Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand UltimaDork
10/25/22 3:44 p.m.

We had great fun at the FIRM for the GRM track day on Monday. My non-SI civic, Vtec-slow, was more or less able to hang with some of the Miatas. I even got a point-by a few times. 
 

I didn't abuse my car, but I pushed it at what I felt was a reasonable pace (all out). My fastest lap on the full course was 1.32.109, with the bus stop I got a 1.49.002. I'm told that's pretty good for a momentum car, and it was my first track day ever (not counting driving horses). The dozens of autocross runs and single track sprint event I've done at the FIRM probably helped.
 

I only smelled my brakes one time, and I did a cool down lap several times through the day. I never got brake fade, soft pedal, etc while on course. 
 

On lunch break, after the car cooled down, the pedal sank much further than normal. The fluid was only down a small bit, and it improved enough after topping it up to go back out on track. The ability to stop the car never changed. 

Hawk HPS pads (I know they are not a track pad, but this car is my daily and back up autocross car), centric rotors, ATE brand DOT4 fluid. They've been on the car about four months, and have 16 autocross runs before yesterday, plus some street miles.

The rear brakes are also the same set up, installed the Thursday before the challenge. The rotors look normal on the rear, they've barely worn off the machining.

On the drive home, the pedal would drop about halfway down before I would get any brake, although they were still as functional as normal.

As you can see, the pads are glazed, and the rotors are scored. My plan is to sand the glazing off of the pads, and do a full brake fluid flush. I have new rotors ordered. Should I pitch these rotors and install the new ones? Do I need to sand the rear brake pads as well?
 

Any other thoughts would be welcome.
 

Since I'm sure it's going to come up: Before I track the car again I'm going to change the fronts to a track appropriate pad (suggestions, please) and a dedicated set of rotors (maybe even the cryo- treated ones).

 

Streetwiseguy
Streetwiseguy MegaDork
10/25/22 7:37 p.m.

Put a straight edge on the friction surface of the pads and see whether they were flexing on the piston side.  My Neon was pretty bad for that, running Hawk blues.

This happens when you think you can get a fourth weekend on a set of fronts, but notice the angled chunk of pad material left on the inner pad.  That's what I would be looking for.  Maybe not quite as ridiculous as this example...

wvumtnbkr
wvumtnbkr GRM+ Memberand PowerDork
10/25/22 8:03 p.m.

I'm thinking this is a fluid issue,not a pad issue.

 

The pads look fine to me for something that was on track.  Rotors have some grooves, but no fire checking that I can see.

 

Go to a motul 600 and see what's up.

MiniDave
MiniDave Reader
10/25/22 8:27 p.m.

I think you're right on the fluid being the problem......

Deglaze the pads lightly and put them back in where they came from if possible. Be  sure to flush all the fluid out of the system to get rid of the moisture.

Sonic
Sonic UberDork
10/25/22 8:27 p.m.

I have the exact same opinion as wvumtnbkr.  Flush the fluid and give it a try before you spend more money and time on it.  HPS should tolerate some light track work in a low power car.  

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand UltimaDork
10/25/22 8:35 p.m.

Plan fits with the recommendations here. Sand the glazed pads, reassemble, thorough flush. 
I'll follow up here. 

Gearheadotaku (Forum Supporter)
Gearheadotaku (Forum Supporter) GRM+ Memberand UltimaDork
10/25/22 8:59 p.m.

I made up some small brake ducts out of pool and spa hose form the home improvement center. Didn't look like much with only a 2" diameter but it made a big differece.

wvumtnbkr
wvumtnbkr GRM+ Memberand PowerDork
10/25/22 9:26 p.m.
Gearheadotaku (Forum Supporter) said:

I made up some small brake ducts out of pool and spa hose form the home improvement center. Didn't look like much with only a 2" diameter but it made a big differece.

No fire checking on rotors tells me he isn't getting the pads or rotors too hot for what is happening.   Can't hurt though.

amg_rx7 (Forum Supporter)
amg_rx7 (Forum Supporter) SuperDork
10/25/22 9:30 p.m.

