Guys, I am aving a heckuva time with my front brakes. I replaced everything including the rotors. They were fine fo awhile but are now pulsating again! I checked the bearing play and the new rotors for hotspots but found no problems. How susceptable are Bronco rotors to warping when over-tightened?

 

Since the rotors are held in place by the wheel studs, there is really no way to overtighten them. If the bearings are fine and the rotors are new, you might want to make sure you haven't got a damaged knuckle or some other problem that is causing the feel of pulsing brakes. Could even be a bad set of pads. HAd a set for my 69 Cadi come out of the box and never did seat onto the rotors for some unknown reason...replaced them after about 200 miles cause I couldn't stand it. Never had another problem.

 

As long as your calipers are free to move in their brackets, warped rotors shouldn't cause much if any pedal pulsation - you DID clean the rust and swarf out of the ways in the bracket, didn't you?
The primary cause of <B>pedal</B> pulsation is thickness variation in the rotor, and this is most often found in a vehicle that has been parked for a while, when the rotors rust everywhere except where the brake pads sit; then the rust gets scoured off when the brakes are used a few times, leaving low areas (where the rust was) and high spots (where the pads were).

This low spot/high spot thing causes the piston to move in and out, producing pedal pulsation that is usually worse at lower speeds, since the rate of pulsation is slower.

It's very difficult to spot this by measuring the rotor(s), since thickness differences of less than 0.001" (one thousandth of an inch) are enough to make the pulsation.
Turning the rotors should fix the problem, but the next time you drive through a puddle, then park the truck for a month, it may well come back.
A good general rule would be to never park the truck for an extended period right after driving in the rain, unless you first get the brakes good and hot.

Good luck;
- R
PS: All these remarks apply only to floating caliper vehicles like Ford trucks, but not to fixed-caliper vehicles, on which warped rotors WILL cause pedal pulsation.

 

do you think it possible that the rear brakes could be causing this?

 

(Slapping forehead) Well yes of course!

But you can sort that out by applying just the parking brake, at the speed where you get the worst pulsation. Holding the brake release handle.

If it's the rears, you'll feel the pulsation in the e-brake pedal.

- R

 

Also, if you went with aftermarket rotors that may be your problem. I have seen and heard about alot of people that used aftermarket rotors and got vibrations right off the bat. Just a thought.

 

I give up on this one - I had new rotors put on and they have a light pulsation since new, they resurfaced them twice and said they were flat but still the slight pulsation. I believe it is because they are cheap, lightweight rotors, and they vibrate a little even when flat.

Next time I will install good name brand rotors like Raybestos or something.

 

The easiest way to determine if the front or the rear are causing the pulsation is to feel the steering wheel while you brake. If the wheel shimmies in your hand, the front brakes are the problem. If you mainly feel the pulsation in the brake pedal, the rear brakes are the problem.

It can be either, or even both. If you get a pulsation right after the brakes were done, then the rotors/drums were warped right out of the box. You should ALWAYS turn new rotors and drums for this reason. If the pulsation developed over time, then cheap parts are likely to blame. Excessive heat will also cause pulsation, so you might have a hanging caliper.

Cheap pads can also cause problems by not seating correctly. That can feel a lot like a pulsation.

The above statement is incorrect about warped rotors not causing pulsation - I think just about everyone knows that.

 

I made a distinction between pedal pulsation and steering wheel shimmy; pedal pulsation is NOT usually caused by warped rotors, not when you have floating calipers.

Pedal pulsation in the front brakes will still cause pulsing of the brake pedal - that's why it's called "pulsation" and not "steering wheel shimmy."

I'm not dealing with what "everyone knows," here, but with facts.

- R

 

what year is your bronco?

Pulsing might just be from the ABS kicking in too soon.

When mine works(rare) my pedal pulses. Maybe thats what u have.

 

Yeah cheap rotors will warp just driving around town. If you didn't use Raybestos rotors I would try them, they use a very high quality steel. Many shops are using off brand brake parts that are made in China or Taiwan and use poor quality steel. I like the Akebono ceramic pads (available from Tire Rack...) and Raybestos rotors (PepBoys). They cost a little more than the off-brand stuff but in critical areas like brakes it just doesn't pay to skimp. On the big Broncos 90% of the braking is accomplished by the front brakes. There is a tremendous weight shift forward during braking because of the extremely short wheel base of the Bronco. The proportioning valve is calibrated to send very little fluid pressure to the rear brakes to avoid locking up the rear wheels. Your rear brake shoes will last 6-8 times longer than your front pads. Its even worse when you lift kit and big tire the Bronco.



Mike
'96 5.8L EB