Brakes

[MoonieGT]

What's a suitable brake setup for a '99 with ~140whp and a full interior? I think I have a leaky caliper, so I am either going to need a stock replacement or an upgrade. The research I have done says that stock brakes are good enough for spec miata so they're good enough for me. Is that the end if the story or should I consider TDR's big brake kit or the wilwood setup? My gut says the wilwood is overkill. Feedback appreciated.

[MoonieGT]

Oh, and I do track the car if that was not obvious.

[EricJ]

I run NAPA Rotors, stock calipers, HPS/HP+ F/R, Valvoline DOT 3-4, stainless steel wrapped lines.
I'm on my last set of HPS for the front and will be moving to HP+. (Rear lockup on track is more dangerous than front lockup autocrossing).

One of the guys on the 318ti board did a study of upgrading brakes. 318ti's have un-vented rotors up front. He found that adding bigger front brakes actually increased the stopping distance because it un-balanced the proportions, causing the fronts to lock before the rears were fully utilized.

I have more brake than tire and don't get any fade in 25 minute sessions at ECR, but I'm a newbie so may not be hard enough on the brakes.

[MoonieGT]

I have Napa rotors with HP+ now. I have not had fade in the past, but I have stickier tires and better suspension now. I was thinking the extra thermal capacity of larger rotors would be a good thing. I may go with the larger "sport brake" setup. I dont think I can justify or afford Wilwoods :)

[black roadster]

The Wilwood BBK is overkill for most. Unless you are FI and or exceeding the limits of the stock brakes, they're plenty good for most people. Get good pads (HP+ or the DTC line), some Motul brake fluid and call it good.

Some nice things about the Wilwood BBK is pad changing is easier and the brake pads are almost half the cost of stock caliper brake pads.

[gabkwong]

Up grade your wheels/tires will drop your stopping distance and eliminate some of the famous Miata locking up the front right corner too. There is good info on this in the Goodwin Racing web site. Last thing you want to run a 15 x 7 wheels with the 225 tires.

[SirHustlerEsq]

Do you have puddles of brake fluid in the wheels?
Describe the problem, please.

[MoonieGT]

The problem is the pedal goes soft with even moderate heat in the brakes. Pedal went to the floor during lead follow at the toy run. I assume air is getting in the system somewhere. The fluid level in the reservoir seems stable. During normal driving on the street I can push the pedal hard and it will slowly drop and get softer. So there has to be a leak somewhere ya?

I'm signed up for COTA on Jan 12 so the car is going to TDR because I don't have time to diagnose myself before then. I think I'm going to just repair the OEM system and perhaps up the front pads to DTC30 and keep the HP+ rear.

[EricJ]

I can push the pedal hard and it will slowly drop and get softer. So there has to be a leak somewhere ya? fluid level in the reservoir seems stable.

The Master Cylinder. If it were leaking at the calipers the fluid level would drop.
It's leaking around the seal in the master cylinder, back into the reservoir.

[SirHustlerEsq]

Do this:
1. Drive the car in a straight line, brake hard.
2. Drive the car and cut left-right like you're warming up the tires (which doesn't really warm them up) then press the pedal.
3. Repeat.

Tell me what happens.

BTW, I have a spare master because I've been down this road before.

[SirHustlerEsq]

BTW, DTC-30 is a dirt-track pad. You wan't 60s.

[ken o]

Do this:
2. Drive the car and cut left-right like you're warming up the tires (which doesn't really warm them up)...

If not, why are my tires hot after an autocross run?

[MoonieGT]

Do this:
1. Drive the car in a straight line, brake hard.
2. Drive the car and cut left-right like you're warming up the tires (which doesn't really warm them up) then press the pedal.
3. Repeat.

Tell me what happens.

BTW, I have a spare master because I've been down this road before.

I'll give this a shot this weekend

[SirHustlerEsq]

brakes.

[MoonieGT]

Doesnt a lot of heat come from sidewall flex?

[MoonieGT]

Just tried your braking drill. Can't say I noticed anything...

[SirHustlerEsq]

Does the pedal require more travel to engage after weaving?

[MoonieGT]

Nothing that I noticed. So that rules out knock back barring me being oblivious to extra pedal travel?

[SirHustlerEsq]

Nothing that I noticed. So that rules out knock back barring me being oblivious to extra pedal travel?

yes.

[EricJ]

The Bentley BMW 3 Series '92-'98 manual has to good set of diagnostics for brakes:
1. Air = spongy pedal, increased pedal force required to stop
2. Master Cylinder
-- Hold pedal down hard with engine running
-- should be solid and stay solid
-- if pedal slowly falls to the floor either
---- master cylinder is leaking internally or
---- fluid is leaking externally
---- look for leaks, if non-found its the master cylinder
3. Booster
-- engine off - pump pedal 10 times and hold
-- start engine, pedal should fall slightly
-- if so, check vacuum at vacuum hose and one-way return valve (do Miata's have a one-way return valve?)

What is knock back?