Do inner tube sizes make that much difference?

Just put some 40mm  gravel tyres on wheels that previously had road tyres on. Needless to say I hadn’t remembered to buy any bigger inner tubes so used the ones for the 25 mm road tyres. Does it really make much difference? They seemed to seat alright but I do notice shops seem to now sell larger width tubes.

Should be fine so long as they aren’t stretching too much. You may find they end up a bit too big for the 25c’s should you change back.

I use 18-23’s for my 25c road wheels, and 30c plus for the gravel tyres.

They will probably be fine for a bit.

They tend to split after a while, or small punctures are irreparable because patches won’t stay bonded.

Or just set the up tubeless.

I was pondering this the other day, or close to it

What size spare tube would you carry if riding a mullet bike?

I had a nightmare punctureathon last year on marathons, it was an overstretched tube so any imperfection, pssssss, had 7 in 2 months.  Did all the usual checks, replaced tubes with 35-40s, 4 quid at asda, not 1 puncture since.

That’s was 35c marathons.

What size spare tube would you carry if riding a mullet bike?

27.5 tubes work fine in a 29 wheel as well

@Onzadog the tubes I have, Schwable I think, list 26, 2.75 & 29″ on the side of the tube.

Tubes with gravel tyres?

What size spare tube would you carry if riding a mullet bike?
27.5 tubes work fine in a 29 wheel as well

29in tubes also will work in a 27.5 wheel to get you home/finish your ride

What size spare tube would you carry if riding a mullet bike?

The smaller size. It’ll stretch enough to work. If you put a bigger one in, it will be impossible to get it in without it folding up. Even if you can avoid pinching it, it will develop holes along the creases. It’ll get you home in an emergency but a slightly too small tube is much less hassle than one that is too big.

25 to 40 is a big jump, that rubber will be stretched very thin so you’ll find they puncture easily.

Also second the tubeless thing.

I found after a puncture and emergency too narrow inner tube on 44mm tyres that the tyre was not stable on the rim. The cheap tubes didn’t seem to fully fill the tyre.
It felt a lot better with the correct size tube in.

Think of the weight saving using smaller tubes

As above, I always understood that if they’re too small they stretch and are easier to puncture.

Slightly different, but I punctured on the road bike the other day and realised when trying to fix it that the two spare tubes I’ve been carrying around in a tool bottle both have valves that are too short to reach through the rims. Fantastic.

I find it only really makes a difference with road tyres. For example 25c is too small for 32c tyres. But I find the quality of inner tube makes the most difference (WTB tubes are garbage….)

I certainly used 26″ tubes (remember them ?) In 27.5 wheels for several years (before going tubeless)

Inner tubes on a gravel bike?!

If you’re not tubeless with inserts you are doing something very wrong!

I’m am old man! The bike is mainly used on the road with modest easy track excursions. If I want to do anything more I have MTBs I can use (set up tubeless).