cooked IT7 brakes

I

IT7DRIVER

New member
Hey fellow IT er's,
about 1/2 thru pro IT at road atlanta last saturday during some hard racing (ok, it was back in 30-35 place, but it was fun), the brake pedal faded to the floor. 1st, I could pump it back up but that soon went away. After a few slower laps they came back, so then I ran off the track & broke the exhaust. There are 2 large hoses going to each rotor from the air dam so there is plenty of air getting to them. How can the fast guys not cook the brakes. The pads aren't burned up & the rotors are ok. They have not gone away this bad during ECR's at roebling or lowes this year & we finished 5th.
What are the tricks to keep 'em working for the whole race? Driving? Trick equipment? Line insulators?
thanks for your help
IT7DRIVER
#66
Andy
Phil
Doug
 
Tell us about your pad make and type, fluid make and type and last flush date, and the duct inlet and outlet location....
 
Sure sounds like you are boiling fluid. Is one of those two hoses pointed at the caliper?
Are you running the big tin shims between pad and caliper? New ones give slightly better feel, but old ones insulate better
Are the caliper seals new? The seal and boot have a role in retracting the pad when pressure is released. Fresh seals also allow less air to seep past them while the brakes cool.
I'm assuming that the fluid is fresh and that you bleed the system before each session.
 
Thanks for replying,
the hoses exit right against the inside of the rotors towards the front of the car & are hung on a bracket on the caliper or strut. So the hoses are against the rotor regardless of wheel position. The air comes in thru large ducts in the air dam below the bumper in line w/ the headlights. The pads are "black" Hawks front & blue rear. The fluid is Motul, I think rated to 500 deg. It is changed regularly. Seals are old I'm sure. This car has always had a soft pedal. Also, I don't think I've ever locked the tires up, even in wreck avoidance maneuvers. Are the rx7 brakes strong enough to lock 'em easy or does it take a lot of pressure, or do we have some adjustments to make? The car stops evenly & front pad wear is 3x's rear wear. It makes for easier driving sometimes when you can outbrake someone w/out the wheels locking. Any ideas?
Thanks for the help.
andy
doug
phil
 
IMHO...it sounds like your boiling the fluid. I use AP 600. The only other fluid I have used in the past that is better is SRF, and its TOOOOOO EXPENSIVE and there isn't really that much of a difference between it and the AP 600 in an IT car. I have had the same experience using other fluids....fluid gets hot...brakes become mushy...

I run (don't take my advice on rotors...I KILL THEM <GRIN>)...Hawk Blues all the way around, and AP 600. ALSO...do you have stainless lines on your car? If you don't, you should make the conversion...its a must.

Again..ALL IMHO.



------------------
Balz
#67 IT-7
www.balz.myip.org
"I live my life one Apex (seal) at a time"
 
I am running Wildwood High Temp fluid, and bleed it right out after a couple of weekends. I run Hawk Blues on the front, no brake ducts at all, and the cheapest Napa pads I can get on the back. All backing plates, and plastic junk is removed. Also a proportioning system, to further reduce back braking. Before the proportioning system, my back brakes would lock up under heavy braking at 125+ mph, and make things really interesting. The back end would start bouncing, and....well you know...need clean underwear.

The brakes seem to work OK, no failures, but I go thru rotors pretty quickly.( In our series here in Calgary, we run stock rotors ) A weekend of racing is about 350 miles all-in, and the front pads last about 3-4 weekends. The rears last a lot longer.
 
I probably run an RX7 about as hard as you can and I have found that one little device does more good than any. Put a screen with atleast 1/8 inch holes over your brake duct inlet. What happens during a long race is that the finns in your rotor get clogged with rubber. I use just regular high temp fluid from Pennzoil (not expensive) and Hawk Blue pads. Then work on your braking habits and try to shorten your braking zones. The biggest mistake I see alot of drivers do is that they brake and then turn. You should try to brake up until the point where you can begin to accelerate. This way you can carry alot more speed into a corner.Braking while you turn takes less braking than braking in a straight line because the car will have a load put on it by the change of direction and that will aid you in your quest to save brakes.

#99IT7..Rick Thompson
 
Hey Ricky, you're right on the money on shortening up brake distances. Brake harder for less time reduces the heat build-up. Hawk Blue all the way around with SS brake lines. One brake hose to the rotor on each side and one hose to the caliper on each side. Work hard on your braking points and don't go over your head. Also you may want to rebuild your front calipers and make sure there is no build up on the piston that would cause the brakes to not release. NOW, Ricky, we have to talk, I am looking forward to seeing you at the SIC. You need to get down in Central Fla. and play soon. Call me.
813-927-9011
 
There is a screen, but the grid is not that small. I was braking @ about 150' at turn 10a ? in Atlanta. I believe I could have gone closer to 100, but I thought I was being easier on the brakes, Guess not. No rear axle bounce in atla. I know I was leaving plenty of time out there. Sat. was my 1st time to see road atl & I missed a practice. I ran some 1: 53's in the pro it. Much slower than ya'll up front. Consistent 1:27-28 @ Roebling before w/out the brakes going.
Braking at 2 for turn 1 @ Roebling, the rear has bounced on a few different laps, sent me backwards thru the grass once, that's a hairy ride. Rick, on braking & turning. The car is real light on the rear under braking, so you must get back in the gas to get it to hook & complete the turn w/ out going around. Definitely the hardest part about driving this car. A lot of flat-tracking if your not back on the gas quick enough. We have to finish braking before turning too much. It wasn't that bad before the tri-link. Will changing shock settings help to eliminate that much weight transfer & calm the back under braking? I like doing the short braking, fun to pass that way, but if you spin in the corner you haven't gained anything.
Any Ideas on the soft pedal?
So 1st thing to do is make sure the pads are retracting. Clean the rotor vents. Change to blues on the front. Redirect a hose to the caliper. Get SS lines.
Shorter brake distances w/out spinning out!
Sorry about the long post.
Our few races, we have finished mid-pack & I want to do better.
Again, I appreciate the suggestions.
thanks
doug
terry
andy
phil
molly
& crazy abby.
 
I can tell you a few things that will help you but only enough to keep you out of trouble. First...You need to run a heavier spring in the front. Second...Put a shock on the back (and front)that dampens only on rebound. High dollar shocks only waste money. Monroe Gas shocks suit me best. And believe me I've tried them all. I like for my car to pull itself down to the track under braking. I use spring rate (not shocks) to acomplish how fast the car makes the transition. The heavier the spring the slower the transition. Dampening the spring on rebound makes it compress the springs on the other end of the car. This helps to lower your roll center. I could go on and on about this but this will give you an idea of what you are looking for. Have fun.

#99 IT7...Rick Thompson
 
Just reading this thread to find advice on how to add ducting to my 1st gen RX-7......

A question or two for those who have done it.....

well...nevermind, I just got my rulebook back and read through it and it's all very clear now......thanks anyway!

------------------
Jake Gulick
ITA 57 RX-7
New England Region
[email protected]

[This message has been edited by lateapex911 (edited September 03, 2002).]
 
I would agree with the other posts - sounds like boiling fluid, but that is only a symptom of other problems. A seal problem usually also shows itself with fluid loss. To be safe, rebuild the calipers, use SS lines. You might also rebuild / replace the master cylinder. I use Motul 600, Hawk Blues all around, and a brake bias adjuster. Use a screen over the air ducts and don't be too conservative on your braking points - the longer you brake, the shorter the time for cool air to get to your rotors.
 
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