meBlaise

Been having braking issues all season on track. Nobody seems to be able to have any idea what the problem could be.

Car setup info (relevant and not):

Chassis:
'92 NA 1.6 - 2450lb weight with driver
No Aero work, using hardtop
V8Roadsters frame rails
Blackbird SD rollbar

Drivetrain
Stock 1.6 - 104whp
Torsen 4.3 from '99

Brakes
NA8 Calipers/Brackets
GLOC pads: 10 Front, 8 Rear (more on this in a minute)
New lines (not stainless) - SS lines on order
no ABS

Suspension
Polyurethane bushings
FM Springs (gen1). No sag or bumpstop-slamming issues that I've noticed.
FM Rear Shock Mounts with included bump stops
FM "Improved" 10mm front bump stops
Tokico Illuminas Set to 4 (of 5) all around
Pinch Weld Height: 5" front 4.75" rear
RB #54107 sway bar on softer setting, RB Brace kit
Stock rear sway bar
Front: -3.0 Front Camber 5.0 Front Caster Zero Toe
Rear: -2.5° Camber 0.06° Toe

Wheels/Tires
15x8 6UL +36mm offset
Yokohama AD08 205/50/15
Had to bend/mold fender liners due to rubbing under heavy cornering

Safety:
Blackbird bar, 6pt harness, halo seat

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

I'm an intermediate-level driver running DE2 with NASA. I'd say I'm one of the faster drivers in my group but I'm anywhere from 5-8 seconds off of SM race pace. Point is, I'm an OK driver in a slow/lightweight car with not much power.

My issue is that I am glazing pads nonstop. This past weekend at Summit went like this:

Thursday: Bolt on G12 pads (pre-bedded) with new rotors, perform bedding procedure for rotors per 949 instructions

Saturday: Arrive at Summit. Brakes feel amazing for first session, 2nd session I start to get some fade so I pulled the wheels to bleed the brakes... and look at the pads. SHINY.

I showed the pads to a race shop who was on-site and does build SM cars but was running vettes that weekend. He said they were DEFINITELY glazed. We discussed for a bit and decided to try an ST43 pad. I didn't have a fresh set of untouched rotors so I ran them on the rotors which I had bedded with the GLOC 12s. The brakes were PHENOMENAL. I was pushing markers and having a blast for my 3rd and 4th sessions.

Sunday: First session was pretty slow as track was around 50 degrees and tires weren't gripping. Second session was repeat from previous day.. started to get fade and pulled the pads:

I scuffed the pads on the pavement and put them back on. Went out, took a few laps for the brakes to really grip, then they were back to being great... until the end of the session when they were fading again. Pull em apart, glazed again.

Put the XP12s back on, tried again, same thing. GAH

Monday: Bought another set of new rotors and bedded them with the ST43s. Also cleaned off the 12s and took them for a spin too.

Tuesday: Back on track, this time at NJMP Lightning. Ruined the ST43s in no time.

Put the XP10s on just because... same thing.

I'm totally stumped guys. To recap:

-New Calipers
-New Lines (SS lines arriving tomorrow)
-3 diff sets of pads (G10, G12, ST43)
-Multiple set of rotors
-New MC
-Sliders move as they should
-Pistons are not seized
-Adding spreaders to the pads did not help

I'm at Watkins Glen weekend after this one and I NEED to have this sorted. I'm beyond frustrated and I've run 10 events already this year with bad brakes. Any ideas? I'm ready for some off-the-wall suggestions.

XP12:

https://i.imgur.com/xJvwiGM.jpg
https://i.imgur.com/OUJszex.jpg

ST43:

https://i.imgur.com/mXlcFGg.jpg

Rotors for ST43:

https://i.imgur.com/3ViJ1qB.jpg

ThePass

iTrader: (3)

The rotors for the ST43 look "ok" (not great but OK). The XP12 rotors were clearly overheated. Not surprised things weren't working right once you started mix-matching the pads and rotors because Carbo/G-Loc pads are very particular about the transfer layer. None of those pads look particularly "glazed" to me... they just look like they've been running really hot. You may just be exceeding the temperature ceilings of your parts. The factory rotor size can heat soak pretty bad. Do you have brake ducts? If not, I'd recommend them. May or may not be the solution but you ought to have them anyways.

Side-note... sometimes intermediate drivers put more heat into the brakes than advanced drivers. Braking HARD is one of the last things a lot of folks focus on getting better at, but when they do get around to working on that they shorten their stopping distance and thus time on the brake pedal and avg operating temp of the brakes can actually come down. Sometimes a beginner or intermediate guy will have the same brake setup as an advanced driver and can't figure out why his is overheating when it's working fine for the advanced guy. This may or may not have any relevance to you.

meBlaise

I appreciate the input. The vendor who sold me the ST43s had the same advice: Don't extend your brake zones. I spent several years on motorcycles and was taught to pick a brake marker, brake as hard as possible, then move the marker if you find yourself to be coasting after you're done on the brakes. That's how I've been treating the miata as well, so I don't think the issue is that.

Please note: Yes, I did mismatch pads/rotors but only once. Yesterday I ran ST43s with brand new rotors. Same with Saturday with the pre-bedded 12s. Only Sat Afternoon/Sun Morning had mismatched stuff, and it actually worked the best and lasted the longest.

