I had a Dinan stage 1 suspension on my '98 540 6-sp. The improvement was unreal. I believe it would out handle my M5 if I had bigger wheels and tires on the 540. I was running S-02pp 235/45 17" all around. It did very well at TWS. My instructor was suprised how good it handled. As far as ride quality, it's a little on the stiff side. Nonetheless, it was a comfortable ride. I was told Dinan uses the same springs they use on 540 for the M5. The shocks are different though. I am going to Los Angeles next week. One of my mission is to visit Dinan and get some first hand experience on their upgrades for the M5. I will keep you posted.
Have the Stage II since last month. Got a cance to drive on Road Atlanta afterwards. All I can say is WOW! Adjustable shocks turned the monster into a go-kart flat ride.
After the track, you just turn the dial back on the shock towers and your ready for the streets again.
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