i run stock 245 16's all the way around (trying to save up enough to buy some 17's); does anyone run 16's up front and 17's in the back?? if so, does it help-any faster or tires holding better? i realize you wouldn't be able to rotate the tires.

 

TTT

 

If you use 275/40-17s they will be the same diameter as the 245/50 16s, so ABS, speedo will be unaffected. With different brands/types of tires, handling could change somewhat. IMO, the car will probably "push" or understeer more with the increased rear bite. When you get the $ for the same size fronts things will return to normal but with better maximum grip.

As far as acceleration, it may slow down a tad because the 17s have more rotating inertia (weight farther from center). If you have a traction problem, the 17s might help launch which might offset the inertia loss.

Obviously you'll have different front and rear wheel appearance, which isn't necessarily bad.

Some guys run 16 in drag radials on the rear with 17 fronts. That sorta gives away the sleeper look if you are going street racing. If you are just posing, put the flashy 17s on the front and tell folks your worn 16 inch rears are stealth drag radials.

My $.02

 

I doubt 17's would help launching due to the shorter and stiffer sidewall. This is why dragsters use 15's and wrinkle walls. You have more give on a taller sidewall absorbing the tire shock making tires less likely to spin.
I talked to a guy that went from 17" to 18" and lost time on his ET.

More unsprung weight and less sidewall height are not desirable for drag racing.

 

i heard going from 17 to 18's makes you slower.

So from what i am reading, it sounds like i will get my fastest time with 16's??

If true that sucks, i like big tires.

 

You will lose time on bigger rims. You don't see too many cars at the track on 18's.