Brake Rotors

click tracy · Oct 20, 2004

Does anyone here have any clues as to why the rotors on my 83 bronco get out of whack causing severe shudder when braking? When it first occured I put new rotors on and about a year later when the shudder got so bad again I had these machined true. This was fine for a while but the problem gradually returned and I just got the truck back from another machining. The bloke at the brake place reckons the problem is closer to the centre rather than the outer diameter of the rotor and he can't offer a cause.

Justshootme84 · Oct 20, 2004

They can warp either from excess heat, or overtightening the lug nuts. Lug nut torque of 100 ft.lbs., some guerillas at a local shop go to 200 and actually broke one of mine. As for the heat build-up, you could try a different pad brand or type. A wheel with more airflow may help, too. Since the rotors are fairly cheap ($25), I would get new ones instead of machining a warped rotor. Calipers are also cheap ($18) if you have one sticking.

bluesman17 · Oct 20, 2004

Do you tow anything?

click tracy · Oct 21, 2004

Not on a regular basis. A load of firewood every now and then.

click tracy · Oct 21, 2004

Sorry about late response but the email notification thingy doesn't seem to work for me.

BigNasty · Oct 22, 2004

Do you have oversize tires?
They can really work the snot out of a stock brake system.
Some ideas are.. bleeding the system out and replacing all the fluids withnew or synthetic brake fluid (IF.. that is IF I recall correctly that it helps disapate heat better)
slotted and drilled rotors (better cooling) and making sure the calipers themselves are in goos shape.
If the (caliper) piston seal is worn out or old, it won't draw the pad off the rotor as it should and will cause a lot of extra heat for the rotor by having the pads dragging on it constantly.

click tracy · Oct 22, 2004

31" tyres BigN. When it was really bad I jacked up the front end and the wheels spun quite freely. Could just feel a slight tight spot every revolution for about 10 degrees so I don't think the caliper is the problem. Good thought though. Bearings ok.
I might try the brake fluid thing as it would be due for a change anyway. Justshootme's suggestion about lugnuts will be explored too.
Thanks Guys

streetgang · Oct 22, 2004

My bet is lug nut torque.....some rotors are VERY sensitive in this respect. It could also just be that you got a set of shitty rotors that are prone to warping. I would just pull off the old rotors (freshly cut or not), and replace them with new ones.....buy the hub/rotor combo, and replace the both wheel bearings on each side while your in there.

FWIW: I will only use Bendix or Raybestos PG Plus rotors.....both brands are available with the hub (new lug studs, and outer bearing races) installed. You will still need to buy the four bearings though......I favor Timkin brand wheel bearings.

mytruck · Nov 13, 2004

Have you checked to see how well the rear brakes are adjusted. if the rear brakes are not working or way out of adjustment the front brakes will be doing over time insted of there job. Since must bronco's are older it is a good thought to bleed the brakes, but very carefully. A older master cylinder will damage the cups in the pistons. I surge bleed brakes with left foot under the brake pedal to keep from pushing piston in far enough to get the pitted part of the of the master cyl. tube. Surge bleeding 1. top off master cyl. 2. pump pedal 3. have asst. open bleeder 4. slowly push the brake peddle to the top of your left foot 5. have asst .close bleeder 6. pump peddle to top of foot and repeat process 2 to 3 times starting with the p-rear,d-rear,p-front,d,front. Do not get in a hurry in less than 30 minutes you can change all the fluid out.