I just put on 17 inch zr1 vette rims a few weeks ago and I went from 245/50/16's to 315/35/17's in the rear(quite a difference in size)...is my speedo off now? Will i need to reprogram it somehow? Will my transmission need to be tuned or reprogrammed or anything? I havents noticed a huge difference but I am n probation with my lisence so I'd like to know how fast im going! Thanks!

If it is off, it is not off by much. I would look into getting it changed due to your situation. The dealer can do it, some shops that tune can do it as well.

Matt

one of these two discount tires ot tirerack has a tire size chart. You need to see if the new tires are the same height. Stock height is about 26 inches.