Inner tube doesn't fit - help!

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Mr C

New Member
Hello all

I have a wheel that takes a 20" x 1.75 tyre (that's what it says on the tyre that was on the wheel when I got it) so I bought a 20" x 1.75 inner tube - but it's far too big, like 2" too big. I've checked the size, in case it's been mislabelled, but it's fine. So I am at a total loss - why doesn't it fit?

You may gather that I'm pretty new to this bike stuff, so it may be something simple and I just don't know what to do. Thanks for your help
 

mjr

Comfy armchair to one person & a plank to the next
Do both tyre and tube have numbers on like 451-47 or similar? What are they? The old inch (Imperial and American) and metric sizes are a minefield, more so in 26" and 20" than 28". It's worth knowing that 20x1.75" and 20x1¾" are not the same!

ETA (Edit to add): the tyre will only have a three digit number (wheel diameter), a dash and a two digit number (tyre width), but the tube may have ranges for both, or a list of several diameters and widths. For example, a tube I often buy is marked 622/630-28/47 which will actually fit both the 622-37 tyres on my roadster or the 630-28 tyres on my road bike - or at least it would if they used the same valve type...
 
Last edited:
Location
Essex
Double-check that it does or doesn't fit by 3/4 inflating the tube inside the tyre but off the rim, maybe? Sometimes tubes are a little bit generous but you can squeeze the last bit in as it kinda compresses itself along its length, iyswim. Depending on the size of the tyre, the inside of the tyre could be a good couple of inches more than the outside of the rim (pi x dia n'all that) ^_^
 
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ColinJ

Puzzle game procrastinator!
Double-check that it does or doesn't fit by 3/4 inflating the tube inside the tyre but off the rim, maybe?
That could actually be the problem! :whistle:

Tubes anything more than slightly inflated off the rim (i.e. without a tyre to constrain them) tend to end up much larger than they are supposed to be, by a couple of inches or more...

PS I didn't spot what you posted about the tube being inside the tyre. I'd be tempted to just to wrap the flat tube round the rim and see what that looked like. If it really IS too big then that should be obvious.
 
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