Tech

My wife just purchased an 04 w/27k miles in superb condition two months ago. This is a California car that had no mountain or winter weather service.

We live in Colorado & do a lot of mountain driving. At speeds above 65mph going down hill the steering wheel slightly vibrates or shimmies under heavy braking. The car is always heavily loaded.

Original brakes w/ well over 50% lining. I have not put a dial indicator on the disc surfaces.

CV joint boots are tight & no grease leakage.

Tires are wearing perfectly, so I do not think it is an alignment issue.

Has anyone experienced this issue? How did you correct it?

Thanks everyone!

RCsGX

It's probably your rotors or it could be a stuck caliper.

I had steering wheel shake that started under heavy breaking then over a few weeks it was happening most of the time I was braking.

I replaced my rotors (barely within specs) and pads (well within specs) with new rotors and pads and the steering wheel shake went away.

gxman1

I had the same problem, as RC mentioned, I also Changes the to OEM Rotors, OEM Pads, and OEM Shims. Its perfect now.

Crispy3M

I had the same thing but in my case, it was a stuck caliper.

It's easy to check. Take the vehicle for a 5 minute drive, use heavy braking then stop and check the temperature of each front caliper.

One side much hotter than the other = Stuck Caliper
Both sides pretty much the same = Look for something else.

Cheers!

caesosa

These are very heavy trucks and do tend to wear a lot of brakes. It is likely the rotors are warped slightly and that will be enough to create a vibration. You may have to change the brakes but does anyone suggest only turning the rotors?

RCsGX

They're not warped, they usually have pad build up.
http://www.zeckhausen.com/avoiding_brake_judder.htm

Stock rotors are 28mm thick, minimum thickness is 26mm. As long as you're within the specs you can have the rotor(s) resurfaced but unless they have really low mileage I wouldn't bother. GX rotors aren't that expensive and it's very easy replace them yourself. If you can remove your tire and use a wrench to remove 3 bolts, you can replace a rotor in less than 30mins.

Tech

Thanks for all your replies & advice.

Once I do all the checks, I will report back on the resolution.

Jeeparn

Any updates Tech?

Also, would this vibration when braking (likely the rotors pads needing replaced) cause a slight steering wheel vibration mimicking an out of balance tire. Reason I ask is because I have the shimmy when braking but too the steering wheel has a slight vibration when driving and the tire dealer says tires and alignment are good.

99suprduty

I was getting a slight shimmy between 55-60, put new tires on and it was still there. Took it back to the shop and had them re-balance the wheels/tires and the shimmy moved to 65-70 mph now. Pretty sure its a wheel balance issue (for mine at least) as I've read that these rigs need to have a "road force" balance (or something along those lines). Its not that big a deal to me at this point, everything else checks out fine.....I'm going to be doing a full service over the summer when I replace the brakes and stuff so I'll re-evaluate at that point.

chiph9

Go to a shop that has a Hunter GSP9700 balancer, and a technician that knows how to use it (you just follow the on-screen directions, mostly..)

http://www.gsp9700.com/

Chip H.

Tech

Yes, I do have an update, but no resolution yet.

I have identified two issues, mentioned in this thread, that may be causing the vibration.

#1 - Left front disc has a runout of 0.0020" as measured w/ a dial indicator

#2 - Right front has a sticking caliper. Inside pads measure 3.69 mm. Outside pads measure 5.98 mm.
Disc runout is 0.000"

I have purchased new pads & rebuild kits for both front calipers. I will also get the discs resurfaced.

I will update after the work is finished.

Jeeparn

Thanks Tech
and Chip that's what I did. Hunter balancer fixed my problems. Well at least the wheel vibration when driving. Still have a little pulse when braking and plan to do the brake job myself when it gets a little warmer. What's odd was that the out of balance tire was also causing a weird pulsing humming noise at 68-80 miles an hour but only when you were on the accelerator as soon as you let off, the hum went away.
Dealer replaced bad rear bearing but didn't fix the hum. Now that it's been balanced, all is well--- for now.

Question? Which pads to use ? Factory or other and if other, which ones?

chiph9

Something to check is the lug nut torque. They're supposed to be 80 ft-lbs, but if you have one or two that are wildly different, they'll pull the rotor out of true. Result is a warped disc and a brake pulse.

Chip H.

Tech

#1 - Rebuilt both front calipers. Although the drivers side brake pads wore unevenly, the calipers pistons were not frozen. I rebuilt them using this link as a guide.

#2 - Had rotors refinished. Passenger side was warped. New thickness on rotors after machining is 27.5mm. Neither rotor had any build-up of brake material on them.

#3 - Installed new OEM Lexus/Toyota pads.

#4 - Bled brakes.

#5 - Tested brakes today on I70 & Rte 40 in the Colorado mountains. No shimmy.

The problem was the warped rotor. I have no explanation for the uneven pad wear on the passenger side.

FYI, another way to warp rotors, is ...after heavy braking...coming to a stop...& holding on the brakes. The rotor does not have time to cool. The rotor will warp in the area where the pads are gripping it when stopped. This portion of the rotor remains hot & its possible for the metallurgical structure to change.

I will report again, if the rotors warp....but I hope the problem is permanently solved.