Torque value for M939A2 combat wheel studs?

[KN6KXR]

Just finished the refit of CTIS QRV's on a 1991 BMY M936A2 this morning. I had to move the wheel weights up front around. 210-240 ft-lbs is what is spec'd in the TM's as well as the retrofit instructions supplied with the kits (for the split rim bolts; lugs are 450-500). This for stock A2 setup. Not sure if that helps but another data point for you. Agrees with what's been posted.

 

[Floridianson]

Just wondering if you torque number could be off since you are running down distorted nuts as they require a lot more torque just to run down. Now if it was regular nuts it would be easy to use torque wrench. Last time I used my one inch M18 fuel set on #4 plenty of oil and no problems and never checked with torque wrench.

 

[HDN]

Just wondering if you torque number could be off since you are running down distorted nuts as they require a lot more torque just to run down. Now if it was regular nuts it would be easy to use torque wrench. Last time I used my one inch M18 fuel set on #4 plenty of oil and no problems and never checked with torque wrench.

I'd think the torque spec would account for the resistance of the distorted nuts. I'm not sure how much a difference oil makes because I've read the labels on the anti-seize bottles and directions for things like engine head bolts saying that the torque spec doesn't need to be adjusted to account for the anti-seize. I think a bead lock insert will also make a difference in the tightness of the rim because it acts like a big spring you're tightening the clamp ring against (assuming you don't cut the bead lock insert down from its original size).

Another thing that'll make a huge difference in the ease the clamp ring nuts come off and go on is the condition of the rim studs. Chase them with a die before backing the nuts off, then chase them again if there's more dirt and rust where the nuts were. My studs were a bit dirty and caked with CARC so it took awhile for me (and plenty of arm muscle with a 3/4" breaker bar and cheater pipe) to get the threads clean and back into shape.

That said, when I did my wheels, I borrowed a nice DeWalt 1/2" 20V impact wrench that, when turned up, cranked out at least 450 ft-lbs of torque when tightening the clamp ring. I took the advice of @glcaines and just tightened the nuts until they stopped turning. I did this following the tightening pattern in the TM. Afterward I used a 1:64 torque multiplier and a 1/4" drive torque wrench to check the torque on each of the nuts to make sure the impact wrench did its job.

 

[KN6KXR]

Pretty sure the torque is accounted for with locking style nuts. I know this mainly from wrenching on racebikes where the rear sprockets use the same style. It's a critical component on the racetrack we paid attention.

This being my first Green Machine I'm noticing a lot more NF (national fine) threads on fasteners than I've seen elsewhere (Ford, Chevy). Other SAE vehicles it seems rare to run into an NF fastener but they are all over on Uncle Sams' stuff. Like the split rim bolts. Fine threads provide for a higher torque rating, better control; more susceptible to thread damage and easy to overtorque. I'm hitting everything I touch with a wire brush and anti sieze. There's a little old anti sieze I'm finding here and there but by this point it's pretty solid from age. So everything gets cleaned as it gets torn into. Anti sieze or oil will help with getting the right torque. Pretty intuitive.

Not a fan of the impacts for tightening. Coming off sure but back on I only go by hand. Maybe I'll use my air impact on the lowest setting to seat lug nuts but the rest of the way is hand tools. Just seen too much damage with them. I have a few 1/2" drive Snap-On clickers I got on eBay and had recalibrated locally. They go to 300 ft-lbs. More than that you go specialty tools.

Finally the question in my head after rattling off my thoughts: for the torque multipliers how confident are you guys that it's getting correctly torqued? I have a 58:1 lug nut wrench but boy that thing seems flaky. There's a LOT of give in the mechanism. Compounding that is the fact that it takes only about 8 ft-lbs input for me to get in range so I'm using my in-lb wrench which is a 3/8" drive itty bitty thing. The wrench on the rear is at a bit of a funky angle against the hub. It's tight in there. The gears have a ton of slack. I find I have to keep going and only when I can get the wrench to click in the same spot repeatedly do I think I've got it. There are a lot of false positives on the way there showing me there's a lot of binding and drag in the mechanism. I'm considering buying a lower reduction unit like 15:1 because that would be 30 ft-lbs (to be at 450 lug nut torque) and I'm thinking with the higher input the drag of the reduction gear won't play as big a part and be less prone to error. It's nice to have that high reduction to spin them off but seems we give up a lot of accuracy and I really don't want to deal with a snapped lug nut bolt on a 5-ton. I'll avoid that drama if I can.

Thoughts?

 

[simp5782]

Pretty sure the torque is accounted for with locking style nuts. I know this mainly from wrenching on racebikes where the rear sprockets use the same style. It's a critical component on the racetrack we paid attention.

This being my first Green Machine I'm noticing a lot more NF (national fine) threads on fasteners than I've seen elsewhere (Ford, Chevy). Other SAE vehicles it seems rare to run into an NF fastener but they are all over on Uncle Sams' stuff. Like the split rim bolts. Fine threads provide for a higher torque rating, better control; more susceptible to thread damage and easy to overtorque. I'm hitting everything I touch with a wire brush and anti sieze. There's a little old anti sieze I'm finding here and there but by this point it's pretty solid from age. So everything gets cleaned as it gets torn into. Anti sieze or oil will help with getting the right torque. Pretty intuitive.

