What's causing chattering front brakes?
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 5,331
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What's causing chattering front brakes?
the front brakes are fine under light braking but under heavy braking there is major thumping coming from them. It sounds like you have majorly flat spotted the front tires when you are moderate to hard on the brakes.
I put new rotors on thinking the stock rotors were wrapped but that was not the problem.
It's a 94 LT1 BTW.
I put new rotors on thinking the stock rotors were wrapped but that was not the problem.
It's a 94 LT1 BTW.
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
What else have you done?
Checked wheel bearings, ball joints or other suspension components?
Is the pedal feeding back the thump, or is noise just coming from the front end?
Checked wheel bearings, ball joints or other suspension components?
Is the pedal feeding back the thump, or is noise just coming from the front end?
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 5,331
Likes: 39
Originally Posted by JrRifleCoach
What else have you done?
Checked wheel bearings, ball joints or other suspension components?
Is the pedal feeding back the thump, or is noise just coming from the front end?
Checked wheel bearings, ball joints or other suspension components?
Is the pedal feeding back the thump, or is noise just coming from the front end?
I haven't done anything but the rotors, the pads were too good to change so I left them. I did just change the optispark and the water pump but this was doing this before.
everything on the car is factory (except for wear items) it only has 45k miles on it.
Burning Brakes
Joined: Dec 2003
Posts: 770
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From: Madison Mississippi
Thumping makes me think it is part of a rotating assembly and since it only occurs when you brake I am leaning towards the rotor. What side of the car is it comming from? Have you turned the rotors recently or got them very hot lately? Also, are you familiar with the brake anti-rattle clips? Nice garage BTW 
Thread Starter
Le Mans Master
Joined: Apr 2001
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Originally Posted by RUBYREDVETTECARD
Thumping makes me think it is part of a rotating assembly and since it only occurs when you brake I am leaning towards the rotor. What side of the car is it comming from? Have you turned the rotors recently or got them very hot lately? Also, are you familiar with the brake anti-rattle clips? Nice garage BTW
I thought it was the rotors too, but I replaced them and still have the issue. pads were too good to replace and the clips were on the pads...i didn't mess with them
Burning Brakes
Joined: Dec 2003
Posts: 770
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From: Madison Mississippi
Well, if you are sure it's not the rotors or loose anti-rattle clips then try this: Jack the car up and spin the front tire as fast as you can. Then, run the palm of your hand over the flat part of the tread and work lightly towards the edge of the tread... try not to stop the tire from spinning. If you have a flat spot in your tire, it will show up as an intermittant rub on your hand. Try it several times on both front tires. Your problem most likely will show up. One other thing, look at the brake pins and cir-clips If your pins have NOT been changed, they are most likely worn on the inside and will allow play in the caliper. They should look like straight bolts, worn ones will be dished out looking. Let me know what you find.
One other thing, look at the brake pins and cir-clips If your pins have NOT been changed, they are most likely worn on the inside and will allow play in the caliper. They should look like straight bolts, worn ones will be dished out looking. Let me know what you find.
Last edited by RUBYREDVETTECARD; Sep 24, 2005 at 01:18 PM.
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Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 5,331
Likes: 39
Originally Posted by RUBYREDVETTECARD
Well, if you are sure it's not the rotors or loose anti-rattle clips then try this: Jack the car up and spin the front tire as fast as you can. Then, run the palm of your hand over the flat part of the tread and work lightly towards the edge of the tread... try not to stop the tire from spinning. If you have a flat spot in your tire, it will show up as an intermittant rub on your hand. Try it several times on both front tires. Your problem most likely will show up. One other thing, look at the brake pins and cir-clips If your pins have NOT been changed, they are most likely worn on the inside and will allow play in the caliper. They should look like straight bolts, worn ones will be dished out looking. Let me know what you find.
One other thing, look at the brake pins and cir-clips If your pins have NOT been changed, they are most likely worn on the inside and will allow play in the caliper. They should look like straight bolts, worn ones will be dished out looking. Let me know what you find.pins are straight...probably the 1st time they have been off the car though. I'm going to put my C5 wheels on the front and see what that does, it will at least eliminate the wheels/tire issue if it still does it.
Race Director
Joined: Apr 2000
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From: Texas
In general if it's a wheel or tire you'll feel the vibration all the time versus only when applying the brakes.
Lay a straight edge across the brake pads. You may have some pad taper on at least one of the pads.
Next thing to check for is play in the front wheel bearings/hubs.
After the wheel bearings, check the ball joints and tie rod ends.
Lay a straight edge across the brake pads. You may have some pad taper on at least one of the pads.
Next thing to check for is play in the front wheel bearings/hubs.
After the wheel bearings, check the ball joints and tie rod ends.
Race Director
Joined: Aug 2000
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Cruise-In II Veteran
A quick visual inspection of the pads may not show you any problems.You should clean them off with brake clean and see if theres any cracks in them.Even a hairline crack and cause some problems.
Also see if the pads have worn evenly on both sides.
I also agree about the tires...check that for bad flat spots and also make sure the wheel bearings dont have excess play.Also,are you sure it isnt the ABS pulsating through the pedal?Seen that happen with other GM cars...the abs would activate everytime you stepped on the brake even though it didnt need to.Something to think about.
Also see if the pads have worn evenly on both sides.
I also agree about the tires...check that for bad flat spots and also make sure the wheel bearings dont have excess play.Also,are you sure it isnt the ABS pulsating through the pedal?Seen that happen with other GM cars...the abs would activate everytime you stepped on the brake even though it didnt need to.Something to think about.
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 5,331
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Originally Posted by 96GS#007
In general if it's a wheel or tire you'll feel the vibration all the time versus only when applying the brakes.
The front tires only have about 1k miles on them, they are not flat spotted. That's just how it feels when the brake are applied.
Jim, thanks for you advice on the opti swap. It was a little chanllenging because it wasn't a unit. I had to reuse the center spacer. Car is running great though and no idle hicups anymore.
btw: the timing chain on the C5 did not fail it was broken by a valve spring dampner that had broken. In fact there were many broken dampners. I have to investigate with the engine builders on Monday as to why.
Last edited by Gary2KC5; Sep 25, 2005 at 11:06 AM.
Race Director
Joined: Jan 2005
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From: Slidell Louisiana
Originally Posted by Gary2KC5
the front brakes are fine under light braking but under heavy braking there is major thumping coming from them. It sounds like you have majorly flat spotted the front tires when you are moderate to hard on the brakes.
I put new rotors on thinking the stock rotors were wrapped but that was not the problem.
It's a 94 LT1 BTW.
I put new rotors on thinking the stock rotors were wrapped but that was not the problem.
It's a 94 LT1 BTW.
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 5,331
Likes: 39
Originally Posted by aboatguy
Not trying to be stupid: but is your moderate to hard braking activating the ABS?
There is no ABS pulse in the pedal.
Maybe I should envoke the ABS and see what happens...