95jersey

I recently installed a BBK and it has been working really well. Compared to the OEM C6Z calipers my pads are lasting 5X's as long. So far it has been well worth it.

After about 5 track days I am at about 50% of the pad. I took everything apart a week ago to inspect and changed out some things and notice I had pad taper on one pad (the outer right side) only. All the other 3 pads were worn completely even and looked great. But this one single pad had some real bad taper. The pad on the inside was 100% even. It almost needs to be thrown out.

Does anyone have any ideas why 1 pad out of 4 had such bad taper?

Just as a note, I did have some mounting issues on that side, when I had spindal ducts put on, I had to buy a couple washers and we had to hand grind them down so the caliper would seat correctly and allow the rotor to move cleanly. I was a PITA and I am sure the faces were not ground evenly. Not sure if this is the cause or not, but I wanted to note it for discussion. I would think if the caliper was slighly lop sided, both pads would have taper, not just one?

0Anthony @ LGMotorsports

Couple things to look at, and I will kind of go over this like we would do the setup on the race car.

How is the pad taper? From the inside of the wheel to the outside or leading edge to trailing edge?

If it is leading edge to trailing edge, then it can be a piston size problem, balance problem, or pad compound characteristic (not likely)

Inside of wheel to outside of wheel is generally a flex problem. Either caliper flex, mount flex, or wheel bearing movement.

1. With the rotor bolted tight to the bearing and the caliper in place, check to make sure that the caliper is centered over the rotor. Remember these are OEM cars so everything has a tolerance and it isn't out of the question for it to be off to some degree.

2. Check fitment of the pads. Since you mentioned an aftermarket kit the caliper is going to be fixed with this car and the pad must be able to slide on the pad brackets inside the caliper. It should be snug but able to slide. Each caliper is going to be different so check with your manufacturer.

3. Check caliper pistons. Are they all working correctly? Do you see any moisture around one of them or does it look like one has not been moving out. In the worse case, pull all of them out and see if there is any markings or rubbings on the piston that might make it hang up on the seal.

Given you are seeing only one pad have a problem I would look to pad fitment to the caliper and/or piston issues.

95jersey

It is leading edge to trailing edge. The caliper is mounted on center (as close as I could get it). Once I got the spindal ducts, it pushed out the rotor, which meant I had to put a couple washers on the spindal to equal it out. I bought a couple grade 8 washers from Home Depot and we had to grind the heck out of them with a cheap home rotary grinder. I am sure they are not ground evenly. But there is no taper from inside to the outside of the wheel in any way, so according to you write up that would negate there is caliper flex and not point to a mounting issue. It is a Wilwood W6A caliper loaded with Thermolocks and a custom bracket mount to fit OEM C6Z rotors.

Here is a photo of the pad. Note the bottom pad which is what the other 3 look like (nice and even), but note the one on top which is dramatically tapered.

flink

I've got you beat!



Those are the wilwood superlites on my e36 race car just after I got it from the previous owner. Only the drivers side was like that - just that one pad.

For some weird reason these calipers have the same diameter leading and trailing pistons, so of course the pads taper. And as the pads taper, the pistons are no longer parallel with the bores (piston cocking).

My theory is that this particular pad became so tapered that the trailing piston started binding in the bore and hence wasn't applying its normal force. It's not a terribly good theory, but it's all I have. There is some scoring on the pistons which indicate that contact has been happening.

I ditched the pads and I diligently rotate them between track days to even up the wear and minimize taper (I get ten days out of a set of pads on this little car). I haven't had any such problems since.

You can actually see the air gap between the pistons and the pad in that photo. When you press the pedal the piston twists off-axis to close that air gap, before real pressure starts to be applied. This is why tapered pads cause a long pedal.

0Anthony @ LGMotorsports

I would tend to agree as well.

I don't know much about the W6A kits, but I would check to see if they are split sized pistons. I would look very closely at that side, and all of the pistons there as well as the seals to see if any hang, or have any kind of marks on the sides of them. Could very well be that it is just hanging there and isn't moving or gets stuck at a certain point.

