Bill Dearborn

While instructing at the NCM Sebring Event I wore out the brand new pads I had in the left front WA6 caliper. The pads in the right front were worn but nowhere near as much.

Some history. I drove the car to the event and planned on driving it around Florida afterwards so had little room for tools or spare parts.

To do this I chose pads that I thought would survive two days on the track and about 3500 miles of street driving. Before the event I rebuilt both calipers, installed Wilwood BP20 pads in the front WA6 calipers and Hawk HP+ pads in the stock rear calipers. Master cylinder was replaced, brakes were bled and I had a solid brake pedal. The tires were brand new Michelin PS2 ZP tires.

Since I had never been to Sebring before I asked an experienced instructor to show me the track. In total I got about 30 minutes of slow track time with him before I got into my student's car. After the student session I got two 20 minute sessions of fairly hard driving on my street tires. Toward the end of the second session I noticed the brakes didn't slow the car properly when slowing from 130+ going into the hairpin turn at T7. I was giving my student a ride and while the brake pedal was hard the car wasn't slowing. Needless to say I blew the entrance to the turn and decided to call it a day and let the guys at XP Motorsports who were providing tech support for the event take a look at the car. They found both brake pads in the left front caliper were worn to the backing plate and had started scoring the rotor. This was with ~ 100 track miles (some of them quite easy) on the pads.

Each time I ran the car I turned off both AH and TC so I am sure that didn't cause the unexpected wear. Luckily, jlutherva had some well used Wilwood H pads that he gave me and the guys at XP installed them for me so I could continue my vacation and drive the car back to NY. While installing the pads they checked the calipers for proper operation and found nothing wrong with the calipers, all 12 pistons extended and retracted as they were supposed to do.

I was wondering why those two pads wore out so quickly. Before this happened the pads in both calipers wore just about equally with just a shade of taper that I compensated for by flipping the pads from one side of the car to the other every other event.

I would appreciate any suggestions or ideas on what I should check before my next track session in two weeks.

Bill

jimtway

That is strange. I would send the front pads back to Wilwood for inspection and to determine if the correct material was used.

CHJ In Virginia

I think that you have a bad flex hose on the left front caliper. Interior rubber is deteriorated and blocking fluid return flow causing intermittant lockup of caliper under high pressure conditions. Have seen it happen a bunch of times on older street driven cars mostly.

Lawdogg

Only time this ever happened to me was when I put in new oem pads at the track in a stock C5 Z06 without any time to bed them in and let them cool. Pads were gone after about 30 laps. Everytime I hit the brakes a cloud of brake dust would appear.

0Anthony @ LGMotorsports

Remember, every track is going to be different on brake pad wear. For us, Long Beach GP is almost the hardest on brakes than any other track and we may go through 2 sets of pads over the course of the weekend.

Pad material will wear differently as well. Have you ran those pads at the Glen before? I'm not that familiar with how those pads wear, and it might be the pad, it might be the track, or a combo of the both.

My first thought is without any kind of temp data, that they just got hot and you burned through the pads.....the calipers maybe, and probably are completely fine if you see no odd wear on the pads other than they are just completely gone.

63Corvette

Bill what kind of lap times were you running?
I tend to agree with CHJ above. I have had brake lines collapse internally and block either pressure to the pads, or fail to release, It sounds like that may be your case.

When I got low pedal at Sebring, it was AFTER the hairpin. That is, I brake hard for turn 7, and then for turn 10, and my car stops OK. However I have very low pedal for the next hard braking turn 13. I never had brake issues at turns 1, 7 or 17 because of the long straights providing cooling.

Bill Dearborn

A lot of good thoughts.

Hadn't thought of that. I have Wilwood Stainless steel lines going to the calipers but they have the same inner teflon tube as rubber hoses. I had to pinch the line last year so I could remove the caliper while doing some car maintenance.

Pads weren't quite brand new. I used them for a few autocrosses over the last 2 seasons but they weren't worn far enough that I could get a spacer between them and the pistons.

Have never run them on a track before. I chose them and the rear HP+ pads because I thought I could get a good street/track pad combo for street tires. I didn't plan on running the car very hard on the track since it was my transportation to many stops in Florida and to home. Overall I put about 2500 miles on the car during the trip. I really didn't run the car hard the first 30 minutes on the track since I was trying to figure out where the turns were and had Dan yelling in my ear where to go.

At the Glen I use Wilwood H pads with Raybestos ST47s in the rear and I can get several hard running two day events out of the H pads. Have always had pretty much equal wear between the two calipers.

I had been thinking about replacing the lines since they have been on there for two seasons.

That also makes me think of an issue I had with the right front caliper when I reinstalled it after the rebuild. I used my pressure bleeder to pressurize the system but the right outside caliper half would start flowing fluid from the bleeder and then stop. I had to remove the bleeder and blow brake cleaner through it several times to keep the fluid flowing. After a lot of monkeying around it seemed to flow correctly so I didn't think of it anymore. When the guys from XP checked the calipers while installing the gift pads they couldn't see anything wrong with the way they operated. I will check right side caliper again to see if it is getting full pressure.

The car never pulled one way or the other during the long drive on the road to and from the track or while on the track. It seems like the car would tend to pull one way or the other if one of the calipers wasn't pressurizing correctly.

I never had a soft or long pedal. It was firm from the day I left NY until I got back to NY. All I had to do was touch the pedal and the brakes were on. Firmest pedal I have had on a car in a very long time.

