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July 19, 2006

New FCABs and RTABs or The Search for Steering Feel

Porsches have ruined me for other cars. Every time I'm able to drive one, I realize just a little bit more of the magic of what makes people coo-coo for them.

It all started with the '05 Boxster S (987) that I test drove before getting the M3. Sweet Mother of Handling Grace! The car is amazing in all kinds of turns, from tight 90-degree city street elbows to sweeping freeway connectors. The balance of the car is just amazing.

Then Derek got his 997 Cabriolet. I recall the first time I really got to drive it for any length of time, and I spent the whole drive swerving back and forth at 55mph on San Tomas Expressway. The feeling of the steering on that car was like a drug -- there was something uniquely rewarding about how it felt shifting weight side-to-side.

A few months later, <a href='http://jkb.org/'>Jan</a> got a base-model Boxster as a loaner while his 996 was having some work done. He let me take it out for a 30 minute flogging session on the "Test Circuit" around work. Even though this is Porsche's cheapest car, its capabilities are astounding. No, it's not going to win any stoplight drag races, but it has a way about it that is unique to any car I've ever driven. Balance and communication, balance and communication.

Jan's 996 is a 2003 Cabriolet with 14K miles on it. I drove it a bit before and after he bought it. That car didn't feel nearly as good as the others -- the front end just felt floaty and disconnected from the road. He wanted to make it handle a bit better, so he ordered the "ROW MO030" suspension from the dealer. This is the "Rest of World" sport suspension -- apparently US cars are more softly sprung and ride almost an inch higher than Porsches everywhere else. Driving his car after the suspension was <a href='http://tcdesignfab.com/'>installed</a> was like night and day. The car felt very agile and planted, and lo and behold, there is that magnificent Porsche communication with the driver through the steering wheel. More joyful swerving down San Tomas.....

I had to have some of this. I've been methodically upgrading the suspension on the M3 since I got it. First were shocks, springs, and camber plates to get some handling balance potential into the car. Next came equal-sized wheels and tires for track days. This made the car extremely fun and well balanced on the track. After that, I got a Ground Control front swaybar to help the front end stick to the road a bit better to help the car rotate through turns (yes, this goes against common advice, but a lowered M3 does not posess a common suspension setup).

The car is nicely balanced and very fun to drive on track or autocross, but driving those Porsches leaves me wanting more!

My search for more communication from the suspension lead me to the soft rubber bushings that connect the suspension arms to the chassis of the car. Under hard cornering, the rubber deforms, changing the toe angles of the front and rear tires in proportion to load. The net result is a car that feels vague and mushy and does not respond well to small changes in steering angle at the limit. Could addressing this lead me closer to Porsche-like nirvana?

Ground Control makes some <a href='http://www.ground-control-store.com/products/description.php/II=162/CA=103'>gorgeous "Hybrid" (aluminum / urethane) bushings for the front control arms</a>. The consensus is that they do a lot in terms of controlling the motion of the suspension arm to its intended axis of motion, while preserving the quiet and smooth ride of the stock pieces. Powerflex makes a pure <a href='http://www.evosport.com/product/default.aspx?catid=552'>urethane bushing for the rear lower control arm</a>, which a very common fix/upgrade for cars whose rubber bushings have torn.

A swift call to <a href='http://dermotorsports.com/'>Dan Law</a> and the pieces were en route from Atlanta. After a nearly unbearable weeklong wait for UPS to deliver the goods, I brought the car to <a href='http://tcdesignfab.com/'>TC Design</a> for installation. It's possible to do the install myself, but with the proper tools it's an easy two hour job, versus 8 hours of cutting, hacking, chiseling and swearing. I left this one to the pros.

Initial impressions from the drive home: The car feels a tiny bit stiffer -- sharp bumps come through to the cabin a little bit more than with the stock bushings. It feels much more agile though; almost as if I went to a stiffer spring. (This is indeed the case, since the entire suspension system from tires to bushings to springs and shocks contributes to the "wheel rate" or the amount of force required to move the wheel some unit of distance.)

I did some brief "testing" on the four varied cloverleaves that connect San Tomas Expressway to Central Expressway. There is a nice mix of second and third gear right-hand corners. This is where I felt the most difference. The mushiness at the limit has been replaced with a very precise and controllable feeling. It seems that I can really feel the tires now -- very nice! The car just feels hooked up; maybe a tiny bit more traction, but I can really feel when the tires start to really lose their grip.

The true test will come this Friday when I'm driving with <a href='http://trackmasters-racing.com/'>Track Masters</a> at <a href='http://infineonraceway.com/'>Infineon Raceway</a>. The next Friday, I'm going up to Willows to drive with <a href='http://pdcracing.net/'>PDC</a> at <a href='http://thunderhill.com/'>Thunderhill</a>, then the next day is a <a href='http://www.justracing.com/ggc_bmw_cca/viewtopic.php?t=278'>BMWCCA Autocross</a>. So the car will really be put through its paces over the next week and a half. My hope is that the additional communication at the limit will give me the confidence to explore the outer bounds of traction, and to make track days more fun!