Bicycle Mechanics - tube question

Hi all,

I have 2 tubes one which says 20-28 and one which says 28-38. Which would be better to use for a 28 tyre, if it matters at all?

Thanks

Daven

Depends on the actual size of 28mm tire. I recently mounted some "28mm" Continental tires and had to use 19-26mm tubes because the 28-32mm tube I tried first was way too big. I managed to get the tire mounted but the tube was pinched between tire bead and rim almost all the way around. Too much rubber and not enough space. However, I've mounted several 28mm Specialized tires using those same tubes without issue.

In this particular case either would be fine. I'd give a very slight preference to the smaller inner tube because it will be easier to fit into the tire caseing.

In borderline cases, I also prefer to use the smaller size for ease of installation.

Also note that tire and tube widths aren't ultra precise. What you might do is fill the tubes to the point that they fill out (aren't flat), but haven't stretched yet, and compare the unstretched width to the tire. If the unstretched width is too close to the tire's width it'll be hard to install without pinching.

in this particular case either would be fine. I'd give a very slight preference to the smaller inner tube because it will be easier to fit into the tire caseing.
+1

cheers all, smaller tube it is then :)