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06-28-2009, 01:24 AM | #1 |
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Question about brake pad life
I go through 2-3 sets of rear pads for every set of front pads, which doesn't seem normal, so I'm wondering what I'm doing wrong. Current setup:
Stoptech front BBK w/332mm rotors, Ferodo D2500 pads H6 rear setup, Axxis Deluxe pads In daily driver use, the wear pattern seems pretty even front to back, but a single track day will wear the rear pads down to the backing plates. I've tried different pads; OEM compound wore even faster (I was hoping the forward shift in brake bias might extend pad life), and the rear bias shift with Axxis ULT pads made the car a bit nervous under heavy braking (lasted the longest, though). Axxis Deluxe pads sit right in between the ULTs and OEM pads in life and performance, as one might expect. Is the rearward bias of the Stoptech BBK combined with the increased torque of the H6 rotor just killing the pads? I'm not particularly attached to the H6 rotor setup; the only motivation was the increased heat capacity of the larger rotor. If I can return to a more sane pad wear pattern with the stock sized rotor, I'll happily throw them back on. ...or is this pattern of pad usage totally normal?
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06-28-2009, 08:07 AM | #2 |
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Well, the first thing I'd say is that all those pads aren't suited for track use. Otherwise I'd say something isn't right. I've had the same rear pads on my tracked STI for 2 years and they're maybe 1/2 worn (PFC 01's). Maybe you got the STI Stoptechs instead of the WRX version?
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06-28-2009, 11:11 AM | #3 |
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^^^Exactly.
2500's, although not great, can hold up to mild track running. The Axxis pads are completely unsuitable for that kind of heat. I'd expect them to only last a day back there. |
06-28-2009, 12:13 PM | #4 | ||
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As for the front BBK -- all the paperwork definitely says WRX, not STi, but who knows. Maybe I should try going back to the stock-sized rear rotor? |
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06-28-2009, 02:20 PM | #5 | |
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Try running 2500's in front, and 2500's or at least HP+'s, EBC yellow, etc. in the rear. Again, you should not be surprised that your mild street pads (Axxis Del.) are going to the backing plates after one track day. They are completely inadequate for the temps you see. You're lucky you're getting a day out of them. Forget the bias, etc. for now. You should be focusing on step 1, proper pads, before looking further into your system. There are countless posts about guys burning through street pads at the track. You should expect nothing less. There's a reason they wear fine on the street! |
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06-28-2009, 04:15 PM | #6 | |||
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Do you folks recommend swapping pads at the track, or is daily commute wear (400 miles/week for me) going to be largely in the noise relative to track days? |
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06-28-2009, 04:22 PM | #7 | |
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Amazed on the price as well , guess it's all down to volume. Have fun! |
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06-28-2009, 11:45 PM | #8 | ||
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-Mike |
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06-29-2009, 08:04 AM | #9 | |
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Further, EBC yellows, while lacking the bite of more serious track pads, are widely hald to hold up just fine for someone just starting out. They are EASY on rotors, and have longevity comparable with other pads. They just lack bite at high temps. Have you even used either of those pads before? |
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06-29-2009, 08:58 AM | #10 | |
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I think you have a more fundamental problem than just pad selection. More likely the front brakes aren't pulling their weight so, the rears are doing too much work. Maybe this is pad selection like, too little pad in the front but, I wonder if your BBK is actually working properly. I've often run track pads in the front and cheap street pads in the back (though not on a subaru) and not had problems with excessive rear wear. You really want an aggressive pad for the front and some lessor pad in the rear. It'll keep the rear in check under heavy braking. |
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06-29-2009, 11:45 AM | #11 |
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I have the same problem with my 08 WRX with Brembo fronts and front track pads (DTC70 or Pagid Yellow). The problem on the 08 WRX rear is that there are very few actual track pads available.
You may want to try to increase cooling back there with some ducting to help but also a real track pad will last much longer if you can find one for that caliper. In the long run it will be cheaper to buy a more expensive race pad (Hawk DTC 60 etc) as you won't have to buy new pads every event. Thanks, Phil Element |
06-29-2009, 01:32 PM | #12 | ||
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That raises the next issue -- BBK + H6 rear rotor + track-ish pad in back screws up the brake balance (at least for me), so I'll step back to the stock rear rotor size. I'm not convinced the additional ~1" in diameter really bought all that much heat capacity on these solid rotors anyway... Any recommendations against the second point above? Quote:
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06-29-2009, 03:00 PM | #13 | |
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And if a pad is capable of not biting at high temps for a reason other than because it's melting away so fast it doesn't provide any friction, I'd love to hear it. -Mike |
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06-29-2009, 04:18 PM | #14 |
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I know the Hawk DTC60-70 have plenty of bite even when cold and I like this in a track pad. The problem however is that when used on a street car the pads will not get to a tempature where the pad is easy on the rotors. At colder temps they are extremely abrasive and hard on rotors but when used at the correct operating temp have proven very friendly on my StopTech 355 kit.
