25mm inner tube in 28mm tyre

[Jules59]

Maybe a daft question but I have lots of 18-25mm inner tubes but I want to replace the current 622 (700c) x 25mm tyres with 28mm. Is it OK or indeed sensible to use the inner tubes designated 18-25 in a 28mm tyre. Obviously they will be more stretched but will a few mm be detrimental?

[Jules59]

no worries - found a link which says it all really
viewtopic.php?f=1&t=127656

[VinceLedge]

Strange coincidence but I had a puncture on my new bike with 28 tyres yesterday and only had a n 18-25 tube as spare, fitted it and managed the rest of the ride fine. I suspect it has a higher risk of failing but not sure there is any evidence to prove that !

[rogerzilla]

It depends on the thickness of the tube. Cheap, thick, tubes may be good for 20-28mm. Lightweight, thin, tubes may only be good for 23-25mm. Latex tubes are the most fussy and may only have a size range of 1mm. Basically, look at what's printed or stamped on the tube.

You can ignore this but there is a higher puncture risk, as well as failure near the valve (where the tube can't easily stretch - try it out of a tyre).

[Ride-sleep-repeat]

I have 18-25 tubes in 700c x 35 tyres on my CX.Run them at 85/80psi with no issues.
TBH I've never really thought about it!I bulk buy 18-25 and use them on both bikes.I can't remember the last time I put a new tube in but the valves are the extra long ones on both bikes so I know the CX has the same tubes as my road bike!

[rogerzilla]

I used to put 24 x 1 3/8" tubes in MTB tyres, because they were much cheaper than "light" MTB tubes. It worked fine until that day when I got four punctures on one thorny ride.Luckily I had a patch kit and my mate had a mini-pump!

[Brucey]

in theory +10mm on circumference so no problem, right?

in practice it sometimes works ok, sometimes not.Try it and see.

cheers

[elPedro666]

I remember one of the early mtb innovators, I think it was Geoff Apps (Cleland), advocating for the largest tubes you could sensibly fit, that way when they were pinched or came into contact with a thorn etc they would be under far less tension and wouldn't (necessarily) fail immediately.

I'm a trendy consumer. Just look at my VOG-L09 using hovercraft full of eels.

[andrew_s]

An undersized tube, such as 18-25 in a 28 tyre stretches to fit, but, being stretched, will puncture more decisively, and will chafe through more quickly if you've something like a rusty eyelet poking out from under the rim tape.

If you use the largest size that fits without creasing, which may be a 32-42, you will find that some punctures leak slowly, sometimes slowly enough to allow you to just top up the tyre pressure and change he tube when you get home, fairly commonly slowly enough that you can get to a gateway or other place off the road.
I've had some thorn punctures that leak slowly enough that they only need pumping every 2 or 3 days (it's best to leave a thorn in place, rather than pull it out).

With small tubes, that doesn't happen, and you've always got to change the tube immediately.

[Jules59]

Thanks everyone.
I subsequently realised that I needed longer valves now - so most of my 25mm inner tubes are no use. So ordered tubes with long valves covering both 25 and 28 - covers all options

[Jdsk]

Valve extenders are available.

Jonathan

[Greystoke]

My mate got a flat tyre en-route to work and the only tube he could get at dinner was 24".....his tyre is a 700c x 35!
It's been fine for a few years.....as he said, rubber stretches.

[tenbikes]

Back when I was racing on the NPS off road I used very undersized inner tubes without any issues. At all. In five years of intensive competition.
Just do it.

[WrightsW5]

There are bad possibilities, I once had a 26x2.3 tube in a 26x2.50 tyre and had a big blowout miles from home. Luckily it was a summer day and I fixed it with 5 puncture repair patches.

[tenbikes]

There are bad possibilities, I once had a 26x2.3 tube in a 26x2.50 tyre and had a big blowout miles from home. Luckily it was a summer day and I fixed it with 5 puncture repair patches.

That's what spare tubes are for