As far as the fronts being undersized it's not really a matter of weight but a combination of many things. I drove a Lotus Evora which has the same rubber as the 328 sport: 225/255 front rear tire width. While it's not ad heavy as 328 you would think it would understeer. Not the case at all. You can make it do pretty much whatever you want. Yes it does understeer under certain situations as it should; cars that oversteer everywhere can be fun, but are slow. What makes a car understeer excessively in my mind is how it responds to inputs that should make it oversteer or how it responds to corrections to understeer. What I couldn't stand about my car stock is the fact that you had to be so drastic just to get the rear to start working let alone slide. Also when it did understeer lifting and backing out steering seemed to do nothing. It's not really a matter of weight and tire width but how the car as a whole utilizes the tires. I drove a no-option 328 with 16" wheels and that thing didn't feel at all like the fronts were undersized and all its tires are smaller than the sport cars. In fact I found the non-sport car more fun than the sport.
Ok here come the driving lessons. I'm not a profestional driver but I have learned a few things from pro instructors. The Dinan suspension is very stiff up front. Along with the m3 arms it's even more stiff. What you are describing on turn-in is attributed to asking the front tires to do too much all at once. Simply put, you're turning the wheel too fast. A larger front tire will help, but even then, the Dinan setup rewards smooth driving. You need to load up the tire before you really ask it to corner. That's why it feels better mid-corner.
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here!
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