I sent an email to Wilwood with pictures of the pads and asked for their advice. It could be a material problem with the pads as suggested above but they are the only ones that can confirm that. Hopefully, they will accept them if I send them in.

Here are the pictures:
Passenger's side on the left and Driver's side on the left


Driver's side

Passenger's side



Bill

6SPEEDZ

There is NOTHING wrong with the wear on your pads. This is normal Sebring wear.

SouthernSon

Did pedal ever get soft and are you running SKF? All the other suggestions are spot on.

Phoenix1911

I can't see one side of the car wearing pads more than the other no matter what track you are running on, it should be relatively even. Issues with the caliper or hose on one side, I would imagine would cause a pull to that side under braking.
I'm seriously thinking the compounds must be different.... From a personal experience I had ordered a full set of Hawk HP+ padlets from a reputable vendor (front+rear), the front boxes while marked properly contained a single piece Hawk pad for the rear. The vendor shipped another set of fronts but it shows mistakes can happen.

Hmmm, as I'm typing this I started thinking about heat, is it possible your left front cooling ducts may have some blockage on one side causing the pads to prematurely wear? And, maybe I'm over thinking this now what if the right side of the car had the blockage, those right pads faded and the left side was the only effective front braking on your laps hence why the pads wore out so quickly.

Bill Dearborn

No. Pedal was hard the whole time. Wasn't driving all that hard until the last 2 20 minute sessions. I took one person for a ride and then took my student for a ride.

As for the thought that is what happens at Sebring I only put 100 track miles on the car. The passenger side pads would have made it through two days so I don't think Sebring itself was much of a factor. Not sure how Sebring compares to the Glen as far as brake abuse but I don't think it is much different.

Bill

John Shiels

your saying the passenger pads in the picture would make two days at Sebring?

6SPEEDZ

Well I disagree, this is typical of Sebring with an ABS car. Now it could be exaggerated by pad compound. BY this I mean the pad he is running could have slow release characteristics. Sebring is a very rough track, you are in the ABS all the time. Uneven wear is normal when you have a situation like the right front goes into lockup and has it's pressure released by the ABS unit. Then the left front is not having this happen as much when it goes into ABS. This is because of a few reasons. Sebring is a right hand dominate track, therefore the left side is loaded more and should have more grip. The right side is unloaded by the turn, locks up due to lack of grip and ABS releases it. The left side in the mean time has to travel a greater distance around the corner with more pressure being applied than on the right side.

I manage the brakes for the World Challenge Cadillacs I have seen similar wear.

0Anthony @ LGMotorsports

I would tend to agree as well....especially since this was his first time on track. Not having much data on those pads I don't want to jump right out and say there was no way it would have went two days, but they could have very easily have just worn out.

Wear side to side could be everything from the caliper not being 100% centered over the rotor, rotor flex, caliper mount flex, air flow side to side, down to weight carried over each wheel.

Every pad is going to wear different, as well as every track is different on pad wear depending on how you use them and the temps involved.

While most guys doing HPDE's, and sprint races don't keep track of pad wear...when you do endurance racing you have to, because you will (on the longer races) plan for a pad change during the race so you need to know when to plan the stop. Sebring isn't the hardest on brakes but I wouldn't say it is a light braking track either.

0Todd TCE

Pads Bill, plain and simple. Nothing to do with calipers, hoses, mounting, flex, rotors or anything else: BP20 pads have no place on a race track with an experienced driver or a track as demanding as Sebring is. Believe me as I've seen it more times than you might think.

This is shown by the quick fall of of the pad at an even 'moderate' temperature level:



From my experience even that graph is optimistic. BP20s are far more a high end street pad or a short life/need pad. Maybe some high speed AX or such. The only alternate in the mid range is Poly E which is actually far more stable than 20s for their life.

Bill Dearborn

Todd,
That is the graph I used when I chose the pads. I didn't want to run H pads while traveling 1200 miles (900 on a train) to the event and I definitely didn't want to run them while traveling (1900 miles) after the event. They looked like they would perform well when combined with HP+ pads (which go to ~800 degrees) in the rear. I got ~ 27 laps out of the pads and the rotors aren't even heat checked.

I will double check everything as I prep for the Glen on the 26th but it makes me feel better that I more than likely made a bad choice when I went with the BP-20s.

Since I got home I have been researching pad compounds for the 6617 pad shape and it looks like I could get that pad with the Raybestos ST47 compound and use that in the front Vs the Wilwood H compound. That way I would at least know I had similar braking characteristics front and rear Vs a SWAG based on incomplete data.

Bill

Bill Dearborn

John,
They have about 50% life left so probably would have made the two days and let me get home since I only planned on driving two sessions on the second day.

Bill

0Todd TCE

I hear ya. I think the decision not to run the H pads on the drive was the right one for sure. You'd have been better served using the BP20 on the way down and then fitting the H pads once you arrived. Keep in mind you'll never find a true, good dual purpose pad.

Can't really speak for the ST47 pad, however I know the ST43 quite well.

Bill Dearborn

ST47 is supposed to be more aggressive than the 43. I do have a set of ST43s to use in the rear as well. I can also get the 6617s with that compound. How does it compare to the Wilwood H? I have been running the H compound since I installed the LG G Stop kit on my 03Z in 05 and really like it. The Raybestos compounds would add 50% to the cost of the pads so really don't want to spend the money if I don't need to.

Bill

0Todd TCE

Maybe time to move to "A" pads for a round. Awesome pad, just hard on rotors at low temps.