Brake 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 an open lapping 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.

To my surprise, I started noticing a shudder in my brake pedal and steering wheel, with slight fade, but only 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.

Maybe my front rotors are shot. Maybe 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.

I may try pulling the shields, and giving the CC pads one last abuse at my next lapping event ...

Wonder whehter the pads or the shields are at fault. To my surprise, my seals and pistons were in great shape when I replaced my stock pads after 20 sessions or so (no melted or deteriorating seals or cracked pistons).

Any thoughts or feedback would be appreciated.

Thanks.

[Pyrat 2]

I had rotor warping with these pads at the track. It happened twice before I ditched the pads. Cool carbons are not track pads and seem fine for the street. For some reason though I had rotor warping problems with them when on the track. I used other street pads at the track with no rotor warping. I can't explain this but won't go back to them for this reason. I've run PFC zrated and EBC red stuff, neither are track pads, with no issues at the track.

[dcaron9999]

Originally Posted by HeelToe

I had rotor warping with these pads at the track. It happened twice before I ditched the pads. Cool carbons are not track pads and seem fine for the street. For some reason though I had rotor warping problems with them when on the track. I used other street pads at the track with no rotor warping. I can't explain this but won't go back to them for this reason. I've run PFC zrated and EBC red stuff, neither are track pads, with no issues at the track.

Thanks for your feedback. So did the Cool Carbons ruin your rotors, and you needed to change them, or using PFC or EBC pads on the same rotors solved your issue?

My rotors do not shudder when cold, leading me to believe that the rotors might still be OK ...

Im not impressed by the Cool Carbons, and may write a complaint to them ...

[Pyrat 2]

Originally Posted by dcaron9999

Thanks for your feedback. So did the Cool Carbons ruin your rotors, and you needed to change them, or using PFC or EBC pads on the same rotors solved your issue?

My rotors do not shudder when cold, leading me to believe that the rotors might still be OK ...

Im not impressed by the Cool Carbons, and may write a complaint to them ...

I can't state that they ruined my rotors (2 sets). I can only state that i went to the track twice with CC and each time had to replace warped rotors when I came back. I have never had rotor warp with the other pads. These experiences are on my e90. This car has been to at least 24 track days over the last 8 years. Again, CC are not track pads. For the record though I have never had track pads at any of the events. Stock, EBC Redstuff, PFC Z rated and CC.

On my 135 I have had 6 track days on my stock pads (2 sets on the front) and just this last event I had some warp on one front rotor and I know its because I didn't have sufficient cool down on the last run of the second day.

[3002 tii]

If could be uneven brake deposit left on the rotors. What's more surprising is new pads, new fluids and titanium plates but you're still experiencing fade.

[dcaron9999]

Originally Posted by 3002 Tii

If could be uneven brake deposit left on the rotors. What's more surprising is new pads, new fluids and titanium plates but you're still experiencing fade.

Thanks for your feedback once again, you are becoming my mentor

You are spot on about the pad deposit, and Im starting to regret getting the CoolCarbons 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.

[3002 tii]

Originally Posted by dcaron9999

Thanks for your feedback once again, you are becoming my mentor

So there are couple things you can do (and maybe you already do) to lessen the brake deposit issue.

1. A lot of new DE drivers tend to drag the brakes as they enter the braking zone. This will cause unnecessary deposit to transfer to the rotors. You really should only apply brake pressure when you need to, or lift throttle earlier to shed speed instead of dragging brakes. I find this is the number one cause for uneven brake deposits. Brake at the end, only when you must, firm gradual pressure. Remember it's always about smooth inputs.

2. I try to get my brakes up to temp during the first lap when it's yellow flag. I'll brake more than I need to at each corner to get them up to temp. This will also help bed them in if there was any deposit left from the previous session. By lap 2 or 3 your brakes and tires should be fully warmed up.

