Machining Discs - 2 part question

[Zilli]

Hey guys,

I recently bought some DBA slotted discs for up front (by recent i mean 6 months ago). They've probably had about 3000kms on them in that time, but as soon as i got them i went to Wakey... been experiencing some shudderring, and i cannot understand why. Let me explain, my understanding of under brake shuddering is the discs are warped... need machining. I did cooldown laps etc, so i cannot identify why they are doing this again already.

BUT thats not the issue (if anyone has any thoughts i dont mind hearing them though)

What i want to know is

1) Can i machine the discs and leave the old pads in? any potential issues come from this? The Ferodo ds2500's are as old as the discs
2) Does anyone know of any DIY's out there that describe this process?

Cheers lads

Kalen

[l3vnd1]

That sounds unusual.

I too was part of this group buy. Put the rotors on with the OEM pads and thrashed it around Wakefield also.

Mine are fine.

Did you clean the hub face before you put the rotor on?

[T-onedc2]

My stock brakes warped a little due to heat only.

If you machine the discs but use old pads the disc will wear unevenly, I was once told to take the pad and rub it on some relatively coarse concrete to even it out.

[EG5]

If you got new disc / machine disc , in theory you should use new pads too to match it

[Zilli]

cheers lads... i might give the pads a scuff then do the break in process again

[Zilli]

interesting because a number of different people have alerted me to the fact that discs dont warp... i dont agree with them...

question though, with the Ferodo's being an "adherant friction" pad, could it be that as a result of heat buildup there are uneven deposits of pad material on the disc? this, being a resultant of an innappropriate break in?

i didnt do the break in unfortunately so this is a weak link, and probably the reason i am where i am... the perplexing thing though is that the first month before i went to the track i drove on the street, albeit for a very short time (it's a garage queen) and it never had the problem...

SO perhaps a combo of overheating on the track with improper break-in?

any thoughts?

my current course of action is to get the discs machined, then do the break in procedure as per manufacturers requirements and see how i go...

[Zilli]

BTW thanks for your nice PM below lol

http://www.ozhonda.com/forum/showthr...78#post2166878


Whew you going to start sending him bad pms also

Really you need professional mental health assistance.

good to see you're still cut :-)

but can you advise on the above anyway?

like a man preferrably... without being derogitory like a bitch?

[Zilli]

wow... it's taking a while... this is gonna be good :-)

[bennjamin]

BTW thanks for your nice PM below lol

http://www.ozhonda.com/forum/showthr...78#post2166878


Whew you going to start sending him bad pms also

Really you need professional mental health assistance.

good to see you're still cut :-)

but can you advise on the above anyway?

like a man preferrably... without being derogitory like a bitch?


boss i have no idea what you are on about. That link is incorrect too.

[Zilli]

the bits in bold were the PM i received from our resident bomb expert :-)

i didnt bother looking at the link :-) didnt care LOL

[bennjamin]

oh ok gotcha. Jeebus you lot need to get over te interweb lol.

Anyway , currently what is your situation regarding the pads etc ? I strongly advice new pads and new discs (or machined)....if you havent already

[Zilli]

:-)

it's entertainment for me man :-) sorry he troubled you about it LOL

good break from study... funnily enough this always happens when im off on study leave for an exam so it helps me relieve some stress :-)

anyway

current sitch is as it stands, i think ill get the discs machined then break the pads in again... not keen on changing pads as they have less than 3000km on them and aint cheap

[aaronng]

I'd start by sanding the discs with coarse grit sand paper, and then bedding the pads in again. If that doesn't fix the shudder, then consider machining. Alternatively, you can also try using an abrasive brake pad for a while and then switching back to DS2500

[Zilli]

thats the advice ive been given too Aaron... i think this might work (just course grit) if it is in fact deposits of the pad material rather than a "warp"

here's an interesting link

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

[Zilli]

cheers for the good info... and generally your thoughts above are in line with my thinking. Have you ever experiences "adherant friction" compound pads though? or is that a marketing gimmick too?

The two things i am having trouble comprehending are

1) How did this happen - sure there would have been a fair bit of heat generate on the track as i was pushing hard and braking later than ever before, but i did the recommended cool down etc. Is the heat generated the first time around on fresh disks and pad more than the following cycles?

2) This concept of "adhesive friction". Supposedly these pads don't work solely on a friction basis. The way apparently they work is that they set some of the pad material on the suface of the disc, then the friction generated with the material on material is what causes the stopping power... is this true? could it be that an improper break-in could have caused inconsistent "lay down" of material on the disc, which then was worsened over time with more heat cycles?

waddaya think?

[Zilli]

sweet... good insights.

Question, why do pad manufacturers all have break-in procedures if they are irrelevant? i mean surely there is a purpose for them yeh?

:-) thanks for clearing up the marketing gimmick bit mate! love the snot ball analogy, makes sense but...

I highly doubt that the heat rating of my pads is the issue, i know fatboy on the forums is using these pads and he is laping 5 second squicker than me, unless im just a shit driver that is too hard on the brakes, i wouldn't need a higher temp pad... and i always do opne cool down lap of the track before i come fof, then a couple of laps of the pits with no brakes... never applying handbrake when i park... i dont get it

[aaronng]

What is the max temp rating of those rotors?
My oem rotors were overheated when I took my 1400kg car to the track. The rotors turned blue in colour and I could see very fine cracks along the surface. Didn't shudder at all during braking after that trackday. It has been 3.5 years since that track day and my rotors are still fine (after another 4 trackdays too).

