How hard can you pump tubes?

**Timbuk2**

I patch my punctures because I am too cheap to throw away the tube. From previous expierences I know that the harder I pump the tube, the easier it is to locate the puncture.

But how hard is too hard? At around what PSI would you expect the tube to explode? I'd imagine it doesn't take much at all to explode it, but I don't actually know as I've never done it. I usually just pump it hard enough so it becomes round in shape.

At what PSI would a tube explode? Would it depend on the tube, or is there a general 'don't-pump-higher-than-this' figure?

72hundred

Are you talking about inflating the tube outside the tyre?

DirkVoodoo

**Timbuk2** wrote: »

I patch my punctures because I am too cheap to throw away the tube. From previous expierences I know that the harder I pump the tube, the easier it is to locate the puncture.

But how hard is too hard? At around what PSI would you expect the tube to explode? I'd imagine it doesn't take much at all to explode it, but I don't actually know as I've never done it. I usually just pump it hard enough so it becomes round in shape.

At what PSI would a tube explode? Would it depend on the tube, or is there a general 'don't-pump-higher-than-this' figure?

It depends on whether it is sitting on a rim surrounded by a tyre or not. I have no idea at what pressure a bare tube would explode at, but when you have a tube that is not only being restricted by atmospheric pressure but the rim and elastic modulus of a tyre, generally you don't want to go past the "max pressure" of the tyre.

A few pumps of a tube should be enough, for smaller punctures just immerse it in a bath of water to find the hole. No need to try and make a bouncing castle out of a tube.

Lumen

DirkVoodoo wrote: »

I have no idea at what pressure a bare tube would explode at

Since you've raised the question, you have a duty to experiment and post your findings.

Just don't do it on Friday night, A&E gets really busy and you'll be waiting ages.

DirkVoodoo

Lumen wrote: »

Since you've raised the question, you have a duty to experiment and post your findings.

Just don't do it on Friday night, A&E gets really busy and you'll be waiting ages.

Ha, should I pop down to the petrol station and give it a go? I have about 20+ spare tubes in the garage.

Sheldon only mentions that butyl rubber tubes "cannot withstand any significant air pressure", not very helpful.

I guess the question is, do we really need to know this?

DualFrontDiscs

**Timbuk2**

Sorry if I was unclear. I meant a bare tube, outside of a tyre.

The reason I want to know is that I want to know if I am being over-cautious when I am only using two-pumps of my pump to pump the tube up when looking for punctures.

I usually use my sink in the back hallway to find punctures (filling it with water). But even sometimes it can be hard to find punctures this way, especially if they're small punctures or slow punctures. That's why I'm wondering how high should I go in order to find them more easily (they are easier to find at higher pressures - but I don't want to explode my tube).

Gavin

DirkVoodoo wrote: »

Ha, should I pop down to the petrol station and give it a go? I have about 20+ spare tubes in the garage.

Sheldon only mentions that butyl rubber tubes "cannot withstand any significant air pressure", not very helpful.

I guess the question is, do we really need to know this?

Come on engineer boy, engineer some stats and then blow up some tubes !

DirkVoodoo

Gavin wrote: »

Come on engineer boy, engineer some stats and then blow up some tubes !

I'm not too keen on an exploding tube in the face:

https://www.youtube.com/watch?v=SLMeIpvvHwQ

**Timbuk2**

OK, after watching this video, I think I can get away with a bit more air than I thought

https://www.youtube.com/watch?v=IP4M18r7A0A

Lumen

OK, I just did the experiment.

A generic cyclocross-sized tube will take on enough air to exceed a diameter of 4ft before exploding with enough violence to make a toddler cry.

rottenhat

Lumen wrote: »

OK, I just did the experiment.

A generic cyclocross-sized tube will take on enough air to exceed a diameter of 4ft before exploding with enough violence to make a toddler cry.

I'm calling the social worker now.

abcdggs

i'm very interested to see the other levels on your scale if one is "make a toddler cry"

DirkVoodoo

**Timbuk2** wrote: »

OK, after watching this video, I think I can get away with a bit more air than I thought

Difficult to compare really, it's a good start but air will be at a much higher pressure than water in the same volume and for the same temperature.

DirkVoodoo

Lumen wrote: »

OK, I just did the experiment.

A generic cyclocross-sized tube will take on enough air to exceed a diameter of 4ft before exploding with enough violence to make a toddler cry.

Did you really?

Lumen

DirkVoodoo wrote: »

Did you really?

It's just a big balloon, however we were protected from the "event" by a double-glazed patio door through which snaked the hose of my track pump.

My warnings about the impending explosion only piqued his interest; in fairness it wouldn't have been a problem if he'd gone to bed like I'd asked.

DirkVoodoo

Lumen wrote: »

It's just a big balloon, however we were protected from the "event" by a double-glazed patio door through which snaked the hose of my track pump.

My warnings about the impending explosion only piqued his interest; in fairness it wouldn't have been a problem if he'd gone to bed like I'd asked.

Did you have a gauge on this track pump?

blorg

I would suspect you can go higher inside a tyre. I have experience of the bead not being seated, the tube getting out at ~100PSI and making a run for freedom... pop!

Stark

**Timbuk2** wrote: »

OK, after watching this video, I think I can get away with a bit more air than I thought

https://www.youtube.com/watch?v=IP4M18r7A0A

Why does he sound like he's trying to take a massive dump?

Lumen

DirkVoodoo wrote: »

Did you have a gauge on this track pump?

Yes. Pressure never really registered (up to 20psi and down to nothing on each stroke) as the tube just got bigger.

**Timbuk2**

Thank you everyone for the responses! Was very interested in hearing the results of your experiment Lumen, thanks

72hundred

**Timbuk2** wrote: »

Thank you everyone for the responses! Was very interested in hearing the results of your experiment Lumen, thanks

Do you owe Lumen a tube now?:P

(@pete: I know I still owe you one!)

blorg

Lumen wrote: »

Yes. Pressure never really registered (up to 20psi and down to nothing on each stroke) as the tube just got bigger.

That would make sense, the tyre would be necessary to restrict the volume the tube can expand into, if there is nothing restricting the tube the pressure would not increase but the tube would just expand outwards...

sy

blorg wrote: »

That would make sense, the tyre would be necessary to restrict the volume the tube can expand into, if there is nothing restricting the tube the pressure would not increase but the tube would just expand outwards...

At least some pupils listened in Physics class