Michelin Pro4 Grip
This tire was made for riding in rain. It has the same casing as the Pro4 Service Course with a different tread — both in compound and in surface. The Pro4 Grip weighs 20 grams more (220g) and has 15 percent more wet grip than the Pro4 Service Course, as measured by Michelin on its wet grip track (see below). Its puncture resistance has tested 20 percent higher than the Pro4 Service Course as well.
The Pro4 Grip tread is immediately distinguishable from the other Pro4 (and indeed Pro3) models, because it is not smooth; rather, it has sipes cut into it. One may think that this would be to guide the water away, and while that effect may be there, that’s not the reason Michelin put them there. Instead, the sipes are there to remove material from the contact area so that the tire is touching the ground with higher pressure throughout its contact patch. By definition, the pressure over the contact patch will be equal to the weight borne on that tire, divided by the surface area of the contact patch. Reduce the area of the contact patch, and you increase the pressure in psi measured at any point on the contact patch.
Michelin claims that if you were to do this type of siping on most tire treads, it wouldn’t work due to the type of tread compound used. Its new compound has a higher durometer (that may surprise you), which thus deforms less to also keep the surface contact area lower and thus reduce hydroplaning.
Why is puncture resistance important on a rain tire? We all know that we get more punctures riding in the rain than in dry conditions. I had always assumed this was simply because the rain washed more debris onto the road, and that the debris stayed on the tire through more revolutions in the wet, rather than just falling off as it might have in dry conditions. While those things may be true, Michelin engineers pointed out that the water acts as a lubricant to allow sharp things to penetrate the tread more easily. So, those engineers put a wider puncture-protection strip that is made out of tougher woven aramid (i.e., Kevlar) fibers, rather than nylon.
Like the Pro4 Comp, the Pro4 Grip sells for $79.99 and is available now.