Fulton 1

After my last track day I noticed an odd wear pattern on my front rotors. There was more pad material deposited on the OD of the rotor face than the ID.

So, last night I looked everything over and installed a new pair of front rotors, swapped the inboard pads to the outboard side, cleaned and re-lubed the guide pins, and checked the wheel bearings for play. Nothing looked out of the ordinary and there was no discernible play in the wheel bearings.

The outboard pads did appear to have a slight taper across their width - the top (OD side of rotor) of both pads measured in the 15.0-15.1mm range and the bottom (ID side of rotor) measured in the 14.7-14.8mm range.

The inboard pads did not appear to have any taper at all and measured a consistent 15.0-15.1mm everywhere.

Pads are XP10s and they did not show any longitudinal taper or backing plate deformation.

This morning I went out to bed the new rotors and when I got back this is what I found.

Driver's side:


Passenger side:


Pictures aren't the best, but you should be able to see that there is definitely more material being deposited at the OD of the rotor than the ID. It is also fairly consistent from driver's side to passenger side. This is the same wear pattern that I was seeing previously with the old set of rotors (and prior to swapping the pads, etc).

I'm beginning to think that I have the onset of caliper spread, but the weird thing is that these were brand new front calipers this year and I only have 3 track days on them (maybe 15 20-min sessions in intermediate run groups) and I'm still on street tires (PS2s). I have brake duct extensions and spindle ducts as well as SS pistons. I had read over the years that caliper spread was an issue with the stock calipers, but I guess I didn't expect to start seeing it this soon. The two tracks we've run at are Pacific Raceways and The Ridge - both can be hard on brakes.

Any thoughts on what would cause this type of wear pattern other than caliper spread?

I have another track day scheduled next week and that will probably do it for me this year, but I was planning on just running it this way unless there's a reason not too...

ETA: forgot to mention that this "incomplete" wear pattern was only present on the outboard side of the rotors previously. The inboard sides looked normal.

Sidney004

When my C5 calipers spread, its just like that but I also measure the actual calipers themselves. I get a long pedal when this occurs.

ErnieN85

C6 calipers are beefier and don't spread so quickly, however I managed to spread mine eventually

froggy47

Everything you said.

Fulton 1

Thanks for the feedback. I think I was just trying to talk myself out of it based on the fact that I only had three days on these new calipers and those on street tires. We did do several sessions with instruction and ended up sitting in the car and chatting after those sessions, which did not afford proper brake cool down. Could be that we (wife and I both drive the car) are just collectively hard on the brakes. Still learning so that doesn't help I'm sure.

Going to do one more event with these brakes since I believe they are still early on and I won't be able to get parts in time at this point, but then it looks like decision time - try the C6 calipers or go right to the AP setup...

Oh well, looks like I needed another winter project anyway

CHJ In Virginia

Caliper spread and taper on pads is a fact of life with stock calipers after track use. Get used to swapping out calipers every other year and flipping pads every event to equalize wear. I use the LG motorsports Wilwood G Stop on my Z06. Relatively inexpensive as brake upgrades go. GREAT performance, no pad taper, fit under stock 17" Z front wheels, and use stock size rotors. There have been numerous threads about them over the past several years.

Fulton 1

I'll do some research on the Wilwoods as I'm not really familiar with them. Thanks for the recommendation.

Bill Dearborn

It is a great setup. The LG G Stop Wilwood kit uses the Wilwood 7420 pad which is thick and is available in a bunch of track compounds that are not too expensive. I ran them for 4 years on my C5Z and recouped the cost of the calipers within two years due to savings on brake pads alone. When I sold the car I reinstalled the stock calipers and sold the Wilwoods separately for about half the cost I paid for them so they were a money saving investment.

Bill

Adam@Amp'dAutosport.com

Check the pricing on the pads below.

CT7420 XP10 $197

Stock CT731 XP10 $212

SunnydayDILYSI

Adam, do you make pads for the AP 3850s as well? I've heard that those are more track friendly than the Wilwood setup.

Adam@Amp'dAutosport.com

Yes, we do in al compounds. I think you mean the CP8350 D50 Center Arc. 20mm Thickness?

sperkins

Not my experience. My C6 calipers tapered pads just as bad as C5 calipers right out of the box.