The most common reasons are the brakes where not bed or bedded improperly, brake pressure is too low, the front to rear proportioning is incorrect, the size or type of brakes are inadequate , brake pad material is insufficient, or not pulling the chute.
New brakes should always be bed. During this process, brake pad material is transferred to the rotor surface. This creates the actual wear surface and protects the rotor. The heat generated will finish the curing process of the brake pad. Common problems associated without bedding are heavily scored rotors, pads cracking or chunks of material missing. The process is relatively simple. It consist of 8 to 10 applications of the brakes, increasing in harshness each time, and allowing the brakes to cool slightly in-between. Do not keep the brakes applied between stops. After the last stop, allow the brakes to cool down completely.
If the rotors are blued, but not warped, this may not be a problem if the appearance is the same on all. Do not resurface them purely for this reason as it will shorten their life. Low pressures generate heat over a longer period of time before the vehicle comes to rest. This can occur if the pedal ratio is insufficient or the bore size of the master is too big. If it’s just the fronts or rears, it could be a sign of improperly proportioned or undersized brakes. Check brake pressures with a temporary test gauge such as our P2360. With a very firm pedal, like setting a line-Iock, the front should read 550-650 PSI and the rear 1,000-1,200 PSI. These pressures assume that you are using an adjustable proportioning valve, similar to our B3369, to balance the braking system. If only one rotor shows excessive heat, it could be pistons sticking in the caliper requiring a rebuild. If you replace pads more often on the front, you may have high line pressure in the front, need larger brakes up front, or low line pressure to the rear. If you are replacing rear pads more, possibly the pads material might be too soft for your application. When using hard metallic pads, it is common in higher MPH cars to leave residue on the rotor surface. This is melted pad material that occurs when they are near their limit and needs to be removed when the pads are replaced. Machining is not required as it can be removed with a sanding disc and air drill.
For cars equipped with chutes it is important to use them. The chute scrubs off a lot of MPH once it is deployed and significantly lightens the load placed on the brakes. Calculating kinetic energy in which velocity is squared, makes increased MPH a real issue. If pulled, you could expect a set of pads to live half to a full season, and rotors for several years. If not, pads maybe every four races and replacing the rotors once a year. Many that don’t pull their chute, will opt for our 2 piece stainless steel rotors (B2794LS / B2794RS) which, in this case, last about two years before requiring resurfacing.