Steering wheel shimmy when braking

RussW · #1 (**permalink**) 08-25-2010, 05:21 PM

In the last couple hundred miles I have started getting a shake/shimmy in the steering wheel only when braking. It started out light and has now gotten to the point of being concerning and almost violent during more aggressive braking. Nothing of note has happened or changed to cause this problem. My initial thoughts are a warped brake rotor. A quick check of the front end seem to indicate everything is tight. Any thoughts or ideas before I start to tear into things?

Thx - Russ

NZCOBRA · #2 (**permalink**) 08-25-2010, 05:43 PM

Hi, an uneven thickness will cause this ,if they were second hand rotors and had hard spots ,when you machine rotors these hard spots will push the carbide tool away, and need to be ground after-wards , or put new rotors on , run them in follow instructions on rotor box. . slight rotor run-out is ok . this will keep pads back.

Tim Brewer · #3 (**permalink**) 08-25-2010, 08:47 PM

It's your rotors, have them turned and put on new pads.

bobcowan · #4 (**permalink**) 08-25-2010, 09:24 PM

Warpedbrake rotors are somewhat uncommon these days. If you have a dial indicater, it's worth checking. But it's probably not the problem.

Here's an excellent article from Carroll Smith: http://www.stoptech.com/tech_info/wp...rakedisk.shtml

Try having the rotors cut. And then lightly sand the surface of the brake pads; no need to replace them.

Rwillia4 · #5 (**permalink**) 08-26-2010, 02:16 AM

Rotors would be the first thing I would check. If it is also change the brake fluid and make sure the calipers pistons are moving freely...something caused it.
Then
Tires- they might be wearing uneven or out of balance, it is difficult to check without equipment
Alignment- Toe could be off, too much under braking
Control Arms- Check bushings and bolts
Steering Rack- Just check to make sure nothing is coming loose

RICK LAKE · #6 (**permalink**) 08-26-2010, 03:09 AM

RussW Russ what brake system is on the car? Is it look stock like 10-11" rotors and single piston calipers? If you are spirited driving, and get on the brakes hard a couple of times, you can warp the rotors. Super heat does this. You also have a 460 motor under the hood. If it's all iron that's about 720 lbs of weight. Aluminum heads and intake is 110 pounds less. Since it only happens when stopping, it's the brakes. You can resurface rotors about 3 times. DON'T bother. Replace them. The problem with a resurfacing is cutting about .008"-.012" to straighten the surfaces up again, and the rotors will warp quicker because they are thinner and get hotter faster. I would tell you to upgrade to a 4 piston brake system and larger rotors in the Min. 12" to better 13". Larger surface more stopping power. Also look at cooling ducts for the front brakes. This will extend the life of the rotors and pads. I an sure Dennis O. can point you in the right direction with a better setup. It's safer too.

Rick L.

Don Barnes · #7 (**permalink**) 08-26-2010, 07:51 AM

Russ, Have you checked the SCOF website, the technical section has this type of info to help you with your SPF. What number are you? Thx, db #2723

Tom Niebrand · #8 (**permalink**) 08-26-2010, 01:23 PM

Quote:

Originally Posted by RussW

In the last couple hundred miles I have started getting a shake/shimmy in the steering wheel only when braking. It started out light and has now gotten to the point of being concerning and almost violent during more aggressive braking. Nothing of note has happened or changed to cause this problem. My initial thoughts are a warped brake rotor. A quick check of the front end seem to indicate everything is tight. Any thoughts or ideas before I start to tear into things?

Thx - Russ

You said your first thought was warped brake rotors. Very good. Then you check front-end for loose parts. If you find loose parts, fix them. Now go back to your first thought with a dial indicator and check for warped brake rotors. If rotors are good and your rotor has a smooth machine surface check your caliper for movement. The next thing you can check, you can do at home, but you will need help from a buddy, not your wife. Jack the car up with wheels off the ground. You lay down in front of the tire. Have your buddy spin the tire by hand as fast as he can and watch the tread to see if it moves left to right. If it does then you have a belt shift. I know some people will jump all over this. Your first thought is a good one.