Need help with Tyre/Inner tube size pls

[boydj]

1. You shouldn't be riding on pavements in order to jump off them!

2. Have you checked that the tyre is seated properly at the valve? You need to push the valve up further into the tyre to make sure that the tyre seats properly at the valve where the inner-tube is reinforced.

 

[ump001]

1. You shouldn't be riding on pavements in order to jump off them!

2. Have you checked that the tyre is seated properly at the valve? You need to push the valve up further into the tyre to make sure that the tyre seats properly at the valve where the inner-tube is reinforced.

Hi

Tyre is definitely seated properly. Checked a guide online and it's in the narrow groove of the rim. Once the tube is pumped it just clings to the rim rather than staying inside the tyre.

I like jumping off pavements 😎

I'm wondering if a tube 35 - 45 will be a better option?

 

[boydj]

I'm struggling to understand what's going on here. A picture would be useful.

If the tyre is mounted correctly, you should not be able to see anything of the inner tube, either before or after the tube has been pumped up, other then the valve coming through the hole in the rim.

 

[ump001]

The tyre is mounted correctly as far as I can tell. The tube however doesn’t completely fit into the tyre, seems like it’s an inch short. So once pumped the tube is clinging to the rim and half the tyre feels empty.

I’ll try and get some pics by tomorrow.

 

[boydj]

The tube should be totally inside the tyre before you start pumping. Just check that you have mounted the tyre correctly, have you followed the following steps :

1. Mount one side of the tyre on the wheel.
2. Insert the valve of the tube through the valve hole, then, with just enough air in the tube to give it a bit of shape, make sure that the tube sits more or less inside the tyre.
3. Gently work your way round the wheel mounting the other side of the tyre, making sure that the tube stays inside the tyre and you don't nip the tube and cause a puncture. When you get to the last piece of tyre, you may need to use a tyre lever to get this on - be particularly careful here not to nip the tube.

If you've done the above, then there should be no tube visible by the time the last bit of tyre is mounted.

 

[vickster]

This. As someone who has managed to destroy a new tyre by having it trapped while pumping (kaboom ), now after fitting tyre and tube, I always run an old ice cream stick (luckily I’m fond of Magnums ) all the way round the rim on both sides of the tyre to check there’s nothing trapped 👍

 

[SkipdiverJohn]

I only put enough air in the tube during fitting to make it take it's correct shape - in order to prevent the tube being installed with twists or folds in the rubber. Some old tubes I've pulled out of secondhand bikes have done a pretty passable impression of a corkscrew!
It was drummed into me from an early age to always do a visual check right the way round both sides of the rim before full inflation, by squeezing the tyre and looking down into the rim well. I've never exploded a tube during fitting as an adult, the trick is in not rushing or cutting corners, much like doing anything. You aren't saving any time if you have to do the job twice and destroy a perfectly good tube in the process, because of not checking.

 

[ump001]

So i tried the tube again and i'm pretty sure the tube is just too short, i had to pump it so much just to feel it in the tyre and now i think i've blown a hole in it.
I've attached a pic of the tube in the tyre just before i placed it on the rim. As you can see its not all the way in properly within the tyre walls. When i pump it just stayed at the edge of the tyre. Most of the tyre would just feel empty.

 

[SkipdiverJohn]

Deflate the tube, fold it in half, and see if it measures up to what you would expect for a 27" diameter wheel. It's possible that it has been mis-labelled, although there is usually quite a lot of leeway in fitting incorrect sized tubes in tyres. After all, if you shove the thing inside a tyre, mount it on a rim, and pump it up - it has no choice but to expand to fill the available volume inside the tyre irrespective of whether it is technically the correct size or not.

 

[ump001]

So i ended up buying some new inner tube: 700 x 32-47 Continental. They fit perfectly

Will have to return the other ones, which should have fit.

How do i figure out how much to pump the tubes, i have a basic bike pump doesn't give me psi details.

Many thanks for your help on this forum.

 

[vickster]

So i ended up buying some new inner tube: 700 x 32-47 Continental. They fit perfectly

Will have to return the other ones, which should have fit.

How do i figure out how much to pump the tubes, i have a basic bike pump doesn't give me psi details.

Many thanks for your help on this forum.

Invest in a pump with a gauge, or buy a standalone gauge.
In the meantime, pump up until they feel hard, should be fine unless you’re very heavy