I presume we are talking about 700x23 tyres here. I would like to move this thread on a little by saying the GP4000 seems to hang on to glass it picks up from the road, and the ride is more harsh than than Michelin Pro 2 race. Same size, same pressure. I am regularly picking glass shards out of my GP4000 tyres but not out of the Michelins on my other bike. I get more punctures with the GP4000 tyres as well. As my tyres get slashed to bits I am swapping the whole lot over to the Michelins. By the way, the ride on 700x20 GP4000 is a shocker.