wOULD AIR IN THE BRAKE SYSTEM CAUSE THIS?

[juiced_94gt]

Awhile ago, i had the pins in the driver rear caliper fail thus causing that wheel to brake at ALL times, well it dug through the pad/pad backing plate/and the caliper piston causing a minor B/F leak, when i installed the new caliper i bleed that wheel just a little bit and didnt change the rotor, for a long time i thought that my car shook during braking because i had warped rotors, well today i changed all 4 rotors and pads and when i go for a test drive BAM it still shakes when i brake (steering wheel and whole car at that) then i notice that all rotors seemed like the pads where grabbing them EXCEPT the driver rear, it almost looks like it's not gabbing at all, you can still see some of the runoff from the brake cleaner...WTF IS CAUSING THIS??? AND COULD THIS BE WHY MY CAR SHAKES WHEN I BRAKE???

 

[GRGT1994]

That avatar rocks!

 

[94_Teal_GT]

Just some questions first. When you changed the rotors, did you clean off the mating surface on the hub? Did you then index the rotors to acheive the least amount of runout?

There may still be air in the line of your suspect caliper, that would stop it from properly engaging. I don't know if air in the system would cause a vibration.

 

[juiced_94gt]

Just some questions first. When you changed the rotors, did you clean off the mating surface on the hub? Did you then index the rotors to acheive the least amount of runout?

There may still be air in the line of your suspect caliper, that would stop it from properly engaging. I don't know if air in the system would cause a vibration.

how do you index rotors???? and what does that do???

 

[94_Teal_GT]

how do you index rotors???? and what does that do???

The ideal way is with a dial indicator, that reads in .001". You attach the rotor, snug it down with the lugs, then put the needle on the pad surface of the rotor, spin the rotor slowly, and check for deviations from .000". You then remove the rotor and rotate it until you acheive minimal 'runout'(deviation from perfect flat). Having alot of runout, will recreate the same condition as a 'warped' rotor. That's also why it's important to clean ALL the crap off the hub, where the rotor touches and verify there are no burrs on the inside of the rotor. A high spot will tip one end of the rotor out.

If you don't have a dial indicator, most people don't. I don't have one at home, so I used a set of verniers(calipers) and measured from the same spot and rotated the rotor, remeasured, repositioned the rotor, remeasured, etc. It's not the most accurate, but it's the best I could do. I don't have any brake judder at all.

Take a look over here, there is some good reading. Stoptech
3) Disc run out and thickness variation: Run out in excess of six thousandths of an inch (0.006") can be felt by the driver as can more than 0.001" of thickness variation and any amount of material transfer from overheated pads. Run out is caused by poor design of either vanes or the junction between the friction surfaces and the mounting bell, by poor machining, by thermal stress or by any combination of the three.

 

[meyers2211]

well now i'm having brake issues too mine make the car shake but nothing that seems out of line.

I think the dial indictor would work best mainly because u can spin the rotor to see high and low spots which would show warping. The reason i would be against the calipers is because thats measuring thickness The rotor could be the same thickness all the way around but be warped. But try the caliper i would measure the whole rotor prolly in 4 spots then bak the caliper off a hair and attempt to slowly turn the rotor in hopes in mite show and abnormalities.

 

[BPA]

ok im a little confused maybe im not reading this right.. did you replace your front and rear rotors and pads after you replaced the caliper?thanks for the clarification in advance. Brian