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      10-24-2012, 11:07 AM   #1
rx7gslse
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Brake pad help!

Ok - I've read and read on here until my eyes crossed and I'm still in a bit of a quandry.


Looking for new pads. This will primarily be a DD (so noise, dust, cold stops etc are the concerns) but I am planning to do at least 1-2 HPDE's a year. (on street tires, so slightly less abusive on brakes)

I can find a lot of good info on track pads, and lot of good info on street pads, and a lot of confusion on what pads can split the difference.


With my old cars I've always been a Hawk guy (HPS or HP+) but it seems like the HP+ are really loud on these E9x cars.

So what would you all reccomend?

In the running:
Portfield RS-4? - can they take track abuse well enough?
StopTech? - these seem to be about teh only ones that advertise double duty, but what is considered "Light track use?"
EBC Yellow - these seem good for the track, what are the drawbacks for street use??
CarboTech?
CoolCarbon?

Out:
Ferodo DS2500 - I don't see 335i rear fitments for these?
HP+ - not looking at these due to dust/noise
HPS - I've faded these well on a miata, I can't believe these woudl hold up to the weight of an E90 well on track.
Track only Pads - DC70, Pagid etc

I'm sure there are others too... Help!

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      10-24-2012, 11:24 AM   #2
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I am not doing any track events, but I have been running the Cool Carbon pads for a few weeks now ... they have been great so far.
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      10-24-2012, 11:31 AM   #3
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If you go Ferodo, then you can pair with a different set of rears, nothing wrong with doing that. They are supposed to be the best hybrid pad out there.
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      10-24-2012, 11:46 AM   #4
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ebc red! i have them and they're great. they are low dust and can handle more aggressive driving without being loud like track pads.
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      10-24-2012, 02:32 PM   #5
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Quote:
Originally Posted by 335iaz View Post
I am not doing any track events, but I have been running the Cool Carbon pads for a few weeks now ... they have been great so far.
+1 on Cool Carbons-excellent street performance pad- what we run on our own cars and always our first recommendation. Also good for light track.
Others rate them 5/5 for street and 3/5 for track we agree!
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      10-25-2012, 10:07 AM   #6
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ok - thanks for all the suggestions here.. Pulled in the inputs from a couple of the local track fiends as well, and then crossed that with costs.


Ended up pulling the trigger on a set of EBC yellows. ~$160 shipped for all 4 for pads that should do well for dual duty and not 'brake' the bank.

I'll report back after the HPDE on Nov 10th!
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      10-25-2012, 10:20 PM   #7
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Originally Posted by raceyBMW View Post
If you go Ferodo, then you can pair with a different set of rears, nothing wrong with doing that. They are supposed to be the best hybrid pad out there.
Actually, this is a categorically false statement and is patently dangerous.

Suppose your coefficient of friction (cF) for your normal OEM pads is 0.35. (cF is an index, so there are no units.) Your average 'street' pad is probably on the order of 0.41-0.46, with that value drifting based on temperature.

Since your bias is a LINEAR relationship to cF (examine Equation 5 for the exact relationship in this thread), changing either the front, or rear, but not both, to the same pad type will yield a potentially dangerous scenario and is almost certain to lengthen stopping distances regardless.

Let's look at the possibilities, since they're few:
  • Scenario 1: race pads up front, cF of 0.55, 'street' pads in rear, 0.45. By multiplying available brake torque per pound of pedal input by 0.45 for the rear, and by 0.55 for the front, you now have an increase of 10% in the front over the rear, thus making the ABS have to make more adjustments to the front to bring the bias back. Any time you have to make more adjustments, stopping distances increase.
  • Scenario 2: 'street' pads up front, cF of 0.45, race pads in rear, 0.55. Again, by multiplying available brake torque per pound of pedal input by 0.55 for the rear, and by 0.45 for the front, you now have an increase of 10% in the rear over the front, thus making the ABS have to make more adjustments to the rear to bring the bias back and balance the car. Unfortunately, by going too aggressive a pad in the rear, the car will have a tendency to lock the rears first, even under ABS conditions, and induce a spin if the car isn't perfectly straight. This only worsens as you build heat into the pads and rotors, as the race pads cF will begin to increase and the front 'street' pads will begin to fade. This is extremely dangerous.
  • Scenario 3: both pads are the same cF. The ABS sees the same bias as presented by pressure sensors on both circuits and reacts according to preprogrammed values. This is ideal until you begin to change the weight characteristics of the car, at which point the only true remedy is to either adjust the ABS tune, which is nearly impossible since there's no real tool to flash the DSC modules, or modify the bias with a proportioning valve.

