2006 TC Kline Racing Carbon Roadster

Motoring Channel Staff - 20/June/2006

BMW's new Z4 M Roadster is a fire-breathing sports convertible that's ready to challenge Porsche and others for supremacy in the German 2-seater roadster market. Powered by BMW's highly strung and world famous 3.2-litre engine, it hammers from 0-100km/h in just 5.1 seconds.

But it would seem that for some, BMW's rock hard roadster ($129,500) isn't enough. Meet the the Carbon Roadster (CR), the first complete car offered by TC Kline Racing Inc. 

North American (Ohio) BMW tuner and car racing team TC Kline have worked hard on the body of the Z4 M, making it not only lighter, but also more aerodynamic.

The 2006 TC Kline Racing Carbon Roadster, which first appeared late in 2005 at SEMA, is claimed to be an ultra high performance sports car by its makers, and tips the scales at more than 200kg under its donor car: just 1215kg (2680lbs) compared to the normal Z4 M Roadster, which totals 1485kg (3273lbs).

So how does the racing company create a road-going sports car that weighs 270kg less  than it's originator? Carbon fibre composites, or CFC to those in the know. 

TC Kline explains that the entire skin of the CR is manufactured from CFC and the changes to the Z4 bodywork create a much more imposing look in addition to the lighter weight and improved aero, giving the Z4 a tough profile that hugs the ground. 

As TC Kline rightly points out, if you walk around the CR you will not find any body lines which do not serve as an extension of function. Therefore,the Carbon Roadster body work incorporates aerodynamic performance enhancements with a larger front air dam, front wheel house vents, side skirts, and a pair of extravagant rear diffusers. The body also has all four wheel arches flared 1-inch wider to accommodate fatter wheels and tyres.

Fitted with huge 19-inch alloy wheels as standard, the US$95,000 (A$128,000) roadster will provide drivers with supreme levels of grip. And thoughthe final design for the wheels has not yet been finalised, the specifications have: all four wheels will be a one piece forged aluminium design for the lightest weight and strength. The Carbon Roadster's standard front wheels are 19 x 9.5-inch at the front and the rears are 19 x 10.5-inch. Optional wheels in 18-inch sizes will be available in forged aluminium as well for those drivers who want to take advantage of a larger selection of ‘R’ compound tyres and/or are interested in a more comfortable street ride. 

The standard tyre aspect ratios for the CR are 265/30 up front and 295/25 at the rear. According to TC Kline, using Sport Cup tyres the car produced a stomach-churning 1.06 G cornering during testing.

As the Z4 M Roadster uses much of the E46 M3's drive line, the modified TC Kline Carbon Roadster is based on that car and shares its 3.2-litre motor, but develops a little more power than the standard car's 252kW @ 7900rpm. Thanks to an aluminium flywheel, the Carbon Roadster has quicker throttle response and improved acceleration, and coupled with TC Kline's specially developed thin-walled stainless steel exhaust system, the final power output is 258kW, up by 6kW. The new exhaust system is also lighter than the stock system, whose tail pipes can be seen poking out between the two large rear diffusers.

In addition to the dropped weight, improved aerodynamics and tighter drive line, the suspension springs for the CR are made in Germany from a light weight alloy steel and TC Kline can tune the car for individual needs. If the car will be a track day special, the suspension can be tuned to be responsive and tight, while everyday use can be softened up somewhat. The Carbon Roadster's front struts are topped off with TC Kline designed front camber plates for quicker turn-in and steering feel, while Delrin bushings replace the standard rubber bushings in the front lower arms and rear trailing arms for quicker response and markedly improved feel.

Another area of the chassis that the American racing/tuning group has paid attention to are the brakes. It has revealed that Performance Friction Corp. supplies the car'slight weight aluminium monobloc calipers for use on the CR. The front calliper is a four piston design with four brake pads (PFC carbon metallic brake pads) for superior modulation and high brake torque working 345mm discs, and the rear calliper is a two piston design sharing the same pads biting 328mm rotors.

Drawing up a contract with Recaro, the seat maker produces a one piece shell performance seat specifically for the Carbon Roadster upholstered in grippy Alcantara and leather. These light weight performance seats feature cutouts for a driver harness and have exceptional support while maintaining excellent driver comfort, similar to the designs seen in the BMW M3 CSL and Porsche Carrera GT.

TC Kline is clearly quite proud of its carbon fibre speed demon, saying "It has 346hp and corners with 1.06G grip. Take a minute to soak that in. The CR weighs 150lbs [68kg] less than a Honda S2000, has the HP of a Porsche 911, and has wider wheels and tyres than a Ferrari F430. Incredibly, the CR weighs 700lbs [317kg] less than a BMW M3 while maintaining the same power."

TC Kline explains that it's strict adherence to the fundamental principals of light weight and dynamic performance has resulted in a true sports car in the Carbon Roadster. And even without the drive line modifications, the carbon fibre body shell ensures that the car is some 270kg lighter than the one it's based on, so with that alone it's 0-100km/h would drop by at least another .03 seconds, taking the 0-100km/h dash to just 4.7 seconds.