Possible rear rotor warping

  • #1

    Possible rear rotor warping

    Hey everyone been trying to put the Z back on the road and ran into an issue on the left rear wheel. When I installed the brake rotor it rubs up against the caliper bracket as I spin the rotor around at the same spot. Thinking it might be either the rotor or the rear wheel bearings I tested out the right rotor and the same thing, just not as dramatic. I'm thinking that somehow my rotors got warped sitting around these past two years because when I measured it with a dial indicator I had up to a .020" deflection.

    Also read online that it might be the rear wheel bearings going out but I got no deflection when I put the dial indicator against the hub and the hub has no play in it.

    Any other advice on what I might try to figure it out or what it might be?
    Bah-chicka-wow-wow
  • #2
    I have never had a rear rotor warp



    1988 300ZX Turbo, Shiro Special #760
    1988 300ZX Turbo Automatic (wife's car)
    1991 Hard-body 2WD

    http://zccw.org/zccw/?page_id=1215
  • #3
    Yeah I've never had one before either, but it's what I'm leaning towards.

    Also forgot to mention that the rotors are drilled/slotted incase that helps.
    Bah-chicka-wow-wow
  • #4
    Remove the rotor, spin it 180, then check runout again. If it exceeds 2 thousandths, you will get a pulsation down the road. Anything over 10 thousandths you will feel right away. There are shims available to correct this, but I'd just replace them.
    5.3 LSx Z31
  • #5
    Oh yes, they can warp for sure. I just replaced mine today that had about 0.012" runout. It felt like the car was shaking apart when braking at freeway speeds, and yes I'm talking about the rear rotors.

    These were original rotors with around 180k miles on them.

    Factory spec is 0.0028" max for what it's worth.
  • #6
    Took the rotors to O'Reilly's and had them put on their machine. Rotors ran true, no warpage. Which means that my issue lies in the hubs. Really hoping it is not the wheel bearings.
    Bah-chicka-wow-wow
  • #7
    Make sure the hub mating surface is clean and free of debris. Worst case, take it to a place that has an on-car brake lathe.
  • #8
    That's my next plan to see if something is up with the mating surface. Unfortunately car isn't drivable right now so won't be able to drive it anywhere.

    It's just odd that this is happening because it all worked fine when I took it apart 2 years ago.
    Bah-chicka-wow-wow
  • #9
    It doesn't take much surface rust to throw things off. Last time I ran into that problem on my old Corvette I used a cupped wire brush to completley strip the hub mating surface. Worked like a charm.
  • #10
    Strange enough I thought I had removed all the rust. Because I went over both the hub and rotor mating surfaces with one of those paint striping wheels with my drill till I had bare metal then repainted the hub.

    Just for shits and giggles went out there today and took a wire brush to the mating surfaces and lo and behold it all bolts up fine now. So I guess whatever was there was throwing the rotor off. Whatever, not going to over analyze it and just be glad I didn't have anything serious wrong.
    Bah-chicka-wow-wow