To say that "Oh, I put different pads in the front and rear and it braked just fine." is simply dangerous advice and should be redacted post haste!

More information about brake bias calculations can be found in my thread here.
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      10-26-2012, 08:34 AM   #8
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Quote:
Originally Posted by p0lar View Post
Actually, this is a categorically false statement and is patently dangerous.

Suppose your coefficient of friction (cF) for your normal OEM pads is 0.35. (cF is an index, so there are no units.) Your average 'street' pad is probably on the order of 0.41-0.46, with that value drifting based on temperature.

Since your bias is a LINEAR relationship to cF (examine Equation 5 for the exact relationship in this thread), changing either the front, or rear, but not both, to the same pad type will yield a potentially dangerous scenario and is almost certain to lengthen stopping distances regardless.

Let's look at the possibilities, since they're few:
  • Scenario 1: race pads up front, cF of 0.55, 'street' pads in rear, 0.45. By multiplying available brake torque per pound of pedal input by 0.45 for the rear, and by 0.55 for the front, you now have an increase of 10% in the front over the rear, thus making the ABS have to make more adjustments to the front to bring the bias back. Any time you have to make more adjustments, stopping distances increase.
  • Scenario 2: 'street' pads up front, cF of 0.45, race pads in rear, 0.55. Again, by multiplying available brake torque per pound of pedal input by 0.55 for the rear, and by 0.45 for the front, you now have an increase of 10% in the rear over the front, thus making the ABS have to make more adjustments to the rear to bring the bias back and balance the car. Unfortunately, by going too aggressive a pad in the rear, the car will have a tendency to lock the rears first, even under ABS conditions, and induce a spin if the car isn't perfectly straight. This only worsens as you build heat into the pads and rotors, as the race pads cF will begin to increase and the front 'street' pads will begin to fade. This is extremely dangerous.
  • Scenario 3: both pads are the same cF. The ABS sees the same bias as presented by pressure sensors on both circuits and reacts according to preprogrammed values. This is ideal until you begin to change the weight characteristics of the car, at which point the only true remedy is to either adjust the ABS tune, which is nearly impossible since there's no real tool to flash the DSC modules, or modify the bias with a proportioning valve.

To say that "Oh, I put different pads in the front and rear and it braked just fine." is simply dangerous advice and should be redacted post haste!

More information about brake bias calculations can be found in my thread here.
I agree - not touching that mix... If it was a race car with adjustable bias, then sure, you could compensate for differenes in friction coefficients. I don't trust teh ABS computer to be able to sort that out in an emergency situation.

Personally - I stick to same pads on all 4. Just seems like the safer bet
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      10-26-2012, 08:52 AM   #9
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Quote:
Originally Posted by rx7gslse View Post
I agree - not touching that mix... If it was a race car with adjustable bias, then sure, you could compensate for differenes in friction coefficients. I don't trust teh ABS computer to be able to sort that out in an emergency situation.

Personally - I stick to same pads on all 4. Just seems like the safer bet
Well, the ABS in the 335i is actually quite good, so even with some measure of funky bias shift, it can accommodate a wide range; still, and what I neglected to mention last night, was that there are even MORE extenuating circumstances once you factor in ∆cF/∆T.

If you're running race pads in the front and street pads in the rear, until you warm the pads up properly, it will be extremely rear-biased. On the street, where it may never see such temperatures, what someone may presume to have a higher front bias is actually inverted as cF rises with temperature on the more extreme pads, or until they reach operating temperature. Sometimes, this shift can be so radical that it easily overcomes the abilities of the ABS. Even BMW will clearly state that the ABS is no replacement for common sense and must obey the laws of physics like anything else.

Your decision to ignore the previous poster's advice was wise. Mixing/matching pads when certified cF standards aren't widely published is an all-around performance-hindering and foolish idea!
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      10-26-2012, 09:26 AM   #10
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The Porterfield RS-4 is a somewhat old compound. They are alright for AutoX. I obliterated a brand new set of these with just 2 track days. Definitely NOT worth the money.

