Frt Brakes Shimmy - until pressed harder - Help?

[MK19]

Looking for some help please.

 

After new Front pads, rotors and anti-vibration pads (all OE parts) were installed (and calipers bled) about 1500 miles back, I've noticed a slowly increasing shimmy in the steering wheel under light braking........the kind you'd get with warped rotors, where the steering wheel oscillates.

 

But unlike warped rotors, it occurs only under light breaking and when I load the brakes (and suspension) under moderate or greater breaking, the shimmy distinctly goes away. 

 

I checked all four rotors......nothing more than about .0015" runout. (The rear bakes have about 50k miles on them, I don't track the car).

 

Everything is tight save for a little looseness between the right steering tie rod and the steering rack on that side.

 

Note also that recently, and after the new front brakes were installed, I replaced all 4 shocks, the front upper shock mounts/bearings, front wheel bearings and the four sway bar drop links, + a full alignment by a competent shop. None of these repairs was related to the shimmy which developed later.

 

Could it need a bleeding..........i.e. unequal break pad pressure due to air on one side?

Note also that I've rechecked everything on all four corners looking for anything loose or out of place and that all the rotors look clean and normal.

 

Any suggestions ???

 

Thanks in advance. MK19

[JFP in PA]

Looking for some help please.

 

 

 

After new Front pads, rotors and anti-vibration pads (all OE parts) were installed (and calipers bled) about 1500 miles back, I've noticed a slowly increasing shimmy in the steering wheel under light braking........the kind you'd get with warped rotors, where the steering wheel oscillates.

 

 

 

But unlike warped rotors, it occurs only under light breaking and when I load the brakes (and suspension) under moderate or greater breaking, the shimmy distinctly goes away. 

 

 

 

I checked all four rotors......nothing more than about .0015" runout. (The rear bakes have about 50k miles on them, I don't track the car).

 

 

 

Everything is tight save for a little looseness between the right steering tie rod and the steering rack on that side.

 

 

 

Note also that recently, and after the new front brakes were installed, I replaced all 4 shocks, the front upper shock mounts/bearings, front wheel bearings and the four sway bar drop links, + a full alignment by a competent shop. None of these repairs was related to the shimmy which developed later.

 

 

 

Could it need a bleeding..........i.e. unequal break pad pressure due to air on one side?

 

Note also that I've rechecked everything on all four corners looking for anything loose or out of place and that all the rotors look clean and normal.

 

 

 

Any suggestions ???

 

 

 

Thanks in advance. MK19

 

Weird.  If you have checked and rechecked everything else, bleeding the system is both cheap and quick.  That said, normally any amount of trapped air in the system would manifest itself as a spongy pedal rather than a "shimmy".  I would also consider reexamining the front pads to see if one pad is making uneven contact with the rotor when slightly retracted.

[MK19]

Thanks. Will ck pad contact and then try Bedding the Pads.

[MK19]

After several attempts at bedding, I ended up sanding both the pads and the rotors back to fresh material and starting over. After bedding, the problem was solved.

Thanks all,

MK