I have an early model Moulton APB. I still have the original tires, Michelin 20 x 1.75 profile and I would like to replace with Primo Comet Kevlar 20 x 1.5 tires. How do I know whether this will work--other than buy the tires and try?

This page (http://www.sheldonbrown.com/tire-sizing.html) on Sheldon's site should help - scroll down to 'width considerations' near the bottom; There's a chart on reasonable width combinations that should definitely help.

I'd say going down in size by as small increment as that should be fine - it's only a few mm in the end.

Thank you!

jrcatalpa

It should work, no problem. Sometimes, putting a fatter tire on a rim normally used with thinner tires can be a little tight, and difficult to get the tire lip to stay inside the rim. However, since you're doing it the other way around, I'd say that you're good to go.

I like the look of older mountain bikes that had fat rims with narrowish tyres on them

I had a Rigida 27X1 1/4 steel rim with a 7/8th" specialized folding tyres. That was a bit of a stretch though. Could see the sides of the rim when cycling along.

That is an extreme case. It probably made the tyre into the wrong shape. Would have affected the handling

You get pinch flats in those extremes though.

One thing I'm finding, tho: 20X1.75-2.5 inner tubes are available all over the place - Walmart has piles of them - but the narrower ones - like 20X1.5 - are hard to find.

yeah. I was going to glasgow on it and flatted on a 1 in 5 decent. swapped tube and went to the next decent and flatted again. Scary 40mph speed wobble.

Had ripped the sidewall of tyre.

Put a normal tyre on it.
Only had the narrow tyre as the bike shop had them cheap

When i google 20X1.5 inner tube I mostly get UK stores. Seems to be a more popular size over there for some reason.