A brake bleed is definitely in order. Whenever I do brakes on my Miata, they tend to benefit from a second bleed after a few sessions. Soft, long pedal is also a symptom of a bad master cylinder so keep that in mind. 
Did you grease the caliper pins properly when you did brakes?

kevinatfms
kevinatfms GRM+ Memberand HalfDork
10/26/22 8:22 a.m.

Motul RBF 600, a little more street/track friendly pad(HP+ or Ferodo DS2500), new fresh blanks(Rock Auto w/ discount code) and fab up some air deflectors with aluminum plate. 


 

TR7 (Forum Supporter)
TR7 (Forum Supporter) Reader
10/26/22 9:03 a.m.

Bleed the brakes, check the caliper slides, check the wheel bearings

dean1484
dean1484 GRM+ Memberand MegaDork
10/26/22 9:08 a.m.

After pads, rotors, and new fluid if this is still a problem I would look at the master cylinder.

Nockenwelle
Nockenwelle New Reader
10/26/22 10:34 a.m.

Doc, I don't see anything concerning with the pads and rotors. They look like they had a track day but aren't in distress. Your pedal drop could be fluid, but also common that the flexible floating stock calipers allow a good deal of taper wear on the pads. That can feel weird (spongy) once things cool back down. Look for small rings of pad contact on the rotors instead of full contact to confirm. No problem, it will wear out. A 7/10 slowdown from high speed with cold brakes (just one, followed by cooldown) can help get things back to normal.

If the pads did overheat, they can also get spongy. Typically they start chunking out and breaking up at the edges when this happens and yours are not, so consider it an unlikely but possible 3rd scenario.

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
10/26/22 11:19 a.m.

Agree this looks like fluid only to me.

Are the factory backing plates and dust shields still there? They often do the good work of getting needed airflow to lines and calipers. 

Also, driving style? Are you left foot braking and maybe not coming all the way off during the straight (missing a return spring on the pedal)? Calipers or slides gummed up so the pads never quite release? It only takes one sticky caliper to boil fluid.

 

sergio
sergio HalfDork
10/26/22 4:39 p.m.
TR7 (Forum Supporter) said:

Bleed the brakes, check the caliper slides, check the wheel bearings

Not saying bad wheel bearings are your problem, but this happened to us. Just a FYI because it baffled us til after the race when we figured it out.

We had one of the front wheel bearings go bad 3 hours before the end of a Lemons race. After taking a left turn the brake pedal would require a couple pumps to come up again. On right turns the pedal was normal. So what was happening was when a left turn put a load on the right front wheel the lose bearing would let the rotor move pushing the pads in a little. Pumping the pedal got the pads back against the rotor and the brakes worked. Finished the race doing the same thing after every left turn.

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand UltimaDork
10/26/22 10:07 p.m.

Bearings seem fine, dust shields in place, no left foot braking.   
 

Pads weren't showing uneven wear or crumbling, just glazed. They're sanded and brakes are flushed. Seems to have done the job. I'll be driving to work the next two days, then it's back to the Firm for autocross and track sprint  on Saturday. 

wvumtnbkr
wvumtnbkr GRM+ Memberand PowerDork
10/26/22 11:05 p.m.

You mentioned glazed a few times.  They don't look glazed to me at all.  They look like they got to operating temp.

Glazed is when they are very smooth.

 

I haven't seen glazed pads since it was necessary to run drilled or slotted rotors.  That was like 20 + years ago.  That was a factor of the outgassing and backing compound.  

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand UltimaDork
11/3/22 10:46 p.m.

Following up. Autocross on Saturday morning, then track sprint in the afternoon.

Between runs in the track sprint, my rotors (measured with an infrared thermometer) were approaching 600°, the hottest brake temperature of any of the cars in grid. I wasn't told the reading for the calipers, just that "they weren't that hot."

I've got a new set of front rotors, and I'll pick some high temperature track pads and higher temperature fluid before I track this car again.

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