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.
TC Kline Racing pulled one more trick from its sleeve. All the springs it sells for its coilovers are designed to have the same static length when supporting the weight of a typical BMW, allowing various rates to be interchanged without having to readjust ride height. A customer can pull the suspension apart, swap springs, put it back together, tweak the dampers and drive away. T.C. said the corner weights aren't affected when changing spring rates on his race cars.
TC Kline Racing's complete coilover system ideally should be complemented with its camber/caster plates. The load distribution ring means they won't overstress the unibody's strut tower. T.C. stated that they don't affect ride at all but dramatically improve turn-in. They also improve vertical wheel control, because the small motions that would be taken up by the factory rubber upper mount are fed into the damper. These camber plates allow a car to be set up with 2-degrees negative camber for the street and be changed to 3.5-degrees negative at the racetrack just by unweighting the suspension and loosening the three upper mounting bolts. Roughly 1/8-in. toe-out is added, which is wanted for best turn-in. TC Kline Racing's camber plates fit all BMW E36 and E46 models and can be used with virtually all OEM struts and aftermarket shock inserts built to OEM mounting specs--coilover or not.
TC Kline Racing's rear upper shock mounts come in rubber for street use or monoball for track use. The monoball version doesn't ride harshly but does transmit noise to the body. That goes unnoticed in race cars but tends to irritate street customers.
The same applies to the firm's aluminum trailing arm bushings and rear lower arms. They improve lap times measurably but are most satisfactory on track- or competition-focused cars. For street-driven E36s, T.C. recommended 1997-up M3 bushings everywhere, including the rear subframe. They are harder and firm up the chassis' feel, especially with an older car like Project 325, but the rubber's damping qualities still absorb noise and road shocks. The one exception is the front control arm rear bushing, where T.C. recommended the 1995 M3 part for maximum caster. If you have the ducats, aluminum front control arms from the E30 M3 are bolt-ons and reduce unsprung weight.
TC Kline Racing uses Racing Dynamics anti-roll bars, but T.C. wanted me to try his suspension with the stock bars for awhile so I could become familiar with it and to isolate its characteristics from those of the bars.
For alignment specs, T.C. recommended the following: Front camber, 2-degrees negative for street, 3.5-degrees negative for track. As noted, this takes just minutes with the camber plates. Front toe, 1/16-in. total in for street, 0-1/8-in. out for track. Caster, all you can get. Rear camber, 1.5 to 2.0 degrees. Rear total toe 3/16-in. in.
For the initial installation, Project 325's ride height was set to minimum to provide best performance in handling tests, but it was apparent from driving on the street that more travel was needed, so I raised it 1 in. and reset the toe before going to California Speedway for skidpad and slalom testing. The stance now looks just the way I want it to, and there has been no issue with bottoming on the street. I didn't have time to shim the front struts to 2-degrees camber, but I did check it, and it was 1.5 degrees and went to 3.0 degrees when I moved the camber plates in. Good enough for a first run. The only adjustment that posed any problem was rear rebound, as my car's rear deck speakers include enclosures that hang down in close proximity to the rear shock mounts. I'll let you know what I figure out.
The ride had been getting choppy and the camber plates were beginning to make noise, so I checked and found the upper strut nut was loosening on both sides. I applied Loctite(R) and retightened them and the problem was solved; the ride was back to plush and silent. This suspension rides the way a sport-model O.E. suspension should, and much better than many do.
At the track, the plates worked as advertised, and it took about 3 minutes to change both sides' camber from street to track settings or back. In prior testing with the 8x17-in. SSR Competition wheels, 235/40-17 Continental ContiSportContact 2 tires and stock suspension, Project 325 did 0.84g on the skidpad and 66.2 mph in the slalom. Those figures increased to 0.88g and 68.8 mph. Turn-in was definitely quicker. None of these figures is astounding nor embarrassing, though I had expected a little more from both setups. In the realm of comfortable street cars, Project 325 is definitely respectable. But it's not ready for the track.
Certainly, much of Project 325's performance can be attributed to the qualities of the ContiSportContact 2 tires, which I am discovering are not focused in the direction to best suit my taste. They ride well and make very little noise, qualities that have won O.E. fitment on many Mercedes-Benz models. In fact, these 235/40-17 tires actually ride better than the 205/60-15 all-season Michelins the car came on. Designed for high-speed autobahn travel, the ContiSportContact 2's carcass limits heat buildup at high speeds, and the wide grooves in the tread pattern evacuate water very, effectively. I was able to inflict a surprising amount of abuse, sliding the car for the lead photo, before they went away. There isn't a lot of water around here, though, and I'm used to tires more aggressively focused on dry handling for my project cars. I have plenty of ideas for when these wear out.
In some severe driving on the bumpier portions of California Speedway's parking lot, Project 325 showed some imperfections with the setup. Partly due to the modest spring rates and partly due to the still-stock anti-roll bars, the body rolls under high-grip cornering to the point that remaining suspension travel on the outside of the turn can be less than needed to deal with surface roughness. Project 325 was transformed by TC Kline Racing's suspension system. It rides comfortably while providing superb control in normal, public-road situations. The track-ready features have been user-friendly: It has been simple to adjust ride height and alignment as needed, and the damper adjustments are easily reached, except for the rear rebound mechanism. Most people who opted for the softest springs would never drive their cars the way I did at the track. Over the coming months, I'll continue working with TC Kline Racing to get Project 325's suspension dialed in to perfection. I'll let you know what that took when I get there.
The Racing Side of T.C.
T.C. Kline invited me to bring Project 325 to the Grand-Am race at California Speedway so his crew could install and set up its suspension. While there, I learned just how close this suspension is to what he races. His 3.0L BMW Z4 race cars are forced to run 225 lb of ballast to keep them even with the competition, which takes the form primarily of Lexus IS300s with 280-bhp, TRD-developed engines and Acura RSXs fielded by Honda R&D engineers with Mugen-built engines. TC Kline Racing's aluminum sixes are completely stock.
One of the first things I noticed was that the Z4s use the same SSR Type C wheels but are 9x17 in. with 245/40-17 Hoosiers. They also have stock-size brakes but with Hawk pads. The interior, headlights and top mechanism were removed and necessary safety equipment added. The ballast box sits on the passenger-side floor.
There was a mix-up that prevented the springs and rear dampers for Project 325 from getting to the track on time, but the problem was easily solved: Extras were pulled out of the race cars' spares bin. TC Kline Racing uses exactly the same parts on Grand-Am race cars that it sells to customers for street use. That's product with a pedigree.