hey guys.

I currently ride an OCR3 with 25C stock tyres.

Thinking of upgrading to a pair of 23C tyres.

Will they increase my speed? if so by how much?

Mic

It's the motor.Make sure they are lighter or they may be slower.

My Michelin 23's are the same size as my Continental 25's were. Every vendor runs a little different. Switching from the HEAVY Michelin Dynamic 25's at 350g to smaller 23's at 250g or so could get you 0.2-0.3mph. If you're racing, that really matters. If you're touring or training, it really doesn't amount to much. Like boudreaux and everybody else here says: IT'S THE MOTOR.

Notwithstanding the above mini-rant, I still think upgrading your tires to match your riding style and the conditions you ride in offers one of the best bangs for the buck out there. I went to the Michelin Axial Carbons for comfort and durability. It's pointless for me to race on the old Trek, and I generally keep up just fine with the tires at just 100-105psi. However, my hands and my **** certainly notice the difference in tire pressure at the end of a long ride.

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Bri
1,000,000 bicycles = 2 megacycles

Agree tires make a big difference in overall ride quality. I think tires have different rolling resistance values also, which may be more important than the weight savings in speed.

Michelin slicks do seem to be comfortable with good road feel (I've got Pro Race on now), but maybe not as durable as the Conti 3000s, in my experience. I've never had a puncture with the Conti's, but have cut several Michelin slicks through. Maybe just my bad luck with the French tires.

Agree on the 100-105 psi. Used to pump 'em up to the sidewall max, 120 or more, but have found better ride at lower pressures with no noticeable increase in rolling resistance. Michelin Pro Race says 87-116 psi on the sidewall, so 100 psi is right in the middle. Best pressure probably depends on weight also, since the contact patch expands with weight.

Dan