I want to buy these
http://store.summitracing.com/part.a...D-080009FC5B5F


They say they work with 5/8inch studs...I think my Grand Prix has 7/16inch...can I still use them? It also says I need 45 degree nuts...which summit also sells, but what thread size is the studs on my 78 Grand Prix?? How do I find out?
chris


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Nice car: 1988 Formula 355, mildly ported/polished Vortec heads, RPM intake, Comp Cams Extreme 268 cam, 650 Holley double pumper, 5-speed/3.73 Richmond gears, and N02 on the way
Old 1/4mile: 13.5@105mph

Evil Car: 78 Pontiac Grand Prix, 500inch caddy motor, edlebrock intake,HP Holley 750 DP race prepped carb, B@M TH350 tranny, 16inch Iroc-Z rims, blacked out chrome, soon to run 10's...

There's no replacement for displacement!

 

BTW do you guys think i should get these:




or these:

 

i dunno man but are you gonna sell the iroc rims?

 

Iroc rims are sold. They SUCKED on my Grand Prix, the backspacing was way wrong, front tires rubbed on any turn and the rear's wouldn't let me run any tire larger than 225 without rubbing. I got the rims for free and sold them for a pretty penny so it worked out great

 

you want to get the wheels with the right hole size. Also with racing wheels you need different lug nuts. OEM wheels use a 60 degree taper and racing wheels use a 45 degree. I suggest that you call one of the wheel manufacturers (Bassett, Bart, Diamond, Aero, etc) they make wheels to order for basically the same price. They offer light weight(about $20 extra per wheel) and economy. I bought wheels from Diamond for my VW Scirocco stock car for about $50 each (economy) with the backspacing, bolt pattern and center hole sized to my specifications. You can pick up an issue of "Circle Track" magazine; they all advertize in there. Email me if you have any other questions. merf23@yahoo.com

 

Chris, I used to have an '82 Grand Prix. From what I understand, the trick is that you need four FRONT IROC wheels all around, and then they'll fit more or less okay.

If you want my opinion on those wheels, I think they're both fairly ugly. In the early '80s, some Grand Prixs had nice looking finned aluminum wheels, but I think they were 14s. How about some Grand National or Monte SS wheels?

I know of an easy way to find out your lug nut thread size. Go to Pep Boys, undo one nut from your car, and take it inside. Go to the section where they sell the chrome lug nuts. There's a display with a whole bunch of studs...you try them all until you find the one that your nut fits on. The chart will tell you the diameter and thread size.