following article describes some of considerations when designing the braking system of the world's ultimate track-day car, the Caparo T1. Whilst most reviewers of this car have waxed lyrical over its phenomenal cceleration, it is generally the braking performance where they notice the greatest difference from any other roadgoing vehicle.

This vehicle posed particular problems for the brake system designers; there follows a review of the materials considered for the major structural component of the brake system, the caliper bodies. The vehicle utilises disc brakes on all 4 corners with Ø355 dia cast iron discs fully floating front and rear, 6 pot billet-machined calipers on the front and 4 pot billet machined on the rear. It alsoutilises a fully adjustable brake bias pedal box and a number of padcompound options available. Similar sized Carbon ceramic discs (CMC) are also available as an option.

The function of the disc brake caliper is to apply a clamping force across

the disc and generate a frictional unsprung rotational mass of the The function of the disc brake caliper is toapply a clamping force across the disc and generate a frictional force between the pads and the disc to retard the vehicle.

In order to reduce the unsprung rotational mass of the vehicle, the caliper assembly is required to be as light as possible and as it also resists the hydraulic pressure generated by the vehicle under braking, it is required to be stiff; a flexible caliper would result in a “spongy” feel to the brake pedal certainly not required for an ultrahigh performance vehicle. The chart opposite graphs the specific stiffness of a range of possible caliper materials.

Aluminum
The vast majority of OE automotive calipers are currently made from Cast Iron whose low-cost, high

strength and good specific stiffness make it an ideal material. As vehicles become more sensitive to the forcebetween the pads and the disc to retard the vehicle. In order to reduce the need to reduce weight the case for Aluminium becomes obvious, being 1/3 of the density with reasonable economics. Surface

Aluminum lithium alloys
The current rules in many FIA formulae including Formula 1 prohibit the use of any material other than Aluminium alloy and furthermore to a stiffness limit of 80 GPa and therefore to make maximum use of the restriction the Aluminium-Lithium materials are used by the majority of F1 teams. This pushes the stiffness from the more normal 72 GPa to t h e m a x i m u m a n d correspondingly also reduces the density from 2.79 g/cc to 2.54 g/cc, an improvement of the specific stiffness of around 15%. The cor responding material cost increase of around4:1 is considered acceptable in the motorsport world. These materials were first used in space applications and are now