The Stovebolt Site Forums The Shop Area General Truck Talk lug nut question--need advice

I am going crazy trying to find some wheels to fit my 1966 GMC 8 lug 3/4 ton. I have measured the backspacing with the tires off of the original split rim and the 2001 GMC 2500HD wheel to make it easier. The backspacing on the original was exactly 5 1/8 inches and the 2001 wheel measured at 4 7/8 inches backspacing. The center holes are same and the bolt pattern is the same. However, the lug nut holes are bigger (14mm) on my newer wheel than my old split rim (1/2 inch). Can I use the newer wheel SAFELY or is there going to be too much slop because the lug is smaller than it should be compared to the lug nut hole on the wheel? Can't I just use some tapered acorn lug nuts or should/can I replace the wheel studs with 9/16 or 14 mm size? Does anyone know if these are screw in or pressed in wheel studs? I thought I had the problem solved until the guy at the tire shop today said there would be too much slop and I would have to keep a close eye on things and keep checking the torque on the lug nuts. That made me nervous! Please tell me if this true or not, I sure don't know.

As long as the seat of the nut is large enough to make full contact with the seat in the wheel, it should be fine. You'll want a 7/8" hex nut to get one large enough. Another solution (as 7/8" hex 1/2" thread nuts are kind of hard to find) would be to upgrade to the 9/16" studs and use the larger nuts. You should be able to swap in the studs for a 1 ton, which used the larger studs. If you can find 14mm studs with the correct knurl and shank, that could be another option, and it would allow you to use the late model lug nuts with the outside threads that will let you use the late model centercaps. Let me check my catalogs, I might be able to get you some part #s.
BTW, they are pressed.

You can take your hubs to a machine shop. And have them machine out the stud holes and put in the 7/8 lugs.

You can do the 9/16s on the front without modifying, use Napa #641-3147. The rear will have to be modified, basically, the stud holes will have to sized up to take a stud with a .625" knurl. Shouldn't be too hard to do, but must be precise to make sure the stud fits tight.

Thank you for your help. LONGBOX55, I hope you can find a brand and a part number for me. Were you able to find any 7/8 inch lug nuts with a 1/2 thread? The center caps won't fit on the back because the axle sticks out a little too far, I would have to punch out the center. Did your catalog state that the rear will have to be modified or do you know that from experience? It is strange that the front will work without modifying the hole, but the rear will. Are the lug nuts on both trucks a 60 degree taper?
Oldtruck 1946, I was a little confused on the 7/8 inch lugs. Don't I want 9/16 or 14mm lugs?

Yes, the new wheels will be the 60 degree taper. On the stud fitment, I cross referenced the knurl sizes from the original equipment 1/2' studs to the knurl size for a 9/16. Unfortunatly, the rear uses a much smaller knurl size than the front (.625" on the front, .558 rear w/Dana axle, .560 w/ Eaton axle). I do beleive there's enough meat in the rear hubs to bore them for a larger knurl, perhaps drilling them with a 39/64 bit (.609"), but you might want to consult a machine shop first.
I have actually seen 1/2" thread lug nuts with a 7/8" hex, I actually have a set on mine (I converted my '55 1/2 ton to 1/2" studs), but I got them from a swap meet vendor, and am not sure where he got them from.

Thanks LONGBOX55! I did find some 7/8 lug nuts with a half inch hole from Gorilla brand company. Does the 7/8 lug just have a wider cup, is that why they work better than stock? I have also found some specialty lug nuts (with external threads)with a half inch hole, but with 13/16 hex head to fit from a few different companies. Shouldn't these work also as long as they are the right taper and seat properly?? I have heard a couple of different opinions and don't which is correct. I have heard that the center hole of the wheel supports the weight of the vehicle and the lug nuts just hold the wheel on and then just the opposite, that lug nuts support the weight of the vehicle and then the center hole just keeps it aligned or doesn't do much at all(I am not sure on this very last part of the sentence). I take it that your set up is working great? Are you using modern (which era)wheels to on your '55 truck?

Yes, wheels can get confusing, as there are many different types. It really comes down to how the wheel is piloted to the hub. Some wheels are stud piloted, meaning that the studs are what aligns the wheel and the center hole doesn't do much. Usually, they have a very loose fit to the center hub. Then there's the hub centric wheels. Those will have a tight fit to the hub, as it is what centers it. Most larger trucks as well as many late model cars are that style. As to what supports the weight, it's a combination of the components, the studs carry the weight by way of the nuts. The nuts will support the weight through the taper seat in the case of your wheels. Once torqued correctlly, they should support just fine. As to the 7/8 nuts, it's the larger seat that we're after, as the wheels you're using were made to run with the larger nut. The hex size really doesn't matter too much, as long as the seat is large enough.
On mine, I'm runing the '73-'91 Blazer Rallye, which was originally intended for use with 7/16" studs. The 1/2" studs clear fine, and the nuts worked well. What happened inmy case was that I came across the late model caps, and really liked them. The vendor also had the nuts. I did have to modify my wheels a bit by enlarging the seats to accomodate the larger seat diameter. I accomplished that by using a 3 flute 60 degree counter sink bit (a really big one! ) and working slow to get the size. I wouldn't necessarily reccomend anyone doing that, though. In my case, I have experience doing that repairing damamged wheels at work. If you would like to see what I've got, click on my signature, it will take you to my pix.

You really do have a beautiful truck! So I can choose between the 7/8 lug nuts or the specialty lug nuts with a half inch hole and you think I will be fine with no problems? I sure hope so! That guy at the tire shop freaked me out. I can't drive my truck now because I live in the snow belt and had to put it away so I didn't get any salt on it. I am undecided to go with painted steel wheels with no OE center caps whatsoever or go with the chrome and have OE center caps on the front and figure something out for the back to cover the axle with even though they wouldn't match the front then. I hate to monkey with the truck too much and possibly ruin something.

I don't see where there would be a problem. Actually, now that I think about it, a freind of mine used to have a '94 Impala SS. We were going to get some police car wheels to put on it for winter so he wouldn't rin the alloys. When we priced them, they were way too hing, but then we saw a second price (about 1/10th of the police price) and asked what that was all about. The counter guy told us that was the truck number, as they are the sam wheels. My buddy just happened to have a set of truck wheels, so that's what we run. Now to the gist, the truck wheels were meant t run with a 7/8" nut and a 14mm stud, the Impala runs 12mm stud. We just swapped out to a 13/16 nut and ran 'em. Hard. Like 100+ hard. Never had the first wobble or loose nut.
I think you'll be fine.

Thanks for your help!! After thinking about it myself I would hope that they wouldn't make the specialty lug nuts with a half inch hole knowing what they were going to be used for if they weren't going to be safe. I have to decide which way to go now.