What's that noise: Wheel Bearing, Caliper, or just Race Compound Pads?
06-08-2017, 01:12 PM
#1
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What's that noise: Wheel Bearing, Caliper, or just Race Compound Pads?
I am trying to diagnose a new noise coming from my 05 350Z with Brembos and I’m hoping those with more experience can try and shortcut my diagnostics process.
Recently I have been noticing that I am getting what I would categorize as brake drag squeal on my Z. This seems to have been getting increasingly worse after subsequent autocrosses and track days; going from unnoticeable, to some squealing, to now lots of squealing while driving straight and not on the brakes. At the beginning of the season I changed to racing compound pads (G-LOC R12 front / R8 rear) and Z1 2pc rotors so at first, I wasn’t sure if it was just that I could now hear the light brake drag (because of the racing pads) that most disc brake systems have or if it was an issue with my calipers or something else.
After my track day at PittRace yesterday I’m beginning to think that it might actually be wheel bearings. I now notice that if I make a slight sawing motion at the wheel (barely enough to wiggle the car) I can make the squeal temporarily go from one side of the car to the other. I only have 30k on the car but I am lowered on a stiffer suspension, with wider and stickier tires, on wider wheels with different backspacing than factory, and I’ve now done 5 track days (2 with new race pads generating significantly more heat) and ~12 autocrosses. I’m not hearing any grinding from the bearings but the ability to change the noise with minor changes in loading really makes me think it’s the bearings.
Any thoughts would be appreciated.
In case it matters, car specs are:
Recently I have been noticing that I am getting what I would categorize as brake drag squeal on my Z. This seems to have been getting increasingly worse after subsequent autocrosses and track days; going from unnoticeable, to some squealing, to now lots of squealing while driving straight and not on the brakes. At the beginning of the season I changed to racing compound pads (G-LOC R12 front / R8 rear) and Z1 2pc rotors so at first, I wasn’t sure if it was just that I could now hear the light brake drag (because of the racing pads) that most disc brake systems have or if it was an issue with my calipers or something else.
After my track day at PittRace yesterday I’m beginning to think that it might actually be wheel bearings. I now notice that if I make a slight sawing motion at the wheel (barely enough to wiggle the car) I can make the squeal temporarily go from one side of the car to the other. I only have 30k on the car but I am lowered on a stiffer suspension, with wider and stickier tires, on wider wheels with different backspacing than factory, and I’ve now done 5 track days (2 with new race pads generating significantly more heat) and ~12 autocrosses. I’m not hearing any grinding from the bearings but the ability to change the noise with minor changes in loading really makes me think it’s the bearings.
Any thoughts would be appreciated.
In case it matters, car specs are:
- 2005 350Z Enthusiast upgraded to Brembo calipers
- Stainless brake lines with Motul RBF600 fluid
- Z1 2pc slotted rotors
- G-LOC R12/R8 pads (similar to Carbotech XP12/XP8)
- Stance Coilovers
- Full SPL Titanium series arms and pretty much every other bushing is Energy/Whiteline/SPL
- Hotchkiss Swaybars w/ Whiteline links
- AAM Twin Turbo system (~420rwhp)
- 18x9.5 / 18x10.5 wheels with 15mm offset
- 265/35 r18 front tires (Currently RE-11 formerly RT615k)
- 275/35 r18 rear tires (Currently RE-11 formerly RT615k)
06-09-2017, 09:22 PM
#2
Try dragging the brakes lightly while turning and see if that changes or eliminates the noise.
The bearings do flex some which could cause the rotors to drag the pads (unlikely under such light loads), but its also somewhat unlikely that both bearings are failing at exactly the same time, in the same manner. But crazier things have happened.
You should do a proper bed-in procedure, which sometimes even on track can be difficult without notifying the officials and your run group. Also it could help to remove and re-install the pads on all corners to make sure everything is good to go.
The bearings do flex some which could cause the rotors to drag the pads (unlikely under such light loads), but its also somewhat unlikely that both bearings are failing at exactly the same time, in the same manner. But crazier things have happened.
You should do a proper bed-in procedure, which sometimes even on track can be difficult without notifying the officials and your run group. Also it could help to remove and re-install the pads on all corners to make sure everything is good to go.