Which tire is getting punctured? Mine happen 99.999% on the rear tire (last week was possibly my first ever front tire puncture); I got tired of it so I installed a tire liner and no more flats! The tube sealant does sound like a good idea. Part of fixing a flat is to wipe a tissue or paper towel inside the tire; anything protruding will snag on it (instead of your fingers); my front tire picked up a tiny piece of agate-like rock shaped just like a sliver of glass, and poked a tiny hole that made for a slow leak.
Another thing; you say you keep your tires inflated as much as possible; do you mean high pressure? If so, you might try less air pressure; the theory goes that less rigid tires will tend to deform around objects rather than jamming into them. YMMV, of course. Good luck resolving your situation.
Originally Posted by
pambam
This is really going to sound very newbie/novice considering all the cycling I've done in my life, but we are fairly new in Germany and I inherited what is called a 'city bike'. Not great for distance riding but great in town for hauling all my groceries! It's super heavy and I have no idea about the wheelset or tires, since I'm still just trying to figure out how to live here in general. And because others are fixing them and I can't speak the language, I don't know what it is. However, had a puncture last week, brought it in, paid 26 euros and then it happened again 10 minutes later. That I suspect is a lazy repairman who replaced the tube and didn't check inside the tire. Or he was getting even with the judge. Here, petty crimes are punished, not with jail time, but having to do bicycle repair. I'm not kidding!