The caR stops smoothly at speeds below 45 MPH...however when the brake pedal is depressed at speeds above 50, I'll get a vibrating feedback through the steering wheel. Any ideas what may be causing this?

 

warped rotor(s).

steviej

 

Warped rotors or excessive buildup of brake pad residue on the rotor surface is the most likely culprit, but not the only possibility. Mine does it too, but there is shaking and steering wheel feedback at a wider variety of speeds. I bought some replacement rotors from Autospecialty and have not been pleased with the rotors and pads at all. I am junking them in place of OEM replacement rotors and the Lexus pads.

 

RA40,
Does it vibrate under 45mph when you panic stop? Does the vibration increase correspondingly with brake pressure applied? A warped rotor should exhibit both qualities. Are your wheels properly balanced?

97 LS have excellent THICK rotors up front and don't usually warp ( if they are OEM ). They do however have a problem with stuck caliper pins, which will manifest as a high speed braking vibration but no vibration under slower speeds.

link13,
because your brakes vibrate at a greater variety of speeds, I would think yours ARE warped.

Regards

 

Nick T

A panic stop sub 45 MPH is smooth and no hint of any vibration or feedback. Smooth applied braking at these speeds is also uneventful. Lightly apply the brakes above 50 and it will shake the wheel at a range of foot pressures till the car is below 40 MPH or so.

 

RA40,
Does the steering wheel vibrate more if you increase brake pressure?

I am leaning towards stuck caliper pins or a wheel balance issue. If you have more then 10k miles on your tires, getting them rebalanced and rotated is a good idea in any case. You can pull the calipers off and regrease the pins yourself.

If the problem still persists, or your brake pads are worn anyways then it's time for resurfacing the rotors and new pads.

Regards

 

Nick T

The vibratiion is about the same when above 50 MPH regardless of how much pressure I apply, light, frim, same feedback. I am due to rotate the tires and with the wheels off, I'll inspect the brake calipers and I'll probably pull the pins out to inspect for any gunky stuff on them. The brakes got done so there is plenty of pad left.

Any recco'd grease for the pins?

Thanks!

 

ABS system malfunction possible.

 

RA40,
Pull the pins, clean and re-lube with high temp brake or wheel bearing grease. You might even splurge and get synthetic ( it's not much more expensive ). I am really leaning towards a slight inbalance or out of round tire however since the vibration does NOT increase with brake force. Best bet would be to do both. Rotate and balance your tires as well as re-greasing the pins ( your mechanic should have done this when he did your brakes, but it's been known not to be done )

Luck

 

Had the same problem with mine, under 45mph it was fine. When I started braking at 60-65 vibration. Changed the rotor and it went away. I bought cross-drilled slotted ones off ebay for $80, and they work great.

 

Removed the pins and they were crudded up. Cleaned the brake goo off them and gave them a slight polish. One of the pins was slightly bent so I'll probably replace it. Didn't have any brake grease handy so I put them in straight. Also put the dial indicator to the rotor but I couldn't snug it up adequately...maybe to 15 ft lbs. It read .006" runout which was obvious but because it wasn't properly torqued, I'm sure it isn't accurate.

There was a dramatic difference, 90% of the feedback is gone. Me thinks that a bit of grease and replacement of that bent pin would get it. I stopped by the Lexus dealer since they did the brakes and it being under warranty, the service advisor said they can check the rotors just to be sure. If there was runout, they'd take care of it.

 

RA40,
Glad to hear you found the problem. FYI and others reading this post, the dual piston lexus calipers are notorious for sticking pins. Often times requiring pliers to remove which ends up twisting the pin much like one of yours. You should always regrease the pins when you do any brake service, the mechanic who did your brakes did a shoddy job. Next time you bring the car in, ask for someone else


Regards

 

I too have wondered about this shimmy, Mine was usually only between 60 down to about 53mph. Rotated and balanced my Michelins...twice. Bought new ones with 6/32 left on the old ones. Still shimmied.
I just picked it up from the dealership, they assured me it was warped rotors and charged $225 to turn them. Old pads still had plenty of life, so, we reused them.
Not noticeable so far, but, I've only stopped a few times on the way home. Now I have too much brake pedal travel to suit me.
I'll post back in a day or two.

 

That seems to have worked on mine. Must have slightly warped the rotors somehow. Panic braking?
Sure feels sweet with the new tires and no shimmy.

 

Mine started doing the same thing at different speeds, but worst at high speed braking. All 4 tires were less than 1 month old. Brake pads was replaced a while ago but not the rotors. Most likely is the front rotor wrapped. I am going to replace the front rotors very soon.

Ching-Ho Cheng