18 - 23 tube in a 25 tyre?

[Genosse Brymbo]

Having only ever ridden 700x23c tyres on road bikes I'm about to try a 25 tyre.  My innertubes (Michelin A1's and a Bontrager I picked up from the LBS) state 700x18c-23c.  Would it be ok for me to use them with a 25 tyre or am I going to have to buy innertubes which cover both 23 and 25?

[PaulF]

Should be fine

[Gaston Lagaffe]

I've done this with no problems, and the other way round i.e a tube for 25- (whatever) in a 23mm tyre.

[Rainmaker]

Have you ever pumped up an inner tube that's not in a tyre?   You may be amazed how big they can go.   You won't have any problems with using your existing tubes.   

[CrazyEnglishTriathlete]

You can get away with a lot.  I discovered in the early hours of an Audax that my two spare tubes were for 26" tyres.  With a small amount of coercion I got the 26" tube onto the 27" wheel and prayed that it would hold for the rest of the ride.  I made a mental note to replace it when I got back.

About 2000 miles later I punctured on a rainy day and wondered why it was so difficult to get the tube off the rim.   

[Biggsy]

Advantages of an 18-23 tube in a 25 tyre:

• Easier to fit without trapping.
• Saves weight.

Disadvantages:

• Needs pumping up more often.
• Will be less durable in the long run.  This is unlikely to be a problem for a standard-weight tube, but an ultra-light one might eventually develop holes or splits.

[Simon Masterson]

Should stretch.

The only problem I've ever had with using a smaller tube was when I had a p-word and only had my useless ancient Raleigh framefit. It's bad enough at inflating tubes that are the right size.

[Biggsy]

Think about how little effort it takes to make a smaller tube reach the size of the tyre.  That happens within the first 10 psi, then you're just fighting the tyre for the rest.  So the size of the tube is irrelevant as far as difficulty of inflation goes.

Those Raleigh pumps were naff indeed, though.  They were rebranded Zefal HP.  (Not HPX).

[Genosse Brymbo]

Thanks very much for the replies.  I'll get the 25 tyre and probably continue to buy the Michelin A1 tubes as  the A2's say 25-32.  The A1's are pretty thick and don't have removable valve cores, which suits me.

[Biggsy]

Yes, A2s do seem enormous in 25mm tyres.  It doesn't help that they're designed for 27" as well as 700C.

[Bledlow]

I've done this with no problems, and the other way round i.e a tube for 25- (whatever) in a 23mm tyre.

Ditto.

[Biggsy]

Disadvantages of a 25-x tube in 23 tyre:

• Harder to fit without trapping.
• Adds weight.

Advantages:

• Needs pumping up less often.
• Will be more durable in the long run.

[LittleWheelsandBig]

In the early days of cut-down Mavic road rims on MTBs, a friend used 700x28C tubes in his 26x2" tyres for a while. They would give way at the valve after a few weeks due to excessive stretching but otherwise fine. You will have no trouble at all.

[hubner]

How would this affect the durability of a repair patch?

A patch that's being stretched all the time would surely come unstuck before one that is not stretched? Even if they are both equally well stuck.

If I've got 25mm tyres, the options seem to be:
18-23mm - lighter but patches might leak earlier
25-32mm - heavier but patches are more reliable

[Veloman]

I have used 18-23 in my 25 tyres as I have changed from 23 to 25.  No problems with using the slightly smaller tubes and I don't repair I just replace and recycle old to those in club that do repair. However, I also have a stock of both Halfords, Decathlon and Continental (inner tube of choice) that are 25 sizing.  I also buy long valve just in case we are having a bad ride and someone with deep section rims has used their spare (I always carry 2 spare).

I have also used an old inner tube (valve neatly removed) for team building and we had 27 people inside the inner tube!

[Genosse Brymbo]

How would this affect the durability of a repair patch?

A patch that's being stretched all the time would surely come unstuck before one that is not stretched? Even if they are both equally well stuck.

If I've got 25mm tyres, the options seem to be:
18-23mm - lighter but patches might leak earlier
25-32mm - heavier but patches are more reliable

I've been using 18-23 Michelin A1 innertubes in 25mm 700c tyres since my original post, just over 5 years ago, completing an annual SR and 1xLEL and 1xPBP in that time.  I'm an ardent tube patcher (I bought a box of 100 16mm Rema patches) and I've had no problem with patches leaking or becoming unstuck.   I only bin the tubes after 6 or more patches.

[toontra]

How would this affect the durability of a repair patch?

A patch that's being stretched all the time would surely come unstuck before one that is not stretched? Even if they are both equally well stuck.

I've been using Continental tubes (rated 18-23 I think) in 28 tyres and can vouch that patches (whether instant or properly glued) regularly fail.

[hellymedic]

My patching seldom, if ever failed but I usually try to use tubes of the right size, though partner's deep V rims and broad tyres make getting long-stemmed, broad tubes a challenge sometimes!

As LWaB posted in reply #12 upthread, tubes can fail at the junction of the valve stem reinforcing patch and the normal tube, if overstretched.

I see undersized tubes as a 'get you home' rather than a long-term, solution.

Having said that, if I'd used an undersized tube, I would not change it until I had another visitation or was about to embark on a long tour or Audax.

[Biggsy]

I have used slightly undersized tubes* long-term ok with Marathon Pluses as it makes these difficult tyres easier to fit without trapping the tube.  I would expect really well applied patches to survive the stretching, but M+ tyres don't give me the opportunity to test this because they never puncture. 

* ?-25 tubes in 28 tyre.