spongy brake feel and long brake pedal travel
#16
Rennlist Member
I don't know if this will help you, but I had the same problem after doing a DE event. Before the event, my brakes were solid and I flushed the fluid with ATE Blue. Still solid. After and during the DE, I found that the brakes had quite a bit more travel than before. Even after cooling, the pedal wasn't as firm as before.
I talked to my mechanic and he said that it's probably not the fluid and most likely the pads. I'm still curious to find out what caused it.
I talked to my mechanic and he said that it's probably not the fluid and most likely the pads. I'm still curious to find out what caused it.
#17
Instructor
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Join Date: Mar 2006
Location: Hattiesburg, MS
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Just an update to put my thread to rest and maybe help someone who has this problem...
The issue was air in the lines. We ended up bleeding the brakes 4 times to get all the air out. We would bleed and then let it sit for a little while, then re-bleed. Multiple bleedings finally firmed up the brake pedal. Hope that helps someone.
The issue was air in the lines. We ended up bleeding the brakes 4 times to get all the air out. We would bleed and then let it sit for a little while, then re-bleed. Multiple bleedings finally firmed up the brake pedal. Hope that helps someone.
#18
Rennlist Member
Originally Posted by murphyslaw1978
I don't know if this will help you, but I had the same problem after doing a DE event. Before the event, my brakes were solid and I flushed the fluid with ATE Blue. Still solid. After and during the DE, I found that the brakes had quite a bit more travel than before. Even after cooling, the pedal wasn't as firm as before.
I talked to my mechanic and he said that it's probably not the fluid and most likely the pads. I'm still curious to find out what caused it.
I talked to my mechanic and he said that it's probably not the fluid and most likely the pads. I'm still curious to find out what caused it.
That is why it is standard procedure on a track car (race car) to bleed brakes after EVERY session.
#19
Rennlist Member
Originally Posted by GUMBALL
It is not unusual for the pedal to get soft after a track session - sometimes the brakes get hotter than you think. The solution....bleed the brakes. Usually, all it takes is a few pumps - just enough to get fresh fluid into each caliper......and, without a power bleeder, bleed a front and a rear at the same time.....
That is why it is standard procedure on a track car (race car) to bleed brakes after EVERY session.
That is why it is standard procedure on a track car (race car) to bleed brakes after EVERY session.
#20
Rennlist Member
Originally Posted by murphyslaw1978
......the brakes still get hot enough to cause gases to escape (if not boil) to some degree. Is this the reason? BTW, I was running stock pads, so that can contribute to the increased heat.
Semi-competition (or full comp.) pads provide a higher friction coefficient. This permits the car to brake "harder", reducing the time on the brakes, which in turn, reduces the amount of heat generated..
Also, as an instructor, I have noticed that many drivers at track events do not use the brakes correctly or efficiently. The tendency is to brake early, not very hard, and stay on them too long.
A fast race driver will brake at the last inch, use the brakes VERY hard, and then quickly get off them. It may not seem that way, but this method does create less heat.
Last edited by GUMBALL; 05-24-2007 at 07:09 AM.
#21
Rennlist Member
Originally Posted by GUMBALL
Heat will cause microscopic bubbles to form in the fluid, and that is all it takes.
Semi-competition (or full comp.) pads provide a higher friction coefficient. This permits the car to brake "harder", reducing the time on the brakes, which in turn, reduces the amount of heat generated..
Also, as an instructor, I have noticed that many drivers at track events do not use the brakes correctly or efficiently. The tendency is to brake early, not very hard, and stay on them too long.
A fast race driver will brake at the last inch, use the brakes VERY hard, and then quickly get off them. It may not seem that way, but this method does create less heat.
Semi-competition (or full comp.) pads provide a higher friction coefficient. This permits the car to brake "harder", reducing the time on the brakes, which in turn, reduces the amount of heat generated..
Also, as an instructor, I have noticed that many drivers at track events do not use the brakes correctly or efficiently. The tendency is to brake early, not very hard, and stay on them too long.
A fast race driver will brake at the last inch, use the brakes VERY hard, and then quickly get off them. It may not seem that way, but this method does create less heat.
