Let's say that theoretically you wanted to take a rear subframe and remove 2 inches from the width. All of the control arms remain the same and you shorten the half shafts by one inch on either side. What happens to the geometry? Would it be ruined? Improved? Let's assume this is a multi link setup like on an E39 or an E90.
Disregarding any structural implications or things like where the spring hats are and a number of other things, for the suspension it should function the same except the track would obviously be 2 inches narrower and the wheels an inch further inboard on each side. The suspension would articulate the same since the arms are all the same length, but narrowing the rear track isn't usually a good thing for performance. Usually people try to do the opposite and go as wide as they can.
1999 M3/2/5 - Titanium Silver - Track/Weekend Toy
Awesome. I know that the ackerman geometry gets messed up if you shorten or lengthen the wheelbase but I didn't know if something similar would happen if you narrowed the rear track via the subframe width. Looking at diagrams it appears the roll center would raise slightly and the instant centers would move outward from the wheels a small amount. I'm not sure what effect that would have on handling though.
You are correct on roll center/ ic. Mostly just the weight transfer will be affected I think, the reaction from each wheel loses its moment arm to act against vehicle roll.
Harrison Motorsports
Motion Control Suspension
Daytona M3
Bookmarks