Spare tyre as air tank

Interesting concept. The max "safe" pressure is usually indicated on the small writing on the tyre (i.e. max pressure 60psi etc) so you'd have to check that out and go from there.

I sometimes over inflate the spares for this purpose.
I would guess that while static they could probably be over inflated by at least 50%, but don't really know.

I also carry a tyre to tyre fitting for my air hose, so I can blow up a flat from the spare.

Cheers,
Peter
OKA196 Motorhome

Hi.

...if you do a forum search of "air tank" you will get a few threads discussing subject in varying degrees. 60 to 70 psi seems to be a figured used a lot but supposed it depends on tyre. The fact that the spare tyre is unloaded may also determine what is a safe inflation limit (?).

Cheers
Greg

KeithB
You can over inflate a tyre, but why would you want to have a tyre continually under more pressure than the manufacturer says is safe? If the continual long term pressure damages the tyre and it then fails it most likely will result in damage to you and your vehicle.

A silly thing to do.

A spare tyre used in such a fashion will mean the over inflated spare can only possibly deliver a half charge to a flat tyre and the spare is then only half too.

Why not buy a suitable good quality compressor and use it when required.
If a cheap skate, buy two cheapies and use one until it fails and then the other one. At least you can blow up more than one tyre in the life of the compressor.
The idea of a compressor is so you don't need a tank at all. If using the air pressure and flow volume for dust blowing or air tools then a tyre is pretty useless.

The flow rate with the valve IN is small and you aren't going to have a valveless spare for more flow.

My MT ATZ are rated to 80psi by memory.
My tank on my compressor is set to 100psi max 80 min by recall. (8ltr Capacity)
Using a spare as a tank would need a manifold to house the relief valve and pressure switch. With a max safe pressure of 80psi it isnt realy a practical solution taking into account what is available today at a resonable price. You can get a tank with all the plumming and safety fittings for under 100$.

When considering why you would need a tank its pointless if you dont have a high capacity compressor to feed it or a very big tank. I utilize mine to re-set tyres and run air tools. Without the compressor to back it up you would need a big tank to keep the workable pressure.

I do exactly that! I have my Big Red Compressor mounted inside the spare wheel holder on the back door of the Patrol and connects to the schrader air fitting on the tyre, air cuts out at 60PSI ( BFG A/Ts max pressure is 80PSI), works well! Michael

Many of us have been doing that forever Keith.

Its very useful and provides a backup to the normal compressor.

For any particular tyre you should read what it says on it of course but for common 4wd tyres I usually limit pressure to around 100 psi (see note I put in Michaels reply).

When on a trip and tyre needs a refill then I put in 85 psi because thats the cut-out pressure in my ARB locker compressor.

85 PSI though is a handy figure as it can top up 4 tyres.

I.E. If tyres were dropped to 18 psi then putting them up to 30 psi takes
4 X 12psi or 48psi leaving the spare with approx 37 PSI. (implies spare is same size as other tyres)


Other useful Features
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Provides omph to re-seat a bead.

Provides air power to de-dust the car, or clean a filter.

Great way to balance tyre pressures.

In practise I usually pump up a tyre or two from compressor while also using spare tyre tank

Its espically fun to rob air out of someone parked nearbys tyres.

Its what I've also done for years, but I only use to for reseating tubeless beads that are stubborn. So I just hook it in when necessary. Need to have the valve cores removed on both tyres to be effective.
Not convinced it adds much for routine reinflation if you have one of those big compressors - I've had a TT3 (150L/min) compressor for about 4 years now and its really quick on a 285 tyre.

Personally I can’t see the point in all this fluffing around with utilizing the spare tyre. It all kind of goes south if the tyre needs to be used so carrying a compressor is still a necessity if required to re-seat, with no spare now is the time that you need this capability. Many modern compressors are capable of running air-tools re-seating tyre etc without a tank. A purpose built tank with all the safety features is well within the price range of most users these days. As for one comment of getting enough air into the tyres quick enough to get to the servo to finish the job, I think I would rather do it once on the track.

Thanks everyone.
This thread has been most educational for me.
Keith