Uneven wear with AP Racing Sprint BBK
 

I've had my AP Sprint BBK installed since July 2013 and I've been noticing uneven wear on the pads and rotors since. The driver's side pads and rotors are wearing significantly faster than the passenger's side.

My car is tracked heavily and my first set of rotors have 8 track days on them and I believe they need to be replaced as of yesterday at Road Atlanta.

First set of CL RC6's that came with my kit lasted 5 full track days and the wear was uneven on the pads (driver's side more worn) and before the 5th track day I swapped the driver's side pads with the passenger's side and finished those off.

My second set of pads were Carbotech XP12's and I wasn't happy with those. They lasted 2.5 track days and they felt softer on the pedal since they aren't sintered and contain kevlar. Bite was great and they never faded, I just didn't like the feel compared to the sintered RC6's.

I removed the XP12's yesterday at Road Atlanta at lunch hour and installed fresh RC6's and finished my track day with much enjoyment aside from this perplexing uneven brake wear issue.

Here are the pics of my XP12's off the car and the rotors on the car. First is my driver's side rotor. The J Hooks are fading away and I can see cracks forming between the gaps in the hat. Deep groove around the outer edge of the rotor.

http://i.imgur.com/FDsyBru.jpg

Driver's side XP12 pads. Note the bottom pad was on the inside.

http://i.imgur.com/UYbjM4E.jpg


Passenger's side rotor. J hooks still look okay and the grooves are less significant.

http://i.imgur.com/Zw6yoQc.jpg

Passenger's side XP12 pads. They are worn significantly less and the slot in the middle is still visible.

http://i.imgur.com/g9B8Vi0.jpg


Disclosures: I do not do the pedal dance prior to tracking my car; I do hold the button down to turn "everything" off. I instruct at every track day and I simply do not have time to fully warm up my car or remember/look up the sequence to do it. I am typically jumping out of my student's car and immediately into mine and taking 20 minute breaks every hour to rehydrate, use the restroom, track talk, etc. I am also running 911 GT3 brake air guides strapped to my control arms to direct air in the wheel wheels at speed to the inside face of the rotors to help keep rotor temperatures under control.


Help, advice and insight is much appreciated. I'm at my wits end.



@CSG Mike / @JRitt / @Racecomp Engineering / @Reaper / @buddy32
Please help me by tagging anyone else with the AP Sprint BBK

Could it be as simple as a sticky pot on the driver side caliper?

What would cause more wear on the driver's side? Could it be something as simple as increased weight from the driver or braking into left corners more than right corners or something like that?

I'm able to push back all the pistons with the same (frustratingly significant) amount of effort when changing pads. No pistons seem sticky or more difficult to push back.


I don't know. I've run both clockwise and counter-clockwise tracks with the BBK. I threshold brake in a straight line and rarely trail brake. I am not engaging ABS into every corner.

This is a good post. Thanks for sharing the info. It seems to me like there could be several causes of this uneven wear. I also think the next step in diagnosing the issue is to turn off all of the nannies. Without doing that, you really don't know how much the brakes are being applied at each corner.
I appreciate what you say about being rushed while at the track. I am sometimes in a similar situation. That said, to do the pedal dance takes almost no time. Therefore, you'll have a tough time convincing me you can't do it easily. The car does have to be warm, of course, which can take some time. Do you have a helper that can start it up 15 minutes before your session? If not, could you just let the car idle between sessions? I know it's wasted gas, but it doesn't burn much if it's just idling. And when you consider the cost and/or complexity of other methods of diagnosis, it still seems like a pretty good option IMO.
I'm looking forward to hearing what others have to say.

I have a hard time believing this would be related to not doing the pedal dance. The chance of it always applying that much more force to the same wheel at every braking zone is essentially zero.

If the rears were wearing more than the fronts, I would blame VSC, but assymetrical wear left to right on the same axle sounds more like a hardware issue.

It also looks like they're wearing significantly more at one end of the pad than the other which makes me think it might be a crossover tube? Are they more worn at the front or the rear? How does the fluid flow through these calipers, crossover at both ends, or only at one end? Which end is the brake line attached to compared to the more worn end of the pads?

Another thought, could the caliper bracket be mis-aligned or bent at all? Can you feel more drag on that wheel with the car in the air

I would start by pulling the scoops off for an event or two, see if those are feeding uneven amounts of air.

