ashmostro

iTrader: (3)

Folks, are you having a wheel shudder problem and haven't been able to fix it, even after multiple wheel balance attempts and even turning the rotors? If so, you might want to look between your wheel hubs and rotors, and the rotor/wheel interface too for accumulated rust.

Get yourself a wire brush bit, chuck it into your drill, and get rid of that rust! Just a small layer can cause runout issues that get misdiagnosed as "warped rotors"... I just fixed this problem on my car this weekend and it now feels like the car is brand new again. No more shudder at freeway speeds, nor under high speed braking (it was bad).

Surfaces to clean: wheel hub, rotor back and front mounting faces (not the pad contact area of course), and mounting area of the wheel. Also, get the hubcentric flange on the wheel as this is what centers it on the hub and if it's got accumulation your wheel can appear out of round to the road surface.

Here's a pic of my wheel hub with 4 of the five lugs cleaned so you can tell the difference:

ashmostro

iTrader: (3)

I should add that after I cleaned each surface, I put a very thin layer of anti-seize on those surfaces to minimize future rust and galling. Don't use too much, and make sure not to let any get near to or on the braking contact surfaces.

LexiG37

Thanks!! I think I have the same problem.

ashmostro

iTrader: (3)

Nice, let me know if you try this! When it comes to the shuddering symptom in general, there are many possible causes in often times more than one at the same time. Consider this one of the possible culprits, but I posted this up because it's one that is easily and inexpensively addressed. That, and most mechanics don't even think, or suggested to look into this.

Other possible causes of shuddering (but not exhaustive):
- Rotor ground out of flat from the factory (not "warped")
- Brake pad deposits and / or rotor microstructure change from pad diffusion and glazing
- Wheel hub or bearing damage from potholes or accidents
- hub or rotor imbalance and de-indexing from removal and reinstallation in a different position
- Tire to wheel imbalance or tire carcass damage (proper tire mounting, or road force balancing should address these)


True rotor warping is next to impossible without extreme temperatures, which would very likely damage the pads, calipers, and lines if that ever happened.

TVPostSound

iTrader: (9)

Not enough to cause wheel shudder.

Here's my theory, all the mechanics trying to solve your issue used an impact gun on your wheels, when you took your wheels off to inspect, you tightened your lug nuts by hand. Problem resolved.

I had some moron at Costco use a gun on my Expedition, those are some large rotors, then used a torque wrench to verify. I drove home and my brakes were shuddering, I jacked the truck up, loosened all the wheels, and torqued them by hand. Shuddering gone.

ashmostro

iTrader: (3)

Incorrect assumption. Look up runout tolerances and the topic of non parallelism. There are a lot of white papers and FAQs out there on this topic on the more professional manufacturers' sites. You don't know me, so I guess I can see why you'd jump to that conclusion, but take a moment and read on before casting this one in cement.

No mechanics have touched my car other than the pros that did the road force balancing. And that was before I have since removed and retorqued the wheels a few times. The shudder was there before that day, and after. That was not the cause and I watched them use a torque wrench to secure the wheels. They prep race cars.

Which is all irrelevant as I do all the work on my car myself. I have been prepping her for the track (fitted an oil cooler last weekend), and did a proper flexhone of all rotor surfaces when switching to a hybrid track pad compound in order to the get the rotor down to virgin metal, but I neglected to clean the hub and rotor mounting surfaces. I've always torqued in star pattern down to 80 ftlbs, and other than the road force balancing, no one else has been allowed near the lug nuts.

I know my car better than most know theirs. The only variable I changed this weekend was the rust I removed. I even kept the rotors indexed the same on all axles when I did that, just to be sure.

quakerroatmeal

iTrader: (3)

If you get your tires serviced at discount tire they actually do this. I've never seen it until recently and asked them about it. They said customers have came back from vibrations bc of all the rust build up.

ashmostro

iTrader: (3)

I really like that company, actually. Back home it's Americas tire and I've always liked their service.