Inox pistons for front calipers VX220 / Speedster

This conversion was made by us to solve the brake-failure-problem, caused by boiling brake fluid during heavy treatment.
We really wondered about this frequent problem, since the OEM brake appears to be dimensioned big and strong enough for a lightweight car like the speedster and should be able to offer stable brake performance.

But only in theory!

Major reason for this problem is the constrution of the OEM AP-Racing 2-pot caliper:
The AP 2-pot caliper is an aluminium caliper with pistons which are made from aluminium as well.
Aluminium indeed is a good choice to manufacture a lightweight brake caliper.
But at the same time it's a bad idea to manufacture the pistons from alloy as well, for the following reasons:
1.: Aluminium offers an excellent thermal conductivity - possibly the worst property of a caliper piston, since this will lead the heat of the brake pads directly to the brake fluid and let it boil.
2.: The standard aluminium which was used for the pistons requires thick piston walls to carry the brake force, while thick walls mean large surface in contact with the pad which again raises the heat transfer.
3.: Since caliper and piston are both made from aluminium, their thermal axpansion coefficient is almost the same. Since the piston'stemperature will raise higher that the temperature of the caliper, the clearance between caliper and piston will sink while the brake becomes hot. This keeps the piston "stuck" in position after pedal release, so the brake pad will never release completely - also in non-braking periods.

Our solution looks like this:
We manufacture caliper pistons from a special staniless steel alloy with the following properties:
ad 1.: Low thermal conductivity (less than 1/12from aluminium!!!)
ad 2: Higher strength of the material allows reduced wall thickness for another reduction of heat transfer.
ad 3: Lower thermal expansoin coefficient to avoid clearance reduction.
As an additional feature, we carve the pistons for ventilation.

The pistons are precisely machined to fit tothe OEM AP 2-pot calipers of the Speedster 2.2 and Speedster Turbo.
They fit 1:1 asa drop-in-solution to replace the OEM pistons without requiring any further modifications - Quality made in Germany!

Fits for Opel Speedster 2.2 and Speedster Turbo with OEM front brake calipers

Scope of supply:
The kit contains a full set of pistons (4 pcs) to modify both front calipers.