Originally Posted by I_bRAD
It'll be so fast you won't be able to stop! Not without disc brakes at least. (because your brakes won't reach the rim, assuming it even clears the fork)
If you make it work it'll be faster, but it would probably be a lot less hassle to just get a 700c bike.
If he makes it work, it'll just be a higher final drive gear ratio. A bigger chainring and a longer chain would net the same effect, probably for a lot cheaper.
I really don't notice much rolling resistance delta between my 26"x1.25" mountain bike slicks at 85 PSI on my hybrid and my 700x25 tires at 100 PSI on my road bike.
The difference in speed between the road bike and hybrid comes mostly from gearing and a more aerodynamic seating position.