With uneven wear like that my guess is it is a caliper issue. I doubt the GT3 air guides or not doing the pedal dance are the primary causes. Have you only done two pad install/swaps on the calipers? I would pull the pistons out of the calipers and give them a good look. The uneven wear like that on a multi piston caliper is most likely caused by one of the pistons providing more pressure. Perhaps there is an issue with the anti-knock back spring behind one of the pistons as well.

Both pads from the driver's side are worn significantly more than both pads on the passenger side though. Would one piston of a four piston caliper cause both pads to wear down that much more?

IIRC....

Carbotech 1521 street pads > CL RC6 > Carbotech 1521 street pads > CL RC6 > Carbotech 1521 street pads > Carbotech XP12 > CL RC6

It is heat. What rear pads are you using? If you overwork the rear, it'll cause the front to work harder. The heat is also a function of how you use your brakes too.

This can be replicated on other brake kits as well. Wilwood is the worst. You'll end up just eating one pad up instead of a pair...lol.

I am currently using XP12 rear pads. On my first set of RC6 fronts I ran PMU Club Racers in the rear. I have been using the original rear rotors since I bought the car. It's finally time to replace them.

Curious, because the topic of VSC came up, I am under the impression that VSC would alter brake pressure by use of the ABS system, individually per wheel. So if VSC were a culprit you should feel the telltale vibration from ABS activation.

Or, does it have the ability to modulate brake pressure more finitely at each wheel transparently, to the point that the driver might not even know it's happening?

Brakes are a dumb mechanism, they rely purely on physical force to do a thing. When brake pressure is applied, its in the same proportion, every time (unless VSC/ABS/etc). Braking in a straight line shouldn't cause any of these variables. If one side is getting hotter to the point that it's visibly expediting wear, I'd suspect something mechanical.

Could be a stuck piston that's not retracting properly, causing the pad to drag excessively. In the DS pad pic, I assume the left side of the pad is the leading edge (points toward rear of vehicle)? That would make sense as the pad wants to be drug out of the caliper by the rotor, that the leading edge can wear more, but not when the opposing pad (and both on passenger side) looks so even. I wonder what the back side of the rotor loos like... I'd check piston movement.

The driver side pads look like one piston is not working correctly. Notice that one pad is worn evenly while the other has a clear diagonal wear pattern.

Can you post a picture of the surface of each pad? Can you also post the inner surface of each rotor?

Easy test: Do the pistons still retract with the same amount of force and/or is there any unusual resistance when you push them in to change pads? If not, chances are youre heating the pads unevenly.

Inner pads typically wear faster than outer pads when you're overheating the system. Based on the wear, and the lack of pedal dance, I'd speculate that you may "trail brake" more into right hand corners; this causes the EBD to work the front left brake more.

I need more pictures to make any more educated guesses.

An alternative, is that perhaps you're too fast for the Sprint kit, and it just isn't enough for your needs; this is why the Endurance kit exists (and why we have it on the CSG BRZ).

Does the drivers side wheel bearing check out OK? I don't know how the AP kit mounts, but is it possible for the caliper to be out of parallel with the rotor (some 4 piston calipers can be shimmed to account for this)

I was referring more to the taper he was seeing on the one pad.

Drivers side XP12 pads. Top is the inside pad, bottom is the outside.

http://i.imgur.com/DyuS5j8.jpg


Passengers side pads. Top is the inside pad, bottom is the outside.

http://i.imgur.com/RHYm1Ye.jpg


No time to jack the car up and take the wheels off at the moment but I glanced at them yesterday at the track when changing pads and they didn't look any better/worse than the outer surfaces.

Yes all the pistons go in with the same amount of force. I am using a spent pad backing plate to evenly distribute pressure on the pistons to push them back. It's a significant amount of pressure required and I use a big pair of pliers to help.

:sigh:

My BRZ is NA. The Sprint kit is advertised as sufficient for much heavier, higher power cars. I do brake HARD as you can see in my videos, but I can't imagine that my 200whp 2700 lb car is exceeding the Sprint kit's capacity.

:iono:

I doubt you are exceeding the kit's capability. Might be time to get some temp strips and an IR temp gun and get a buddy to check some temps in the hot pits when you come off track especially to see the differences side to side.

