PaulDaisy

I am trying to figure out what wheels I have on the truck to help decide whether to buy new wheels for new tires or not. Currently, I have 305-70-16 mounted on the wheels and they look good, no bulging or anything. The rims, however, don't look 6.5" wide at all. Yet they do look stock, same design.
On dodgeram.org I found that the wheels are hub centric and have offset (I assume it is a typo and they mean backspacing) of 4.75". This means that they are 9.5" from edge to edge. Taking 6.5" bead width (stock are supposedly 16x6.5), one is left with 3" of... what? The lip is usually just 0.5-0.75" per side, seems like.
So, either they are not hub-centric, or the bsp of 4.75 is not correct.
Am I mistaken somewhere?

dozer12216

History - hubcentric means the wheel centers on the hub and the lugs hold it on as opposed to holding and centering
Backspacing / offset - means the flange of wheel is 4.75 inches to rear lip of rim. or 1.75 inches from rear of flange to outside lip of rim.
This seems correct for spacing of OEM wheel. JMHO

PaulDaisy

Ok, I measured a stock wheel.
Front spacing is 2 7/8 or 3", couldn't quite get that 100% accurately. Back spacing is 4 3/4". This means offset is 0.875", or +22 mm (plus minus 1 mm). Rim bead mounting width is 6.5". Center hole is 4.75" (at least that is what the rear hub diameter is).
This may be helpful for people choosing offset to help keep the load properly distributed on the bearings. With a 7.5" wheel, the back spacing should be about 5.25" and it appears to me that a 16" wheel may not clear the rear drums.

sheriffav8r

I thought all our rims were lug-centric. Only a small portion of vehicles are hub-centric, which means that the hub hole has to be perfectly sized and centered or the tire won't balance. I think the key is to look at your lug nuts. If they are conical and the lug holes are larger than the bolts, you are lug-centric. When you tighten the lug-nuts you center the wheel between all 8 lug bolts. The 4.75" backspacing is from the inside of the rim (facing inboard) to the back of the rim hub flange. If you put wider tires on your truck you want less backspacing so the rim is pushed out farther from the hub. It's either that or the other way around or a combination of both. Or neither. I'm sure of it....

STate

I too understood that our wheels were Lug Centric. For Example: I thought the purpose for the H2 wheel modification was to convert it from Hub centric, to Lug centric by removing or machining out the center portion that sat on the GM H2 hubs. Correct me if Im wrong.

Paul Daisy, Thank you for all the backspace and offset info regarding the steel 2nd gen wheels. Ive been looking for that info for a while.

SIXSLUG

Old mercedes have a perfectly milled hub hole and also use the conical lugs, but they are bolts, not nuts. A very tight fit regarding the hub, any corrosion and you had to knock it loose with a hammer.

My stock wheels, the aluminum type, are supposed to be 16x8 IIRC.

The stock steelies are narrower, I think 16x6 and the dualies front wheels use a spacer, so the offsets are different re: them. This is so all 6 can be rotated if desired.

Kurt

PaulDaisy

The "hub-centric" statement was something I came across on one of the web sites, can't seem to find it again. In my ignorance I took it to mean the wheel has zero offset, which made no sense with 4.75" back space. I'm sure people are right that the wheels center on the lugs, all the wheels I ever dealt with, whether with lug nuts or bolts, had conical mating surfaces on them and mounting holes were a bit oversize and conical as well. Which means, they all were lug-centric.
I spent probably 4 hours on the web looking for the dimensions of a stock wheel, and left more confused then before I started. It took me all of 20 minutes to measure them on two different rims. I learned one thing while doing the measurements: sometimes just doing it is simpler than trying to find all the information out there.