The Stovebolt Site Forums The Shop Area Engine Shop 8 bolt 17 inch front rim pilot

I just got a 1953 one ton 3800 and I see that the front rims do not pilot on the fron hubs -- they just are centered by the 8 bolts. Is this supposed to be like this?

The rear wheels which uses the same rims do pilot on the rear hub.

looks right to me - all the series are that way in front - it's not that you've got the wrong rims!

Bill

If you're saying that the hole in the rim center is bigger than the hub, that is wrong. Rims need to fit snugly around the hub, both front and back.

The lugs are then carrying all the weight of the truck, and they're not designed for that, the lugs only load in tension and compression, but are not designed to carry shear loads (up and down). You can get away with this for a while, but eventually the studs will break, especially if you haul a heavy load.

Hey im looking for some help here. Now I got two responses and one says I'm ok and one says I'm headed for trouble. I need at least one more vote on this subject.

On the front of this truck which I believe to be all original, the front brake drum does pilot on the hub but this pilot does not extend out though the drum to pilot the rim. Is this correct?

Hah. Fred will go out and look at his trucks pretty soon and come back with a correction.

The stock front end on my 3/4 ton is the same as yours, piloting on the bolts. The late '70s IFS I put in is the same--the front hub sticks through the rim a bit, but there is maybe a 1/16" gap all the way around. Much less weight on the front than on the rear under heavy load conditions.

Now for the surprising part, at least to me. The rear rims don't actually register on the hub, either. They're close but they don't touch. I just looked at the rear end I took out of my truck, which had stock rims, and at the rear end from a 3/4 ton parts truck which also had stock rims on it when I got it, and it's obvious that there was no contact between the inside of the hole and the outside of the hub. The rear end that came off my truck has a heavy coat of paint on it, and only a few high spots were knocked off. Just guessing, I'd say the hole in the stock rim is maybe .020"-.030" larger than the "pilot" on the hub.

I can recall having an awful time getting brake drums off the hubs on 1/2 ton trucks. They do register on the hub surface, and after they've been on a while they do *not* want to come off. But I don't recall ever having to break a wheel loose the same way on the 3/4 ton trucks I've had. The wheels are always loose as soon as the last lugnut is loosened.

I'm amazed. I always took it for granted that the rear wheels registered on the hubs on trucks with full-floating rears.

Joe

The rims should be close, but not necessarily pilot on the hub. Look at a late-model F*rd wheel sometime, and you'll see the rims do ride on the hub, with flat lug nut surfaces that only hold the wheel on. The Chevy and early F*rd rims use tapered lug nuts to center the wheel on the studs. The new design is a better idea, but it's only come into use recently.
Jerry

Yes, Joe, I did go check. Front rim hole to hub has a gap of .008. Rear rim to hub is .012 at the bottom, .016 at the top. The studs and acorn nut joint will flex enough to close that gap when loaded.

Why would GM have wasted the money to bend the flanges on the rims and machine the hubs on the axles and front drums if they weren't supposed to carry loads? Also, the design of the nut to rim is so that shear forces cause it to slip when a heavy load is applied.

My 1951 1 Ton GMC does not pilot on the front hubs, just on the rear, in the original configuration.