spent a few weeks getting new tires for my gm rally wheels,getting them mounted and balanced and finally getting new lug nuts. took the american mags off and could not get the rally's to go on. they were off just a small tiny bit. hub is the same and i hate to get the step bit and go at it. here's what i found and i'm open to all opinions. my new 7/16 lug nuts are too small. the studs on the axle are 1/2x20. what i think happened is someone put 1/2 inch studs on the rear to put the american mags on and they seem to be a little wide for the rallys. everything is GM passenger cars stuff. is the 81 bolt pattern metric just enough to mess me up? bottom line is i should have paid more attention to nuts and bolts but i ASSUMED everything was on the up and up. that old saying came back to bite me in the butt. never assume anything. thanks to all
rallys on my 81malibu
- Thread starter denny
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It is possible, and happens a lot, that somebody used an 82+ rear axle assembly. This is the case with the wagon in my avatar. These rears will have 12mmx1.50 studs, which can be mistaken for 1/2x20.
Look closely at the end of the stud, it may have an M stamped in it, which is for the metric studs. Obviously, 1/2-20 SAE nuts will go on, but THEY WILL NOT TIGHTEN PROPERLY. My late father's S10 came back to me from his mechanic with 1/2-20 SAE nuts on it's metric studs...luckily, I trailered it home and caught it before something bad happened. Just one of the many hacks I found they had inflicted on it.
Look closely at the end of the stud, it may have an M stamped in it, which is for the metric studs. Obviously, 1/2-20 SAE nuts will go on, but THEY WILL NOT TIGHTEN PROPERLY. My late father's S10 came back to me from his mechanic with 1/2-20 SAE nuts on it's metric studs...luckily, I trailered it home and caught it before something bad happened. Just one of the many hacks I found they had inflicted on it.
If you have 12mm studs, the wheels should fit. I used a metric stud rear in my '81 & the wheels fit. Like posted by Ribbedroof, look for the "M" on the stud.
thank you very much for the reply. the american mags that came off said 1/2 inch 20 on the lug nuts and were tight. i have put about 4 years and about 3000 miles on them. the PO had drilled the brake drum out to fit. i had a spare junk rally and the studs looked like they hit the very outside of the hole in the rim. by the time i enlarged the hole, the hole set up was junk. 7/16 lug nut just fell through the rim hole and the 1/2x20 lug nut was not very square in the enlarged hole. rear end looks like it has been there since 1981. i have thought about installing the original 7/16 studs because there are 5 unused holes in the axle flange not counting the 1/2" holes. i'm gonna have to think about this project and confer with my race buddies. something is not right so i better stop.
this was a small v8 car when new,appears to be a 7.5. front is tight. studs i'm working with in the rear are 1/2 inch and the nuts are 1/2x20. i'm beginning to wonder if metric plays a role in this problem. also do the american mags require 1/2" studs and if so thats why the po installed them?the axle has 10 holes in it and i may have to install the original 7/16" studs to fix this problem and thanks very much for the help.
thank you for the reply and advice. the studs are 1/2x20. no M on the studs. it's like the studs don't line close enough to the bolt pattern on the wheels. just off a little off on every stud. could someone have used a different bolt pattern with the american mags on the rear? i'll bet the other 5 holes in the axle are for the 7/16 original studs. don't know why someone would put 1/2 studs on a non performance car in the first place. can't wait to solve this problem
i checked the bolt pattern on the axle and it was 4 3/4 and the bolt pattern on rallys is 4 1/2. not good . can't believe it.someone went to the trouble to redrill their axles so their wheels would fit. pretty tough drilling. appears to be a run of the mill 7.5. every once in a while you get nailed. there are still 5 holes on the axle that are empty. could they be the 4.5 bolt pattern holes?
i stand corrected. saw where the g-body is 4 3/4 bolt pattern. i keep learning. anybody know the best way to mount these nice rallys to my g-body ? thanks
Aftermarket axle shafts maybe?
Can't imagine why someone would drill the flange for a second set of studs unless it was a different pattern.
Rally wheels are available in different bolt patterns also, might start by checking to see what exactly you're working with
And FWIW, people do weird stuff to old cars (new ones too, I guess), often with no apparent logical reason
Can't imagine why someone would drill the flange for a second set of studs unless it was a different pattern.
Rally wheels are available in different bolt patterns also, might start by checking to see what exactly you're working with
And FWIW, people do weird stuff to old cars (new ones too, I guess), often with no apparent logical reason
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