#22
Originally Posted by GUMBALL
Heat will cause microscopic bubbles to form in the fluid, and that is all it takes.
Semi-competition (or full comp.) pads provide a higher friction coefficient. This permits the car to brake "harder", reducing the time on the brakes, which in turn, reduces the amount of heat generated..
Also, as an instructor, I have noticed that many drivers at track events do not use the brakes correctly or efficiently. The tendency is to brake early, not very hard, and stay on them too long.
A fast race driver will brake at the last inch, use the brakes VERY hard, and then quickly get off them. It may not seem that way, but this method does create less heat.
Semi-competition (or full comp.) pads provide a higher friction coefficient. This permits the car to brake "harder", reducing the time on the brakes, which in turn, reduces the amount of heat generated..
Also, as an instructor, I have noticed that many drivers at track events do not use the brakes correctly or efficiently. The tendency is to brake early, not very hard, and stay on them too long.
A fast race driver will brake at the last inch, use the brakes VERY hard, and then quickly get off them. It may not seem that way, but this method does create less heat.
#23
Rennlist Member
By a4sfed:...I disagree with this statement a braking system converts the energy of the moving vehicle (speed) into heat. If the same speed is removed from the vehicle then the same area under the temperature plot should be observed in the braking system.
#24
Rennlist Member
Originally Posted by GUMBALL
Heat will cause microscopic bubbles to form in the fluid, and that is all it takes.
Semi-competition (or full comp.) pads provide a higher friction coefficient. This permits the car to brake "harder", reducing the time on the brakes, which in turn, reduces the amount of heat generated..
Also, as an instructor, I have noticed that many drivers at track events do not use the brakes correctly or efficiently. The tendency is to brake early, not very hard, and stay on them too long.
A fast race driver will brake at the last inch, use the brakes VERY hard, and then quickly get off them. It may not seem that way, but this method does create less heat.
Semi-competition (or full comp.) pads provide a higher friction coefficient. This permits the car to brake "harder", reducing the time on the brakes, which in turn, reduces the amount of heat generated..
Also, as an instructor, I have noticed that many drivers at track events do not use the brakes correctly or efficiently. The tendency is to brake early, not very hard, and stay on them too long.
A fast race driver will brake at the last inch, use the brakes VERY hard, and then quickly get off them. It may not seem that way, but this method does create less heat.
So let's say you have a car with 200 horsepower vs 400 horsepower. The 400 horsepower will accelerate faster. The same can be said of brakes. Most brakes on a Porsche far exceed the engine, so to bring a car from 100-0 in 10 seconds might consume 500 horsepower vs 100-0 in 7 seconds might take 1000 horsepower.
So if stopping a car faster requires more horsepower, then how can that generate less heat on the braking system?
#25
Rennlist Member
It isn't the amount of energy produced to slow the car that creates the problem. It is the amount of heat transferred to the fluid. The longer the pads and rotor are in contact the more heat is transferred through the caliper to the fluid. Dragging your breaks for a few blocks will heat things up much more than one panic stop.
#26
Rennlist Member
Originally Posted by Charley B
It isn't the amount of energy produced to slow the car that creates the problem. It is the amount of heat transferred to the fluid. The longer the pads and rotor are in contact the more heat is transferred through the caliper to the fluid. Dragging your breaks for a few blocks will heat things up much more than one panic stop.
#27
Scott
If you pump the petal all the way to the floor trying to bleed the system you can trap air in the system. That was happening to me. I purchased a power bleeder pumped it up to 5lbs and flushed the system. Breaks are working good now.
If you pump the petal all the way to the floor trying to bleed the system you can trap air in the system. That was happening to me. I purchased a power bleeder pumped it up to 5lbs and flushed the system. Breaks are working good now.
#28
Rennlist Member
Originally Posted by Charley B
It isn't the amount of energy produced to slow the car that creates the problem. It is the amount of heat transferred to the fluid. The longer the pads and rotor are in contact the more heat is transferred through the caliper to the fluid. Dragging your breaks for a few blocks will heat things up much more than one panic stop.
Precisely. Thank-you.