For the winter I put some winter tires on plain black steel wheels. I did this the yesterday and only on the front. The snow tires (and wheels) are a little bit smaller than my regular all-seasons on the back. I can't remember the sizes -- I'll look it up tomorrow in the light -- but it is noticeable when looking at the wheels. But on the way to work today, just about a 3 or 4 mile drive, the "!" light and ABS light came on. Could this be the computer thinking something is wrong because of the different wheel size causing them to spin at different speeds?