Inner tube

Are they 27" inner tubes (as opposed to 700c)? I'm thinking that would make them ever so slightly larger in diameter.

Inner tubes as far as I know are interchangeable between the two sizes, but Tires are absolutely not. Someone else may have something to add.

When lighly inflated do they sit a little better on the rim?

Thanks for the reply.
To be honest I didn't try the tube on the rim without the tyre but just to be clear these tubes were on the bike from new all I've done is change the tyres. I just feel that when I'm pushing the slightly inflated tube up into the tyre there just seems to be a little more tube than there should be.

Jiroma

FWIW. In the past, Hybrid bikes often came with 700x42 tyres ...

If your old tyres are similarly sized AND you are now trying to put 700x28-or-smaller tyres on your current wheels, then you will need to get another set of inner tubes ...

If the glove doesn't fit ...

BTW. YOU need to be sure that the new tubes have the same type of valves as your current tubes -- probably SCHRADER (automobile type) rather than PRESTA.

YOU need to see if there is a label on the rim which indicates its size BECAUSE if it is too wide (e.g., 622-22, where the second number indicates the bead-to-bead distance in millimeters) then you may find the fit of the new tyre to be unsatisfactory ...

That is probably a long way of saying that you can probably put a 700x32 tyre on your current rims if they originally had a 700x42 tyres, but smaller may-or-may-not be problematic.

inner tubes tend to be a bit wider in diameter than the rim even if sized correctly, but the opposite is also true, inner tubes do come on different sizes

All is well. The tyres that were on the bike originally were 700 x 37 and the tubes were a type that covered 35 to 45. New tyres I bought are 700 x 32 and new tubes are 25 to 32. These were a much better fit and everything went together much better. Also discovered my pressure was way below what it should have been so all in all I've learned quite bit about tyres.

Jiroma