Not a fan of the impacts for tightening. Coming off sure but back on I only go by hand. Maybe I'll use my air impact on the lowest setting to seat lug nuts but the rest of the way is hand tools. Just seen too much damage with them. I have a few 1/2" drive Snap-On clickers I got on eBay and had recalibrated locally. They go to 300 ft-lbs. More than that you go specialty tools.

Finally the question in my head after rattling off my thoughts: for the torque multipliers how confident are you guys that it's getting correctly torqued? I have a 58:1 lug nut wrench but boy that thing seems flaky. There's a LOT of give in the mechanism. Compounding that is the fact that it takes only about 8 ft-lbs input for me to get in range so I'm using my in-lb wrench which is a 3/8" drive itty bitty thing. The wrench on the rear is at a bit of a funky angle against the hub. It's tight in there. The gears have a ton of slack. I find I have to keep going and only when I can get the wrench to click in the same spot repeatedly do I think I've got it. There are a lot of false positives on the way there showing me there's a lot of binding and drag in the mechanism. I'm considering buying a lower reduction unit like 15:1 because that would be 30 ft-lbs (to be at 450 lug nut torque) and I'm thinking with the higher input the drag of the reduction gear won't play as big a part and be less prone to error. It's nice to have that high reduction to spin them off but seems we give up a lot of accuracy and I really don't want to deal with a snapped lug nut bolt on a 5-ton. I'll avoid that drama if I can.

Thoughts?

5 tons use fine thread on everything. 915s use course thread. So I am assuming it is for the road vibrations

 

[HDN]

Finally the question in my head after rattling off my thoughts: for the torque multipliers how confident are you guys that it's getting correctly torqued? I have a 58:1 lug nut wrench but boy that thing seems flaky. There's a LOT of give in the mechanism. Compounding that is the fact that it takes only about 8 ft-lbs input for me to get in range so I'm using my in-lb wrench which is a 3/8" drive itty bitty thing. The wrench on the rear is at a bit of a funky angle against the hub. It's tight in there. The gears have a ton of slack. I find I have to keep going and only when I can get the wrench to click in the same spot repeatedly do I think I've got it. There are a lot of false positives on the way there showing me there's a lot of binding and drag in the mechanism. I'm considering buying a lower reduction unit like 15:1 because that would be 30 ft-lbs (to be at 450 lug nut torque) and I'm thinking with the higher input the drag of the reduction gear won't play as big a part and be less prone to error. It's nice to have that high reduction to spin them off but seems we give up a lot of accuracy and I really don't want to deal with a snapped lug nut bolt on a 5-ton. I'll avoid that drama if I can.

Thoughts?

I checked the slop in the torque multiplier I used against my big 3/4" drive torquemeter because I was wondering if I was off on my gear train slop estimate when tightening the clamp ring since a wheel I finished was losing air. I was originally assuming 15% slop, which is what to assume with the Snap-On torque multipliers. Using one of the rims I was restoring, I tightened one of the rim nuts a set amount - I think I used 150 ft-lbs as a reference - with the torque multiplier and a 1/4" drive torque wrench (I 3D-printed an adapter to interface the two tools). I then used my big torque meter and tried backing the nut off. It turns out that I was off by about 5% with my slop estimate, which I don't consider a huge difference. So the Chinese cast iron torque multiplier I was using has 20% slop - or torque loss - through its gear train.

As for the wheel that was losing air - it wasn't that the clamp ring wasn't tight enough, but one of the original CTIS brass elbows was cracked on a flat side and leaking

 

[US6x4]

I found a difference between the 5-ton and the HEMTT wheels (on my wheels at least) that may explain the difference in torque values: the 5-ton wheels are using deformed-thread lock nuts, where as the HEMTT wheels are using just plain flange nuts without any locking feature.

 

[Floridianson]

My 5 ton combat and Hemtt wheels came with new distorted nuts.

 

[HDN]

My 5 ton combat and Hemtt wheels came with new distorted nuts.

Were the nuts already installed? Otherwise I wouldn't consider them new

 

[Floridianson]

No I had / bought NOS wheels both Hemtt and combat from GL and they came with new distorted nuts in the bags with O rings. If I ever needed to service the wheel I would order new distorted nuts. Lucky no problems with any of my wheel so far and I think I have a full set of distorted nuts floating around here some where. Also myself I use oil to install all nuts as it washes off easer after the wheel / tire is put together and installed. Then I repaint all the wheel studs / hub studs with a light coat of paint. I got lucky when Pete P&C trans had his tractor and flat bed trailer and GL Ohio was dumping Hemtt wheels we got like 60 NOS of them cheap and split them. I have checked my one inch M18 fuel at different settings with a torque wrench and trust it for doing the two piece wheels. I use my torque wrench when doing the tires / wheel install on the truck but they are not distorted nuts.

 

[simp5782]

Or just get one of these.

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