|Originally posted by theogre:|
[QUOTE]Originally posted by hyperv6:
Another issue is the so called warped rotor issue. Many people think rotors warp and often spend a lot of money and never really solve the real issue. Drilled rotors and warped rotors are two of the most misunderstood things on a car today.
"Warp" rotors are often cause by caliper and/or hydro problems too.
Example: 84-87 rear bakes are known to has problems and can cause "warped" rotors, boil brake fluid, ever fires.
I've turned and even replaced two or three times rear "warped" rotors... Cause was bad caliper pistons dragging the pads even after tried several brake adjustments. Even replace w/ rebuilt caliper had same problem after driving a year. I restored the brakes w/ brake recall kit (no longer available) and haven't had problems in years.
you might not feel the problem thru brake pedal because of power brakes but the car can have uneven brake performance trying to stop. Often More obvious at low speeds because behaves similar to anti-lock brakes active but slower modulation (often related to parallel surfaces problem) And/Or you can hear metal to metal noises when caliper etc move sideways when remove the brake pedal pressure to inch forward the car in slow traffic. (often related to rotor and/or wheel bearing runout problem.)
Well that is a true issue but not warped rotors. It is really called RTV. Rotor Thickness Variation. The rotor does not warp but the run out is worn in. I know it is similar but warped generally implies the thickness is the same just out of run out. In this case the metal wears uneven.
Not trying to be nit pick but that is how the industry defines it.
One of the greatest causes for RTV is on today's positive off set wheel set ups. This is because many of today's cars use ball bearing vs roller tapers. It is hard to damage a roller taper but a ball bearing can be damaged very easily. I think if I recall .003 of play can let a rotor wobble enough that it will wear uneven and create RTV. If you note the complaints have risen much since the advent of these new hub bearings that are ball bearing on most cars. They went to them as they roll better and get better MPG but at the price of durability.
Another issue is the problem of modern brake material getting hot and embedding on one area of a rotor. This is like if you spilled a Coke on the floor and create a sticky spot and then try to slide across the floor in your socks. It grabs.
This is generally caused because few people ever bed or seat their pads in on their cars. This is a series of stops that will coat the rotor evenly with pad material and will help prevent this build up.
Unseated pads on a hard stop say on an off ramp can adhere to the rotor at the stop light at the end of the ramp. This material sticks to the rotor and creates a spot it will grab. Often once it starts it will add more material and get worse. In some cases it can even go away with general wear if it was not too pronounced.
Generally a light cut will clean it or a hit with a sanding disc lightly will clean them up. Racers often will have a set of very aggressive pad they will install to clean the rotors up in practice and then go to the race pads in a race.
But you can generally get rotors red hot and they will not warp. We have done it often on the race car and the rotors are never an issue.
I do agree hanging caliper pistons can be an issue but generally they just wear out a pad as it normally drags all the time. Some of today's cars also get corrosion build up under the stainless slides on the caliper bracket. This scale does not look like much but it will grow the cast steel to where the pads hang up and the caliper will drag the pad on the inside. Very common on many cars even my Malibu. I cleaned the brackets and painted them with a paint to stop the rust scale and it solved the issue. Many people have replaced other parts and missed the bracket scale. I did the first time till I was taught what to look for.
Brakes are very different today than in the past with the new bearings and pad materials. Many older mechanics fail to keep up and miss seating the pads in because with the old semi metallic it was not a problem. Same on the older roller bearings as they rarely failed. The new hubs are sealed and few people know they are ball bearings. Because they are even RWD cars are now using positive off set wheels to keep the weight centered.
My tech seminars have been a big help keep up since I am in the office much anymore. But at home working on my cars along with family and friends it helps me keep up with the changes.
The key to today's cars is just because it looks the same don't assume.