[RED92LX50]

I'm sure you realize this, but - you are going from a 28" tire to a 26" tire. This will throw off your spedometer, and will affect your RPM's/MPH at shift points and at the end of the track (there are calcualtors in the "Analyzer" section of this site).

If you wanted a 26" tire with a wider tread, you could try a 275/50-15. Also, rim width plays a big role in the contact patch of the tire. If you are using the same rims (which it sounds like you are) I would guess that the 275's were very "bulgy" and the 235's will fit the rim better - otherwise, if the 275's fit the rim fine before, then the 235's will be way to narrow.