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Author Topic:   fading brakes
leftturn73
Member
posted May 06, 2002 07:29 PM
Help I can't stop!!!
I am experiencing brake fade then back from the start, middle to end of race. I run the large GM brakes with Wildwood pedals and Afco master cylinders. New to this car I have been having problems with the bakes just completely going away then returning???
I just put two new master cylinders on 1" front 7/8" rear all calipers move freely with Hawk (black) pads, still have problem.
I have blead the brakes completely over and over. Pedal assembly is hanging type. All flex lines look fine. In the pit/garage pedal is fine. I even wedged a rod on the pedal in garage for 3 hours straight and no fade. All the rotors are true. I am at the end of my rope.
Any thoughts would be welcome.


jammin
Administrator
posted May 06, 2002 07:40 PM
What kind of brake fluid you using?

It sounds like your fluid might be boiling and then when it gets to a boil, you dont have enough friction to keep the temp up on the brakes, so it cools off and you have brakes again. Just a needle in the haystack, but might be worth a try to use some different brake fluid.

jammin

[This message has been edited by jammin (edited May 06, 2002).]

dirtracer14
Member
posted May 06, 2002 08:33 PM
I can give you some things that we had probs with. You say that the rotors are true? but are the bearings loose if they wobble then it pushes the piston in then when you hit it the first pump just gets it out and not much pressure applied the other is the brake brackets in the rear are the straight or off just a bit? We had probs with both of these the easy way we found the rear problem was put rear end on jack stands and put it in gear let it spin some and try the brakes? Just a few things to ponder.


leftturn73
Member
posted May 06, 2002 10:36 PM
Thanks for the reply,
I am using Wildwood 570 fluid. I do have one brake line that I am going to reroute it is 2.5" from the left header. Not sure if this is a problem but easy to fix. I checked the bearings all ok. The idea of the back brackets I'll have to check this.

Thanks again

Greggie
Member
posted May 07, 2002 12:40 PM
The other question to ask is when your brakes fade, do you get loose or does the car push or is it a total fade? If you are getting loose, then I would have to say that your line close to the header is definitely a problem.

Me

leftturn73
Member
posted May 07, 2002 10:03 PM
When I say fade I should have said pedal almost to the floor. I am starting to lean toward the fluid boiling because as I've thought about it the more I push the car (increased RPM) the more I loose the pedal. If because of trafic I have a slow lap or out of the gas the pedal is better. Possible less temp, although I didn't think the temp would fluxtuate that much.
Thanks again for any thought any one may have.


Dirt2race
Member
posted May 11, 2002 10:36 AM
What type of chassis are you running? If you have your right rear caliper too close to the spring, it can cause this and it takes forever to figure out. Look at your caliper and spring to see if they are making contact. What happens is the spring compresses and swells out. It in turn pushes the caliper in and the fluid is forced out of the line. When you go to the brake pedal, there is none. I lost a brand new chassis due this exact problem. Harris 4 links are the worst for this if you mount your spring in the inside of your mount. That is why the harder you run the car, the worse it gets, you are commpressing the spring farther, thus pushing the caliper in farther. When this happens, you will have nothing for a pedal. This is a very dangerous situation because you will have absolutly no brakes. The first person that suggested this to me, I thought he had flipped his wig, but what he told me was exactly right. I hope this helps.

[This message has been edited by Dirt2race (edited May 11, 2002).]

Racer111
Member
posted May 11, 2002 02:21 PM
You should have a pair of 7/8 M/C on it not 2 different sizes.Your main problem sounds like fluid.I run Motul and never have a problem.Also what size of lines are you using ?

[This message has been edited by Racer111 (edited May 11, 2002).]

kong
Member
posted May 13, 2002 12:05 PM
Thanks all for responding. I ended up verifying free movement with all calipers then installed new pads even though the Hawk pads on the car were like new. I then relocated the brake line which was a little close to the header??? This past week end the brakes did not fade one bit. My guess the solution was the brake line. I made up for the last couple weeks of brake problems. I won by lapping all but 2 guys and won by a 1/2 lap. Got to love them brakes. Again thanks for all the responses.
See you at the races.


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