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Did the military use run flats in any M939A2?

dilligaf13

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Yeah, I knew the gun trucks ran run flats but they weren't exactly a standard truck. I've never dealt with any of the Frankenstein ROPS trucks so I was unaware they had them but it makes sense. Anyone every retro-fit their trucks with them or is the PITA mounting and balancing them too big of a turn off?
 

simp5782

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Yeah, I knew the gun trucks ran run flats but they weren't exactly a standard truck. I've never dealt with any of the Frankenstein ROPS trucks so I was unaware they had them but it makes sense. Anyone every retro-fit their trucks with them or is the PITA mounting and balancing them too big of a turn off?
Use the 3 piece Hutchinson runflats that bolt together. Much easier to install. Rubber ones are too much work unless you have heavy equipment or the ratchet tool. Feltz tire has the 3 piece inserts.

Rubber Runflats can cause blowouts from overheating if you don't use the proper liquid lubricant to put a barrier between them and the tire.
 

dilligaf13

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I was able to pick some 3 piece run flats from Feltz. Seems like there’s some sort of lube on some of them. Is this lubricant necessary for anything (heat dissipation like the rubber 1 piece run flats) or is it just aid in ease of installation?
 

simp5782

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I was able to pick some 3 piece run flats from Feltz. Seems like there’s some sort of lube on some of them. Is this lubricant necessary for anything (heat dissipation like the rubber 1 piece run flats) or is it just aid in ease of installation?
It reduces heat without it it'll blow in the hot summer
 

dilligaf13

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Looks like I need 5 tubes of lubricant per tire. I’m not having much luck finding any online.

Any idea who might have some or is there a more cost effective alternative, because the recommended lube is listed at $35-$50 a tube
 

gringeltaube

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It should be noted that the runflat inserts (all versions) are always much smaller in diameter than the inner tire. So, for the 395s and 14.00s it takes about 5" for the tire to actually touch the RF, so that would only occur after much deflation, e.g. during emergency use; or a mayor air leak, after a tire puncture.
In normal use there is no contact between tire and RF, ever.

The only reason for that "grease" layer to be there is to reduce heat due to friction, once the tire inside started "rubbing" on the RF.
(to Wes: I know you are talking from your own experience, but I've yet to find any technical literature confirming that it also keeps tire temps lower, in normal conditions...)

So, in case of a blow-out or sudden loss of air AND with the proper lubricant in place, a safe slowdown run from 60mph to stop - and/or driving in limp-home mode (for a few miles) is still possible.
Without any lube the tire would probably catch on fire, pretty soon.
 

dilligaf13

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What I saw was without the lubrication, in a run flat (emergency situation) the tires will last 1 mile. With lubrication, in the same situation the tires will last 30 miles. I don’t remember what size tires/vehicles this applied to but I’ll try to find the literature again and post it on here.

I’m looking to start by putting the runflats in the 2 steering tires I’m already replacing as an added layer of safety in the event of a blow out, not to drive on, so I’m not worried about driving for 30 miles on a flat tire. I just want to make sure that failing to add lube won’t cause heat during normal operation.

If I have to drive on a flat tire I’m replacing it regardless of run flats or how far I drive on it. I’ve seen too many blowouts from broken sidewall belts and the results ain’t pretty.
 
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Mullaney

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What I saw was without the lubrication, in a run flat (emergency situation) the tires will last 1 mile. With lubrication, in the same situation the tires will last 30 miles. I don’t remember what size tires/vehicles this applied to but I’ll try to find the literature again and post it on here.

I’m looking to start by putting the runflats in the 2 steering tires I’m already replacing as an added layer of safety in the event of a blow out, not to drive on, so I’m not worried about driving for 30 miles on a flat tire. I just want to make sure that failing to add lube won’t cause heat during normal operation.

If I have to drive on a flat tire I’m replacing it regardless of run flats or how far I drive on it. I’ve seen too many blowouts from broken sidewall belts and the results ain’t pretty.
.
So, I am not the person with all the answers - but the little bit of reading I have done says - the lube is to resolve potential motion inside the tire (friction) by the runflat.
 

gringeltaube

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charlesmann

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Im asking bc i dont know. Would a tire mounting lube paste work?
 

simp5782

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It should be noted that the runflat inserts (all versions) are always much smaller in diameter than the inner tire. So, for the 395s and 14.00s it takes about 5" for the tire to actually touch the RF, so that would only occur after much deflation, e.g. during emergency use; or a mayor air leak, after a tire puncture.
In normal use there is no contact between tire and RF, ever.

The only reason for that "grease" layer to be there is to reduce heat due to friction, once the tire inside started "rubbing" on the RF.
(to Wes: I know you are talking from your own experience, but I've yet to find any technical literature confirming that it also keeps tire temps lower, in normal conditions...)

So, in case of a blow-out or sudden loss of air AND with the proper lubricant in place, a safe slowdown run from 60mph to stop - and/or driving in limp-home mode (for a few miles) is still possible.
Without any lube the tire would probably catch on fire, pretty soon.
When using sand or any other low pressure settings on the ctis, the tire and runflat can and do connect especially with flexing sidewalls in offroad environments
 

gringeltaube

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When using sand or any other low pressure settings on the ctis, the tire and runflat can and do connect especially with flexing sidewalls in offroad environments
Sure, but that would be more like momentary contacts only, at low speed (<15mph). And it is clear that with extreme low TP the increased flexing work alone will create a lot of heat in the tires. Not exactly what I was referring to as "normal use".

What I have yet to confirm is what you have stated before: that the RF lubricant actually also reduces the tire temps in hwy mode, at "normal" TP & speeds.
 

simp5782

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Well I can confirm that my 445 65 22.5s run about 15 degrees cooler with a 3 piece runflat in them. Yes a 22.5 runflat. That is with a 17k or so steer axle weight
 
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