The following was a response to a thread posted in the RX8club.com forum. Please read the full thread here.
There are different types of calipers:
- Floating type single piston CI caliper - Typically for stock OE calipers such
as RX8 (Grand AM allows only stock calipers but can use two piece rotors).
- Fixed type multiple piston aluminum/CI calipers - Axial (leg) mount like some
stock caliper: RX7, Sti, EVO 8 (Al) or heavy trucks (CI)
- Fixed type multiple piston aluminum calipers - Radial (top) mount like
RB4000 caliper BBK for RX8.
- Fixed type multiple piston aluminum calipers - Radial (top) mount but with
differential bores like
RB400 caliper BBK for RX7.
Caliper deflection is unavoidable due to cantilever stress; however several
factors can affect the degree of flex or deflection:
- The axial distance (disc center to spindle mounting surface) - The
shorter the span the less of the deflection -
RBís center mount two piece rotor design requires less span
surface mount two piece rotors.
- Caliper design including how itís mounted - Leg (part of aluminum
body) mount will flex more than radial or top mount with high strength alloy
- The radial distance (diameter of the rotor), the smaller the rotor the
less of the deflection.
- The caliper material - A more rigid aluminum material means less flex.
Type of uneven pad wear:
- Between inboard and outboard - Typically seen in stock floating
caliper due to the sequence of applied pressure, inboard side is engaged with
caliper piston before the outboard side is engaged by retracted claws.
- Between outer and inner edge - This can cause due to caliper flex and
uneven temperature, usually outer edge wears more than inner edge.
- Between leading and trailing edge - Leading edge engaged with rotor
before trailing edge, this can be alleviated by piston size differentials -
smaller piston for leading and larger piston for trailing.
A better designed and well built brake system not only can provide a more
responsive and powerful braking performance but also extend the life of pad and