Brake Pulsation - Coming from front or rear?

[charleyk]

I am wondering if someone can suggest a way for me to determine if my brake pulsation/shimmy is coming from the rear or front. I'm trying to make an educated guess here cause I don't want to waste any money.

It almost feels like it coming from everywhere. Steering wheel shimmies, Brake pulsates.
And the warmer it is and the faster the speed at which I brake, the worse it is.

I am leaning towards replacing the front rotors and pads. Pulled wheels and everything looks fine, but I understand I wont see anything even if rotors are warped.

Any suggestions? Car has OEM rotors in front with aftermarket pads. I understand that's a no no, but that is what mechanic installed about 6 months ago. Rear has After market rotors and pads installed by guy about 20k miles ago and have had no problems until now. So I'm thinking to start with the fronts.

And I'm gonna do it myself.

 

[bioskyline]

does sound like the fronts are warped. if you take them off and lay it on a mirror you should be able to see if there warped. if its the rears you wont feel it in the steering wheel very much, but the rear will feel llike it wants to pass you, but remember your front brakes do most of the work as thats were all the weight is.

 

[hvyman]

Runout needs to be measure not looked at.

Running aftermarket pads with stock rotors is fine and actually is better. Drilled and sloted rotors are a waste.

Prolly the front since they do most of the work.

Can always take them off and have them turned for either free or cheap at some local auto parts places or maybe at like a small shop. Or just buy new rotors and good pads.

Also good aftermarket pads like ebc or porterfield need to be broken in.

 

[charleyk]

Thanks. If it's the front, will the brake pedal pulsate much? Would the whole car feel like it's shaking?

 

[hvyman]

Yes during braking.

Pulsation depends on how bad the runout is.

Id also check for play in the wheel bearings while your there.

 

[charleyk]

OK. Is there any reason I can't reuse the current pads on new rotors? They look like they have like 90% of life left.

 

[bioskyline]

should be able to, but depending on how hard they are, might take a while to wear into the new rotors, so braking might suck for a bit

 

[charleyk]

I think I'll have enough of a time figuring out how to do the brakes. Not sure I want to tackle wheel bearings yet. Are you saying it's possible a bad wheel bearing is causing this problem and not the brakes? All else seems fine except 4 when I brake over like 40-50 MPH.

 

[hvyman]

Could be but youd most likely have some noice to. All you have to do is grab the wheel at 12 and 6 and push in and out. IF there is no play its fine.

Id sand the pads down a tad to get a fresh surface with new/machined rotors.

 

[charleyk]

Any recommended grit sandpaper?

 

[hvyman]

Just what ever. Doesnt really matter anything like 200 and up.

 

[charleyk]

Thanks for your help, everyone. I replaced the front pads and rotors and no more vibration. The pads were cheap enough so I just figured I'd start fresh.