The Michelin Pro3 was a pretty popular tire, but it seemed most only ran them on race day. They gripped like you wouldn't believe, but they were a bit prone to flats under normal use. Well, we're happy to report that Michelin fixed the bad, and improved the already good in the Pro4 Service Course. They've altered the rubber compound a bit and added a full-tread nylon breaker to help resist against road debris, sharp rocks, and anything else you might encounter on a normal training ride. In addition to the different rubber and anti-flat reinforcement, the Pro4 has a new shape designed to offer even more traction when the bike's leaned over in a turn. This shape, combined with the new rubber compound, adds up to a 16% increase in turning traction over the Pro3 Race --the grippiest of the Michelin tires.