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Ride was going so well at the weekend until I realised all too late that my Stans had evaporated and it was stick a tube in time. I am 25 miles from home at this point.
Pulled out my brand new Pirelli TPU tube - only to discover that the valve is at a 90 degree angle to where I would expect it to be. No amount of pretending to be the bloke at kids parties that makes balloons into dogs would help.Â
Is this defective, or am I missing a trick? Thankfully managed to source another butyl tube, or would have been completely in a pickle. 
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Surely you stick it in the valve hole and it will be fine?
absolutely not.... and we tried. But it would then twist itself into the valve hole as you inflate -Â to be lost inside the rim. Which made deflating it to get it out again an impossible task. And the valve does not have a valve nut... so it isn't like you can hold it in place to prevent that.
Surely you could have just drilled a small hole in the rim wall for it? Pop to the nearest Screwfix, job done in no time.
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Has the added benefit that it will make a tuneful tinging noise on the seat stays and chain stays as you're riding along.
With TPU tubes you are only meant to put around 5psi in them before fitting to the wheel, if you put more in before fitting then it can affect the shape of the tube/valve rotation
I know Ride Now TPU tubes have to have the valve rotated inwards before inflating slightly for fitting
Only thing I can suggest is removing all the air from the TPU tube and laying it flat and move the tube using your fingers and thumbs so the valve is on the inside and the tube is evenly flat all the way around then try inflating to 5 psi and see what happens
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All inner tubes twist if you inflate them enoughÂ
You only need enough air to stop them getting trapped when you pop the tyre on
We tried at low pressure, to no avail. And it was only a very low psi while outside of the tyre to try and understand wtf was going on!
My Pirelli space saver spare doesn't do that & it's come to the rescue half a dozen times.
With TPU tubes you are only meant to put around 5psi
0.5psi
It's really 'some air in the tube' not any pressure at all or they distort.
Having said that, if you overinflate them they don't distort like that, like a lot of 'rubbery' polymers (lightly cross linked) they blow up like a snake that's eaten a large meal due to the S-shaped stress/strain curve. Initially the modulus goes up as the chains interact, then beyond a point those interactions break and the material stretches rapidly until you reach a point where individual chains are straightened out and the relationship goes back to something much steeper and vaguely linear.Â
All inner tubes twist if you inflate them enoughÂ
I've f***ed up a few TPU tubes and they've never twisted like that, that's IMO a manufacturing fault. TPU tubes don't stretch into the tyre like butyl tubes, it's more like a (thin) solid plastic. Expecting it to stretch and find a natural position when it starts like that isn't going to work.Â
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Manufacturing issue. I'd be chasing a refund.