The kit is advertised for average drivers, and you're not an average level driver. I wouldn't discount the possibility.

What do you use for data acquisition? Can you post me a log of your driving?

Specifically, I need (GPS) Speed, Brake pedal pressure, Front left/right wheel speeds, steering angle, and (GPS) Yaw rate.

Still need to nut up and buy an AIM Solo DL. All I have is my GoPro. I quit using Harry's a few events ago because my Nexus 5's GPS is too slow.

:mad0260:

What tires and sizes are you running? Trying to gauge the load on the brakes.

245/40/17 Bridgestone RE-11A

My car is setup reasonably close to yours, on 235/40/17 RE-11As, and likely driven just about as aggressively and I get 4 days on XP12s and over 8 days on the rotors, using stock brakes.

The only significant difference is that I've got the TF brake cooling ducts and I always use the Pedal Dance. I've noticed that using the Pedal Dance significantly reduces ABS activation during trail braking which I'm assuming comes from the deactivation of the brake force distribution. This almost certainly has an effect on brake wear.

If you don't want to have to deal with the dance, there is a box coming to enable/disable it: https://www.facebook.com/86nannycontroller

I used to have the TF brake cooling kit with stock rotors but since the backing plates aren't compatible with the AP BBK I sold it and strapped the GT3 air guides to my control arms to get some (apparently not enough) cooling.

I actually still have an original 86 Nanny in the bag, never got around to installing it. I may send it back to him and wait for the pedal dance device as that's what I really need.

I've seen cars with NACA ducts under the car to catch air for the front brakes, would it be possible to use something like that to direct air towards the GT3 guides?

Or something like the R32 GTR uses to direct air towards their brake guides?

http://www.r33skylineproject.co.uk/i...brake_duct.jpg
http://forums.gtrcanada.com/general-...rake-duct.html

If there's a way to pull air from the high pressure at the front of the car and direct it towards your air guides, would that help? It doesn't necessarily need to be physically connected to the brakes by a hose to point air in the right direction.

That would be activating the rear brakes most likely though, and unless you're driving on an oval should be pretty even left to right.

Ian, I'd check all the mechanical things again. Is the left wheel harder to turn with the wheel in the air (dragging pad or mis-aligned caliper)? Is it possible the fluid passages in the caliper are partially blocked?

No, it definitely affects the brake activation in the front.

Have you run any tracks other than Road Atlanta...maybe one with more brake zones leading into left-hand turns?

I spied your coilovers in your first pic. Was your car corner-balanced taking driver weight into account when you installed the suspension? What is the weight split on the front left to right?

Have you taken disc or caliper temperatures on both front corners with a pyrometer or temperature strips?

Is your duct setup the same on both front sides?

What does your tire wear look like on the driver front vs. the passenger front?

Nothing you wrote sounds like a brake hardware issue to me. As mentioned by CSG, brake calipers and discs are a rather 'dumb' system. That said, the electronic braking/traction nannies can be really messy. We see it all the time with systems that are on or partially turned off, etc. They try to vector the car by applying the brakes, which leads to all sorts of wear that one wouldn't logically expect.

It definitely sounds like your driver front is running hotter than the passenger side front. We need to understand why that is happening, and I don't believe the answer is in the calipers or discs. My hunch is that you're weight balance, alignment, track configuration, trail-braking technique, etc. are all potentially contributing towards getting more weight transferred up and over the driver front wheel, which is taxing the brakes on that side to a greater extent than on the passenger side.

My advice would be to first get some good temperature data to see just how dramatic the difference between the left and right fronts actually is. I'd also love to see those corner weights and your tire wear on both sides. With all of that data in hand you can paint a better picture of what's going on with the car as it gets into braking zones.

Yes we do have faster more powerful cars running similar kits without issue, and no I don't believe you're exceeding the Sprint Kit's capacity. "Exceeding capacity" would mean that you are running the kit so hot that you're experiencing significant pad or fluid fade. My understanding is that you're not experiencing either, and it sounds like you're actually enjoying the brake kit overall. You're simply wearing through consumables faster than you'd ideally like to be, and the wear appears a bit wonky. :)

I've talked about this on this forum before, but in professional racing, parts are designed to make it to the end of the race. Then they're basically free to explode, melt, or spontaneously combust. If they last significantly longer than the end of the race, then they were overbuilt, too heavy, etc. Obviously we try to give our aftermarket customers a balance in this area. We know that nobody wants a brake system that will barely make it through a track day, and we'd never design such a product. We want the kit to perform fade-free under the conditions in which they're driving, providing a safe and confidence-inspiring experience in the process. Some people will however require a little extra 'fat' built in. They'll want to change pads and discs less, bleed less often, etc., and they're willing to deal with a little extra weight in exchange for that convenience. For those customers we have the Endurance Kit.

