I have RS's on the e60 and would concur with Big H's comments on them in the wet. However, one of the ways of achieving this is to make them fairly soft and squishy on the sidewalls, even with 50 profile on the e530i they do mean it isn't the sharpest steerer. I can only imagine that they might feel a bit loose on the iS. I had some positive experience with Vredstein Sporttrac's in a close size on an e36, but that was a few years ago. No recent experience.