My Jake the Snake commuter bike has 700c wheels with 28mm width tyres and I need to replace the inner tubes- the one's supplied have no markings at all.

I asked Continental tyres for advice and they recommended the Race 28 tube but that's a 700x18/25 which I'm guessing means it works with tyre widths 18mm to 25mm? If so then the guy from Conti has given me incorrect advice.

Looking at the tubes pages on the Conti website (near the bottom of the page) I reckon the tubes I need are the Tour 28 All or the Tour 28 slim.

Can anyone confirm or advise what the tube designations mean and the correct tubes for my wheels/tyres?

TIA

Johno

i'd suggest tubes with the lower number matching the tire casing width,
so inflation will stretch the tube the least, as a thicker tube wall will retain air
longer than a narrower one ballooning out to fill the space..

The Cross 28 will work as well. Basically, tubes have a lot of stretch so a tube rated to 25mm will work on a 28mm (that's what I was running on my commuter because I was too cheap to buy new tubes when I went to 28s on it). If you are near (or slightly above) the max size, the tube will stretch more and, therefore, be thinner. If you are near the minimum size, it won't stretch as much and will, therefore, be thicker. (Of course some tubes are made thicker than others so what you end up with will be a factor of the type of tube and its size.)

The two other factors in tubes are the valve type (presta or shrader) and stem length. If you have shrader (like on a car), they usually don't come in different lengths. If you have presta, there are a lot of different lengths depending on your rim (deep rims need longer valve stems).

+2

18/25 tube will certainly work in a 28mm tire but it's really a dumb recommendation considering it will lose air faster than a larger tube (as mentioned above, all other things being equal.)

If I were walking into a bike shop to get a tube for a 28mm tire I'd look first for a 28/32 tube, but would be willing to settle on many other similar sizes.

Thanks everyone for the very prompt replies, I'll probably go for the Tour 28 Slim which are 700x28/37 - I don't ever envisage using tyres less than 28mm width on my rims.

Good choice.....

Don't worry, if you do it works the other way too. With care a fat tube will fit just fine in a narrow tire. I've fit a 32/35 tube in a 25mm tire plenty of times without issue.

Is there any evidence to support this claim? I've heard it said over and over, but it hasn't matched my experience at all. In fact, I've routinely kept inner tubes inflated to several times their normal size (outside of tires) around for months, and they don't seem to leak any faster or slower.

Basically, it doesn't really matter, most any tube can fit in most any tire. If it's smaller, it will be easier to install, lighter to carry, but may by some peoples reckoning (pending proof) loose air faster. If it's bigger, it's just harder to install.

How much pressure were these tubes outside of the tires holding? 50 PSI? 100 PSI? More likely less than 10 PSI. Tubes at lower pressure will leak more slowly. Thicker tubes, all else being equal, will leak slower.

As 10 Wheels said: "Good choice"

I've used a 23/25 tube in a tire that measured 34mm wide @ 60psi. No problems at all.

Well, can we assume that air leaking out of a tire follows Darcy's Law for the rate of flow through a permeable membrane?



While the pressure difference is much lower (it's hard to get a bare inner tube much beyond a few psi), the path length of the material should also be significantly less. I'm not quite topologically adept enough to figure out the surface areas of the torus, in fact I'm kind of stuck on it. Does anyone more mathematically inclined want to chime in?

I'm inclined to think it's going to be an inverse square thing, but I can't actually justify that assumption just yet.

If I can't have the correct size I would rather use a tube slightly smaller than slightly larger, better fit, less likely to wrinkle, lighter and easier to carry.

I switched to Continental tubes five years ago, as they don't lose as much air as other brands. I've been using them in my road bike with 23mm or 25mm tires, and they'd drop 4-7psi in a day.

Our tandem has 28mm tires, and we asked our dealer for ten tubes so we were ready for lots of riding. I was a little surprised when I saw ten of the same tubes I've been using for five years. They do lose 15-25 psi in a day, but otherwise they've held up well. (I chose a real bad line over a railroad crossing, and six weeks later we had a broken rear wheel; I'm pretty sure the RR crossing was the trigger. Nonetheless, no pinch flat with the same Continental tubes we always use.)

I have tubes rated as 23/28 on my bike right now with several patches in 38 tires tight with no problems.

Thanks for that. I've just switched from 32 gatorskins to 38 panaracer panatite on my commuter bike but the corresponding 34/37 conti tubes won't arrive for another couple of weeks. I thought if I put 28/32 tubes in the bigger tyres they'd pop, but as your running a smaller tube in the 38 tyres, I'll give my old 28/32 tubes a go 🙏