Here's the problem: I'm morbidly obese (245lbs, 5'11"). As a result, I get flat tires every ten miles or so.
I've had three different mechanics look at the bike and tell me that there's nothing wrong with it. The tubes are new, the rims and rim tape look good, the tires are kept inflated to the maximum pressure for the tires (120psi), and the tires are almost new Continental Ultra Gatorskins (700x25c) which are supposed to be relatively resistant to pounctures. On top of my considerable body weight the bike typically carries about 20 pounds of gear.
I'm riding the bike around the city, and although this means sometimes the bike has to go over cobblestones and cracks that cause the rear wheel to jump and drop, on the whole I'm not doing anything unusual.
The wheels use Shimano Sora hubs, and Alex DA22 32h rims. The tubes are Novara Presta tubes, 700 x 20-25.
I'm at my wit's end with this: none of the techs seem so think that my body weight is an issue, yet the equipment apparently isn't an issue either, and yet the problem keeps happening.
At this point I'm thinking the only option I have to is to get gastric bypass surgery, and put aside the bicycle until I've lost 100 pounds by that means. However, this is an extreme solution and if there is any mechanical way to stop this from happening, even with my body weight as it is right now, I'd like to give it a try.
So, is there anything I can do here?
For what it's worth, the flat tires always seem to be preceded by the rear wheel dropping, e.g. over poor concrete that causes it to bounce. I never ride over curbs (instead walking the bike over them) so we're talking about unavoidable cracks in the middle of a lane of traffic that I can't avoid.
Should I keep the tires inflated to something LESS than 120psi?