Well I wore out my 26-10.50 ET streets and found a pair of 26-11.50 ET streets to replace them with. Now the 11.5s are not only wider but also about 3/4" taller. Went racing Saturday night and found that the extra height cost me .04-5 in the 60' and .1 in ET compared to an almost identical night 2 weeks ago. I use a cheap home weather station with temp, baro, and humidity to compare conditions at the track from one outing to the next.
I had no idea that my car would be so sensative to such a minor change in overall gearing. My 3.42s must be hurting me more than I thought. So my next project will definately be a 4.10 geared, spooled, 12 bolt.

 

That doesn't surprise me. The last time I went to the track, I went with my new BFG drag radials (255/50/16, compared to factory 245/50/16) and I was running almost ~.1 seconds slower across the board (and about ~1/2 mph slower too). They're barely 1/2" taller than the factory tires, but with the height and the fact that they're "stickier", I think that's what slowed my car down? I got my fastest time (13.02 in sig) running on street tires!?

BTW, 4.10's are great.

 

Did your mph go up? Mine did when I went from 26" to 28" tires...

 

Nope it was down about a half a mph.