If you are serious about track days, I would recommend Performance Friction. Yes, they are bit noisy, they clunk a lot because they don't have retaining pins, but they do withstand track abuse quite nicely. I've done 3 track days with them so far and they've not budged. The pads have a very good initial bite and they maintain grip throughout the heat range. I've not been able to get them to fade so far.
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      10-26-2012, 10:01 AM   #11
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The hysterics about running different pads f/r aside, I wouldn't attempt to run one pad for track events and street - it'll suck for both. Get a good street pad and spend the hour swapping them before your track event.

I'd recommend PFC pads for the track. 01's or 08's.

Last edited by DallasBoosted; 10-26-2012 at 11:26 AM. Reason: Thanks Vas
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      10-26-2012, 11:08 AM   #12
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PFC 06 compound is not available for the front 335i. Only 01 and 08 compounds are for the front.

The 06 compound is available only for the rear.
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      10-29-2012, 03:49 PM   #13
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Quote:
Originally Posted by p0lar View Post
Actually, this is a categorically false statement and is patently dangerous.

Suppose your coefficient of friction (cF) for your normal OEM pads is 0.35. (cF is an index, so there are no units.) Your average 'street' pad is probably on the order of 0.41-0.46, with that value drifting based on temperature.

Since your bias is a LINEAR relationship to cF (examine Equation 5 for the exact relationship in this thread), changing either the front, or rear, but not both, to the same pad type will yield a potentially dangerous scenario and is almost certain to lengthen stopping distances regardless.

Let's look at the possibilities, since they're few:
  • Scenario 1: race pads up front, cF of 0.55, 'street' pads in rear, 0.45. By multiplying available brake torque per pound of pedal input by 0.45 for the rear, and by 0.55 for the front, you now have an increase of 10% in the front over the rear, thus making the ABS have to make more adjustments to the front to bring the bias back. Any time you have to make more adjustments, stopping distances increase.
  • Scenario 2: 'street' pads up front, cF of 0.45, race pads in rear, 0.55. Again, by multiplying available brake torque per pound of pedal input by 0.55 for the rear, and by 0.45 for the front, you now have an increase of 10% in the rear over the front, thus making the ABS have to make more adjustments to the rear to bring the bias back and balance the car. Unfortunately, by going too aggressive a pad in the rear, the car will have a tendency to lock the rears first, even under ABS conditions, and induce a spin if the car isn't perfectly straight. This only worsens as you build heat into the pads and rotors, as the race pads cF will begin to increase and the front 'street' pads will begin to fade. This is extremely dangerous.
  • Scenario 3: both pads are the same cF. The ABS sees the same bias as presented by pressure sensors on both circuits and reacts according to preprogrammed values. This is ideal until you begin to change the weight characteristics of the car, at which point the only true remedy is to either adjust the ABS tune, which is nearly impossible since there's no real tool to flash the DSC modules, or modify the bias with a proportioning valve.

To say that "Oh, I put different pads in the front and rear and it braked just fine." is simply dangerous advice and should be redacted post haste!

More information about brake bias calculations can be found in my thread here.
I completely agree, going race fronts and street rears or vice versa is a bad idea, and one I never would hope no one would recommend. What I said was in specific regards to the Ferodos, which are a street pad and paring them with another street pad. Even HPAutoweks made recommendations to me in that regards.

So no, don't mix street and race pads, but that should be a given. However I think many have been pairing the Ferodos, which only come in front fitment, with the Hawk HPS/Porterfield R4S or Stoptech Streets in the rear with good results with Harold at HPA's advice.

I am definitely no expert, but HPA does know their stuff, and I would hope they would not be making such recommendations if it were "dangerous" as you put it.
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      10-29-2012, 11:12 PM   #14
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I realize OP already got his pads, but just to fill in the blank with my exp: Carbotech XP12 juttered pretty bad after about 4-5 laps of each session. I had to cool them down religiously. As for my credibility, I had about 15 days this season, having tried 3 sets of rotors and 4 sets of pads. Ive heard and tried every single theory about breaking in, braking, and brake cooling down techniques.

Cool carbons were even worse.

Trying PFC01s this weekend.
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