Specialty File
Considering the way we swoon for the driving dynamics of the BMW 3-series sedan, you'd think a roadster built with the 3-series suspension would be paradise. But that car, the Z4, has failed to impress. Here's what we said in a comparison test: "On less-than-perfect roads, the Z4 has a nervous, darty feel. The wheel constantly steers itself if you hold it loosely, or fights you when you grab tight."
The "why" portion of this conundrum is debatable, but the Ohio-based owner of TC Kline Racing, namely, T.C. Kline, claims he has the fix. Kline's solution is a $3542 suspension package that he says turns the Z4 into the sports car it deserves to be.
That's a decent chunk of change, but compared with the cost of a Z4 ($34,995 with the 184-hp 2.5-liter and $41,995 with the 225-hp 3.0-liter) it's not outrageous. BMW's own Sport package costs $1300 for the 2.5 and $1200 for the 3.0. Sure, that's significantly cheaper, but we haven't found BMW's Sport package to be so sporty.
So we decided to see if his solution gave the Z4 some much needed handling chops.
It turned out his Z4 had undergone the typical treatment for any tuner car that makes the rounds at car magazines—it had far more goodies added on than just the suspension package. The biggest item was an engine rebuild for $9340 (including labor) with new cams, an increased compression ratio, and an additional 25 horsepower. There were also 19-inch wheels and tires, a Recaro racing seat, a Momo steering wheel, an exhaust system, and various other details that blew up the total to $20,332.
The wheels were covered with Michelin Pilot Sport Cup tires. That's notable because you typically find those tires only on race cars. They have a wear rating of 80 (the wear rating is a rough guide of how long a tire will last) compared with 220 for the Michelin Pilot Sport PS2.
The Pilot Cup tires trade long life for high grip, and even though Kline says he gets about 10,000 miles out of a set, we don't consider them street tires. Our testing rules mandate gas-station fuel and tires with wear ratings greater than 140. So we asked Kline to swap the Cup tires for PS2s.
With the new tires in place, we drove out to the track, taking in some curvy roads along the way. Kline's car felt precise, sure-footed, and very nimble. We felt confident pushing the car the way we would a 3-series. We'd always hoped to push a Z4 like this but never could until now. The car's nervousness was gone.
There didn't seem to be much, if any, ride penalty, which was surprising because in addition to lowering the car by about an inch, the springs and some of the suspension bushings are stiffer than stock. The car felt buttoned down but compliant, too.
The new suspenders had us looking at the Z4 in a new light, like the frog that gets kissed and turns into a prince. High praise, we know, and we wish we had had a stock Z4 around for comparison so we could confirm the dramatic difference we suspected.
At the track, Kline's car clawed around the skidpad at 0.95 g, a 0.03 improvement over the best of the three Z4s we've tested. We also ran the skidpad with the Pilot Cup racing tires—for curiosity's sake—and the Kline car pulled a heady 1.06 g. That was simply for fun, though, and the official result for this Z4 is 0.95 g.
We have a hard time imagining anyone springing for the exact car pictured here. With all $20,332 worth of stuff added to a base $41,995 Z4 3.0i, you'd have spent enough to get a nicely loaded Porsche Boxster S. True, Kline's Z4 was the quickest Z4 we've ever tested, running to 60 mph in 5.2 seconds, but for the same money, we'd go for the Porsche.
Keep to the basics—just suspension and tires—and you could have a Z4 that handles like it ought to.
TC Kline Racing, 4163 Lyman Drive, Hilliard, Ohio 43026; 614-771-7744; www.tcklineracing.com.
