I want to swap over a knobbly 406 x 1.75 and a slick 406 x 1.5. Thus, the 1.75 will end up on a wheel originally hoding the 1.5, and vice versa. Are there likely to be any problems?

Thanks

It depends upon the rim widths and frame/component clearance.

It's a bad idea to use a tire that is skinnier than your rim.

Normally there are no wheel/tire issues with running wider tires, however you might find that a wider tire rubs against the frame or fender, etc.

Tires need to be drastically wider than rims before improper bead-seating issues arise.

More accurately, it's a bad idea to use a tire whose stated diameter is less than 1.5 times the width of the rim channel. On a 19 mm rim channel on an ISO 406 rim, you should run at least a 1.5 x 19 mm = 28 mm diameter tire (406 x ~1.125" is not the same as a 406 x 1-1/8"). I use 406 x 1.35"... = 406 x ~35.

Sheldon Brown has a chart showing tire-rim witdth compatibility here.
Jonathan

maunakea:

What is the difference between a 406x1.125 vs. 406x1 1/8? Calhoun lists the Conti Grand Prixs and Sport Contacts as 406x1.125" though Stelvios are listed as 406x1 1/8. But I assumed this was just a writing quirk and not an actual size difference.

sb11 I tried the 406 x 1-1/8 Stelvios on my stock DT FS rims (marked Dino 20 x 1.5/1.75). To get the Stelvios on, I had to use 200 psi to seat the rim, then deflate to 120 psi. The 20 x 1-1/8 seems to have a smaller lumen diameter than the decimal fraction tires for ISO 406. I checked with a few bike techs I trust before trying the 200 psi trick. I decided that if I flatted on the road, I would never be able to reseat the bead, so I exchanged the Stelvios (thank you, Calhoun Cycle) for Primo Kevlar Comets, 406 x 1.35. I can't tell the difference between the two, but I like being able to remount the tire when on the road ( ) and the Kevlar. (Haven't flatted yet, but it's a matter of time. I have to ride on some disgusting shoulders.)

maunakea: interested in your high pressure seating methods. Can you say a bit more about it as I often have trouble getting my Conti Grand Prix's seated evenly onto a 1.5" rim without a small bulge. Any details you can offer? And how do you get to 200. That must be some track pump!

LittlePixelI have a monster air compressor. You may want to try the 406x1.35 tire size or change to fractional rims. I can't detect any difference between 406x1.35 and the smaller size, but gain Kevlar and easier mounting in the deal.

Thanks for the explanation, maunakea. Interesting info for sure.

Although shock pumps don't pump alot of air per stroke, they do go to 300 - 400 psi, and are fairly inexpensive (USD 30). You would have to adapt from the shock pump fitting to a tire valve, if that is possible.