The other thing to at least look at is if it has gotten something that is blocking the fluid to the other pistons. If you pull the bleeder out you will notice that it is drilled all the way through the caliper down to the cross over, that is how it supplies fluid to all of the pistons. If a piece of metal, or powder coating has moved and is blocking one of those ports that could cause an unbalanced pad wear as well.

rikhek

In our PM discussion and your post you stated terrible taper to the point of throwing the pad out. In my experience what you're showing in the picture is minor and not unusual. You're never going to get even wear across all 4 pads.

Flip it over and put on the inside to even out the wear. The wear on outside and inside pads as well as left to right all vary to some degree.

As far as taper goes that's childs play.....


Rick

95jersey

For the past 10 years, in using OEM calipers, Wilwood SL6's and C6Z calipers (one peice pad), that is the worst taper I have seen (maybe I have been lucky). I still don't think it is right though

0Anthony @ LGMotorsports

Well you will almost always see some sort of taper, but it shouldn't be just on one pad.

Take the ALMS car, I might see a leading edge of 0.865" and the trailing edge 0.783" both inside and outside pads are typically within 0.050" of each other. And that is after 3-4 hrs of track time. While front to rear maybe different they are generally the same and the same taper on each side so I can flip them to get a more even wear out of them.

gkmccready

I wonder if the pad itself is hanging up on something. Like the SS bits the pad slides over are real dirty or bent or the pad itself is just a little tight on that end.

flink, the FSL Wilwoods without staggered pistons are super cheap, that's why. :-)

fatbillybob

So lets say you got a leading edge and a trailing edge psiton 4 piston caliper. Where do you see more taper leading or trailing edge on most calipers? Where should the piston be smaller diameter leading or trailing?

0Anthony @ LGMotorsports

I haven't seen any difference with how the caliper is mounted but the leading edge of the pad is generally what takes the brunt of the force and will wear the quickest.

0Todd TCE

Given we've already have this conversation on the phone.... and I put up much the same info above, I also referenced the potential to bending that would or could be created by the use of such hand-ground washers as spacers.

Knowing the brackets are within less than maybe a thou, by having a potential shim that tries to distort its mounting or angles the bracket can easily. A brake mount will tend to twist some under high pressure as it tries to align its mount plane to the rotor centerline. That's why radial mounts, by being placed closer to the rotor center are generally considered more durable for extreme pressure use. Not knowing the extent of the hand job given to the fit of the parts for the sake of a brake duct mount it raises some questions.

In addition to the mount plane both a difference in pad temps and air flow as well as a possible single pad that has a questionable mixture of the matrix can all lead to the shown taper. As taper goes (and without hard numbers to compare) it's certainly not desirable but not extreme.

*The FSL taper shown above can be controlled in part by the fit of pad wear spacer which will ensure more piston to bore compliance over the duration of the .800" pad btw.

ghoffman

OMG, is that a W6A? On any caliper, the leading edge of the pad is "self energizing" and that is why with a properly designed system the pistons are smaller for the leading edge. In the old days when we had drum brakes, you realized this self energizing effect, and the "shoes" moved with the drum. I cannot see why anyone would even make a 4 pot caliper that did not have stagger bores. It is normal to have some taper, like Ant described, but the amount shown here is unacceptable and dangerous. The pistons will **** in the bores and cause premature caliper bore wear and likely seal failure. On our new T1 kit, the piston bores are 44mm and 39mm and the caliper is exceptionally stiff, even at elevated temperatures, for this reason. Your only "fix" would be to swap pads each and every run, even though it is a royal PINA.

naschmitz

Here's what the pad taper looks like after 250 miles at Calabogie Motorsports Park using the AP8350 T1 Kit Gary talked about. Pads are Ferodo DS1.11s. In each set, one side has 0 taper, the other side had 1mm of taper:



Just for comparison to show much wear these pads had yet still had very little taper, here they are next to a new set of 20mm pads.

0Todd TCE

.050-.060 would not surprise me really, even Anthony references up to about .085 on the racing app measured. Obviously exact amounts can depend and a number of variables already covered.

