[stevenjoywell]

yeah, i think so,You should be OK with 700x28 on those rims. Personally I would not use narrower tires than 28c. Not for towing trailer. Not for touring. For racing, sure, but I don't race.

[cderalow]

I found the eventual answer. 23C is too narrow, 25C is good for riding/trainer, 28C would be better with towing, though 32C would probably be best.

[MNRider]

Look on the rim lable. Most manufacturers list the inside width of the rim along with the actual diameter in mm. Check with the manufacturer or your LBS but in most cases you can install a tire that is as little as 3-4mm wider than the rim. My touring bike has 22.5mm wide Salsa Delgado rims (inside dimension) and I ran 25mm tires on it all last year (about 3,000 miles) with no problems. I switched to 28mm tires for the comfort this year, but wouldn't have any problem putting the 25mm tires back on if I had to.