Won't stop over 110 mph!
 

I have finally sorted out a 1995 FMII turbo Miata that I drove at Road Atlanta this weekend. The car is seriously fast and handles great but any attempt to stop at speeds over 110 mph results in a firm pedal but no stop! I'm running Carbotech pads which worked great before the car was turbocharged.

Before I dump a bunch of cash on a big brake kits do any of you have some suggestions.

Thanks

George S.

Um, WAT?

Did you drive it to the track and did it stop on the way home? What Carbotech pads are you using now? ABS? Bone stock? Prop valve? What fluid are you using? Thermal shielding on the master cylinder and brake line? Heat shield for the turbo? GIVE MORE DATAS!

I'm guessing you cooked the hell out of your master cylinder and brake lines with all the fresh heat the downpipe is dumping into the engine compartment.

It stops fine at any speed under 110 mph, street or track.

Carbotech XP10 Front Brake Pads and Carbotech XP8 Rear Brake Pads.

No ABS.

SS brake lines, stock rotors and calipers.

No proportioning valve (stock).

ATE Super Blue Racing Brake Fluid.

Heat shield on turbo and air intake only.

My diagnosis is the brake pads and rotors are over heating.

Firm pedal is either overheated pads or positive pressure in the brake booster. If you're on XP8/10/12s, make sure you still have a working check valve in the hose from the brake booster to the intake manifold (the OEM hose has one, if you didn't change it). If you're on 1521s, you need a pad upgrade.

To be honest, if you continue to do track days with a turbo system, you need a Wilwood-based BBK. Stock brakes are not adequate, regardless of pads or ducting.

I thought that a big brake kit would be needed. I don't have any ducting and still have the back plates in place but if I have to spend another $450 for new Carbotech pads and rotors I guess I should just bite the bullet and install ducting to a big brake kit.

The Version 4 BBK offered by Good-Win Racing looks real solid. It appears to offer more features than what Flyin Miata offers at a lower price.

Any thoughts here.

I'm biased, but if you can fit it under your wheels, there's no better option than my 11.75" kit. Low rotor costs and excellent pedal feel. Combine it with OEM Sport rear brakes.

Trackspeed Engineering 11.75" BBK

I don't track, but I have the TSE BBK and sport rears and it's the most amazing pedal feel in the world. Absolutely glorious.

In for replacing check valve. I'm guessing the sustained boost getting up to 110 is getting past a leaky valve.

Great call on the potential leaking check valve. Braking hard after a short straight I would get a hard pedal with little braking force and then suddenly a lock up. I guess the lock up was occurring after the master cylinder was finally seeing some vacuum from the manifold off boost.

I'll track down a replacement check valve and spring for some big brakes.

Thanks folks.

I can say that, if budget is not a major hindrance, the full TSE BBPK* (Big Boy Pants Kit) is pretty stellar. I finally got to run mine recently and the pedal feel, consistency, and stopping power are silly.

Full disclosure: I have never driven another Miata with another BBK, so I can't comment on relative performance.


* TSE 11.75" front brake kit, TSE ducting, M-Tuned rear adaptors, Sport rear rotors, Hawk DTC-60 pads

I'd put Wilwoods in the rear as well, Flyin' Miata has a kit that would go well with the TSE front setup.

I just got through installing the 11" front from 949 and the 10" rear from FM, but my car will always remain NA, and the lowest weight was the priority.

I'm running something similar to the 949 Wilwood 11" kit w/TSE ducting and non-sport rears and non sport master/booster/prop. So far, its all kinds of win.

It's been said many times: 11.75" TSE Kit w/prop valve + M-Tuned/Sport Rear Rotor + Sport booster & Master + ducts = bestest brakes.

I've got the M-Tuned brackets and sport booster/master in the garage should I need to upgrade beyond my current setup.

^If you're getting serious, I'd go with Wilwoods in the rear too. This is what I put on the rear, but with Carbotechs.

Flyin' Miata : Chassis : Big brake kits : Flyin` Miata four piston rear brake upgrade - track

TSE was supposed to have something for the rears awhile ago, but I couldn't wait any longer.

Quite honestly, the FM Wilwood rear seems like overkill, plus expensive. There are a lot of guys running the M-Tuned/Sport rears without issue so I tend to stick with and recommend what has been proven to work. I mean, maybe it'll let you get away with changing pads/rotors once a year or something for the average HPDE enthusiast but ROI on that seems excessive. Seems to me that $500 would be better spent on time behind the wheel.

Hell, maybe I'm wrong and its the best thing evar. FM does tend to put out a solid product so I wouldn't expect them to slack on something like this. :dunno:

The FM rears seem best suited for guys with dual purpose cars that want quick pad changes at the track and a working parking brake Monday through Friday. Of course Wilwood peeking out behind all 4 corners makes some good bling for folks that can't let their laptimes do the talking.

I will own up to being slow. I figured if I was taking +2 on brakes, might as well go as light as possible.

Excellent point. If you are taking points for brakes, you might as well do anything/everything allowed since most CCRs are '+x for non-OEM brakes'. The weight savings is significant.

There is a non-parking brake version of the FM rears. $100 cheaper too.

Yeah but then you have to come up with your own solution for a parking brake, like the JR dragster calipers and connecting another hydro master to the stock ebrake cable, or using some mechanical caliper. Too much work, press the easy button. Unless your car doesnt go on the street and isnt required by the rules to have a redundant braking system (I don't see why kind of psychopathic, uninsurable rules would let you do that).

I went for the non-parking brake route.

I think Keith mentioned the parking brake is basically there for rules compliance (SCCA) and will hold the car on a slight incline.