I just bought a set of Marathon + (700 X 25c) from Bike Tires Direct for $34/ea. They are really difficult to mount. I have Xero XSR-3 rims and I had a difficult time of mounting the tire, really stiff. After I got it mounted and inflated the tire I had a blow out when I got up to 100 psi, the bead was push out by the tube in one area then the tube poped. I tried this a second time and took the tire to 90 psi. I thought I was done and about 8 minutes later the same thing happened. Third time was a charm. However this time I slowly inflated the tire to watch for any problems with the bead. Sure enough it worked it way out of the rim again at 80 psi but this time I was able to avoid a flat by deflating the tire. I had to reset the bead not once but three times before the bead would engage the rim. I have tire inflated to 70 psi and it has held for 24 hours. I just mounted the rear and experienced the same problem with the bead working out of the rim. I deflated and re-adjusted the tire and got it to hold at 70 psi.

Everyone raves about the ride and puncture resistance of these tires. Did I say they are extemely stiff? Before mounting the tire with the tube, mount the tire wiithout the tube so as to help shape the sidewalls before inserting the tube. Also make sure they are warm and flexible and have a good set of tire levers. I did the pre-mount on the second tire and it really saved me a lot of time.