Hardbar T1 Brake System for C5 & C6 Corvettes

Disc Hat Mounting Instructions

Mounting the Hardbar hats on the AP Racing discs is a simple procedure that only takes a few minutes.  Hardbar has put together a short video that details the procedure.  It can be found here.

T1 Brake System Development History

A few years ago we (Essex Parts) requested a new race caliper from AP Racing that would directly target the Wilwood Superlight four and six piston calipers in professional racing. Most notably, the Wilwood SL6 and SL4 were very popular in asphalt Late Model racing. Our primary goals with this new caliper were to offer something that was substantially stiffer and more durable than the Wilwood’s, while retaining a commonly available pad shape and low weight. That caliper was produced, and became very successful in circle track racing. Customers noted that the increased stiffness provided superior brake modulation, less pad taper wear, better pad release, and an overall longer service life for the parts.

What we've done now is to take those professional grade parts and make them available to club racers. We’ve optimized the components for the production-based racer who is starting out with a street car. The Late Model version of the calipers was an axial mount. In other words, there are two ears on the back of the caliper used to mount the calipers on a Late Model spindle. We changed that to a radial mount caliper, which is what most people in the aftermarket are familiar with. The caliper rides on a carrier bracket that was custom designed for the Corvette by Hardbar USA.  We also made sure to size the caliper pistons properly, so our T1 customers could retain their stock master cylinder and proper brake bias.

We added some other trick features as well. Stainless steel pistons keep heat out of the brake fluid, and 4lb. springs keep pad knockback in check. The calipers come in a durable, heat resistant anodized finish. Only the best high temperature seals will be used, and we’ve incorporated some protection for the bleed screws as well. The outer bleed screws and crossover tube sit in a little cove that protects them from impact. That means you’re less likely to trash your calipers if you happen to them when changing your wheels. We also used the same pad shape that Wilwood uses. Why reinvent the wheel? This caliper uses a 20.5mm thick pad, which is thicker than most of the competitive systems on the market (which typically use 17mm thickness). That means greater insulation/thermal barrier between your disc and your brake fluid. We wanted a pad shape that is available in just about every flavor imaginable from all major pad manufacturers. That means our customers won’t get stuck without pads at the track. They’ll be able to beg, borrow, or steal some pads that will work in a pinch. It also made it less painful for the Late Model Wilwood customers to upgrade to the AP’s if they had a bunch of already purchased pads in their trailer.

Concurrently, a new AP Racing disc was developed to accompany that caliper. It was a trickle-down product. Essex and AP had previously put their heads together to design the ultimate floating brake disc for NASCAR Sprint Cup. Some of the design objectives with that new disc were increased airflow to keep temperatures down, increased crack resistance, less distortion, longer wear rates, and the best slot design for increased bite (and to reduce stress risers by promoting even heat transfer throughout the disc).  The CP3908 disc was derived from that experience and learning. Essentially, it was a miniature/compact version of the discs being used in Sprint Cup.

Another objective with this kit is to provide a compact system that fits under 17" and 18” wheels. While a show car guy may want enormous discs and with red calipers to fill his wheels, the racer wants to squeeze the maximum performance out of as little as possible. A smaller diameter disc has a lower moment of inertia, and all else held equal weighs less (unsprung).  A lot of the systems on the market use gigantic 14-15” discs.  If you’re endurance racing you may need the thermal mass of that giant disc, but for shorter sprint races/sessions we wanted to go as small as possible while still getting the job done.  Any excess fat is just weight and money wasted in the wrong place.  We therefore retained the 325mm x 32mm C5 factory size to remain within the letter of the T1 rules.

Hardbar has designed and is manufacturing some very cool, high airflow floating hats to ride on these discs. The design details put into the disc and caliper design will allow the kit to compete favorably with a system with a much larger diameter disc. In other words, all of the little details I described above transform what initially appears as a “stock-sized” system into something much greater.