OK, here goes. Occaisionally, when I hit the brakes, especially on a hill or when they're under a heavier load, I get a pulsing in the pedal and a shimmy in the steering wheel, once it seemed serious yesterday. I'm assuming it's in the front discs but I don't know what to look for. What's the likely problem to look for when I pull off the wheels, and how serious is this problem? I have stock brakes, front disc, rear drum.

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1987 Camaro Sport Coupe LG4
700R4 with 2.73 open rear
Hypertech chip, 180* stat
L69 Dual snorkel air cleaner with K&N air filter
CK rods with B hanger
Hooker catback
Pioneer DEH-P4000, Pioneer speakers front/back

 

ABS brakes will tend to pulsate under hard braking, such as panic stops. That is normal.

It could also be another problem. Do you or your mechanic use an impact gun to tighten the lugnuts on the wheels. Impact guns are fine for taking off wheels, but when putting the wheels back on a torque wrench should be used to tighten the nuts(especially with alloy wheels). What happens when a wheel is tightened with an impact gun is that the nuts can be torqued down to different specs. These unequal pressure points (the five lugnuts) will eventually cause waves to form in the rotor. When you step on the brakes you are feeling the pads moving along these waves (and it feels like pulsations).

If you think that could be the problem, you/your mechanic can check for waves with a dial incicator and a magnetic base/stand. If there are waves, and enough material left on the rotors, you can have the rotors machined smooth.

 

Not ABS on the 87s .....

Sounds like the rotors are warped.

As far as you seeing anything that looks wrong, that aint going to happen.

Sometimes when the rotors are REALLY warped you can tell by just taking off the tire and spinning the rotor, it will drag in some spots and not in others.

I would replace the front rotors and pads, don't forget to check/repack the wheel bearings and replace the seals.

(I say replace the rotors cause they are cheap and usually the warp will return}

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

R.I.P. #3
"He can see air"

[This message has been edited by Engineboy (edited May 08, 2001).]

 

Wow! I didn't know that the warps could return. I guess you learn something everyday.

 

they dont always return, mostly when they start to get a little thin.

I just replace if possible.

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

R.I.P. #3
"He can see air"

 

Thanks for the info, Engineboy.

 

Thanks guys. Off to the garage I go...