Front Wheel Disc Brakes

[BTanzini]

I just developed a problem with my front disc brakes that I have never had before. While applying brakes at 50-60 mph the front end did a very bad simmy for some reason. I have noticed it a couple of times so far. I have 108,000 miles on 1996. I checked the brakes and bearings and found nothing wrong. Has anyone had this problem or does anyone have any suggestion on the what might be wrong?

 

[PHaller]

Your rotors are out of true. Take them off and have them turned or better yet have them turned on the truck to true them up. The shimmy is caused from the by trying to clamp the rotor that is spinning out of true. The faster it spins the worse the shimmy will be.

-Paul R. Haller-

 

[eGarwood]

I agree with Paul... I think you should look a little deeper though, at what may have caused your rotors to warp. I had a VERY bad problem with the brakes on my 95 right from the start, had it back to the dealer within the first week. It would dive left or right with no particular pattern, shimmy, shake, vibrate, and pulsate. Finally after at least a dozen dealer trips and 3 COMPLETE braking system changes found out Dodge F-ed up and put 3/4ton Regular Duty wheel cylinders on my 3/4 ton HD truck this was causing the front brakes to carry too much of the braking proportion. After the dealer installed the correct wheel cylinders

I had zero troubles. Now when my truck starts doing the shimmy/

shake, I know it's time to run the adjusters out on the REAR brakes and leave the front ones be. My point is CHECK YOUR REAR BRAKES for proper adjustment... . I'll bet they could use a tightening. Ed3

 

[Steve Campbell]

Possibly the track bar on the front axle?

 

[Joe G.]

Bill,



You should do a little diagnostic stuff before spending a lot of money. As Ed says, try adjusting the rear brakes first. If that doesn't help then check the run out on the rotors with a dial indicator. The tolerance is . 005". Also check rotor thickness. The manual says to make at least four measurements around the rotor. Thickness should not vary by more than . 025". If the rotor is within specks then no need to change. Then check to see that the calipers move freely on the pins. If not the wear will be uneven and so will braking. The pins are easy to lube. Remove them one at a time and grease them up with a silecone grease or NAPA's Silglide. You can check the track bar with someone in the driver's seat to turn the wheel with the engine running. There should be no visable slack in the ends.

 

[raychem]

Bill, I have both a 2500 and a 3500 with over 130k on both of them. I go through brakes on my trucks every 20 to 25k miles. but with the mileage on your truck, I would go ahead and replace the entire rotor. the reason being that evey time they are turned (cut and resurfaced), they become thinner and lose their ability to decipitate heat causing them to warp. New rotors run about 150-200 dollars a peice from Wagner but will solve your problems. Don't buy the rotors from the dealer or they will rape you with their prices. While you are there, you might also want to check the wheel bearings, rear seals on the rotors, and change the pads. Of all the parts in a car or truck, the brakes are the most important ones in my book. If you need any info on anything, e-mail me.

 

[illflem]

I paid $62 each for Bendex rotors from carparts.com (now JC Whitney) and have heard they are even cheaper from NAPA...

 

[Champane Flight]

Once

I was working in local shop and had a guy come in three times with warped rotors in one year. The first time he only had the truck for two weeks. We replaced the rotors and pads the first time. The second we had them turned. The third time,we put new ones on again and asked him exactly what he was doing to warp them. He said nothing,but when further questioning we found out he would take it to the car wash after long trips. Imeidiatly after long trips!Of course spraying cold water on a hot rotor is a real good way to warp em.....

 

[illflem]

Hard braking, such as coming down a steep grade, then coming to a complete stop and holding the brakes in one place for a couple of minutes is also a good way to warp rotors. If you find yourself in this situation use the parking brake.

 

[georgej]

Bill



I believe the correct tolerance for rotor thickness variance is . 001



when measured about 1 inch from the outside edge of the rotor.



Take your readings at 4 to 5 spots around rotor.





George J

 

[Joe G.]

You're right George. I guess I have to get my eyeballs calibrated. It's . 025mm (. 001").

 

[BTanzini]

Thanks for all your inputs to my problem. You will not believe what I found. I checked both rotors all bearings and suspension and what I came up with is the front shocks where shot so I replaced them with a set of monroes and that seemed to solve my problem. I have not noticed the simmy at any braking speed. I would not have thought that shocks would cause such a violent reaction to the breaking system. I was sure that My rotors where worped or I had some bad bearings. Thanks again guys