Printable View
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.
Oh, and I do track the car if that was not obvious.
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.
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 :)
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.
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.
Do you have puddles of brake fluid in the wheels?
Describe the problem, please.
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.
The Master Cylinder. If it were leaking at the calipers the fluid level would drop.Quote:
Originally Posted by MoonieGT
It's leaking around the seal in the master cylinder, back into the reservoir.
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.
BTW, DTC-30 is a dirt-track pad. You wan't 60s.
If not, why are my tires hot after an autocross run?Quote:
Originally Posted by SirHustlerEsq
I'll give this a shot this weekendQuote:
Originally Posted by SirHustlerEsq
brakes.
Doesnt a lot of heat come from sidewall flex?
Just tried your braking drill. Can't say I noticed anything...
Does the pedal require more travel to engage after weaving?
Nothing that I noticed. So that rules out knock back barring me being oblivious to extra pedal travel?
yes.Quote:
Originally Posted by MoonieGT
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?
I only vaguely understand knockback. The basic idea is that some combination of the rotor, hub, disc bend a bit while under cornering load. This movement pushes the pad/piston back a bit. Then next time you go for the pedal, the piston has farther to travel so you get a softer/longer pedal for the next application of the brake.
Worn-out bearing races let the rotor flop around, pushing the pistons into the calipers.Quote:
Originally Posted by MoonieGT
While originally designed for dirt-track, both the DTC-30 and DTC-60 are great track pads. (DTC = Dirt Track Circuit IIRC) The big difference it the temp range scales up for the DTC-60. The DTC-30 are temperature rated from 100° - 1200°F The DTC-60 are temperature rated from 400° - 1600°F. Hawk doesn't make the DTC-60 if you have Sport brakes. The DTC-30 are a great compromise and more street friendly.Quote:
Originally Posted by SirHustlerEsq
Nice try.Quote:
Originally Posted by black roadster
Dynamic Torque Control
Well I got the other parts right! ;)Quote:
Originally Posted by slowchildmiata
http://www.isitlowt.com/Quote:
Originally Posted by black roadster
Yes, you got the 30 and 60 right ;). I actually used to think it meant Dirt Track Compound once upon a time... :)
i havent had the problem with my miata, but on my boss 302 i had hell with the brakes. the first time out i over heated the fluid, went to wilwood dot 4 and the next time out i was running HP+ pads and over heated the pads. moved to a better pad (RP2 XP8 combo) and had problems with the fluid again, next time i used better dot 4 fluid and finally cleared it up. if the brakes go soft and come back at all it cant be air. once air is in there it wont leave until you bleed the brakes.
if you over heat the pads, the pedal will come back unless you overheat the pads to the point that they crumble. i have seen that happen to several people at ECR. Not all dot 4 fluids are equal either, i had problems with a couple brands and then moved to brembo lcf 600+. its about $20 per 500ml, but it wont fade and doesn't compress when hot.
i had a problem with some wilwood dot 4 fluid where the brakes didn't fade (had the same stopping power), but the distance where the pedal engaged the brakes would change because the fluid compressed more when hot. i get the impression that your brakes came back at least a bit between the fade, is that correct? if so id say you were overheating the pads. i can tell you from experience if you are moving at ECr, HP+ and HPS pads aren't ideal. you probably don't even need to be moving all that fast in heavy traffic like you had at ECR if you have poor ventilation to the brakes to begin with. do you have any brake cooling?
while we are talking about brake issues, is there any cooling benefit to be had from cutting the dust shields off the rear brakes on these cars?
Master cylinder was the culprit. I'm sure half of you will yell at me, but I went with DTC30's. I didnt get the 60's for two reasons: 1) I want the pads to work on the street, and 2) I have only just begun to overheat the HP+, the 30's give me an extra 3-400 degrees of temperature range. Should be good until my skill goes up. Maybe I'll get 60's next time...
I am very happy with the Sport breaks that Track Dog (you)installed on my NA. I am currently running HP+ all around and have plenty of break for my car.Quote:
Originally Posted by black roadster