There are some pads which are downright freightening until up to temp but the Hawk stuff isn't that way. They will squeel like crazy however on the street (pad deposits wear off). LOL! |
06-30-2009, 02:48 PM | #15 |
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Well, while going back to the stock-sized rear rotors, I also discovered that my piston boots have been pretty badly scorched. So clearly too much heat back there.
What are some suggestions for getting cooling air back there? It's not like the fronts, where the solution is pretty direct... |
06-30-2009, 03:36 PM | #16 |
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im betting the boots are burnt up becuuase the pads got worn to the backing plates and left little to no insulation to protect the rubber parts. With a full depth pad that isnt wearing out super fast you should see much longer component life and no need for rear cooling
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07-01-2009, 05:09 PM | #17 | |
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Take a look at friction coefficient graphs for any brake pads, they have an ideal operating temperature, under or over which friction falls off. The pad doesn't have to be "melting away so fast", it can just be operating out of its ideal friction range. Like yellows, their coefficient falls off soon after 1000 degrees, but will still last plenty long when run that hot. So yes, quite certainly you can be above a pads ideal operating temp, but not so much that you're melting the the material off. |
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07-01-2009, 05:53 PM | #18 | |
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07-01-2009, 10:18 PM | #19 | |
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EBC Yellows are on order from Jamie. Really looking forward to trying out this new compound! |
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07-01-2009, 10:43 PM | #20 |
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With your current setup, how hard is it to lock up the front wheels? I'm just curious if the front brakes are pulling their weight. I can lock up my brakes at will at any speed with just the factory Brembos,decent pads and decent rubber.
Like Mav1c, my rears just don't wear. Since the fronts are supposed to be doing 70% of the braking, the rears shouldn't be wearing or getting THAT hot. I still have this sneaking suspicion that the rears are being asked to do too much because the fronts aren't pulling their weight. Something like the piston sizes being wrong so, your brake balance is WAY off. |
07-02-2009, 12:42 AM | #21 | |
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For what it's worth, I did call Stoptech tech support and suggested this (i.e. incorrectly sized pistons) as a possibility. Didn't elicit much of a reaction. Not sure what that means. I've said this several times now, but it probably bears repeating -- in addition to the (say) WRX-specific BBK I'm running, I was running the H6 rear rotor. You guys must know what I mean, right? It's an inch larger in diameter than stock. The tech support guy balked at the idea that I was running the larger rear rotor, given that the BBK already shifts bias 10% rearward. Can't say I was entirely happy with the conversation, BTW. Like most tech support types, he seemed more interested in talking at me than talking with me. But that seems to be the way of things. Last edited by FromageTheDog; 07-02-2009 at 12:52 AM. |
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07-02-2009, 07:14 AM | #22 |
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My rear pads and rotors don't wear either. I've have the same set of rear pads for over 15 track days and they still have plenty of life left.
-Duncan |
07-02-2009, 08:43 AM | #23 | |
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That kind of behavior is quite common. In general, I'm not sure what point you are trying to make, we all agree why his rear pads went so quickly. But your assumption that you can't heat a pad past ideal and not melt it off is flat out wrong. Last edited by REX8; 07-02-2009 at 08:53 AM. |
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07-02-2009, 08:46 AM | #24 | |
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Ran a set of HPS's in the rear my first track day (200 whp WRX, XP8's up front). From new to plate in 3 sessions. Ran Red-stuff on the back of an S2000's in a pinch as well. From 3/4 to plate in 2.5 sessions. Those Axxis pads are MUCH less capable than redstuff or HPSs. You should fully expect to destroy them in a hurry, at least in my experience. Not to mention 05 WRX's are much harder on rear brakes with their auto-bias feature. |
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07-02-2009, 09:14 AM | #25 |
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Check the rear caliper, and see if is actually still in working order.
My guess is the overheating melted something, so dirt could get in seizing the caliper. |
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