Joshboody

New rotors with 2 track days. First day was good, but 2nd day longer pedal with uneven braking. I did fair amount of street driving and didn't rebed them between days. ST43 pads

Look normal or not?

stuiephoto

I had similar issues with the st-43 pads. The car eventually felt like the rotors had mountains on them and looked similar to how your rotors do. Street driving did make the situation happen sooner versus fresh rotors at the track. I did not find a solution.

Joshboody

My theory is that I wore the transfer layer off during street driving and they needed rebedding. I'm thinking to street drive then rebed them before next track day.

fatbillybob

St43 supposed to be race pad but that rotor looks overheated with uneven pad transfer that happens when you are smokin your pad.

rfn026

Remove them. Sand them with a 200 grit sander. Then clean with with Brake clean. Followe that with soap and water until no material shows up on a white paper towel.

Then break them in - very carefully.

Breaking in Brake Rotors.

Richard Newton

froggy47

I don't think you can get away with street driving those pads.

63Corvette

OR, use Cobalt Friction race pads. Owner Andy Lin says they do NOT need to be bedded to work properly.

JRitt@essex

Yup...those are covered in uneven pad transfer. All of those splotches are giving you the judder. You may be able to get them clean by just running an aggressive race pad cold, but they look fairly well coated. You may need to go with something more aggressive like sandpaper.

Here are two videos we created that may be helpful:

Joshboody

Thanks for the feedback... I'll put some sandpaper to them and rebed.

Actually i I didn't have any jitter this time and the rotors are pretty smooth... but a longer pedal for same stopping power and kinda inconsistent. I was pretty easy on them braking early since I was not comfortable. I have had jitter in the past, but typically goes away after the 1st session.

My cooling ducts I only have the DRM kit and NO spindle ducting. So using speed sensor as locator and mostly pointed at the spindle. Wonder if these are not so useful since not well angled toward the hub.

tmtraylor

You are on stock calipers??? If so, my gut says the "long pedal" is from the pad tapering and not directly related to the pad "smear" on your rotors. But ... if you are getting everything toooo hot, b/c lack of cooling then it all could be related to that issue. Pads could be wearing too quickly with the heat, smearing on the rotor and etc....(all semi-educated guesses) based on "been there, done that".

I run ST-43 and still drive on the street on occasion. No issues for me with transfer layer and my rotors do not have the deposits like you have. The only issue for the street in my experience is the squealing/noise. I have moved on from the stock setup and taper still exists but to a much lesser degree.

Good luck!

Tim

spearfish25

Most pads can be placed in either half of the caliper. That should avoid any taper issues if you periodically swap them.

Joshboody

Update:
I sanded and cleaned the rotors, but no real change in appearance. And they were very smooth to begin with. Pedal travel was scary long at first, but after some light bedding... 60 to 40... pedal was short and hard. But appearance is still basically the same.

They feel good now. Before a track day I typically shake down the car putting much focus on brakes, getting them hot. But this last one, I did not do this and seems to be the diff in good/bad feeling brakes.

I think this is just the nature of race pads... I don't necessarily understand it, but I'm learning. I've only used ST43s once I graduated from street/track pads.

spearfish25

I used an air die grinder and a green roloc disc. I was able to remove those deposits and the rotors look clean. Unfortunately there was a bunch of waiting around because those die grinders are air hogs and I'm working with a 20gal compressor.

YYZ06

That's my solution. I had a similar build up on my rotors when I tried some PFC 01s. I didn't spend enough time bedding them in (a few runs up and down the access road at Mid-Ohio) and got an incredible vibration going into the turn at "China Beach". I put on a new set of Cobalt XR1s at lunch and ran the rest of the day with no issue.

While Andie says they don't require bedding, he does say they will last longer if you go through a bedding cycle. Bottom line is, they work great either way.

X25

I had brakes fade with XR1, where ST43s held up the same day, so I would not really trust XR1s. At least I know for sure that in my case, it fades sooner than ST43s.

I bet all your issues would go away after a hard session, with your pads properly re-bedded in and everything is in harmony. Using them at the street (which I also do) scrubs the bed-in material since they are harder when cold, which might cause these issues, but fix is always a session away, at least in my case.

Joshboody

This has been my experience until this point. I think I just failed to do a good initial bedding with these new rotors. I kinda noticed more even covering of the surface with a light bedding. I'm going to do a harder attempt with covered ducts soon.

fruitsalad

I was also having issues with longer pedal travel and spongier feel after street driving between track days on ST43s. Didn't think to re-bed them each time, since they're normally said to hold up to street use. Thanks for the reminder.

Joshboody

Ha, this could be a bogus thread. May have bad MC… again.

Did another bedding session, getting real hot. Brakes felt great during and after! Few days later pedal almost to the floor… WTF. See vid of MC below… has to be bad seal right? Fluid is recirculating into the reservoir for the whole pedal travel, but no leaks.

Ordered Cardone warranty replacement.

froggy47

Joshboody

And here's the new MC. This is my 3rd one:
O'reilys, but I'm not sure it was actually bad.
Cordone above which had 5-ish track days... seems it would work when hot, but eventually totally crapped out.
And my replacement Cordone, which I'm skeptical of now.

So, this thread is a combo of insufficient bedding and a deteriorating MC.