Hi folks,
There's been a topic recently on the Yahoo list concerning wheel studs, wheel nuts and Cosmic alloys and as I know many of you folks are also on the list, rather than comment there I thought I'd use the modern technology of pictures to add a few notes about a recent modification I've done on the car.
My car has 13x5 Cosmics and one plan for next year is to try some 15" wheels, but an important (to me) option is to retain those 70s Cosmics for when I want the car to look "period". To use a modern wheel it seemed I'd need to install thicker and longer wheel studs, together with new wheel nuts, and this is just one way to achieve that.
Unfortunately this isn't a job you can do easily, all the hubs need to be removed to get access to press in the new studs. Even if you tried to the job in-situ by pulling the studs through using a spacer & nut there isn't enough clearance at the rear of the front hubs to insert longer studs without removing the disc. And likewise the drum backplate is too close to allow the new stud to slide in at the rear, so this is not a job you'll knock out in ten minutes over a coffee break.
The OEM studs are 3/8", quite small by modern standards and on my car have always looked a bit on the short side for the alloys. But they've worked for 40-odd years and if not for changing the wheels I expect they'd still be working fine in another 40yrs.
For the replacements I used 12mm studs as fitted to MG, Rover and many other modern cars. This is a well trod path and I took advice from other owners before going for this particular diameter. There are lots of variations in overall stud and threaded section lengths but the parts I bought were from a Metro hub, p/n NAM8116. These would be ok with my proposed 15" wheels but an unknown quantity for use with the Cosmics, which seemed to have a thinner bolting section when I compared wheels. The first measurements indicated that the wheel nuts would bottom out on the Cosmics with only minimal pressure which is clearly not acceptable.
Two options; one is to use thin spacers or the one I went for which was to shorten the new studs. The first photo shows the new studs before & after modification, I took roughly 1/4" off the end of the studs and blended in the threaded section. With hindsight, I should probably have picked a shorter stud but the logic was that it's easy to cut a bit off, harder to stick a bit on
The second photo shows the modified studs against the OEM ones, significantly longer and thicker but the splined section is identical in diameter and slots easily into the hubs. The difference is even more obvious on the third shot, a front hub with 2 new, 2 old studs in place.
But the Cosmics didn't take to the new studs willingly. As you might expect, a wheel designed for 3/8" (9mm) studs is going to have problems accepting a 12mm stud and so I had to drill out the holes. Plenty of meat to do so, and they still retain enough of the angled seat area to centralise the wheels when you bolt them in place.
I used aftermarket chromed wheel nuts with a diameter at the widest point of 24mm, a depth of 34mm and taking a 19mm or 3/4" socket size. These just fit nicely and although wider than the OEM nuts I've had no problem with either of my 1/2" or 3/8" drive sockets. Admittedly it's a tight clearance and I did wonder, but in practice it all fits neatly together. (Incidentally, if you're wondering about the MGF nuts shown in the first photo, they are too wide at the conical section and only intended for the 15" wheels.)
Brian