I never got numbers off the single W6a pad in post #3 but I'd agree it's more than you'd expect. But because we don't know what was up with the mounting (a bracket out of square would certainly not help much) the root cause remains a mystery. From shimming to cooling to a wheel bearing to something as simple as a 'bad pad' perhaps. I'm seeing about the same light taper in the other as shown in #14.

Now about the FSL in #4.....come on now; let's invest in some pad wear spacers and not let that get so out of hand! I agree with Gary's comment on the value of differential bores but not everyone wants to pay $500ea for a caliper either. The AP is clearly the better choice over the FSL, but some folks don't mind the pad flipping and are on a budget too. Been a lot of races run and won on square bore calipers so I don't throw them under the bus so quickly.

I'm sure he'll submit it's also superior to the W6a too. I'm not so sure I'm feelin' it just yet. I really did think Gary you were going to come up with something a bit more 'high tech' than this part given all the exotic brake **** pics! lol All good however, it's a worthy option for anyone to consider for their track use.

ghoffman

OK, let me get this correct? You think the kind of taper shown above with the square bore caliper and the W6A is acceptable? Forget the $100 extra for the caliper, do you really think that is safe or reasonable? We discussed 1 year ago today, the W6A. The extreme taper is not an economic or labor issue, it is an indicator of a design problem. It is a street caliper, and is not safe for track duty. I rest my case.

0Todd TCE

I agree with you totally. I don't think it's acceptable to that degree in either caliper.

Obvious lack of attention on the FSL isn't hard for anyone to figure out really. It's not a caliper issue..it's a design byproduct and can happen to anyone using a square bore design. I think even the poster tongue-in-cheek realizes it's not a parts issue, it's a user issue. But that doesn't prevent him from addressing it and getting good results from it with proper attention.

As for the W6a I guess I'm not quite so quick to jump the shark for the visuals of one pad that by the owners admission had some non product related issues. I'm really guessing that I'd have heard a lot of horror stories by now on equally or more demanding track use...so far that's a big negatory. Certainly open to more input on it and willing to help analyze it more if asked.

Safety...? Common Gary...that's a bit of a reach. Let's just stick with the pad taper issues and not cloud the topic.

Seriously; you've done a nice job with the Ap kit so be happy. If you keep re engineering the competition you won't have anything to sell....!

rikhek

Gary,

I run the W6A calipers and am very happy with their performance.

You and I have spoken numerous times and I know you have strong, negative feelings regarding the W6A caliper. They work for me and they are also what Jerry Onks is running on his race car. I spoke with him and he says they work every bit as well, if not better, than the Stoptech brakes he previously ran. He stated the Wilwoods would be gone in a heartbeat if they didn't perform well.

Jerry is the points leading and winningest vette in STO right now in the SE region. His achievements are provided below.

FWIW, his complete Stoptech system is offered for sale on the forum right now. He's sticking with the Wilwood W6A:

http://forums.corvetteforum.com/auto...-for-sale.html


SCCA Club Racing


96 STO
Dr. Jerry Onks

2009 National T1 SE Division Champion
2009 Daytona Speedway Track record
2009 7th Place Runoffs
(1st C5 across finishline)
2009 Road Racer of the Year

2008 5th Place Runoffs
2008 3rd Place SE Division T1
2008 Road Racer of the Year
2007 12th Place Runoffs
2007 3rd Place SE Division T1
2007 Memphis Motor Sports Track Record
2006 Nashville Superspeedway Track Record
2006 Road Racer of the Year
2005 3rd Overall One Lap of America

0Todd TCE

That's both good new and interesting.

Apparently he didn't get the memo on how unsafe they are for track use...

John Shiels

so he won the above with Stoptech? He is selling Stoptechto lose 100 lb.? Not that I give a hoot either way just to make it clear for myself and the rest here. I like my SL6 & 4 from Wilwood. For the price (1100 with thermolock pistons) and time they are great. True racers may have a different priority than a budget HPDE track guy in that he will trow the pads away after one race if they taper. Cost of a set of pads is nothing if you want to win.