Originally Posted by wroomwroomoops
140 Kg? Well, your rear wheel is underinflated, for such weigth. The rear wheel always carries more weigth than the front, and should be inflated to a higher pressure to avoid pinch flats.
I don't know many cyclists of such high weigth, so I don't have experience with the set of problems they might have. I am not even sure many tires are designed for such heavy cyclists.
The conti gatorskin are certainly good tires, though.
OP is from the US, so I'm assuming he meant 140 pounds. 140kg, you'd have a pretty large contact patch even while pushing the pressure limits of the tire (125 psi), be like me running at 60 psi and 150 lbs. Not optimal, and would be somewhat prone to pinch flats and the like, but averaging one every 20 miles is still kind of extreme. But if the unit of measure is in fact kg, I'd be running something larger than 23mm tires, for sure.
As far as the recurring problem - I'm not sure what kind of tires he's using, but if it's not a racer they're probably not that expensive - I'd get a new tire and throw that on while I worked on diagnosing the old one. If the current tube half life is about 15 miles, I'd drop an extra $20 for a tire while I figured it out.