SM guys can't run ducts. They seem to do fine and are running faster into the turns and with more aggressive tires. I'm happy to add it through if you think it will help - after all this is just DE.

At this point I've tried 3 diff sets of pads, and the R12s are rated to 1850*F. I'm struggling to think the issue is needing a 4th set of pads.

sixshooter

iTrader: (12)

Are you still using the rotor splash shields or have they been removed?

meBlaise

They're bent back/cut as I have NA8 brakes on an NA6 car.

Suggesting I remove them?

Two things I thought of last night: There's a thread from there where a guy was dealing with the same issue and it ended up being a bad booster. I've PMed him. Other thing was that I didn't adjust the rod length when I put in my new MC. So there's a possibility I could be preloading the MC?

Present plan for attack:

1) Remove MC and check rod length on booster.
2) Use IR gun to check whether the brake temps climb on a normal drive without application of brakes.
3) Possibly replace booster?

sixshooter

iTrader: (12)

You need to eliminate the splash shields and let the rotors breathe.

flier129

iTrader: (7)

+1 on removing splash shields, but I ran a whole season with them on my TTE car with R7s/XP8s on a 2400lbs car, no issues.

Do you have any pad sticking issues? Maybe you're MC rod length is too long or your pedal adjustment is way off causing the pads to drag excessively?

meBlaise

This has to be the issue. Emilio/949 is convinced there's pad retraction issues, but I'm running spreaders and the pistons and sliders both work as they should.

I'm planning on driving my street and track car back to back in the same exact conditions (no brakes used) and comparing rotor temps to see if I can verify that I have drag. IR sensor arrives today.

flier129

iTrader: (7)

Different car, but I recently had major pad sticking issues on my Z with Brembos. Car would be fine from start-up until about ~10min of regular city driving and then the pads(DTC60s) would stick/drag enough to stop the car on level ground. The calipers functioned fine, even rebuilt them with new seals. Went through half a dozen bleeds, a bunch of grease on the sliders, even bleed the master. Turns out adjusting the brake pedal fixed it. So in the same theory, modifying the rod engagement length into the MC could be the fix....maybe.

ThePass

iTrader: (3)

Fresh calipers mentioned in the first post is why I didn't suggest pad retraction or stuck caliper but that was my first thought.

DNMakinson

iTrader: (3)

Recommendations for street car? Same, or leave shields? Begs the question, what is the OEM purpose?

sixshooter

iTrader: (12)

I don't have a problem on the street. Those shields are designed for stock rotors getting hot and then you driving through a puddle and splashing cold water on them, possibly warping the rotors. I've had the shields off since 2010 and haven't warped stock or Corrado or 11.75 V8R and have done an incredibly wet track day or two.

acedeuce802

iTrader: (1)

I've witnessed a VW at the track with a failed return spring on the brake pedal causing excessive dragging. It confused their team, because out on track it was bad enough to cause excessive smoke from the pads, but by them they limped it to their paddock the pedal would return and they couldn't narrow down the issue. They eventually found out that if they used their toe to pull back on the pedal on the straights it was fine, until they got a new return spring.

I don't think your experiences are typical, so I don't think it's just undersized rotors, underspecced pads, etc. I would guess it's something unexpected going on, like a master that's sticking, pedal sticking, caliper not returning, etc. Unfortunately I don't have much help to give on narrowing it down.

engineered2win

Are you running the stock brake pad shims/backing plates?

I run G-Loc R10's in the front with NB Sport brakes and a new set of pads will not fully release with the shims installed.
I've found the R10's overkill and had to block off my Singular brake ducts to keep the temps up. Never had a single issue with my setup and a regular RBF600 flush before an event. My NB1 is similar weight (2475lbs w/ driver) and is making an extra 25hp. I can get a whole season of NASA HPDE on a set of pads.

Also what do you mean by fade? Does the pedal get mushy or does the car just not want to stop?

cabowabo

Something is definitely amiss, sticking pads or otherwise. I run XP8's/Centric blanks (NA8) all around on RC1's at ~2400lbs/124whp and splash shields still in place. Typically about 1 second off NASA SM pole for reference and haven't managed to get a hint of fade from that setup all season. Removing splash shields might help, but that's clearly not the root cause.

meBlaise

^ Agreed.

SS lines and IR gauge showed up last night. I work tomorrow but on Sunday the plan is as follows:

1. Drive street NA8 and track car back to back in same conditions with minimal brake use and compare rotor temps. I'm expecting this to show a significant difference and the track car rotor temps to climb without brake usage.
2. Remove MC and check for booster rod/MC length match.
3. Install SS lines all around, bleed entire system (obviously). Adjust rears. I can cut the splash shields up front too.
4. Drive car around again, use IR gauge to compare setup again.
5. If no help there, install new brake booster.
6. If that doesn't help, light car on fire.

Sound good? I guess at that point I'll also consider swapping spindles too.

Steve Dallas

You left out ducts. Brake ducts should be near the top of your list.

meBlaise

Why? Nobody else at my power/weight/tire level needs them. Spec Miata guys certainly seem to do fine....there's another problem to solve here.

Not trying to bandaid a bigger problem.

sixshooter

iTrader: (12)

Spec Miatas don't use splash shields.

meBlaise

And I will remove them. But the splash shields aren't the cause for me overheating pad after pad with my slow lap times.