Suspension is the most important part of a car. Engines and brakes are comparatively less critical, because suspension does its work, defining the driving experience, whenever the car is in motion, whether driving to the grocery store, commuting on the freeway, carving up a mountain road or hitting the racetrack for some maximum-grip enjoyment. Project 325is needed something good.
T.C. Kline has been autocrossing and road racing cars in almost every major American series for nearly 20 years. He's been most closely associated with BMWs for several years and has developed his own line of suspension components to make them work on both street and track. During the time TC Kline Racing was involved with Pro Parts USA and its Koni rebuild center, T.C. started developing his own damper valving, working with the idea that it should be possible to make a BMW ride comfortably on the street and work well on a racetrack, too.
The coilover system he came up with is meant to confound what most people "know" about suspension compromises. It is designed to be extremely user-friendly, even with adjustable ride height and adjustable damping in both compression and rebound. A conservative customer who puts it in a car with "street" spring rates and leaves the dampers at their lowest settings will have the same stiffness as typical sport springs, but the significantly better valving will make the car ride better than stock. TC Kline Racing stocks springs from 300 lb/in. to 650 lb/in.; the same dampers can be adjusted to work equally well with higher spring rates as the customer's level of track focus increases.
TC Kline Racing's dampers are built to its specifications in Holland by Koni. The internals are racing parts, so these dampers go down a special line where they are hand-assembled in batches of 100 or 200. The Koni workers build dampers all day, every day, so mistakes are unlikely. TC Kline Racing's rebound adjustment is Koni's standard external mechanism, twisting a knob at the top of the shaft, with a range of 2 1/4 turns. The compression adjustment is made by means of a screwdriver at the bottom of the damper, with 12 clicks. The mechanism compresses a Belleville washer, increasing or decreasing preload in the twin-tube damper's base valve. (If this paragraph lost you and you want to learn more, check out "Suspension Basics, Part 6" on europeancarweb.com.)
TC Kline Racing contracted Vogtland to build its springs. Vogtland also happens to build springs for some of Koni's suspension kits and uses Koni dampers in some of its own kits, but that's not why T.C. chose it. Vogtland's springs are lighter and have more travel than others he considered, and "that's what we wanted."
Vogtland's secret technology is its VVS wire. Produced in only one mill, the steel contains a proprietary alloying element that allows a high-tensile spring material to be worked at higher stress levels without fatigue problems. The wire manufacturing process is more costly, and Vogtland has to do some of its own post-coiling processing to improve fatigue characteristics. The result is that thinner wire can be used, reducing weight and allowing the spring to compress a greater distance from a given free length before it reaches coil bind. Vogtland North America's president, Richard Jonec, mentioned that the weight reduction for TC Kline Racing's rear springs was about 35%, especially notable.