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      06-26-2012, 11:07 AM   #1
von_zoom
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Uneven brake pad ware

Recently, I had excessive wear on my right front pads, Perf Fric 01 race pads on stock calipers. The other three wheels were showing "normal" wear, consistant with my track use. My Bimmer store checked the calipers, and determined the pins were not allowing the caliper to slide without difficulty, most likely not releasing completely, causing the wear on the right pads. The pins were removed, found okay (not bent) and did not require replacing, only lubrication, and appear to be functioning properly now. It is suspected that heat was the culprit. Will be at the track next week, sporting new PC front pads, so we will see. Has anyone else experienced simular problem(s)?
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Last edited by von_zoom; 06-26-2012 at 11:31 AM. Reason: Excuse the typo in the title.
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      06-26-2012, 12:57 PM   #2
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I have not experienced this with my M3, however I did have this problem on previous cars.

Now, as a preventive measure, I try to lubricate the pins every time I change the pads. The joys of single piston sliding callipers .
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      06-26-2012, 02:01 PM   #3
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Quote:
Originally Posted by CanAutM3 View Post
Now, as a preventive measure, I try to lubricate the pins every time I change the pads. The joys of single piston sliding callipers .
Thanks much for the tip. Live and learn.
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      06-26-2012, 02:11 PM   #4
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IIRC per BMW the stock guide pins aren't supposed to be lubricated for whatever reason.

Solid brass guide pins do require lubing if that's what you have.

If not, they may cure your issue.

http://store.bimmerworld.com/solid-b...e-kit-p46.aspx

http://www.turnermotorsport.com/p-41...grade-kit.aspx
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      06-26-2012, 03:44 PM   #5
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kaiv
Thanks for the info and not to take issue, but I am told that the brass pins in your link will not fit stock E92 calibers, and lubrication is the generally accepted method of keeping the stock pins free.
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      06-26-2012, 07:22 PM   #6
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I thought we needed to lube the stock guide pins too (I've been doing it with every pad swap). But kaiv's answer made me double check my e9X Bentley manual.

It says "Clean brake caliper guide bolts (7mm Allen). Replace ones which are not in perfect condition. Do not grease."

Granted, the calipers referenced in the Bentley are not for the M3, but they are a single piston design so I won't be lubing them anymore.

BTW, the tightening torque is 30 nM (22 ft-lb).
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      06-26-2012, 08:05 PM   #7
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Lubricating the pins is definitely not required. The lubricant does not last very long with the extreme temperatures of track use. I still do it as a preventive measure. So far so good .
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      06-26-2012, 10:28 PM   #8
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The pins shouldn't be lubricated because it will make them stick.

The pads wore faster because they were running hotter. That's the way PFC-01's are. I have one PFC-01 pad on my Mustang Brembo that's thinner than the rest and will condemn the whole set when it wears out first. I'm trying PFC-08's next - will be interesting.
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      06-26-2012, 10:39 PM   #9
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Were you driving with dsc on? This can cause individual brakes to pulse and produce a hot caliper.
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      06-26-2012, 10:41 PM   #10
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Can you swap the lefts with the rights to even them up? IIRC, there's no spring clips so they should be able to be left or right.

I had one set of Hawk HT-14's that wore on only the inner pad of one front wheel. The pads before and the pads after didn't do the same thing.

One thing I wonder about is could it be possible that the good side got a little grease or something that made them work less. Did you feel anything in the pedal/wheel?
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      06-26-2012, 10:57 PM   #11
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Quote:
Originally Posted by JAJ View Post
The pins shouldn't be lubricated because it will make them stick.
Really, then I guess I have been lucky thus far . I'll examine the pins next time I change the pads. Any visual clues to be watchful for?
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      06-26-2012, 11:01 PM   #12
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That's what BMW claims. YMMV. I believe they collect dirt when they're lubricated, so as long as they're kept clean, they'll work fine, lubed or otherwise.
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      06-26-2012, 11:47 PM   #13
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I have not noticed this issue yet but I noticed that the piston dust boot has been heat damaged to the point that I can see the damage. I wonder if extreme heat like that is contributing to or causing your guide pin issue. I'll run the stockers til either they fail or I save up enough to swing a BBK. I really wish BMW didn't put floating single piston calipers on the M3 though...
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      06-27-2012, 06:57 AM   #14
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Thanks, a lot of good info to consider.

