Morris Minor Owners Club

I got my new tryes and picked up a set of second hand powder coated wheels. I took them to my local garage and when they went to fit the valves one of the holes was a different diameter from the other 3! The valve holes should be about 12mm dia and one of the wheels the hole is approx 16mm dia. The garage said they only have one size of valve.
I am about to plod round the local tyre fitters and see if you can get a larger dia valve.

Does anyone know if you can get larger valves or suggest a solution?
Only thing I could think of would be to fit a tube.

Trouble is,of course, that the tubeless valve has to be a leakproof fit,
I have no idea if a larger type is available but the only solution I can think of otherwise is to have the hole brazed or welded so that a new normal sized hole can be drilled into it. I have tried this exercise with
a wheel where rust had eaten away some of the hole and it was a dismal failure,probably because I used epoxy!

Local tyre places no good. I managed to find an alloy wheel specialist. He thinks he maybe able to do something for me and I have left the wheel with him and have to go back on Tuesday - very frustrating!!!