Cool Carbon Brake Pads - pedal shudder when hot

[dcaron9999]

Last week-end, I installed Cool Carbon brake pads, 0.5mm Titanium heat shields, and bleeded my brakes on my 2011 135i, with Gulf RF800 brake fluid (prefer Motul RBF600, but could find any locally). I bedded my brakes as per instructions that came with the pad. First reaction I got is that brake bite seemed stronger when warm than my OEM pads.

Once cool, the bite is really not as good as OEM, but more gradual.

Took my car to the track for a couple of hours this week-end for a free tracking session, and when I started fealing brake fade, I would slow down and cool down the brakes for one or two laps, then back at it for another 30 minutes or so. After a few hours of this, I started gaining confidence, and eventually ran faster, without traction control and DSC turned off completely.

I started noticing a a shudder in my brake pedal and steering wheel, with slight fade, when the brakes got hot. Fast forward two days, and the same thing happened at the track tonight towards the end of each of my three 20 minute sessions tonight. When the brakes are cooled down or warm, I have no such shudder to report.

Prior to this, I had stock pads which had 30% life left in them, and no heat shields and I never experienced this shudder. I suppose I was not as fast or agressive on the brakes at the time. I only started lapping about two months ago.

Are my front rotors shot? Is there too much heat build up in the pads and/or rotors, since the shields are blocking the heat transfer to the calipers and brake fluid?

Maybe I can try pulling the shields before my next session ...
Wonder if the pads or the shields are at fault. To my surprise, my seals and pistons were in great shape when I replaced my pads (no melted or deteriorating seals or cracked pistons).

Any thoughts or feedback would be appreciated.

Thanks.

[Stohlen]

Cool carbons aren't really ideal for track duty. The nicest thing about them is the low dust, which isn't exactly ideal for performance

[fboutlaw]

Welcome to the problem with cool carbons. Once you've cooked them on the track, they're trash. This is a problem I've experienced first hand as well as a lot of friends in BMWCCA.

Likely the rotors have uneven build up on them, but the only way to get that off is to swap pads.

If you're going to track, get track pads, or at least high performance street pads. They will actually be able to survive the temps. You can swap back to cool carbons (a new set) for street driving, but I'd actually recommend the OEM pads.

Many stories short, don't run cool carbons on the track.

[dcaron9999]

You live, spend, and learn ... I regret getting the CC now, but will give them a last bedding blitz before yanking them off the car.

Just got this reply from Cool Carbon, which I thought would be good feedback for this post for others that may stumble across this:

"Hi Daniel- If you search the forums enough you will find the same issue with many other brands of Street/ Street performance pads when used on the track including Stoptech, Hawk, OE, etc


One possibility is in fact pad deposits.

This is generally caused during the bedding process procedures being too rapid, incomplete or simply allowing the car to come to a complete stop while the brakes are hot.

Also possible following a 15/20 minute session if brakes are too hot when parking between events-many use parking brake for final stop to avoid any localized deposit.

This can cause pad print/ deposits and is often seen as a print on the rotor in the shape of the pad.


This localized deposit creates a high spot which can cause vibration and should be removed.

Removal can be accomplished by one of the following procedures:

1) Driving the car over a period of 1-2 weeks until removed

2) Aggressively rebedding the pads

3) Cleaning the rotor with a green Scotchbrite pad and Brake Kleen

4) Cleaning the rotor with a 3m pad as per attached (extreme cases)


There are however other possible causes for what you experienced:

1) Warped rotors

2) Contamination on mating surface between rotor and hub

3) Contamination on mating surface between wheel and rotor

4) Inconsistent wheel bolt torque

5) Front control arm bushings

6) Other causes



We would suggest rebedding per our procedures as a first step as this is the easiest to accomplish.


The formula that we use is unique.


The BMW pads are grabby and gives about 20% of full braking on initial apply with no modulation below this and are not very linear above this initial apply.



The Cool Carbon friction level is just above BMW OE cold 0.41 vs 0.37 and increases with heat to just over 0.50 mu.

The Cool Carbon pads are actually stronger all the way from 0 to ABS and are very linear without the grabby feel which is sometimes confused with initial bite.

A very good formula should allow full modulation of the brakes throughout the range of braking.

The difference between the OE and the CC may take a short adjustment period, but the CC are very comfortable as a daily driver and become more aggressive at higher temperatures.


The CC pads come with a stainless steel shim that blocks heat 3x better than steel; Ti shims block heat 5x steel and are better in this respect. We would suggest to use one or the other but not both.


Also keep in mind that this formula is a Street Performance pad , not a true track pad, but many do use this pad for light track use with good results.


Hope this helps"

[dcaron9999]

I tried bedding the pads agressively a second time, while following instructions on CoolCarbon's web site. The pulsation was back at the end of both cycles of 15 stops, but only around that point. After cool down and during the first 10+ hard stops or so, braking was pretty powerful, and gradual.

I did not remove my Titanium shields, but might try that to see if heat is then better dissipated into the caliper and brake fluid. I just hope that I will not fry my caliper piston seals or crack my pistons with heat generated by the "Cool" Carbons.

Ive had the car for about 3 months, brought to the track once a week for the last 2 months. During this time, the pads, rotors, caliper pistons and seals survived, and still looked good prior to switching to Cool Carbon pads. Never got any pulsation with my stock pads.

I have brand new M3 control arms, all bushings are in perfect shape, and wheel nuts are allways torqued properly with torque wrench. There is no contamination between wheel and hub; all surfaces are clean.

With the Cool Carbons, I do not feal any vibration during street use, and occasional hard stop, only after successive hard stops, such as when bedding, or track use.

My conclusion is that the CoolCarbon may not be the best pad to drive agressively on a 3300 pounds, 300HP car.

[dcaron9999]

Just got this note from "HardBrakes.com" ... Sounds like I need to experiment, WITH & WITHOUT the shields ...

Hi Daniel,


We've had lots of customers, including some pro-level racers, using the heat shields on the 135i without problem. I would suggest trying different combinations of heat shields and pads to isolate where the issue is. I am not familiar with the Cool Carbon performance. We do sometimes find that when using the heat shields a more track-oriented pad with higher heat tolerance is in order. Let me know how it goes.


Regards,