I have a 2006 350z with the factory Brembo brakes installed, running StopTech Street Performance brake pads and Powerslot rotors front and rear. Ever since I took the car out of the garage for the first time this season (back in March) I have noticed a very vague feeling in the brake pedal, almost like the brakes are not grabbing hard enough based on how hard I am pressing the pedal. There is also a pulsation / force feedback to my foot through the pedal when I apply the brakes, regardless of speed.

At higher speeds it is a rapid pulsation, and at lower speeds it is a slower pulsation. In fact under light brake pressure at low speeds, like when slowing to a stop at an intersection, I can feel the car lurch forward a bit seemingly once every wheel revolution, like the brakes momentarily "let go" once per wheel revolution. It almost feels like have tire(s) with a flat spot, but this phenomenon only occurs when applying the brakes so I know it's not a flat spot on the tire(s).

There is no shimmy/vibration in the steering wheel, which leads me to believe it is not a problem with the front brakes. So this weekend I popped off my rear wheels and noticed that the rear driver side rotor has a darkened area across its face, a little shorter than the length of the brake pad. When I run my finger nail across this area it has a noticeably different texture than the unaffected brake rotor surface. I do not recall whether the same condition existed on the passenger side.

Looks to me like maybe the brake pad "cooked" itself on the rotor at some point, leaving the textured blemish I found. My questions are:

1) Based on my description and observations above, does it seem that this area on he brake rotor face is causing the braking feel / pulsation issue?

2) A new set of rear rotors (both sides) can be had for around $200. By the time I take the car to my independent shop of choice (car is out of warranty, no more Nissan dealer for me) to have them diagnose and possibly fix the issue, I'm into probably 1 hour of labor at $90/hr. Assuming I can manage to remove the Brembo caliper mounting bolts myself, without stripping the thread in the caliper (which I managed to do on my old STi), I could swap the rotors myself in the driveway in an hour.

3) If the rotor is indeed "burned" in this location, is it even possible to repair by removing material (i.e. 'turning down') the rotor? Or does the burning process go too deep into the metal and prevent it from being fixable?

4) I think I know the answer but I'll ask anyway: Is it OK to replace just one rotor? Assuming I only find the suspected issue on the rear driver side, can I just replace that one rotor? These rotors have less than 10k miles and have been used lightly, except for whatever event occurred to cause this problem.

Thanks in advance for any advice and/or similar anecdotes of your own.

 

Looks like pads crystalized due to grease on rotors or pads. This happened to me try resuficing the rotors and replace the pads if not get some sand paper and sand a layer off the pads untill they feel rough again. Btw since I just mentioned that check your pads to see if they are actually crystalized. Youll notice the surface of the pads very shiny.

 

Hmm in for answer, my folk's 07 Camry does the same thing. I did notice that the dealership super air wrench torqued the wheels on, thinking this may have warped the rotors?

 

Try this first to clean off the residue from your pad:

http://www.ehow.com/how_4421355_clea...ke-rotors.html

If that doesn't work you may have warped your rotors

This is what I am most afraid of now that I don't drive my Z everyday which is the pad seizing with the rotor since I park on a hill and I have to keep the parking brake engaged

 

Thanks for the advice. Just to make sure we are on the same page - you are talking about the surface of the pad and not the rotor, correct?
My first thought in all of this, preceding my post today, was that there is an issue with the pad(s), but since it seems to be a once-per-revolution sensation I am inclined to believe it is a rotor issue. I will take a look at the pads while I'm in there anyway.

I will let you know what I find out. In my case I do not suspect warping, at least due to lug nut torquing, because the only people who have touched these rotors are R/T Tuning for the installation (reputable shop, definitely not impact-wrench junkies), and myself (always torque to 85-90 lb-ft in star pattern).

Thanks for the link, I will try that out.
I didn't really notice this issue before putting the car away for the winter, but when I started driving it in the spring it was immediately noticeable. But I don't think the brake pads are in loaded contact with the rotors when the car is parked. I leave the car in first gear with the parking brake pulled up just slightly, in my garage. The p-brake isn't really doing anything, just the car sitting on my level concrete slab in first gear to keep it from rolling. Maybe some sort of weird chemical reaction between the pad and rotor materials. Maybe I washed it, rolled it into the garage and let it sit for 1 or more months....you know how when you let it sit for a day after washing the pad has to become "un-stuck" from the rotor? I wonder if I had that condition manifesting for weeks and weeks and it caused permanent damage to the rotor?

 

That's what I was thinking

 

OP you need to get a measuring caliper and draw four equal points on the rotor, measure to determine if warped ,if it isnt visible already, by taking the caliper and setting it to the first point and running it along the edge of the rotor to the next point. This will tell you if you need a new pair of rotors, you always want to replace rotors in pairs like tires.

To me it sounds like you just have warped rotors, if its burned in one spot, and you feel the rotor "turning" as you press on the brakes, than there is your problem.

Also try to do what Waizz stated, check for grease using his method, but i believe your pads are either going out or the rotor is warped.

 

I tried to get a good picture of the blemish / rough spot that is on the rear driver side rotor. See pic below, specifically the orangey rust-colored area near the slot at the lower right of the rotor as pictured. Any clearer idea of what's going on?

 

That is pad contact with rotor just as we thought, try to get it refinished

 

This shouldn't be too difficult to sort out. Try taking your Z to a shop that can check rotor run-out and turn the rotors on the car. That should be sufficent to remove the pad residue, but as others have said, you may need to use a light sanding on the pads themselves to bring them back to full effectiveness.

BTW- it wouldn't hurt to have the shop do a power brake bleed to make sure you have fresh fluid to all four corners and no air trapped. Use a good quality brake fluid like ATE Super Blue or Gold 200 and those Brembos should feel and stop great!

 

^^ this. warped rotor

 

Thanks for the feedback gents. Scheduled for a visit on Tuesday. I will update the thread once I know what's up.

 

I have this exact symptom on my brakes. What was the final resolution?

 

Have you tried taking your Z to a shop that can check rotor run-out and lightly turn the rotors? You can also lightly sand the surface of the pads to remove any rust residue to bring them back to full effectiveness. No need to go much further...