[Zilli]

hmmmm

stock car, stock rims (but with semi's) stock motor coloivers high temp pads slotted rotors with an average driver...

Just not making sense... but you are right, only one way it could have happened un der the theory you are presenting...

Anyway.

Aaron, they are the 4000 series dba slotted... cannot find a maximum temp rating...


Another interesting thread here

http://mrtperformance.com.au/forums/showthread.php?t=2

apparently bedding new discs with new pads isnt such a great idea, you need to go easy for 200kms apparently, this is with the exact discs i use, and the reply is by a rep of DBA... although i would have driven 200kms on them... 100 of them would have been normal driving, the remaining on the way to Wakey... which doesnt exert much braking pressue at all...

looks like i leant on them too hard too fast...

[aaronng]

What I usually do for new pads is drive normally and gently for about 500km. By then the braking force would be similar to OEM pads, not good at all for a performance pad. Then I do the hard breaking in of the pads which then restores the braking force to that of a performance pad. This way it takes longer but at least I have already done the generic running in of the rotors and pads, hopefully avoiding problems caused by heat cycling.

I will be getting new rotors in a few months because I'm hitting 80,000km on this set and there is a slight lip. So I'll do my long-winded break in procedure again. I would most probably be going for DBA4000 as well. But I personally prefer blanks and not slotted rotors.

[VTECMACHINE]

This is why I don't like DBA rotors... they warp so quick. But meh, they are cheap.

You will need to get them machined. When you get them machined, they will warp quicker the next time, as you are taking more of the heat treatment off them.

As for the pads, just put a bit of sandpaper on a flat surface, and rub the pads on them. Flatten them out a bit.

Put the machined rotors back on, and the sanded pads - and you are good to go, for like another 3 sessions at Wakefield before they warp again. lol.

Make sure you do at least one cool down lap, and drive around the pits for 3-5 mins after to get the air running through your brakes.

[l3vnd1]

There is nothing wrong with DBA 4000 rotors.

People just need to learn how to look after them properly.

[VTECMACHINE]

There is nothing wrong with DBA 4000 rotors.

People just need to learn how to look after them properly.

No there is nothing wrong with them at all. But slightly more exxy ones last for longer. In the long run... its cheaper to use something more exxy but better. (Whoopse forgot to write IMHO)

[l3vnd1]

Fair enough.

What would you say are better discs? Because I have heard some bad stuff about RDA.

[aaronng]

Make sure you do at least one cool down lap, and drive around the pits for 3-5 mins after to get the air running through your brakes.
3-5 minutes in the pits is useless. The 10-15 km/h limit there doesn't get much air. I usually go out onto the road and take a 80km/h cruise around to get the heat out.

[Zilli]

fair enough Ricky, well when i was buying the DBA's the guy at Race BRakes offerred me BRembo's for 100 more but not slotted... i think the tosser in me wanted them slotted...

i do one col down lap, then laps in the pits for a coupla minutes... but this still happenned...

i do agree with you though, pay a bit more and you get a better product, but for predominantly a street car i didnt feel the need...

live and learn

[string]

Maybe try blanks? My RDA blanks cost me half as much as the pads. Deep down inside you know you're not getting any more performance with slotted.

[aaronng]

Nothing wrong with RDA. As with most things in life, you have to take care of them if you don't want anything to go wrong. And it is usually the more expensive items that need more care. i.e. Ferrari vs Honda. :p

[VTECMACHINE]

Fair enough.

What would you say are better discs? Because I have heard some bad stuff about RDA.

Well i'm a brand whore... So I would say something like Dixcel or Endless - Project Mu rotors aren't bad too. RDA, and DBA aren't badddd... but there are better. There is always better.


3-5 minutes in the pits is useless. The 10-15 km/h limit there doesn't get much air. I usually go out onto the road and take a 80km/h cruise around to get the heat out.

Yeah I take number plates off during track work, so can't drive on the street. From my experience the 10-15 km/h speed in the pits does quite a bit.

[Zilli]

So an update

I found a local bloke (Ace Mobile Disc Machining) who came out yesterday and machined the discs. He actually measured them up and he gave the following diagnosis

1) Discs warped - explaing how i had used them to him, he said it could have been the heating up of the rotor too quickly, possibly due to not getting a proper heat cycle into them before hitting the track, but also possible due to the use of a rattle gun to tighten the wheels back on... he told me to never use the rattle gun to put the wheels on, and if i need to take the discs off to mark them and get them oin exactly the right way in the future, as the hub part may be slightly untrue

2) sectioned - A trait of slotted rotors apparently, where the trailing endge of the slot gets more wear as it is the first thing to hit the edge of the pads, eventually this creates "sectioning" from slot to slot... he explained how it affected his VK race car.

He explained that the best thing to do is use quality, blank rotors, which kinda makes sense, and reminds me of the guy at Race Brakes trying to sell me the Brembo rotors when i got the DBA, they were blanks, but the wanker in me wanted slotted!

All in all, lesson learnt, he did say that this may happen again, and the best way to mitigate it is to give them a good solid heat cycle as a bed in before any more road and circuit duties...

and he did them for $90 on the car!

will update when i bed them in again.

[T-onedc2]

That's a great price and great advice I reckon :thumbsup:

Can you tell me what it means to give it a good heat cycle? I'm guessing it involves getting some heat into the brakes to a fairly high temp, but not too quickly?

[Zilli]

precisely!

he told me to do about 20 cycles of 60km/h to 20km/h at medium pedal pressure

Different to the pad manufactuers directions which were much more forceful and brutal... but yeh im happy to go with what this guy's saying... pit crew for Forza racing must mean something!