Leaking 2pc rims

[charlesmann]

I have 2 L/FMTV rims that is leaking, even with a new oring and wire brushing and wheeling the halves and fresh coats of paint. I ordered some tar caulk strips, which we use when installing windows in aircraft.
it took 6pc of caulk strips to go around oring and laid it between the studs and the edge of the oring and encircled the hole for the valve stem, which is where the two halves were not seating properly, causing a slight leak.

im sure other uses can be found, esp in a road side emergency. Just thought id share it with y’all.

 

[INFChief]

I have 2 L/FMTV rims that is leaking, even with a new oring and wire brushing and wheeling the halves and fresh coats of paint. I ordered some tar caulk strips, which we use when installing windows in aircraft.
it took 6pc of caulk strips to go around oring and laid it between the studs and the edge of the oring and encircled the hole for the valve stem, which is where the two halves were not seating properly, causing a slight leak.
im sure other uses can be found, esp in a road side emergency. Just thought id share it with y’all.

I just changed over 7 tires & rims. In addition to your neat way of checking for O-ring sealing I would add a couple of suggestions for those who have yet to experience the joy of FMTV tire changing.

Not all soldiers use a bead breaker to drop the tire bead off the rim. Whether they use a pickaxe or a tankers bar to drop the bead, you might find some marring or raised metal slices around the bead seat on the rim. I filed them down or used a pneumatic sanding disc to smooth them out.

Before mounting the new tire inspect the rims and clean up these blemishes. I’ve also found that the rim half where the O-ring sits might have a bent / disfigured O-ring shield. The split rim presses this O-ring shield out as the split ring is tightened down on to the O-ring. If the shield isn’t fairly straight the split ring won’t compress on to the O-ring correctly.

Also be sure to check the flat surface contact area where the two halves of the rim meet when assembled. Build up of crud will prevent the split rim from fully seating and compressing the O-ring. One of my rims had a low spot in the horizontal mating area near where the valve stem comes through. When spraying soapy water on the rim while it was on the vehicle to find the leak I saw bubbles coming out between the rim halves at the valve stem pass-through. After disassembling & few adjustments with a sledge on both halves did enough to remove the low spot and allow the O-ring to seal.

I got away with reusing 4 out of the 7 O-rings. They all looked good but upon closer inspection of the O-rings I had to replace I saw they had a flattened side due to being compressed and compressed for a long time.

I replaced all of the valve stems. Mine came with valve cores so be sure to check and remove them if you’ve kept the original CTIS set up.

I used a slick tire lube to get the bead locks in and also in the O-ring to prevent it from being repositioned as I tightened the split ring down. I didn’t have a tire spreader which would have made inserting the bead much easier.

I did 4 out of 7 tires / wheels on my own but if you can snag a helper - do so!

 

[simp5782]

3m super 77 spray works well on the silicone O rings to prevent leaking.

 

[charlesmann]

I actually have a rim that the o-ring shield is not round anymore. Some pvt or depot worker must have jammed something between the bead lock ring and the rim half, for whatever reason, bending the crap out of it.

I came across that issue on my 7th tire of the day, replacing the fmtv oem valve stem with the combat rim stems. So i guess you could say, it was my 14th tire to break down that day.

With it being very much dark and using only a headlight to work by, i didnt notice the bent shield when i put things together. The nxt morning i went to air it up and it was leaking, so i forked it to the side, which was a yr ago.
I had a tire blow out the sidewall, luckily, just sitting in the yard and decided to break that last tire down to check everything, which is when i noticed the shield bent flat in places, and the rubber strips on the bead lock were over that shield also. After farting around with breaking it down 3x that day, i went to napa, order that caulk strip, and picked it up the nxt day and proceeded to seal the wheel up. I put 70 psi in it and left it for 2wks while at work and checked last wk when i got hm and was holding at, best i could tell, 69, almost 70 psi.

The hell with fighting orings, and oring shields again, and breaking tires down multiple times. ill just use the caulk after inspecting/reusing and or replacing the oring.

 

[G744]

I converted all mine to tubes, haven't had to put air in any of them for several years.

One dissassembly, one assembly, done.

DG