Obviously nobody really knows until they thrash the system if it is best for their scenario. After collecting as much data as possible, we may ultimately find that the Endurance Kit truly is the better choice for your situation if you want to go longer between servicing the brakes. Or, we may find that you're carrying far more weight on the driver front corner when you get into brake zones...or find that the brakes wear perfectly even at a different track. Don't worry though, we'll do our best to try and help you determine that, and to get you where you want to be.:cheers:

Jeff,

The calipers are the same between the kits, but are the rotor hats? If they are, all that would be necessary to upgrade was new discs and new brackets, right? What would the taller disc do to front/rear brake bias?

I am an old guy and like KISS (keep it simple stupid) approach. A small amount of leading edge wear is not unusual. Yours is more than normal. Traditionally this is caused by a poor surface on the disk. This dose not have to be large imperfections, it can be microscopic surface characteristics that can be caused buy heating and cooling over time. These are castings that are finished machined not machined from a solid piece of steel. swap right to left and see if the problem follows the disk.

JRitt makes a good point about looking at tire wear, maybe find something external from the brakes thats making one side work harder. Also looks to me like your getting to fast for the brakes haha

I've run one counterclockwise track, Atlanta Motor Speedway (roval), and Barber MSP a few times as well since installing the BBK. Road Atlanta turn 5 and 10A are left handers that are very very heavy on brakes.

No, I don't have those.

Yes, I'm running the 997 GT3 brake air guides on both sides

http://986forum.com/forums/uploads01...1331427924.jpg

...that mount to the control arms in the same fashion they do on the GT3, only using zip ties for security

http://i.imgur.com/0pDnSJ8.jpg

Myself and several others who are running them believe they are functional at drawing in air from the wheel wells at speed and redirecting it to the rotors.

http://i.imgur.com/QRXThgP.jpg


At Road Atlanta and Barber it does appear that my left front tire gets worn a bit more than others but I constantly rotate them and I've gotten pretty even wear on all 4 by doing so after every other event.

Thanks for the advice and willingness to help me. After speaking with a few other helpful and knowledgeable people last night, I have a plan of attack after replacing the rotors.

-Get the car realigned and possibly corner balanced
-Get some datalogging going (Aim Solo DL) and share the logs with the knowledgeable folks here
-Get temp strips and/or pyrometer and check temps on hot pits
-Start doing the pedal dance religiously (get the 86Nanny pedal dance device once its available)
-Adjust my braking method to brake slightly earlier into faster corners and see how that affects my times
-Look in to revisiting brake ducting to get some extra air to the rotors
-Last resort would be the Endurance kit upgrade. Questions on that: Would I keep my calipers and just get a different mounting bracket and Endurance rotors and pads that would be it? Would the Endurance kit fit under my Mach V Awesome wheels?

Again I really appreciate the response and I am still happy with my BBK and the way it performs on track. I hope that if anyone else is experiencing the uneven wear that they'll speak up about it so we can come together and find the root cause of the issue.

I'll try to keep this thread updated with my findings. It may be a month or so before I start cracking away at this as I have some other financial obligations to take care of first.

For the price of new brackets, hats, and rotors, you'll be better off getting a new Endurance kit, and selling your Sprint kit. The only components you'd be keeping are the lines and calipers.

Also, the Endurance kit has built-in brake duct air guides :)

IMO, those GT3 brake ducts aren't likely doing a whole lot for you. More and more cars these days have that sort of plastic piece on the undertray. The C7 Corvette Stingray is another good example. Realistically however, for brake ducts to be moderately effective, the air needs to be dumped directly into the area where that air is needed. Otherwise the air is just diffused...it spills all over the place. In your case, you need cooling air in the center of the disc flowing into the vanes. Otherwise, most of the air isn't reaching its intended target. Please see the pic of our Endurance Kit integrated duct below. That is what a proper duct termination at the disc end looks like. The air only goes where it is supposed to go, and there's not really anywhere else for the air to go:
http://www.essexpartsblog.com/media/...eBracket01.jpg

No worries...That's what we're here for!

