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OT Old GM 15 truck rim

R

rossow (mn)

Member
I am rebuilding a small (4x7) trailer. It has an old beam-type axle from a GM truck, probably a 3/4-ton. The rims are tube-type 8-hole 15x5.5. The tires are old tubeless radials but have tubes and are rotted. The trailer will rarely see off-property use but I want to retain the on-road, short-trip option. I want to use modern 15" radials -- with tubes to accommodate the old rims, of course. (Caveat and apology: I'm only familiar with one-piece automotive-type rims.)

I have a couple of questions:

(1) The rim has an outer ring that is free to rotate on the rim when tire is off; the tire bead seats against that ring. Does that ring affect method for mounting/dismounting? I ask because I usually dismount toward the shallower offset but had a rough time getting the old tire off.

(2) Does anyone know of a more modern rim that will fit the old truck hubs? Tubeless rims would be great.

I appreciate your advice.
 

I believe that 8 hole rims are pretty much standard as far as the bolt spacing goes. The difference will be in the center hole diameter.
 
I think Rusty is correct. Six things create a match with rims: The number of bolt holes (obvious)
The bolt circle diameter (not measurement from hole to hole. The 8 bolt is 6.5 inch bolt circle on Ford GM and Dodge Full size Trucks)
Then center hole size (some are actually intended to be a tight fit to a ridge on the hub to assure centering and others do not)
Next is tire rim size, 16 inch might be easier to find, and will work if clearance is available to fenders
Next is offset, (distance from the back side of the mount surface to the concrete if the rim is laid flat sideways with no tire on it, and the outside of the rim and the rim is facing up)
The last is rim width from inside of bead flange to inside of bead flange (should be about 70 to 80% of tire width. See attached. Jim
Wheels data
 
A lot of guys on this site seem to hate snap ring rims. I have no problem with them. They aren't any more dangerous than any other rim if you pay attention to what you're doing. You have to remove the ring to mount and dismount a tire. In my opinion they are easier to work with for heavier tires. If it was mine i'd use the rims you have unless they are rusted out or something is wrong with them.
 
You said, "You have to remove the ring to mount and dismount a tire."

I'm admittedly ignorant here -- how does that ring come off? It's loose enough to rotate around the rim when tire is off, but.... Does it pry off? I'm confused. Can you offer further instructions?
 
If you are gonna use those rims, please take them to a tire shop with experienced people. Even then people have been killed with them. If you use those rims you will need radial tubes and radial flaps. My good friend was killed by 1 blowing apart. It had been repaired several hours earlier and was leaning against the wall, blew apart as he walked buy. You can buy White spoked trailer rims and mount your tires tubeless. I was in the tire business 22 years and seen the results of the explosions. Its really Scarry when you have 20" tires and rims that blow up when the truck is hauling propane.
 
If looking for replacement wheels since '99 pherd has used metric bolt circle wheels 190 mm vs 6 1/2".
 
There should be a pry notch in the rim. I have a tire iron just for that but a big screwdriver will work. Stick it in the notch and pry the ring out then work your way around. Once the ring is off the tire can be pulled right off and set back on. Take a small hammer and tap the ring gently back into place. Make sure it seats completely. If it doesn't then the ring can blow off. I've seen regular rims blow off the bead as well so no tire is safe when people don't pay attention.
 
(quoted from post at 23:40:15 09/09/18) There should be a pry notch in the rim. I have a tire iron just for that but a big screwdriver will work. Stick it in the notch and pry the ring out then work your way around. Once the ring is off the tire can be pulled right off and set back on. Take a small hammer and tap the ring gently back into place. Make sure it seats completely. If it doesn't then the ring can blow off. I've seen regular rims blow off the bead as well so no tire is safe when people don't pay attention.
Click to expand...

Doesn't that ring have to be rotated to a certain place on the rim before that notch is exposed?
 
"8 on 6-and-a-half" is a pretty common bolt pattern. All you have to do is measure from the center to center between two studs directly across from each other.

You probably won't be able to find a tire shop to work on those locking ring rims because they think they are "split" rims. Unless you have an old school tire shop in the area.

If you're going to work on them yourself, study up. When you don't know what to pay attention to, these can be dangerous.
 
"There should be a pry notch in the rim."

Yes, I found that notch. I'll pry the ring off and see what I find. Thanks for the advice.
 
I did remember today that some of the old snap rings are a solid ring. I've seen them on one truck but never had the opportunity to work on those. The way I understand it they are harder to wiggle that ring off. The ones I have worked on have a split in the ring that you line up with the pry notch, then work it off going around. Just take your time and if you feel like you are fighting them just stop. That means you're probably doing something wrong so try it differently. Like I said before when putting the ring back on make absolute sure the ring is seated in all the way and isn't sprung. As others have said you can find rims pretty easily so if you don't feel comfortable with these rims just get others.
 
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