Originally Posted by
mcours2006
I'd hardly consider 35 mm tires fat. The difference might be a km or two, if that, slower. But the versatility/comfort of wider tires is worth the minute sacrifice in speed. And if it's only a 10-km commute, it's even less relevant. Your riding position and fitness would make a much bigger impact on your speed.
I've ridden my 20-km one-way commute on 23's, 25's, 28's, 32's, 35's, and currently 37's. Different bikes too, and while the 23's and 25's are on racier road bikes and usually for the warmer months when it's dry, for all-round, all-weather stuff I run the 35's (studs) and 37's.
Well, I guess such things might be relative. I consider my 23's skinny (and perfect) and 25's as thick as I would want to go for strictly highway commute riding. But not everyone see's it this way, obviously, especially with the newer trends to have bikes for gravel roads. But that was not what the OP said so I was replying to his stated type of commute ride of all highway.
But again as I indicated above for the entirety of his original post I would recommend TWO bikes or TWO wheelsets, with different tires on his bikes or wheelsets.