How much air is required to fill a tyre??
Say a 26″ 2.3

To what pressure…

Surely the volume in the tyre is the same regardless of the pressure it is at 😉

druidh – my point as well (arguing at work)

Are you talking about the volume of the air or the volume of the tyre?
A ten litre cylinder filled to 10 bar has 100 litres of air in it.
A ten litre cylinder filled to 100 bar has 1000 litres of air in it.
The volume of air is compressed by the pressure but the internal volume of the tank remains the same.
HTH

A ten litre cylinder filled to 10 bar has 100 litres of air in it.

Not quite: a ten litre cylinder filled to 10 bar has the quantity of air that would occupy 100 litres at 1 bar (atmospheric pressure) assuming temperature is the same

You could work out the volume of the tyre – it’s sort of like a cylinder 2 and a bit inches in diameter and 26 inches high..

to fill a 2.3 tyre to 30psi

Around 355 cubic inches.

http://www.engineersedge.com/volume_calc/torus.htm

Assuming that the tyre is a perfect torus where a section through it would be a circle of 2.3″ diameter.

euain
I was trying to keep it simple without involving too many variables. To that end I also used bar and litres rather than psi and cubic inches.
The problem with bike tyres is that the sizes vary wildly so it is hard to give a cubic capacity. One brands 2.35 is like another brands 2.1.

I make it about 5.5 litres at 1 bar, so about 11.5 litres at 31 psi (2.1 bar). Of course there is still actually only 5.5 litres of air in there

Reason i ask is trying to make an inflator for tubeless tyres by suing a garden pressure sprayer. Wondering to go for a 5 or 10L version

by suing a garden pressure sprayer

Where there’s a blame there’s a claim!

grrr – need to sort out using and suing!

I make it about 5.5 litres at 1 bar, so about 11.5 litres at 31 psi (2.1 bar). Of course there is still actually only 5.5 litres of air in there

I agree that the volume inside that size of tyre is approx 5.5L, but when you inflate a tyre to 31 psi (2.1 bar) you are inflating it to that much above atmospheric pressure (or above the 1 atm, reference side of a fixed guage). So you will need roughly 17 L of atmospheric pressure air to fill a tyre to that pressure.

so if i buy a 5l version and pump it up then i will be fine?

I’m guessing that you’re trying to use it to quickly seat a tubeless tyre?

In which case you’ll need to get it up to 60psi so that when you inflate the tyre you’ll effectively be doubling the volume (not quite as tyre is 5.5l rather than 5l)and therefore halving the pressure.

If that’s not your goal then ignore me 🙂

spot on

Then 5l if you can get it up to 60psi before the safety valve pops or 10l at 45psi (I think)

Just buy tyres that’s don’t need a compressor, just set up some flow rims with High Roller 2s 60a EXO Kevlar bead with a track pump and no soapy water…..soo easy

Safety valve on a 5L sprayer is about 3 bar or about 45PSI. Get a 10L, the valve will be the same.

Coincidentally, I use my 5L sprayer to clean up to three bikes after a winter ride.