Quote:
Originally Posted by Orb
FWIW, the club sports at 500 lb/in front 800 lb/in rear is far worse for inducing under steer. The Clubsport spring specification for 335i is a joke with 400 lb/in front and 570 lb/in rear. The rear motion ratio is about 0.58^2 which mean the rear suspension is very soft and is a major change from the OEM setup for balance. A track car (no aero dynamics) and road car will have the suspension frequency in the front equal or lower than the rear and in a very few cases you might see a 0.1 higher frequency in the front. BMW cars seem to have front suspension frequency 12% lower than the rear for a flat ride. The KW suspension frequencies are way outside the norm with a 0.2 to 0.45 higher front suspension frequency than the rear. Furthermore, the rear suspension frequency is so low for the Clubsport that optimizing traction for R compound tire is not possible as we need a frequency of 2.2-2.3 HZ+ in the rear. The rear KW Clubsport is about 1.7 Hz
Let’s do the math for wheel spring rates as this is what matters:
OEM M3
• 160 lb/in x 0.96^2 = 148 lb/in
• 550 lb/in x 0.58^2 = 185 lb/in
KW v3 M3
• 285 lb/in x 0.96^2 = 262 lb/in
• 630 lb/in x 0.58^2 = 212 lb/in
KW Clubsport M3
• 500 lb/in x 0.96^2 = 460 lb/in
• 800 lb/in x 0.58^2 = 269 lb/in
Look like we will get under steer given nothing else has changed other than springs. This is not a guess but a fact as the load transfer will be biased towards the front considerably (at least 9%). It can’t be corrected without a roll bar change not to mention that the cars pitch is a mess now and over compensated by heavy front rebound damping. The only thing that the KW setup will do possible is make the car feels softer but this is far from what a performance setup should be. One thing is for sure BMW engineering is a lot better than KW’s.
Orb
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Wow!!! Nice way of making your point Orb. Thanks for the info!!!