Nat writtificated
Quoted message said:I wonder if any of you have ever encountered this problem. Every time
I try to change the back wheel, I have some inner tube left over which
causes a bump. It is almost as though the wheel is just a bit too
small. I've been changing my own inners for years so I know all the
'tips and tricks' but this darn thing won't blooming go in!
Firstly, I very much doubt the rim is the problem. If the circumference
had been significantly changed after an accident, or if it was
significantly undersized in some way then you'd have all sorts of major
problems (like tyres not fitting, zillions of broken spokes.
Secondly I always seem to have a bit of inner tube left over and have to
coax it into the tyre. I suspect this is because:
- Many inner tubes are designed for 622mm and 630mm rims[1]. It is
possible to buy tubes designed only for 622 rims, but I'm haven't
bothered seeking them out to use. I wouldn't trust the lack of a
"27xwhatever it is" on the packaging to indicate it's only for 622 rims.
I'm not even sure whether Continentals 630mm compatible tubes are any
bigger than their 622 only tubes. Even if they are I doubt 8mm would
make much difference on a 622 rim.
- I stick a bit of air in the tube, put it into the tyre, then put the
tyre onto the rim. I will try putting the tube into the tyre *before*
putting the bit of air in them. That would prevent any chance of
stretching. I should really fit one tyre bead onto the rim before I put
the tube in too.
I suspect our problems are due to bad technique, but I'm going to put all
the blame on some tubes being designed for rims 8mm bigger in
circumference 🙂
This lists Continental's inner tubes:
<www.conti-tyres.co.uk/conticycle/accessories.php>
This is wheely helpful for when understanding the complete mess that is
rim sizing.
<www.sheldonbrown.com/tire-sizing.html>
[1] e.g.
700x18/25 Continental Race 28 Light inner tubes are rated for 18/25-
622/630
700x18/25 Continental Race 28 Supersonic are rated for just 18/25-622