That looks like a good/logical plan of attack. I have a feeling that addressing your corner weight and alignment will not only make your car handle substantially better, it will help even out your brake and tire wear. That alone should save you money and time in the long haul. On all of my track cars over the years (Integra Type R, miata, Z06, and 350Z), it was unbelievable what a proper setup from a legit race shop did to the handling. I believe it's money very well spent. You won't have to fight the car to do what you want it to do, you'll dramatically decrease your steering input in many situations, you won't have to throw it into certain turns, or rely on brakes to get it rotating...the list goes on. Just make sure you have the car configured as closely as possible to the actual condition it will be when you're driving it in on the track (your weight in the driver seat, half tank of gas, etc.).

As for going to the Endurance Kit, I agree that should be your last resort. Frankly, I don't think you'll need to go that route once you have the car properly sorted. If you do end up going that route, your best bet is to sell your complete Sprint Kit on the used market and start fresh. The cost of the components individually is greater than the cost of the entire kit. Just contact me if it comes to that I'll do what I can to help you out.

On wheel fitment I have the Mach V Awesome 17x9 as a confirmed wheel fitment without a spacer, but I don't know the offset. Someone on this forum has tried it successfully though. You can always check the template to be 100% certain.

You probably aren't going to see a ton of posts about odd wear rates from other owners. We've sold many hundreds of these kits over the past few years, and the only time we typically hear from our customers is when they buy fresh pads and discs or win an event. Very few of them are having any problems, and the AP Racing hardware tends to be fairly bulletproof. Every once in a great while there are some minor malfunctions after the parts have been flogged unmercifully on the track for long enough, but it's nearly unheard of to have a manufacturing defect, etc.

Anyway, keep us in the loop. I'll be curious to see the results as you work down your list. Again, I think getting the car setup properly is going to pay big dividends for you. The car should feel a lot more planted and stable under just about all conditions, and particularly so in brake zones.

ps I forgot to say...I had my Miata set up with no passenger seat in the car and my body weight in the driver seat (roughly 200 lbs). When I put the passenger seat in and had a 200 lb. passenger, it was unbelievable how much worse the car felt! The thing didn't want to turn worth a darn (relatively speaking). I think on lightweight, low power cars like we have, the car is particular sensitive to changes. You don't have big power, big fat tires with huge mechanical grip, etc. to overcome any flaws. You lose speed and it takes you forever to claw it back!

So I ordered new rotors on 4/2 from CSG (drop shipped form Essex)

They finally shipped today after learning the purchase order was left open all month without any further processing or recognition and my rotors have been sitting on the shelf at Essex. :thumbdown:

Track day on Saturday to hopefully pedal dance and modulate my brakes away from this issue.

:iono:

I'll add to this since I'm on the opposite coast and have experienced this for myself. (Vegas really, but lately I've been driving to SoCal for 86Cup events) Like the OP I have experienced brake pad taper and equate it more towards not being able to do the pedal dance because of inadequate time for vehicle warm up. I've noticed if not done, and trail braking that the traction light will come on while trail braking into most corners. After a few hot lapping sessions without pedal dance I would end up with pad taper on the loaded front wheel. With pedal dance done properly I wouldn't have the traction light flash while trail braking and obviously brake pad wears more even. CSGMike and David have been a tremendous help with my braking issues. I used to do 3-4 events on a set of race pads like XP10s, ClubRacers on stock calipers. Now with the Sprint kit I've been seeing 8 events on my most recent pads PMu 999s. It is integral to pad life to make sure the pedal dance is done especially for more advanced drivers. This mostly relates to HPDEs and time trials. I have yet to pull the ABS fuse to see how the car really reacts to analog braking. I hope this sheds some more light into the matter.

@heeltoe86 I'd be interested in hearing your report with no ABS. That's IF you don't mind sharing once you've tested with the fuse pulled. I expanded my device from pedal dance with a button push to also controlling ABS as well for drifters in mind. I have a unit testing at round 2 of lone star drift this weekend, but the more data the better.

any update on this ?