brake tech: mclaren slr

Modern formula racecars often make use of carbon brake rotors. First introduced to Formula 1 by Brabham in 1976, these carbon discs are now the norm in top level racecars, where late-braking heroics mean super-high operating temperatures and glowing red brake parts.

The super-high temperatures that make carbon brakes so effective on the racetrack, however, are rarely (if ever) seen on road cars.

“It’s all marketing” explains Hartmut Feyhl. “A lot of people want to have these carbon brakes and things on their car because it sounds good, but even on track days, most drivers will never reach the kinds of temperature you need to get the most out of those brakes. And you never see it on normal roads.”

If anyone is qualified to make that kind of claim, it’s Feyhl, who worked as AMG North America’s technical director before starting RENNtech, his own tuning house, in 1989. RENNtech is generally regarded as the nation’s foremost authority on Mercedes-Benz tuning, and their expert engine-building and superb brake packages, in particular, were the foundation that reputation was built on.

“As soon as we got the car here, we changed all that out,” says Feyhl. “My customers are concerned with performance, and especially usable, real-world performance.” To that end, Feyhl’s crew in Lake Park replaced the race-spec carbon setup with huge 16.2” discs and RENNtech-specific 8-piston calipers. Visually, the effect is stunning. “When you look at the wheel, you can’t see any space between the rim and the caliper.”

It’s a tight fit, but the new RENNtech brakes, combined with RENNtech’s lighter-weight 10 spoke “Monolite” wheels, noticeably improve braking performance and “feel” out on public roads, where these cars are likely to spend the majority of their lives.

“It’s the kind of package that separates a ‘real tuner’ from the kind of ‘tuner’ you see on MTV or Discovery Channel,” says Feyhl. “‘Customizer’ might be a better term for those companies that are all about spoilers and body kits and flashy wheels. For us, it’s all about getting the best performance out of these cars.”

RENNtech’s McLaren SLR program includes the wheels and brake package mentioned above, as well as intercooler upgrades, ECU tuning software, and a revised supercharger pulley kit good for over 720hp.