As well as the size you need to ensure that the taper of the wheel matches the taper of the nut, ie the cone of the wheel matches perfectly the cone of the nut and the 2 cones lock together nicely. (wheelnuts are rarely dead flat, unless they have are designed to take a washer as this is what centralises the wheels on the studs). I have 3 sets of Minilite replicas (not all for Commer I hasten to add) all taking UNF size, but none of the nuts are interchangeable due to slightly varying wheel castings. They look the same at 1st glance but slowly work themselves loose after a few 100 miles due to not seating properly. [:0]
I dont want to be a wet blanket but i learnt the hard way and dont want it to happen to anyone else, took me a while to discover the problem too.
Cheers
Jules
RatSport www.ratsport.co.uk