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Login to post Forums » Grassroots Motorsports » Beveled brake pads...Huh?

Oct. 17, 2011 12:59 p.m. SVreX SuperDork

I was looking at the brake pad display at one of the big box auto parts stores recently.

I noticed the highest "performance" pads (ceramic, or otherwise) are designed with a pretty big bevel (3/4" at each edge?) at the leading and trailing edge of the pad.

I don't get it.

Looks to me like the contact surface area of the pad is reduced by 20% or more. How does that increase braking power?

Is it for reduced squeal, or chatter?

I don't see the point.

Yes, I understand these aren't real performance pads. I'm just trying to understand what they are selling.
Oct. 17, 2011 1:02 p.m. 92CelicaHalfTrac SuperDork

Maybe more surface area as the pad wears down to compensate for less heat sink abilities as the pad wears?

Doesn't make sense, for sure, but who knows?
Oct. 17, 2011 1:13 p.m. Cone_Junky HalfDork

Less noise, smaller contact area also equals more pressure per square inch and less heat sink.

I've noticed new BMW pads have half the contact area because it's beveled so drastically.
Oct. 17, 2011 1:50 p.m. AngryCorvair SuperDork

modal analysis shows where to remove material to reduce noise. chamfers are cut accordingly. or, aftermarket pad supplier copies shape of OE pad, LOL.
Oct. 17, 2011 3:08 p.m. porksboy SuperDork

I just put a set of Hawk HPS on the CRX. The pads were the same way. Leading and trailing edge both beveled. I dont remember the last set I put on that werent beven led.
Oct. 17, 2011 3:25 p.m. bigbens6 Reader

EBC red's are the same, all i can think is contact surface increases with wear to offset thermal changes due to decreased mass.....
Oct. 17, 2011 3:45 p.m. SVreX SuperDork

bigbens6 wrote:

EBC red's are the same, all i can think is contact surface increases with wear to offset thermal changes due to decreased mass.....

Oooo- I like that idea! I don't know if it's total BS, but it sounds good!
Oct. 17, 2011 3:45 p.m. SVreX SuperDork

AngryCorvair wrote:

modal analysis shows where to remove material to reduce noise. chamfers are cut accordingly. or, aftermarket pad supplier copies shape of OE pad, LOL.

Does it also improve braking?
Oct. 17, 2011 4:00 p.m. wearymicrobe HalfDork

Cone_Junky wrote:

Less noise, smaller contact area also equals more pressure per square inch and less heat sink.

I've noticed new BMW pads have half the contact area because it's beveled so drastically.

Also BMW and Ford found they used to get horrible buildup on the leading edge of the pads when they did not bevel the edges at least a little bit.
Oct. 17, 2011 4:24 p.m. AngryCorvair SuperDork

if the pad is your heat sink, ur doin' it wrong.
Oct. 17, 2011 4:28 p.m. SVreX SuperDork

Don't think I'm getting it, AC.

Sounds like you are saying the chamfers are for noise reduction, designed by OEM's, and stolen design by aftermarkets, but that they do not improve stopping power.

Is that right?
Oct. 17, 2011 5:25 p.m. Chas_H New Reader

I've beveled the edges of race brake pads to quicken bedding in but only about 1/8". The last set of Akebono ceramic pads I installed were heavily beveled. Stopping power is not closely related to pad size, pad life is.
Oct. 17, 2011 9:37 p.m. Toyman01 SuperDork

IIRC the Porterfield's we run on the Civic for Lemons are beveled too.

I know the pads I put on the wife's van this weekend were.
Oct. 17, 2011 9:42 p.m. DrBoost SuperDork

I was doing side work and most people who look for a "backyard mechanic" buy cheap brake pads. I had a few complaints about squealing and chattering. I started putting my own chamfer on the el cheapo pads and never got a complaint. I think it was the build up at the leading edge, but I'm no engineer. I just copied the pricier pads.
Oct. 17, 2011 10:55 p.m. AngryCorvair SuperDork

SVreX wrote:

Don't think I'm getting it, AC.

Sounds like you are saying the chamfers are for noise reduction, designed by OEM's, and stolen design by aftermarkets, but that they do not improve stopping power.

Is that right?

some aftermarket suppliers do noise analysis and arrive at chamfer shapes of their own, others copy the OE pad shape. either way, the chamfer does not improve stopping power. it is there only for noise abatement.
Oct. 18, 2011 6:00 a.m. 92CelicaHalfTrac SuperDork

bigbens6 wrote:

EBC red's are the same, all i can think is contact surface increases with wear to offset thermal changes due to decreased mass.....

You said it a bit better than i did, i guess.
Oct. 18, 2011 5:32 p.m. SVreX SuperDork

No, after I posted I noticed you had said the same thing.

I'm a little thick sometimes.

Next time I'll give credit where credit is due.
Oct. 18, 2011 5:35 p.m. 92CelicaHalfTrac SuperDork

Nah, he did say it a bit better, i'm not too proud to admit that.
Oct. 21, 2011 1:48 p.m. bigbens6 Reader

AngryCorvair wrote:

if the pad is your heat sink, ur doin' it wrong.

If you think pads do not absorb heat and this that absorption of heat does not effect their performance you kidding yourself...

It's not a heat sink, but does absorb heat, and its ability to absorb the heat and dissipate it will be effected by a change in mass or potentially surface area...
Oct. 22, 2011 7:51 a.m. SVreX SuperDork

Umm... bigben:

Apparently you don't know him too well. Angry is a mechanical engineer who designs brake systems.

He is the king of sarcasm, but reasonably knowledgeable on the subject.
Oct. 22, 2011 9:35 p.m. curtis73 Dork

The bevels are there for preventing noise, chatter, and binding. It doesn't have anything to do with heat or mass... at least not that I know of.

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