tNuvolari

So I decided to try some latex tubes and picked up a couple of Challenge tubes. When I went to install, I blew them up about 20psi to install. The first one was fine but the second began bursting out like a pregnant snake that just ate a fat mouse! It did this in three different places on the tube. I'm just wondering if this is normal or will the tube fail? I haven't ridden on it yet but a bit worried about it. Have you guys seen this before? thanks for the help and a couple of pics cuz everyone loves pregnant snake pics....



The pregnant snake lives--Is this bad?





Less than 20psi

krakhaus 

Why would you pump a tube to 20 psI?

Geepig

That is a high pressure!

Even when checking for a puncture I would only take it until it takes a tubular shape, just a few pumps on my hand pump.

HTupolev

Don't attempt to pressurize a free inner tube. Tubes are just thin rubber, like party balloons: if you put more air in them, the pressure doesn't significantly increase, they just stretch and get bigger to make room for the additional air (until they stretch so much that the rubber tears and they explode). Tires are able to contain high pressures without exploding (or even stretching much) because their casing contains fabric plies.
It makes sense to put some air in a tube before installing it, so that it holds its shape. But that's about it. Once the tube is full of air, you shouldn't keep pumping.

Anyway, it's typical for latex tubes to stretch thin and unevenly like that if you pump them up too much outside of the tire.

tNuvolari

Uh, that's pretty much 20psi. Less than that was not enough for it to even take shape. It's literally maybe one pump!

Every instruction I've ever read about installing tubes & tires says to inflate the tube slightly. I admit I almost never do it with butyl tubes but with these Challenge latex tubes, they were small and tight and I could not install them without inflating slightly to stretch them enough so they would even fit around the wheel. I only inflated enough to allow this. I don't know if Challenge tubes run small or if all latex tubes do but I could not install without inflating a bit. And 20psi is basically nothing. And furthermore, one tube handled it without bulging and the other did not. I don't think I did anything crazy or excessive. I guess I'll find out soon on future rides....
Oh, and according to my gauge, the pressure is less than 1 bar so looks like about 13psi.

Geepig

Maybe the small pump I have lying around the garage for such tasks needs some maintenance then: first pump and tube is still floppy, on the second it yawns and by the third it starts to consider getting up

Usually I only pump a bit in for my 20" and 24" wheels as it can be difficult getting into the tire to align the tube, while for my 26" wheels and bigger I usually feel my tubes into place and then maybe give a puff or two from my olde bycycle pumpe when things do not feel right.

Iride01 

Blowing a tube up before containing it in a tire serves no purpose except to have it behave like a balloon.

Crankycrank

It's not all that unusual for a latex or very thin butyl tubes to balloon in spots like that. Tubes only need to be slightly inflated and less than in your photo for tire installation. The tube just needs to hold it's shape to prevent twisting and helps from getting it caught under the bead when mounting the tire.

dsbrantjr

The tube will be constrained within the tire, which is what gives the strength to the assembly. The tube just serves to seal in the air. There will always be a thinner spot into which the air will preferentially go but this will not happen inside of the tire.

Troul 

I'd exchange the tube after that occurring. It might bite you in the end, now that the preggo snake happened.

HTupolev

20PSI is not "basically nothing", it's a perfectly good riding pressure for a lot of people in cyclocross and MTB. I suspect that your pump gauge is not producing meaningful data at low pressures, which has given you false notions about how to use it and what it means. I was not joking when I said that tubes mostly just get bigger when you pump air into them, rather see a significant increase in pressure: on my pump, I can take a 26er tube and pump it until it's blown up significantly larger than a 29er tire, and the gauge will still read basically 0PSI.


Yes, but this isn't something that you should be looking at the gauge for. The idea is to air the tube so that it holds a round shape, not so that it holds a certain pressure.

Troul 

inflating the tube prior to install is to aid in preventing a pinched tube from occurring.

phughes

You don't need that much air in a tube to prevent pinching.

Riveting

Prior to being placed inside the tire, I inflate my tubes with my mouth, which a quick Google estimates at ~2 psi.

Troul 

exactly. just need enough.

bikemeister

Looks like what the cardiologist does during an angioplasty. Yuk!

79pmooney

The really sure-fire way to inflate tubes enough for easy installation and never over-inflate them is to blow them up by mouth. Also fast and easy.

Edit: I see Riveting beat me to it. Didn't read all the posts because nobody says this on bicycle forums!

cyccommute 

“Slightly inflating a tube during installation” is one of those things that I’ve never quite understood. Lots of tires are difficult to mount and adding a filled tube doesn’t make the process any easier. I’ve always put my tires on with the tubes completely flat. The tire slips on easier and there is less likelihood of nicking the tube during installation.

I’m not getting how the tubes you are using are helped by slightly inflating them so that they can fit around the wheel. If they don’t fit around the wheel, they are the wrong size. Even if you had to stretch them to get them around the wheel, keeping them flat isn’t going to cause a problem.

genejockey 

Because it's easier to get a tube with just a bit of shape to it into the tire and into the well of the rim. Once it's there you can let most of that air out as you put the other bead on the rim.

Iride01 

I used to ever so slightly inflate my tubes to help get them in the tire and rim. Once in the tire and rim, they had to have most all the air let out to easily get the bead of the tire over the rim without levers.

However, more often now, I don't put any air in the tube till the tire is completely on the wheel.

woodcraft

This is just what happens when you inflate a (latex) party balloon, so not surprising.

The OP says that the tube has to be stretched onto the rim when uninflated. I don't see how the tire could go on without pinching the tube like that, so it has to have some air in it.

cyccommute 

Never had a problem betting the tube into the well of the rim. The tube goes in just fine without all the fiddling with adding and removing air.

cyccommute 

With that I agree. Latex has is very thin and has little structure to it.

To my way of thinking, if a tube needs to be “stretched” to get it onto the rim, whether inflated or uninflated, it is the wrong size. A tube should need to be stretched. It also should have to be stuffed into the tire with folds left over. It should fit “just right”. It fills the void when inflated.

On the other hand, if the tube does need to be stretched over the rim to get it to fit, it will sit in the well of the rim like a rim strip and will be out of the way of the tire bead. That might make the tire even easier to mount because there is nothing in the way.

woodcraft

A road tube & CX tube on the only handy clincher rim. When stretched a bit it's narrower but not much.

Geepig

I cannot speak for anyone else, but I generally only do it for my 20" and 24" wheels, which with my arthritic fingers, sometimes very stiff tire walls and tight rim curve, can make getting the tube in straight difficult. I always have a pump to hand, so it is not a great extra effort.

New tubes are often highly folded, so a quick puff helps, while older tubes can lack any shape or seam to guide you in aligning the tube - so a slight inflation is quicker, and then helps in not getting pinches because they have generally stretched a bit over a 20-30 year life time. I like to replace tubes, but it is not always an option when it is someone else's bike.

The other week I had a 1980 20" wheeled bike that had been in someone's basement since 1995 and was still on the original tires and tubes - the tires were effing tight and the tubes completely seamless and fairly shapeless when empty.