Late Model GMC Wheels

[aphaynes]

I was looking at some late model GMC Sierra wheels the other day...planning down the road again...and was curious how they would fit my 65 GMC 1000. Turns out they have the 6x5.5 bolt pattern, but the center bore is only about 3 inches rather than the 3.5 inches the hub of my truck measures. So down the road, if I wanted to go with newer GMC wheels, what besides the hub assembly would have to change and is it a relatively easy change? Thanks!

[Funky61]

Those wheels have about 6 inches BS, so some folks use wheel spacers. Also you would need the lug nuts that are threaded on the outside, to use the center caps.
Here is a pic of my suburban when I used to run those wheels. I used 2" spacers front and back.

[aphaynes]

Thanks Funky. Nice looking Burb.
Interesting, so with those spacers the lugs are taking the load rather than the hub (lug centric rather than hub centric)?It seems newer wheels are designed to be hub centric, but did not know if that mattered when putting them on an old ride. There is that much extra room up front with steering etc.?

[Funky61]

Yes, the lugs are carrying the load. I took a look at my stock steel wheels on there now and the hub does not seem to be supporting them either. I checked fronts and backs and there is a gap where you'd think the hub would support; but it does not seem to be resting on anything. Maybe support is on the inside that I'm not able to see.

I first bought special lug nuts to bolt these wheels on. They were Standard thread but had the outside threaded as well, so I could mount the center caps. As you mentioned the center hub was too small, so I had two wheels opened up for the front. The rears were OK I believe, but again the offset was not right.

I went with spacers on the rear first and just mounted the fronts with my new special ordered lug nuts. With stock drums the front wheels rubbed on the inside; either the control arm or caster arm not sure. Chewed up the stick-on balancing weights. Using the spacer eliminated the rubbing issue.
I have/had driven it for over 450 miles around town using those spacers, without issue, and she drove very smoothly with those radials (235x70x16) all around.

*The challenge becomes when you want to change a rear tire. When my Burb was lower, it required two jacks and/or supports. I'd first lift to get it off the ground; position jack stands, then move jack to the rear bumper area and lift to take body weight up off the suspension just enough to work out the rear tire.
This would not have been an issue with the stock suspension as my suburban sat pretty high, and only applies to the rear. I had a 4 or 5" drop in the rear.

Currently I run the stock steel skinnies with 1 1/2" block drop and stock rear coil springs and front torsion bars turned down slightly.

[aphaynes]

Lot of good info there Funky! Thanks for sharing. If I end up doing something like that I hopefully can skip some of the heartburn you experienced.

I had seen those nuts with external threads for the caps when I was trying to determine the differences between late model wheels and 1965 wheels in terms of bolt pattern etc. I found some that had the late model 14x1.25 thread and then some "special" ones that had the 7/16 thread. With this being my first car/truck that is older than I am, I guess I am used to seeing the hub centric wheels. In my mind I could just see the lug bolts shearing off in time if they were supporting all the weight...but I know little about these old designs. Learning everyday though.