I think I know the answer but I'll ask anyway. Is it ok to use foam cans to seal leaky alloy rims or do they make so much mess you shouldn't?
I've got Mini Sprite alloys on my trailer. It's used infrequently but the tyres are always flat when I use it. They hold air long enough for the odd trip but it's becoming a pain.

Have you thought of fitting inner tubes. Not sure how new the tyres are but might be a cheaper option than replacement.

Most spray cans are for emergency 'get you home' use only.
Most modernt tyres arent suitable for use with Inner tubes IIRC.
It should be fairly simple to find where its leaking from with some soapy water sprayed around the edges and the valve.
Its propably a bad finish around the bead that just needs to be cleaned up with a wire brush or a flapwheel drill attachment.

The can will only seal the tyre tread --- the foam gets distributed round the tyre by centrifugal force.

First thing to do is check the tyres are not leaking round the rim this can be sealed by knocking the tyre off the bead and sealing with lots of tyre bead lubricant (tyre fitters soap).

If it is the actual rims that are leaking then removing the tyre, cleaning the rim (and check for cracks) then lacquering with a 2K aerosol should work.

[Edited on 14/5/11 by britishtrident]

Rear leaky tyres in my tractor (thorns from cutting the hedge) have been sealed with cheapo foam for 4 years now
Best thing since sliced bread.
All I had to do was replace the valves when I decided to check the pressure last year.

BTW the foam does distribute itself on the rim - just replace a tyre to find out you have to clean the rims with solvent - I used brake cleaner

Cheers!

Probably caused by corroded rims where the tyre should seal, a fairly common problem. Remove tyre , use a wire brush in an angle grinder to clean and apply tyre bead sealer, refit tyres job done.

try letting the wind out
walk round the bead the put some sillcone round the bead.

worked on my alloys

A lot of alloys can become porous, a racers trick is to tape the inside.