how much time whould i pick up puting a 15x3 in the front from a 16x8

 

Depends on how fast you're going now and how well your suspension is working out. Based on weight and rolling resistance loss, hopefully .05-1s in the 1/4mi.

 

Yeah all you can really count on is that: A. The tire/rim combo should weigh a LOT less than your street setup. B. They cut down on aerodynamic drag since they are skinnier. C. The rotating mass is considerably less also.

All of these things add up and My guess from what I've actually witnessed, is you'll drop .1 and gain an extra MPH. Goodluck!