slotted or blank

[Daveho1]

hey guys,
its been commonly accepted for ages that slotted or cross drilled rotors are superior to blanks because they force the gasses created from breaking out and are super heat sinks and are fans and are just better cause they cost more and Ferrari do it so must be good.
which for ages i thought that slotted was the way to go too but there seems to be a alot of talk about blank rotors being superior due to the added friction aria and that the slots are no longer needed for gassing out due to new brake pad compounds.
any one out there that knows there stuff wanna tell me whats real?

[Hondarally]

Here's an extract from a guy I know who is an Engineer working for a large brake manufacturing company (has been there over 10 years). I'll let you draw your own conclusions, but given the amount of time he has spent testing these things, I think he probably knows a bit more than the average brake salesman. NB I admit I ripped this quote from another website, but I know the source.

Aaah, the fabled "outgassing" that is so often talked about on Interweb forums (and the real-world gatherings of enthusiasts that predate them), but which has never been observed in the sheltered world of brake engineering.
I've had good pads and *****ty pads that have nearly burnt our dynos down because they get too flamy.

Actually, it's only relatively good pads that get that hot. *****ty ones tend to self-regulate. They get slippery at high temperature, which puts an effective limit on how hot they can get. Can't get any hotter if they're not absorbing any energy. W00t, we're back on the Papal Decrees of Thermodynamics thread.

Anywho... the conventional "wisdom" of slotted rotors is that they clean the decomposed friction material off the surface of the pad, so you have good fresh material ready to do the work. But the decomposition/combustion products that you get at the surface of friction materials are part of the material design.

Most modern materials - especially high-performance ones - are scorched in production (sat on a 600° plate for ~2 minutes) to get this surface chemistry started, rather than waiting for it to develop in use. Without a scorch layer, performance is shyte.

If your salami-slicer rotors scrape the scorch layer off, you're losing the good stuff.

All the testing I've done confirms that friction levels are lower, and less consistent, on slotted rotors. And the pad wear rate is just ridiculous.

One particular Australian OEM wanted to sell slotted rotors in their blingbling "genuine spares" shop, which meant they had to get them through ADR testing that requires equivalent brake performance to OE - no better, no worse (within 15%). Everybody assumed that would be no problem, because everybody knows that slots are just a cosmetic thing with no performance benefit. Turned out they failed the ADR brake test, because the fade friction went through the floor. So there are no slotted rotors in the blingbling department.

Of course, that's using normal road pads. But I've seen the same thing using higher performance pads too. Ones that will quite happily turn rotors translucent red and burn all the seals out of calipers until the brake fluid pours out to cool the pads down.

I'm always confused when I see slotted rotors being used by people who should know better than I do what the effect is. Wondering whether there's something that they know that I don't. I'm yet to see any evidence to suggest that they are used for anything other than cosmetic reasons.

[Daveho1]

thanks for the post

[dougie_504]

I was under the impression that blanks are better for braking and all you need is good pads for higher temps. Brake vents are optional to keep the temps down a little if you're serious about racing.

Rest is bling.

[Daveho1]

the more i read into it im inclined to agree, look at f1 cars not a slot or cross drill in sight.

[curtis265]

it's all bling

looks damn cool too haha

[bennjamin]

always used blanks. Cheaper - and should be considered a consumable anyway.

[EKVTIR-T]

porsche use crossdrill and theyre one of the most highly regarded braking on street cars so....

[Daveho1]

true but do the cross drills contribute to that or is it the ceramic compounds used, as previously stated F1 cars dont use slots or cross drills but they do use ceramic, like Porsche

[DreadAngel]

porsche use crossdrill and theyre one of the most highly regarded braking on street cars so....

true but do the cross drills contribute to that or is it the ceramic compounds used, as previously stated F1 cars dont use slots or cross drills but they do use ceramic, like Porsche

As above, check out Skyline BNR32 and Cross Drilled Disc to see what happened to them...

[mocchi]

As above, check out Skyline BNR32 and Cross Drilled Disc to see what happened to them...

what happened to them?

[Daveho1]

DA isnt into give us all the answers, we gotta earn the knowledge.
end of the day the consensus of people in the know seem to agree blank is superior, even if slotting or dross drilling makes a difference (hasnt been definitively proven) it dosnt justify the sometimes double or tripple price tag.
thanks guys.