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Calipers

Q:   How much more expensive are powder coated Calipers over anodized calipers?

A:  It varies with the caliper model. Contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support for exact pricing.

Q:   What advantage is there in having a radial mount Caliper over a lug mount caliper?

A:  Radial mount calipers and brackets offer a much more rigid mounting system than a lug mount design. The radial design also accommodates rotor diameter changes with a simple spacer rather than a whole new bracket. A customer with a 13” rotor kit that wants to upgrade to a 14” rotor would only require longer studs and spacers rather than a completely new taller bracket.

Q:   Which is the more ridged Caliper, a two-piece or a monobloc?

A:  Everything being equal, a properly designed two-piece caliper will flex less than a monobloc caliper. Stiffness is a function of the material’s modulus of elasticity. Steel bolts have an elastic modulus approximately three times that of aluminum bridges. There are some exotic aluminum alloys that were developed for F-1 racing that have almost the same elastic modulus as steel; however, they are expensive and not normally seen in after market brake kits. Steel has the added benefit of not losing its elastic modulus as things heat up. As a matter of fact, steel’s elastic modulus actually increases in stiffness as temperatures rise above 200 degrees F by approximately 30 percent, where it stabilizes at 400 degrees F. Aluminum on the other hand, loses approximately 50 percent of its stiffness by 300 degrees F.

Q:   How often should I be rebuilding my Calipers?

A:  The short answer is, “on condition.” For street use it would depend on the type of driving you do and the environment. If the calipers are not leaking or binding, there is no reason to rebuild them, sans some other anomaly. It is advisable to change your brake fluid annually. This will help preserve your caliper piston seals as well as other brake system components.

In a racing environment, the calipers must be regularly inspected for leaks and o-ring elasticity. Sustained high heat, over 600 degrees, will cause the o-rings to lose elasticity and will require more frequent replacement. Professional racing teams competing in NASCAR often rebuild the calipers after every race.

Q:   What's the purpose of having a big piston and a small piston in a Caliper (staggered pistons)?

A:  Multi-piston calipers, normally with six or more pistons, have bore sizes that increase in size from front to rear.

This allows a pressure differential between the leading and trailing edge of the caliper, thus providing an even wear pattern along the entire length of the brake pad, hence it controls brake taper. This is necessary because incandescent material and debris from the leading edge of the pad is trapped between the pad and rotor; it tends to float the trailing edge of the pad off the rotor. A larger piston at the trailing edge of the pad provides more pressure to compensate for this debris buildup and keep the pad flat against the rotor.

Q:   Do you offer a Caliper that will bolt onto the existing factory brackets?

A:  At this time we only offer three direct replacement calipers. The D8-4 caliper is designed as a direct replacement aluminum caliper for the C2 and C3 Corvettes that bolts directly to the OE brackets. We also offer the GM 3 and GM metric calipers that are designed for specific racing applications where the braking specification requires a single piston OE type caliper. We just released the D52 caliper that replaces the popularly used '68 and later GM caliper. You can also contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:   Will bigger Caliper pistons stop better?

A:  Larger caliper pistons will provide more clamping pressure on a given axle, and therefore increase the braking performance of that axle, providing the tires and suspension are able to transfer that brake torque to the road effectively. If the caliper pistons are too large for the application, they’re likely to cause excessive pedal travel and an adverse change in front to rear balance resulting in longer stopping distances. It is also possible that clamping forces can become so strong that pre-mature lock-up will occur, making brake modulation difficult. Wilwood’s big brake kits are specifically designed for each application, while maintaining or improving system balance.

Q:   What is the difference between fixed and floating Calipers?

A:  The primary difference between a fixed or floating caliper is in the mounting design. Fixed calipers are solidly mounted to the spindle or bracket, and floating calipers float on a pin that is attached to the spindle. Fixed calipers have opposing inner and outer pistons. Floating calipers have only inner pistons and rely on outer pad carrier movement to apply pressure to the outer pad. Floating calipers tend to be more forgiving to OE manufacturing tolerances hence they are used on the vast majority of production cars. On the other hand, fixed mount calipers that transfer PSI within the caliper into braking performance with a much higher efficiency are typically used on high-performance cars and for vehicles exclusively employed in racing for that purpose.

Q:   Why can't I get the Caliper to fit over the rotor on my rear axle kit?

A:  The most likely problem is that the offset of your axle is different than the offset specification for the kit you purchased. If the kit you purchased specifies a 2.5” axle offset, but your axle actually has a 2.36” offset, the caliper will not center over the rotor.

Wilwood’s rear brake kits are designed for use with the factory offset for a given housing flange. If the offset of your axle is different than the brake kit was designed for, it will be necessary to have your axles re-machined to the factory-offset specification. If you have any questions, please contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:   How do I bleed a multi-piston Caliper with the four-bleed screws?

A:  After the master cylinder has been bled, begin bleeding the calipers starting with the wheel farthest from the master cylinder, usually the right rear and start with the upper outside nipple, then move to the upper inside nipple (never bleed the lower nipples). Repeat the process with each wheel, moving successively toward the wheel closest to the master cylinder. For best results the upper nipples should be pointing straight up because air migrates to the top of the chamber. If you have any questions, please contact a Wilwood Sales Technician at 805-388-1188 or email Sales/Tech Support.

Q:   What is Caliper piston area? How do measure it?

A:  It is the total surface area of all the pistons in one half of the caliper.

The piston area can be determined using the formula: Area = pi x the piston radius squared x the number of pistons. For an example, lets use a six piston caliper and for ease of math, let's say that all the pistons are equal in diameter at 1.5 inches: 3.14 x .5625 x 3 = 5.29 square inches.

Q:   What is a crossover tube?

A:  Crossover tube is the external tube on a caliper that transfers fluid from one side of the caliper to the other. Some calipers have internal fluid passages and do not require crossover tubes.

Wilwood Engineering, Inc
4700 Calle Bolero
Camarillo, CA 93012
Phone: (805) 388-1188
Fax: (805) 388-4938

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