M939 tire clearance?

[Mos68x]

I'm seriously considering build a dedicated frame to mount an ISO container to the truck, but I need to know what the tire travel (14.00s) is above the frame?

I already did the load bearing calculations for frame and would need to use 3x4 (7g) tubing, assuming a load of 6,700lbs. I'm sure I could go less since that is more than the tare weight of the entire container just for one beam, but since I don't know what total weight will be I would rather err on the side of caution. I have an idea that I could try if I need to make more clearance for the tires, but if it ends up being a considerable amount I would rather just put spacers between the frame and chassis instead.

 

[VPed]

I lightly rub the bed cross members above all four rear tires on full trunnion articulation with no load in the bed. Truck is an M927 with Goodyear ATs.

 

[Buffalobwana]

There are rubber "stops" installed to stop the travel. Measure on level ground, then you have a good starting point to figure out the travel. You can use smaller tires too if you miss it by an inch or so.

 

[Mos68x]

There are rubber "stops" installed to stop the travel. Measure on level ground, then you have a good starting point to figure out the travel. You can use smaller tires too if you miss it by an inch or so.

I was going to use that to start with but that doesn't say anything about a load though.

 

[Buffalobwana]

I wonder if it's buried deep in the annals of the multiple TMs. Somewhere in those thousands of pages is a footnote saying what deflection can be expected with full articulation at certain loads.

What are you doing where you are going to be encountering extreme terrain with an ISO container? I'd be afraid of tipping it over before rubbing tires. Or are you just planning for worst case scenario?

Im wondering if you will reach max height, before you can even start adding inches on top of the frame to avoid rubbing?

Dont know if this is helpful or just chatter. But it's my thoughts!

 

[TCD]

Rear tire articulation

FYI

Lightly loaded 923 with 14x20 Goodyear AT2A tires.



Tom

 

[Mos68x]

Took the truck out to a local spot and had a little fun, also happened to answer some of my question. Now I just need to find a dummy load of about 8k.

 

[simp5782]

Get away from 14.00s. They are getting old and harder to find. 395s give you 1.5inch less height on top and bottom.plus they are cheaper and easier to find.

Dummy load could be a concrete companies ecology blocks or borrow a transfer barrier.

Sent from my SM-G935P using Tapatalk

 

[Mos68x]

14.00s is what came on it, and until I get some money saved up to get new ones these will have to do for a while.

 

[Buffalobwana]

Pull your pickup truck into the bed.

 

[Buffalobwana]

I am switching 2 trucks to 16.00's in the next two weeks. So I'll have 14 of the 14's gathering dust for a while. Until I get a truck that needs new shoes or I decide to switch back.

I know 395's are the sensible choice. Increased acceleration off the line, cheaper, common etc. but, I didn't get into this hobby because it's sensible. But, that's just me. At some point, you do have to make sensible choices. 16.00's come at a cost, both financial and mechanical (especially with a truck that has abnormally slow starts off the line.) I'll live with it.

 

[Nomadic]

What size are the 395 tires converted to the same unit of measurement as the 14's? I'm confused on how to differentiate the sizes.

 

[Buffalobwana]

I believe they are 3" shorter? I forget. Someone posed a pic of 395, 14's and 16's. The difference just from one to the next was pretty big. A 395 next to a 16 is huge difference. Width and just overall size was an impressive difference.

 

[Buffalobwana]

The 14 and 16 are easy. 14.00" from the rim (on each side, top and bottom) plus 20" rim = 48" add an inch of inflation (1/2" each side) and real height is 49"

16.00 are 16x2+20=52" + 1" inflation= 53"

395 is an aspect ratio I believe. I don't know that formula. But I do know how to google stuff.

 

[Mos68x]

395 is an aspect ratio I believe. I don't know that formula. But I do know how to google stuff.

That's just as easy, you just have to remember that the first number is in mm instead of inches. the second number is the sidewall ratio in percentage of the main tread.

395*.85=335.75*2=671.5mm sidewall total
671.5/25.4(mm per in)=26.437in
26.437+20=46.437in

 

[Swamp Donkey]

Metric to standard conversion.



Empty truck with 14.00×20 Michelin XLs. Those rubber bump stops will squash flat on an empty truck if you completely lift a tire or even come close. I wouldn't even count them in your figures. If you need to adjust travel distance go with some urethane bump stops or make some spacers to lower the bump stops.

 

[red]

What size are the 395 tires converted to the same unit of measurement as the 14's? I'm confused on how to differentiate the sizes.

The military surplus 395's measure from 46-47" depending on which model.

 

[Bhpdbrad]

Anyone consider just raising the bed off the frame by using a 4X4 wood spacer on top of the frame instead of the standard 1X installed?

 

[Bhpdbrad]

Buffalowana - I asked in another thread - but you may know...
I was told by someone that has and/or works on the 923 & 925 A2's - that said when airing down for 'Sand' on the CTIS the 1600's will rub. I was trying to wrap my head around the notion of how less air increases tire diameter.... unless the increased sidewall buldge rubs?? Do you know?

I am switching 2 trucks to 16.00's in the next two weeks. So I'll have 14 of the 14's gathering dust for a while. Until I get a truck that needs new shoes or I decide to switch back.

I know 395's are the sensible choice. Increased acceleration off the line, cheaper, common etc. but, I didn't get into this hobby because it's sensible. But, that's just me. At some point, you do have to make sensible choices. 16.00's come at a cost, both financial and mechanical (especially with a truck that has abnormally slow starts off the line.) I'll live with it.

 

[98G]

Anyone consider just raising the bed off the frame by using a 4X4 wood spacer on top of the frame instead of the standard 1X installed?

I've done exactly that. ..