Brake Caliper Tech
PAD WEAR: As long as your pads are wearing evenly across the pad surface, the pads can be used almost down to the backing plate. Spacer plates may be added behind the pad backing plate as it wears so the caliper pistons will not have to be exposed to the abusive track dirt and grit.
A regular check of the brake pads for excessive wear and taper is necessary to ensure proper disc brake performance.
CALIPER BLEED SCREWS POINTING UP: When bleeding the brakes, make sure the bleed screws on the calipers are pointing straight up so there is no possibility of air bubbles getting trapped. If the calipers are mounted on an angle, you will need to unbolt one ear from the bracket. Pivot the caliper so it points straight up and place a spacer between the pads to prevent the pistons from coming out of the housing.
WEIGHT REDUCTION: Finding areas to cut weight is becoming increasingly more difficult, so if you are evaluating whether or not to take weight out of your brake system, here is something to keep in mind: A caliper’s size (and weight) is largely affected by the size of the brake pad it needs to hold. If you can go to a smaller brake pad (without running out of pad before you run out of event) then a smaller lighter caliper may be for you. For example, if your pads last about 10 races, consider going to a smaller pad that will require changing a bit more frequently. Remember, if you go to a smaller caliper, you won’t affect stopping performance provided piston sizes stay the same. Also keep in mind that pad wear is heavily dependent on operating temperature, so if you are going to experiment with downsizing, make sure you have adequate cooling.
CALIPER MOUNTING: Brake calipers should be mounted square with rotor to prevent excessive piston knock-back and uneven pad wear. While looking at brake area, have someone apply brakes. Caliper should not move (square itself to rotor): only the pistons and pad should move. If caliper is not parallel with rotor, shims should be used between mounting bracket and caliper ears for proper alignment. Caliper brackets should be strong enough not to deflect under heavy braking. All caliper mounting bolts should be of the highest quality and lockwired for safety.
CALIPER SELECTION AND MOUNTING: Most Wilwood extreme performance calipers are one directional because of the differential piston bore design (one end of the caliper having larger pistons than the other); the caliper must be mounted in a specific position relative to the rotor rotation. All Wilwood Ordering Information calipers are marked with a rotor rotation arrow on them. The caliper should be mounted so that the smaller piston end is closest to the rotor entrance, and the larger piston end toward the rotor exit. The larger piston end provides slightly greater clamping force to compensate for pad taper that can occur under extended severe use applications. An improperly mounted caliper (reverse rotation) will cause increased pad taper and reduce overall braking efficiency.
Note that differential piston bore calipers cannot be used interchangeably from side to side - there is a left hand caliper and a right hand caliper. Also, calipers differ depending on whether the mounting is behind or in front of the spindle - this affects bleed screw position. Make sure to properly analyze these criteria when ordering and mounting or replacing Ordering Information calipers.
PAD SELECTION: Proper selection of friction pads is a critical part of a high-performance disc brake system. It is important to analyze your vehicle’s braking requirements based upon track demands and driver braking tendencies, then select a pad compound which satisfies these needs. The proper compound for you can be found through a trial and error process, or contact Wilwood’s technical department for recommendations.
CALIPER PISTON AREA: A calipers piston area is calculated by finding the total piston area from one side of the caliper (this is true for a single piston caliper also). The graph provides the piston area for individual piston diameters. Note that differential piston bore calipers will be the total piston area of the different size pistons.
Example: For the six piston GN III caliper (1.38, 1.38, 1.75” pistons), the effective piston area would be: 1.50” + 1.50” + 2.40” = 5.40 square inches.
CALIPER REBUILDING: If you race on dirt or drag race on a weekly basis throughout the year, you should disassemble your calipers mid-season and inspect the caliper seals for excessive wear or hardness caused by heat. Asphalt racers generally experience more heat and should do inspections more frequently, especially after racing on a track where high temperatures are reached. NASCAR’s Winston Cup, Busch GN, Craftsman Truck and Road Race teams usually replace caliper seals after each race to ensure proper disc brake performance. Disassembly and replacement of the seals is a simple process and can prevent catastrophic brake failure.
AIR DUCTING FOR SHORT TRACK STOCK CAR RACING: Proper air ducting has become critical for effective performance of short track stock car disc brake systems. Short tracks, and most road courses, require specific air duct considerations to maximize the brake systems effectiveness. For complete information on stock car air ducting for short track and road racing.
Copyright © Wilwood Engineering, Inc.