We are using Schwalbe Marathon Plus tires on our tour and have had nothing but great experiences with them so far. We've now come nearly 7500 miles and have only gone through two tires on the three bikes. In short, we are pleased beyond all expectations.

However, we have some friends who have had lots and lots of trouble with their Schwalbe Marathon Plus tires. Today, they had their FOURTH tire blow up. Some of the blowouts have happened when the bike was just sitting - not even while riding it. Anybody have any idea why this is happening? Schwalbe has been great to them and has sent out replacement tires, but they would liek to figure out why it's happening so they can prevent it.

They are riding tandems with kids in the back. Even though they have all their gear in panniers rather than trailers, they shouldn't have too much weight on the bikes since the stokers are kids.