I have a 2003 350z touring 6 speed. I've had a pretty bad vibration when braking over 50 mph for quite some time. The faster I'm going the worse it is.

I last did rear brakes and rotors roughly 25K miles ago and did the front brakes and rotors 10K miles originally. the problem started somewhere in between those 2 brake jobs. I used the cheapest rotors with generic ceramic pads from Autozone.

Thinking the crappy rotors warped prematurely, I just replaced the front brakes and rotors with Centric brank premium type rotors and brake pads this past weekend and am seeing no improvement. My next thought is to do the rear pads and rotors but I don't want to just throw parts at it.

****I've pulled the E-brake while going 80 mph on the highway to see if I get the vibration while just using the rear brakes and there is no vibration when doing this but I'm not sure if that is a valid test ****

Tires are the same all around and replaced at the same time 7500 miles ago. They were balanced and a 4 wheel alignment was done at that time.

I also just had my rear differential bushings replaced last weekend and this had no affect on the vibration problem but did get rid of my clunky shifting. The mechanic said that the on front lower control arms the "rear" (not sure if he really meant inner or outer) bushings are starting to tear but that everything else suspension related appeared to be in relatively good shape. He said he had a Volvo with a similar vibration and new axles solved the problem.

Based on this scenario can anyone point me in the right direction so I don't just throw a whole bunch of parts at this problem with no guarantee that anything will be fixed?

 

Warped front rotors....have them machined.

 

Yeah definitely the rotors. Machined or replaced (if they've been machined before, usually you arent able to do it again). It's about $180 to have a shop replace the rotors completely.

It'll cost you about $50-$100 depending on what brand if you do it yourself. Or spend a few hundred and get some drilled or slotted rotors!

Edit: Actually read your post. How long ago did you replace them, because unless you're tracking your car they should last a pretty long amount of time. Could it be a caliper dragging? Not sure if that'll cause a similar vibration.

 

In most common cases, it's just uneven pad material deposit on the rotor surface.

Have it re-surfaced and then bed your brake systems properly. Do a quick search, it's been discussed here a number of times.

 

http://www.ebcbrakes.com/automotive/...ibration.shtml

Very informative link

If you decide to go with new rotors, check out my thread on Rotorpros.

 

Hey, guys, read the OP's third paragraph. He says he's already replaced the rotors and pads with new parts, and it didn't make any improvement.

"Thinking the crappy rotors warped prematurely, I just replaced the front brakes and rotors with Centric brank premium type rotors and brake pads this past weekend and am seeing no improvement."

For the OP:

Pulling the E-brake doesn't prove anything. There are small drum brakes inside the rear rotors, so the E-brake doesn't use the disc or pads.

Do you have a dial indicator to measure the run-out of the front rotors while they are turning? That would tell you if it's the rotors themselves.

Is it possible there's trash or corrosion behind the rotors where they fit to the hub? That would make the rotor wobble.

 

Thanks for the tip but I literally just replaced the front rotors and pads last weekend with a better brand than the ones I did last November

 

I literally replaced the front pads and rotors last weekend. The rear pads and rotors were done about 25K miles ago and they were the cheapest ones autozone had so those are the ones I'm thinking may be warped. Just wanted to see if my symptoms jive with warped rear rotors or maybe point to something else.

 

Thanks for the tip. I did read about that. It sounds like I essentially do 10 hard stops (90% braking power) from 60 mph to 10 mph righ in a row without giving the brakes much time to cool in between. And I'm also not supposed to keep my foot on the brake pedal if i come to a complete stop in between each run. Does that sound about right or am I missing something?

 

Maybe there is some crap, dirt, rush in between my hub and rotor. I didn't really clean the hub off when I replaced the rotors. I'm going to try that, as it may be an easy fix.

 

I unfortunately don't have a dial indicator. I'm pretty much an amatuer when it comes auto mechanic work. I'll pull them off and clean up the hubs and rotors real good to make sure its a clean flat surface. Hopefully that does the trick. I'll also see if my buddy has a dial indicator I can borrow.

 

I'd say you gradually increase brake pressure. last 2-3 brakes should be at 90%.

If you replaced the front brakes and you still get pulsations, then it could be the rear rotors. Try resurfacing them first, maybe?

See if there's any play on your wheels too while the car is up on the lifter.

 

Just replaced the rear pads and rotors and no more shaking! The right rear rotor was in awful shape and part of the smooth surface was rusted through!

These rotors were new and so were the pads when I replaced them about 25K miles ago. The pads literally outlasted the rotors! Just goes to show that you get what you pay for - no ore autozone cheapy rotors!