Originally Posted by genejockey;[url=tel:23187197

23187197[/url]]If you want to test whether it's faster, don't do what I did: My Canyon runs Conti GP5Ks in 28, but has lots of room, so I thought I'd try 32s. I didn't want to cough up > $65/tire, so I ordered some 32mm Vittoria Corsa G2.0s from Bike Closet (I think the bought up Vittoria's stocks when the Corsa Pro was introduced last summer). Swapped them for the 28mm Contis, and pumped them up to 70/75 F/R, based on Silca's calculator. When I rode them, they felt slow, my speed was lower than usual for that bike everywhere on the route, and the average speed for that route (which I've done dozens of times) was about 0.4 mph slower than the average of all rides on it.

I was puzzled, till I looked up the rolling resistance on bicyclerollingresistance.com and saw that the Contis have 4w lower rolling resistance than the Corsas. Double that for 2 tires and you've got 8w more resistance. I checked bikecalculator.com and sure enough, 8w would work out to about that much slower average speed.

The moral of this little fable: Get the same make and model of tire, or your results will be meaningless.