3. Anticipate the cool down lap. I know some folks try to squeeze every lap to the fullest but problem is by the time you see the checkered flag, that may not actually be enough time to properly cool the car down. Assuming a 25 min session, I start going easy on the 20 min mark. I actually look down at the time on the speedo and sure enough by the 20 min mark, the checkered flag usually appears a half min later. Once I enter the paddock, I never apply the brakes. In fact I might even do a lap or two around the paddock just to cool the brakes down more and when I finally park, I put it in gear but don't touch the brakes!

For what it's worth, if your rotors have that much deposit, bedding them in might not do the trick. I once had really bad deposit from driving in cold rain. Should've thrown on the street pads but I was too lazy. The rotors were pretty messed up as a result and despite bedding them in 3x (2x on street, once on track), it was too late. I could've cut the rotors but for the cost/time, it was just easier to get new blanks from Tirerack.

Originally Posted by 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.

The reason the issue might not be evident during normal street driving is because your pads aren't even getting near optimal temps. You said it yourself in your first post.

Originally Posted by 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.

And for the record, I'm not a fan of Cool Carbons. I have friends that ran them on the 335i but once you go PFC, you don't go back. You're not the first person to report this issue with Cool Carbons. Shame they don't have anything in the 135i, yet....

[Kgolf31]

These pads are just not meant for the track. Easy as that.

As well, not to question your driving ability, but are you certain that you're braking correctly? Braking light, early braking, or just not going to threshold braking can leave pad deposits even with full track pads.

I've ran Hawk HP+ pads for my past 2 track days, and now I've switched to PFC 06s. The Hawks were good, but I didn't have full confidence in them on the big braking zones and was experiencing them overheating at the end of sessions

[dcaron9999]

I brake hard and fast - close to lock up - and off the brakes ASAP - no dragging.
PFC does not make pads for the 135i, unfortunately, would have loved Z-rated pads ...

[3002 tii]

Originally Posted by dcaron9999

I brake hard and fast - close to lock up - and off the brakes ASAP - no dragging.
PFC does not make pads for the 135i, unfortunately, would have loved Z-rated pads ...

Hard and fast is not what I was getting nor should you be getting off it ASAP. Pedal travel should be smooth in, and smooth out. Hard and fast implies stabbing the pedal or stomping on it, but I'm going to assume this is just semantics and you brake correctly.

Z rated is street pad, for track you'd go for 01, 06, 08 and 11's but I believe the 06's have been phased out and the 01's are going to be phased out if not already. PFC swears the 08's are better than 06's but I recall the 06's grabbing harder. I really wish they'd continue making the 06's.

Try focusing more on cool down but if that doesn't do it for you, start looking at another pad. Maybe DTC-70 or something more aggressive.

[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,

[3002 tii]

Makes sense and that's what KGolf said as well. If you visit the track as often as you do, why not just get a real track pad? Your other comment about wishing to run PFC Z's confirms you're still looking to run an aggressive street pad. You can try them all, CC, HP+, Z-rated but the results will be the same. Many have tried to find the perfect dual setup but it doesn't exist (unless you buy race car from factory, ie GT-R, 911, etc).

I ran stock brakes and sticky street tires for the first 2.5 years. I recently changed over to a Stoptech kit after I started doing open track days (30 min sesions, off 30 mins and back on for another 30). Fade was just unavoidable with these extended repeated sessions, especially at the tracks I attend where there's heavy braking zones. And I'm now for the first time making the switch to R-comps. The point is as you get faster, you need the supporting hardware. While stock or aggressive street pads may be sufficient for the green driver, seems like you're already approaching intermediate and you need something more durable. Do it right the first time so you can avoid this type of trouble shooting (finding why a "compromised" track setup isn't working out for you).

[dcaron9999]

Advice well taken. Main reason for hesitation is that lapping season ends in two weeks, and car is also daily driver as I mentioned.

