I found a set of spare lug nuts for my XJR that must have been quite abused by a previous owner, because they wouldn't even accommodate a 7/8" (22.2mm) socket on them, much less the correct 22mm one. On a whim, I decided to cut the covers off and see if I could do something with the separate pieces. As expected, the usual open-ended nut was underneath, and it measured exactly 21mm as confirmed by my digital caliper.

As it turns out, there's a lot of aftermarket plastic slip-on lug nut caps that are supposed to fit a 21mm nut, so I may get a cheap set of those. Alternately, I may try to reform the shape of the original cover by simply hammering it or pressing it with a hydraulic press. The main issue is whether or not this would cause problems with the trunk toolkit in case I have a flat tire and need to remove a wheel; not a problem in the workshop, but definitely so on the side of the road.

 

they are 7/8 caps as far as i know and it’s not a trivial difference. some 22s are just too tight and you need to hammer them on.

 

I took the stainless caps off my stock lugnuts and use them under the hubcaps of my Solars.

For my 20-spokes with exposed lugs, I run Gorilla 73187SMB which have a 13/16" drive.

Both work with a 21mm tire iron I had left over from when I migrated my Miata to 19mm drive lugnuts.

 

I tried the uncapped nuts with the original tire iron, and it seems to work fine for both tightening and loosening. I've just ordered a set of plastic 21mm caps and will see how they fit.