resistance to cracking, i.e. a straight slot is much more prone to developing a crack than is a curved slot because a straight slot is a more direct force pathway than a curved one.


Your 6th paragraph... can you please elaborate on this point:
- Increase in rotor surface area from slots+crossdrills

At it's basic level it's to do with surface roughness, a smooth surface has less surface area than a rough surface for the same apparent area. It's like the two farmers arguing about who has the most land, one says "look at this map, I've got 100 hectares", but the other farmer says "on the map I also have 100 hectares but I still still more land than you have because mine is full of hills". Assuming both blocks of land to be otherwise identical as seen on the map (say both are square blocks), if the first farmer were to walk from one side of his flat land to the other with one of those measuirng wheels he'd find the distance from one side to the other to be X. If the other farmer did the same on his hilly land he'd find the distance to be X+. Multiply these measurments by 2 to find the actual surface area and the second farmer indeed does have more land.

This affect goes from the macro down to the micro, and is why two otherwise identical surfaces painted the same colour, but one gloss and the other matt, will dissipate heat at differring rates, i.e. the matt surface is microscopically rougher than the gloss surface, and as such has a greater surface area from which to radiate heat. This is despite the surface areas seeming to be the same if you measure it, it's just that you only measured it in two dimensions not three.

It's the same with holes and slots, you add 'topography' to the surface and thus increase the surface area in three dimensions even if the 'map' dimension remains constant. With holes this extra area exists on the walls of the hole, so long as the hole's wall area is greater than the area on the rotor face surface removed when the hole was drilled.

[JohnL]

Also, JohnL.. are you by any chance a law student or work in the profession? :p you and tinkerbell should have a debate about something lol.

No, are you?

I've just studied this sort of stuff from personal interest and for better understanding the dynamics in order to better be able to set up my racing vehicle (kart).

I would like to think of myself as reasonably articulate and able to structure a cogent argument. Just how successful I am at this is for others to judge I suppose. Judging from the number of times I've had to expand / defend my arguments in this thread I may not be so good at it as I'd like to think!

[ek4-guy]

lol you gota love the enthusiasm in this thread

[EKVTIR-T]

FFS guys....
http://www.steveaddison.net/wp-content/uploads/2006/09/flogging%20dead%20horse.jpg

[Limbo]

man you guys post too long i didn't even bother reading the rest after a while was giving me a brain strain just thinking about it ;P

[JohnL]

There are still a few twitches left in this old nag!

[philBo]

hahaha

Who u calling tinkerbell bitch.

Yeah i am over this thread. I got my own car problems LOL

Sean


ROFL!!!!!

it will be okay to respray your calipers with paint...there may be some slight heat problems yada yada yada but they are sooo negligible that the OP shouldnt need to be inundated with all this bitching.

[dsp26]

Hot Chicks thread fixes all issues!!!!

[EUR003act]

Hot Chicks thread fixes all issues!!!!

mmmmm jail bait