Made it out to the track tonight and I know there are a lot of variables involved but I was hoping to improve upon my 12.55 time on stock tires since I now have 305's on the back. I ended up running 4 runs (12.65, 12.67, 12.72 and 12.74) so while pretty darn consistent I gained a tenth and my trap speed went down by about 3 mph. The only thing I can figure is that since I have wider and heavier tires that I lost a little top end and while I'm not spinning as much I guess it wasn't that beneficial, kind of disheartening.