I am wondering if I change my run flats to regular tires will the suspension be too soft? Should the springs or shocks be swapped out?
I don't think this will be an issue for you at all. The chance your suspension (ride) would be too soft post a change from RFTs to regular tires is pretty much 0. I did the change-out from RFTs to conventional tire and while the ride isn't close to as harsh as it was prior the change, trust me - you can still feel the suspension's sporty, firm ride.
Just got my winter non-rft's off and back to my Michelin PS2 ZP. You can definitely tell the difference between the softer winter tires and the high-performance summers, but there is IMHO little difference in the actual ride. Let's be honest: with tire profiles in the 35%-45% range, the ride's going to be firm (!!!), sporty and twitchy no matter what the spring and damping rates are.
You can tell a difference. Its going to depend from tire to tire, but I changed my Bridgestone RE050AII RFT for the Potenza s04 Pole Position last summer. They are both tires in the same performance class. Basically, with the non RFT the ride is much improved over broken pavement and they behave more predictably, but the initial turn in isn't quite as crisp as with RFT. For me, living where I do, having to deal with bad roads, it was a good tradeoff.
