Here's a Question For Ya! (6-Lug Studs)

[nsuengineer06]

What are the differences between the 6-lug studs on a factory 67-68, and the 6-lug pattern on the 99-xx half ton trucks? Is the pattern the same? I know the studs are smaller on the earlier trucks.. Does anyone know the sizes (new & old)?

[Blazer1970]

They are all 6 on 5 1/2". The new trucks have a smaller center hole diameter, and the offset for the new wheels is completely different, but the lug pattern is the same.

[mclairmo]

I realize this is not your question but just want to let you know (just incase) that later model 6 lug wheels with the small center bore will not fit the older trucks with the larger bore. I know because I tried it. The later model wheels would need to be machined to enlarge the center bore. Also, the later wheels will tuck in too much and look bad.

[nsuengineer06]

Let me lay it out for ya. Currently my truck is in pieces all over the place, so I'm not worried too much about wheels fitting at the moment. But since you brought it up, it concerns me now.

I have a set of wheels off of a 99 silverado I used to have. I was planning on using them during the build of my truck since I am keeping it 6-lug. They will not be the final wheel used. I test fit one of them on the front when I first got the truck and it fit fine. (The back may be another story.) I have yet to try them on my new rotors from CPP either. So, since you brought it up, I'm kinda worried that I won't have wheels to roll it around and work on it! If the center hole is the only problem, I will probably grind it out to fit and make it work..

Anyway, my original question was more directed at the lug pattern (which I now know is the same on both.. 6 on 5 1/2 thanks Blazer1970), and the size and thread pitch of the studs. I haven't measured the ones that came in my new rotors yet, but I'm hoping they are bigger than original. Also, I want to drill out and replace the studs in the rear axles with bigger ones. Just don't know what sizes there are out there.

I will do some test fitting and measuring tonight or tomorrow after work and let ya'll know what I find. Thanks.

[melvin]

The new silverado's are a 14mm stud (standard equivalent would be 9/16"). The 67-70 6-lug was 7/16", while the 71-72 5-lug was 1/2".

Not sure on bigger studs, back would be easy (just some drilling, plenty of material on the flange). The front disks on my GMC Pauls 6-lug conversion kit are the same 7/16" stud, and don't look like they have enough room to go any bigger, but I could be wrong. Somebody else may chime in on that.