Miata brake problems - HEEEELLLP

Naturally, less than a week out from track time and now is when I've got issues.

1992 Miata. NA8 (94-97) brakes. G-LOC (Carbotech) XP-10 front pads, XP-8 rear. No other mods, standard rotors. Pretty much the standard issue miata setup.

6 weeks ago I installed these pads with a new set of rotors. Amazing, like being hit by an oncoming train. Lots of noise but totally worth it. Great bite. Did 2 days with them at NJMP, no problems.

A week or so after the track I noticed that I was getting a steady squeak-squeak-squeak from the right front. Took apart calipers, sliders looked good, piston looks good, etc. Put it back together. Still squeaked.

Took it back apart again, this time noticing that when spun, the RF came to a stop much faster than the LF. Compressed piston, tried again - now it spins great. Checked sliders again, checked piston again - no binding there. Looked CAREFULLY and noticed a tiny amount of play in the wheel bearing. Ordered a bearing and threw it on a few days ago.

Now my brake feel is AWFUL. The noise is gone (both consistent and when on brakes) and so is the bite. It's not unsafe to drive on the street or anything, but I'll be at NJMP on Saturday and Sunday - even with 90whp I want my brakes back. It basically just feels like there's no friction until I really stand on it.

Been trying to get ahold of 949racing (brake vendor) with no luck since Thursday, I think they're out on an extended racing weekend so I'll update if they get back to me.

Under heavy braking, the car seems to pull left. That makes me think the RF brake is definitely the culprit. Took the brakes apart again last night, here's pics. I gave em a light scuff with sandpaper, cleaned em off with brake cleaner. No change. The two pad pics are different only in that one pic was taken in shade and one in sun to show possible glazing.

I'm no expert, but it sure looks like the pad on the right lacks the rotor wear pattern of the one on the left. Combine that with the change happening when you prevented the rotor from "floating", and it seems to me like something's stopping the caliper from aligning properly.

Have a good close look at the carrier where the pads' backing plates rest, for some sort of notching that's preventing movement? Replace the sliders on principle?

I have the same setup as you except 1.8L. Did you readjust the rear calipers after changing pads? Having one rear off from the other can cause a pull too. Does the steering wheel pull under braking also? Check for a stuck piston in the front as well.

Ransom wrote: I'm no expert, but it sure looks like the pad on the right lacks the rotor wear pattern of the one on the left. Combine that with the change happening when you prevented the rotor from "floating", and it seems to me like something's stopping the caliper from aligning properly. Have a good close look at the carrier where the pads' backing plates rest, for some sort of notching that's preventing movement? Replace the sliders on principle?

Sliders are 6 weeks and probably 3 months old depending on side. They look perfect. Can't find any strange issues aside from the minor wear pattern which I sanded off.

PMRacing wrote: I have the same setup as you except 1.8L. Did you readjust the rear calipers after changing pads? Having one rear off from the other can cause a pull too. Does the steering wheel pull under braking also? Check for a stuck piston in the front as well.

One caliper is 6 weeks old (found leak when I checked night before track). Other is maybe 2 months old, found leak when doing all new lines. How do I check for stuck pistons? Seems very unlikely on a new pair of calipers but considering they both do work (if I compress the RF one it does come back out when you press pedal).

I did adjust rear calipers bc I installed all pads at once.

What sort of bedding have you been doing? Did you have the rotors turned before you installed the Carbotechs?

Keith Tanner wrote: What sort of bedding have you been doing? Did you have the rotors turned before you installed the Carbotechs?

I did bedding 6 weeks ago when I put them on. Carbotech/GLOC/949 recommends track bedding but there was no way I'd get enough heat into them on the track in group 1 during first session of the year so I did them on the street. New rotors. Then had 2 days of track use starting the following day. Worked amazingly well.

Since then, has only seen normal commuting.

XP10/8s aren't really commuting pads. Try bedding them again, see if the bite comes back.

Possible that you got brake fluid or grease on the pads or rotors with all of the work???

Keith Tanner wrote: XP10/8s aren't really commuting pads. Try bedding them again, see if the bite comes back.

I'm aware. Anything I should do before re-bedding? I still have my other rotors and street Hawk pads but hadn't read anything negative about commuting on them aside from the noise/dust.