Ill probably keep the pads on the car until next spring, or go back to my used stock pads. I will decide what I do then (April/May 2014).

• I cannot afford a dedicated track car, nor do I have the space for a third car.
• I dont want obnoxious loud screeching brakes on the street on my DD.
• During lapping season, I will probably take the car to the track once a week or very other week, so I dont want to be swapping street/track pads that often.

There's my dilemma... ;-)

[3002 tii]

Originally Posted by dcaron9999

Advice well taken. Main reason for hesitation is that lapping season ends in two weeks, and car is also daily driver as I mentioned.

Ill probably keep the pads on the car until next spring, or go back to my used stock pads. I will decide what I do then (April/May 2014).

• I cannot afford a dedicated track car, nor do I have the space for a third car.
• I dont want obnoxious loud screeching brakes on the street on my DD.
• During lapping season, I will probably take the car to the track once a week or very other week, so I dont want to be swapping street/track pads that often.

There's my dilemma... ;-)

For a while my Z4 was my daily. I had 2 sets of pads (PFC Z-rated for street, 06 for track) and 1 set of rotors. Being that both had similar compounds, I was able to run 1 set of rotors without having to constantly rebed the brakes. I would switch pads before and after each event but that only lasted for a year. Call me lazy but by my 2nd season I just ran the track pads all summer and only switched to the street pad during the off-season. And if you're seriously thinking about hitting up the track every other week next year, you're not going to have any fun at all running a street pad, I guarantee it. This sport/hobby comes with its costs and unfortunately this is one of them. You thought it was just annual dues and event registration, pshhh...

I think ALL of us went through this... but after you do enough track days, you realize you just don't care if it squeals. So what if someone looks at you funny at a light, tell them its a race car and move on with your day lol. I used to wash the car after every event in order to get the tire marks off the paint... now I keep them on all season. They're like my battle wounds and when I roll up to the light and my brakes squeal... people KNOW what this car is all about!

In all seriousness, the biggest concern for me was to make sure I switch back to a street pad during the colder months. Give it a thought, you'll enjoy your expensive track days more, the car will be safer and you'll be able to progress as a driver (brake deeper/later).

[MMisencik157]

Originally Posted by 3002 Tii

For a while my Z4 was my daily. I had 2 sets of pads (PFC Z-rated for street, 06 for track) and 1 set of rotors. Being that both had similar compounds, I was able to run 1 set of rotors without having to constantly rebed the brakes. I would switch pads before and after each event but that only lasted for a year. Call me lazy but by my 2nd season I just ran the track pads all summer and only switched to the street pad during the off-season. And if you're seriously thinking about hitting up the track every other week next year, you're not going to have any fun at all running a street pad, I guarantee it. This sport/hobby comes with its costs and unfortunately this is one of them. You thought it was just annual dues and event registration, pshhh...

I think ALL of us went through this... but after you do enough track days, you realize you just don't care if it squeals. So what if someone looks at you funny at a light, tell them its a race car and move on with your day lol.
.

Definitely agree with this

[dcaron9999]

Cool Carbon is sold as an "agressive street pads, that you can take to the track". Should have known better than to go on this, and that I would eventually grow out of them.

Tonight, I removed my HardBrakes.com Titanium Heat shields, and cleaned up my caliper, and brake pads, and rotor with a wire brush and brake cleaner. I will be bedding my pads one last time later tonight on a stretch of deserted highway. I have little faith in the CoolCarbon pads when I saw their state after one week on the car, 1 full day of lapping, and two bedding sessions. Pad thickness is down by 50%, surrounding paint on exterior of pad was burnt away, pad was pitted, and backing plates unglued.

Lesson learned. Next pad will be back to BMW OEM's for off season, and a separate set of entry level race pad, that I can use on the street for the rest of the year (opposite of what I got with Cool Carbons).

