Oshkosh mk23 mods for practical use

Camoguy

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Hey guys, I am new to steel soldiers. I found this site researching mods for my MTVR. I purchased this truck because it has one of the most desirable engine trans combos and bonus the tak-4 suspension.
My plans are to turn this into a daily dumptruck. I will have many questions to follow but to start. Im wanting to reduce the tire size to make it a little more practical for civilian use. (Currently 16.00R20 Im wanting to drop down to a 12.00R20) Thats about 11” lower. Lets be clear I have research and I am aware of the gear reduction from going to a smaller tire. What Im trying to figure out right now is weather I can just order some 12.00 R20 military tires and slap them on my rims? Has anyone tried this? Another solution would be to somehow find out what wheels and tires are used on the pierce fire trucks that have the rear Oshkosh tak-4 suspensions? If you are a firefighter and work with one of these trucks a lug pattern measure and tire/rim size would be appreciated. Im sure the hubs and lug pattern are the same but worth a confirmation.
 

MTVR

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You won't even be able to do 55 mph with 12.00R20 tires.

Plus, you'll be putting less rubber on the road.

And the speedo and computers (transmission, etc.) are all calibrated for 16.00R20 tires.

Do they even make 12.00R20 tires in the correct load capacity, or were you planning to downgrade that?
 

simp5782

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12R20s are not made for a 10inch wide wheel. Which is what the MTVR has. They are skinny tires for dual setups. They are rated for 8, 8.5, or 9in wide wheels. They do not make a narrow wheel in 330 hub pilot to my knowledge. The 1200R20s that are made are the G272 style which are rated at 8200lbs each

Shortest tire you could go to would be a 365 80 or 85R20. They are not common. So basically a 395 85R20 is the shortest and most common tire available to swap on it at 46 inches tall for the MTVR wheel.

Below is a picture of a 1600 vs 1400 vs 395
 

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Camoguy

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12R20s are not made for a 10inch wide wheel. Which is what the MTVR has. They are skinny tires for dual setups. They are rated for 8, 8.5, or 9in wide wheels. They do not make a narrow wheel in 330 hub pilot to my knowledge. The 1200R20s that are made are the G272 style which are rated at 8200lbs each

Shortest tire you could go to would be a 365 80 or 85R20. They are not common. So basically a 395 85R20 is the shortest and most common tire available to swap on it at 46 inches tall for the MTVR wheel.

Below is a picture of a 1600 vs 1400 vs 395
Good pics!! Thanks
Have you ever seen what wheels are used on the rear Oshkosh axles of pierce fire trucks? I would imagine they are the same lug pattern? I just cant figure out who makes them.
 

Camoguy

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You won't even be able to do 55 mph with 12.00R20 tires.

Plus, you'll be putting less rubber on the road.

And the speedo and computers (transmission, etc.) are all calibrated for 16.00R20 tires.

Do they even make 12.00R20 tires in the correct load capacity, or were you planning to downgrade that?
Im going to re gear the transfer-case to tire size once I figure that out. Then a shift schedule reprogram. I think🤔... this may sound expensive but compared to buying a $150,000 dump truck this is actually cheaper and more fun.
 

simp5782

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Im going to re gear the transfer-case to tire size once I figure that out. Then a shift schedule reprogram. I think🤔... this may sound expensive but compared to buying a $150,000 dump truck this is actually cheaper and more fun.
Put in a Oshkosh 55000 2spd case. It has a .98 overdrive and 2.77 low
 

Nomadic

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Im going to re gear the transfer-case to tire size once I figure that out. Then a shift schedule reprogram. I think🤔... this may sound expensive but compared to buying a $150,000 dump truck this is actually cheaper and more fun.
Post back about the transfer case re-gear.
 

Camoguy

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Post back about the transfer case re-gear.
I had sent these guys an email.


Have not heard back yet. The last suggestion for the 55000 may be the way to go.
 

simp5782

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Has anything come of this investigation yet? I just picked up an MK23, and am interested in possibly going with a shorter tire as well.
Why do you want to go to a shorter tire? You are limited to a 20in wheel so shortest you could really go is a 395 85R20 which Is 46in so 3.5in shorter
 

Darrel

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Why do you want to go to a shorter tire? You are limited to a 20in wheel so shortest you could really go is a 395 85R20 which Is 46in so 3.5in shorter
Just a wild hair, thinkin if I could get the frame rails down enough, I might be able to pull my 5th wheel, and gooseneck trailers with the truck.. I still havent taken exact measurments of anything yet, but ran across this post, and figured I would see if anything came of it.
 

simp5782

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Just a wild hair, thinkin if I could get the frame rails down enough, I might be able to pull my 5th wheel, and gooseneck trailers with the truck.. I still havent taken exact measurments of anything yet, but ran across this post, and figured I would see if anything came of it.
They pull trailers with the MK31. It would be cheaper to modify your trailers over slinging drivelines that are spinning too fast

Some folks have ran gooseneck off the back of the m939s with a modified pintle hitch
 

Camoguy

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Has anything come of this investigation yet? I just picked up an MK23, and am interested in possibly going with a shorter tire as well.
I got a hold of a fire department that has one and they told me the wheel and tire size of the tires they have on the rear axles and it’s actually a 22.5 inch wheel on the firetruck. Problem is I don’t know where to get the wheel.
 
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