Shouldn't need to do anything. Just keep in mind that track pads need hotter temps to bed. I'd do about 10 stops from 60-5 mph. The amount of heat goes up with the square of the speed increase, so 60-5 puts nearly twice as much heat into the brakes as 50-5.

It may not solve the problem, but it's an easy thing to do and I've seen track pads suffer from being run cold for too long.

Keith Tanner wrote: It may not solve the problem, but it's an easy thing to do and I've seen track pads suffer from being run cold for too long.

Thanks a ton Keith. This will be first thing I'll try, despite 10 runs to 60mph in a stock 1.6 taking approximately 10 minutes.

EDIT: 949 suggested the same thing. I guess my 17 mile commute down 95 isn't really ideal for these things.

Double Edit: Both Carbotech and G-LOC both suggested swapping inner/outer pads. They said there's no way to remove the transfer layer. Great UGH

You say that you scuffed the pads, would it be worth scuffing the rotor also? That sure seems to have a nice shine to it. Was helping a friend with a V8 Miata who had almost the same complaint and that solved his issue.

Need lots of heat. I bedded my Carbotech XR3's in on the street, but honestly they didn't truly get bedded in until I went to the track. Towards the end of my first session they started to come around and really bite.

I was able to stop just fine before, but pedal feel and bite got better and better the hotter I got them.

The track/street Miata my dad had didn't stop real well on the street. Went through everything twice, no change. Finally, someone suggested changing pads to something softer, and it made a big difference.

Brake pads are like tires. You don't expect race tires to do well in the snow, and snow tires melt on the track. Pads are designed to work in a specific temperature range. How they work outside their design range varies - some (Performance Friction PFC97, for example) will stop the car but destroy the rotors. Some will just feel like blocks of wood. Keep in mind that if you ever have to do an emergency stop on the street, it'll probably be on cold pads.

There's no such thing as a do-anything pad. The PFC97 is close, as long as you don't mind replacing two sets of rotors for every set of pads and making an ungodly mess of your wheels. Great rally pad

Swapped inner/outers per GLOC and Carbotech advice. Seems to have worked, although the pedal feel is still not good I do have lots of friction. Gonna bleed em after work and see if that solves pedal feel.

NOHOME wrote: You say that you scuffed the pads, would it be worth scuffing the rotor also? That sure seems to have a nice shine to it. Was helping a friend with a V8 Miata who had almost the same complaint and that solved his issue.

Neither carbotech nor GLOC suggested doing this. They saw the same pics. Hmm.

Keith Tanner wrote: XP10/8s aren't really commuting pads. Try bedding them again, see if the bite comes back.

^^This is the right answer. XP10s are not a street friendly pad. If I commute 2-3 days after an HPDE with my Carbotech pads in, then the transfer layer scrubs off and the pedal feel (and noise) go to hell. That serves as an indicator that the rotors are cleaned up enough to throw OEM pads back in and re-bed.

They'll feel great after you get a few laps into them. After your track day, drive on them a day or two and then switch back to Hawks.

It's really interesting that the vendors (949) and users (Tyler, Keith, others) say the transfer layer scrubs off.... but the pad makers say there's no such thing.

Not in any way trying to contradict anyone just trying to figure it out.

I did get them NICE AND HOT last night after swapping directions. Had them properly fading and then let em cool. Like I said they feel like they grip fine now they're just quiet and the pedal feel still sucks. Wonder if I cooked the fluid it a bit... will bleed em tonight.

I don't know exactly what the mechanism is - if you're scrubbing off a transfer layer, or evening it out, or adding to it. I just know it helps Note that you don't necessarily have to make them fade (too hot can be as much of a problem as not hot enough, although that's hard to do with XP10s), you're trying to get them up to temp and keep them there for a while.

Carbotech has strong feelings about mixing their pads with others on the same rotors. I know they don't want you to mix XPs and Porterfields.

Fluid doesn't un-boil. Once you've got those air bubbles in there, it's time to bleed. If you can boil your fluid on bedding, you need fresher and possibly better fluid.

It's RBF600. I wonder if I coulda boiled it from heat when the bearing had a little play.