Are stock 16"x5" rims different on '71 & up disc brake trucks?

[Clanky]

Hello,
In my searching for stock 16"x5" 6-hole wheels for my '71 GMC K1500 Custom, I read this thing about the wheels changing so they'd have room for the 'new' front disc brakes on '71 +. Are they different? Should I be looking for '71 and up wheels?
Thanks!

[GASoline71]

They will be 5 lug instead of 6 lug. So you have a '70 and earlier, non-disc 6 lug, on a '71?

Gary

[SS Tim]

K10/1500 6 lug 16s were all tube type, I thought. There is a large section in the parts manual on wheels that should be reviewed. As I remember it specified which wheels were approved tube and tubless applications. Here is a '71 K10 tire option clip for you showing the RPOs R61, R64, R65 and R69 you might want to watch for.

[wilbilt]

The wheel centers have a different contour to clear the calipers on disc brake trucks. Drum brake wheels had a "flatter" center, if that makes any sense.

A typical 71-87 6 hole GM wheel looks like this (although this one is 15")



The older wheels were not as deep in the center section where the lug holes are and may have hubcap clips or the rivet holes for them.

[Clanky]

Thanks you guys for your responses, I know way more now what to look for. Wilbilt, on the wheel photo, I see 4 nubs for the hub cap, but I swear I've seen wheels with only 3, do you know if there were both or is there is some significance there year or plant wise?

[wilbilt]

Originally Posted by Clanky

Thanks you guys for your responses, I know way more now what to look for. Wilbilt, on the wheel photo, I see 4 nubs for the hub cap, but I swear I've seen wheels with only 3, do you know if there were both or is there is some significance there year or plant wise?

I don't recall ever seeing any with 3 nubs, although I suppose they probably exist. Wheels were sourced from various vendors (Kelsey-Hayes, Firestone, etc.) as well as GM production. As SS Tim posted, there will be a code stamped on the wheel designating the size and rim contour that you may be able to match up in factory data. The one in the photo is a 15 x 6 JJ, which is typical for a welded wheel designed for tubeless use.

Many tube-type wheels have centers that are riveted in place (not airtight) and lack the circumferential ridge on each side near the bead seat that helps maintain bead pressure to hold air. It also seems like tubeless wheel are thicker (heavier), or maybe I am just getting older.