Originally Posted by jeffreylin

I spoke to Mike and he told me that the Mugen cars seem to work opposite to conventional wisdom when it comes to roll center. Effectively, if you raise the roll center in the rear you increase bite and lowering it you decrease bite. Thus, by removing the shim you are lowering the roll center and you decrease side bite and reduce the tendency to traction roll.

I don't know why this is the case but testing on the track confirms what Mike said. I am just guess but perhaps it has to do with the relative position of roll center and center of gravity? If someone know the reason please share. Thanks.