Ive recevied recommendations for :

• Carbotech XP10 (front) and XP8 (rear)
• PFC when they finally sell their brand new "11" compound (sprint/medium distance race compound) and their relatively new "08" compound (endurance compound) made for the stock 135 calipers
• HawK HP Plus
• Hawk DTC60
• Ferrodo DS2500
• Pagid RS29

[3002 tii]

Originally Posted by dcaron9999

Cool Carbon is sold as an "agressive street pads, that you can take to the track". Should have known better than to go on this, and that I would eventually grow out of them.

Tonight, I removed my HardBrakes.com Titanium Heat shields, and cleaned up my caliper, and brake pads, and rotor with a wire brush and brake cleaner. I will be bedding my pads one last time later tonight on a stretch of deserted highway. I have little faith in the CoolCarbon pads when I saw their state after one week on the car, 1 full day of lapping, and two bedding sessions. Pad thickness is down by 50%, surrounding paint on exterior of pad was burnt away, pad was pitted, and backing plates unglued.

Lesson learned. Next pad will be back to BMW OEM's for off season, and a separate set of entry level race pad, that I can use on the street for the rest of the year (opposite of what I got with Cool Carbons).

Ive recevied recommendations for :

• Carbotech XP10 (front) and XP8 (rear)
• PFC when they finally sell their brand new "11" compound (sprint/medium distance race compound) and their relatively new "08" compound (endurance compound) made for the stock 135 calipers
  
• HawK HP Plus
• Hawk DTC60
• Ferrodo DS2500
• Pagid RS29

Take HP+ off that list, I mentioned already that's a street pad. And if you're running 2 separate pads, then there's no need to get anything "entry level". I think the term you're looking for is an endurance pad, ie something that will be easier on your rotors compared to the most aggressive track pad.

And I never understood why some people run a weaker pad in the rear when the rear brakes do so little to begin with. If anything many racers will go a little harder on the rear to even out the bias a little.

[MMisencik157]

Originally Posted by 3002 Tii

And I never understood why some people run a weaker pad in the rear when the rear brakes do so little to begin with. If anything many racers will go a little harder on the rear to even out the bias a little.

There are so many variables that would cause people to stagger or keep the pad compound square. Say you switch to non staggered tires or a more aggressive tread compound, your front axles are now doing a larger percentage of the braking. On a front engine vehicle, going to a more aggressive rear could cause the rears to lock or engage ABS under braking (especially trail braking). For street pads or less aggressive track pads its not a huge deal, but when you start getting into compounds with a big initial bite and high torque output it starts to matter.

If you're using square pads and are happy and not having problems with the rear being squirmy under braking then don't change. XP10/8 10/10 12/10 and 12/12 could be used successfully on a 135 depending on the drivers braking style and tracks used at.

I started with square pads, switched to staggered pads, then went back to square pads. I personally prefer running the same front and rear but I use EHP street tires. If I were to use level 1,2 or 3 R-comps I would likely stagger the pads as I feel Im right at the threshold of having too much rear brake.

[nearlydigital]

What did you end up going with? I need to get my cool carbons off, as I experience the exact same issue as you. Once they heat up past a certain point (have experienced this "off the track" as well), they are absolutely terrible... and in my opinion, dangerous. The fade and huge pulsation is astonishing.

[dcaron9999]

Originally Posted by nearlydigital

What did you end up going with? I need to get my cool carbons off, as I experience the exact same issue as you. Once they heat up past a certain point (have experienced this "off the track" as well), they are absolutely terrible... and in my opinion, dangerous. The fade and huge pulsation is astonishing.

Went with XP10 front and rear as Performance Friction (PFC) brake pads are still not available for the 135i calipers. Front Carbotech (CT) XP10 pads are already wearing down more quickly than I expected. Very little noise on the street, on rare occasions, very solid and consistent on the track. Pretty happy with CT pads, but would be ecstatic about perfect fitment PFC pads, and various compounds.

Not holding my breath for PFC's release agenda though ...