Given a 20x622 rim, how narrow can tyres be

[allenlux]

I need to replace the existing ancient 28-622 tyres on some rims marked "20x622 (28 x 1 5/8)".

The shops here in Luxembourg don't have a big range of sizes and types of tyres - the best selection is of size 23-622 (marked "700-23").

I've looked at the usual references and I have the impression that my rims are too wide for 23-622 tyres, at least for an optimal fit. Can someone confirm this?

John Allen
Bofferdange, Luxembourg

 

[marinyork]

If the internal rim is really 20mm conventional wisdom is 28mm is the narrowest you can go. It was Sheldon Brown I think where I read a ratio of tyre to rim width should be a minimum ratio of 1.4. So you're stuck with 28s.

 

[allenlux]

marinyork, thanks, your advice was helpful.

I did another round of the bike shops here and tracked down a pair of Michelin City tyres in 28-622 size. They seem fine for my purposes - not too wide, not too much tread pattern, some kind of anti-puncture layer, plus a reflective strip around the side of the tyre.