No, do not run with dsc (or anything else on).
My car is teched very carefully each time prior to track events, with particular attention given to brakes. Nothing of interest occured until we noticed the excessive (when compared to others) wear on the right front pads. The caliper did not move as freely as it should, which brought attention to the pins. When I could not get new pins where my car was teched, I changed pads back to stock, ran the event, then took the car to the Dealer for service. There, they removed both front calipers, inspected them, cleaned and lubed the pins. Stock pads returned to the box, new PF 01s were installed, and I am now off to the track.

I agree, heat is most likely the enemy. Ventilation will be added very soon, particularly with my added track schedule using the E92.
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      06-27-2012, 07:33 AM   #15
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I think you are just driving TOO fast
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      06-27-2012, 09:05 AM   #16
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Quote:
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I think you are just driving TOO fast
Not so sure Martin- the Miatas still run in front of me, and most likely, the Hondas too
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      06-28-2012, 12:09 AM   #17
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Nothing wrong with your car. The front wheel on the outside of the track will experience the most wear because it has the most traction, especially if you trail brake a lot to get this 4K lb pig to turn. It should mimic tire wear for the most part. Get used to rotating pads left/right.

It you get tapered wear issues (coning of the pads and rotor) it's because the caper is flexing when hot...not much you can do without cooling or a stiffer system.
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      06-28-2012, 08:38 AM   #18
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Quote:
Originally Posted by jml View Post
Nothing wrong with your car. The front wheel on the outside of the track will experience the most wear because it has the most traction, especially if you trail brake a lot to get this 4K lb pig to turn. It should mimic tire wear for the most part. Get used to rotating pads left/right.

It you get tapered wear issues (coning of the pads and rotor) it's because the caper is flexing when hot...not much you can do without cooling or a stiffer system.
Thanks, and makes sense. Will consider pad rotation as inspection and the year continues. Given the number of track events on the car, and the first time this appeared, all was new to me, and surprising.
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      06-28-2012, 08:51 AM   #19
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Quote:
Originally Posted by jml View Post
Nothing wrong with your car. The front wheel on the outside of the track will experience the most wear because it has the most traction, especially if you trail brake a lot to get this 4K lb pig to turn. It should mimic tire wear for the most part. Get used to rotating pads left/right.

It you get tapered wear issues (coning of the pads and rotor) it's because the caper is flexing when hot...not much you can do without cooling or a stiffer system.
Interesting, I have never observed this. How would you explain this phenomenon? I have always assumed that the brake system force distribution left to right would be equal regardless of tire grip (unless ABS is invoked) thus balancing wear on both sides. Is your assumption related to DBC?
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      06-28-2012, 11:00 AM   #20
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My theory is that the outside front wheel in a turn is at an angle that blocks air flow, while the inside front wheel is at an angle that exposes the brakes to additional air. The outside brake runs hotter than the inside brake.
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      06-28-2012, 11:19 AM   #21
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Were there more left or right turns at the track you are on? If you are turning left a lot more, it makes sense for the right side to wear down faster if you brake anywhere while turning.

I would say this is pretty normal. You should see the outside of the front right tire worn down more than the left if this is the case.
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      06-29-2012, 12:26 AM   #22
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ABS is multichannel in the front, and also most modern cars have brake force distribution, so one side will be worked more at the limit when a corner is involved, and it's a function of traction. The other is heat, which has an impact on performance as well as wear. The hotter things get (and tire heat does impact local/ambient temps for brakes), the less performance, and therefor the more input. Kind of a downward spiral effect.

It really turns out for me to be traction correlated. You push on the brakes until you run out of traction....which tire(s) have the most traction?

A braking engineer is best to answer this question, I'm really just commenting on experience driving cars at 9-10/10s of their limits. .
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