16:00 tires with CTIS on an A2

[Andyrv6av8r]

I tried searching with no luck; maybe I didn't use the right words. I was wondering if anyone has swapped out the 14:00 tires/wheels on an A2 939 series truck with 16:00 tires/wheels and kept the CTIS working? I saw a few pictures of a 7 ton MTVR truck today and the question crossed my mind.

 

[Castle Bravo]

Although I can't say for sure, I suspect it would work fine. I don't think the CTIS would know or care of the difference in tire size. About the only thing I can think of that would matter is that the CTIS controller tire pressure settings may not match up ideally with the 16.00R20 tires.

 

[hklvette]

Although I can't say for sure, I suspect it would work fine. I don't think the CTIS would know or care of the difference in tire size. About the only thing I can think of that would matter is that the CTIS controller tire pressure settings may not match up ideally with the 16.00R20 tires.

About that, has anyone opened up the CTIS controller to see if it can be adjusted? It may be all in the firmware, but its also possible that there's a group of pots in there to allow adjustment for any situation.

 

[Suprman]

It is adjustable via a computer program. Which is available for download online. If you could only find the Y cable that plugs in between the harness and controller you would be all set. This cabłe was only sold in combination with a controller upgrade package.

 

[Andyrv6av8r]

Although I can't say for sure, I suspect it would work fine. I don't think the CTIS would know or care of the difference in tire size. About the only thing I can think of that would matter is that the CTIS controller tire pressure settings may not match up ideally with the 16.00R20 tires.

That's exactly what I was thinking; the controller wouldn't care. I was just curious if anyone had done it before. And if everything ( wheel valve, weights, etc ) would bolt up to the HEMTT wheels.

 

[wheelspinner]

Matt (vintage iron) has.

 

[Castle Bravo]

That's exactly what I was thinking; the controller wouldn't care. I was just curious if anyone had done it before. And if everything ( wheel valve, weights, etc ) would bolt up to the HEMTT wheels.

Not sure about the HEMTT wheels. I suspect it would not matter on the rears, as the CTIS does not interface with the wheel on the rear axles. On the front, it might work if they bolt spacing and size is the same on the HEMTT wheel and the M939A2 wheel. I don't think the CTIS protective cover on the front wheel would work because of the different shape and backspacing of the HEMTT wheel.

I also don't know if the studs are long enough for HEMTT wheels, but I'm sure someone here has covered that before.

 

[Tornadogt]

CTIS works fine on 16.00 x 20s.. just keep the 5 ton combat wheels and all works out.

 

[spook]

Backing up tornadogt, I swapped 16.00's onto my 925A2 and the CTIS still works perfectly.

 

[JamesH]

Backing up tornadogt, I swapped 16.00's onto my 925A2 and the CTIS still works perfectly.

How does your truck handle the highway with the bigger tires? Do you notice any power loss issues?

 

[spook]

I had already tuned my injector pump and governor as per the instructions/discussions in this thread:

http://www.steelsoldiers.com/showthread.php?74925-So-who-has-bumped-the-power-on-a-6CTA-cummins

and ditched my muffler and re-worked my air-filter,

so I had way more low-end power and acceleration than stock. My truck ran so well to the bumped governor limit that it just felt like it needed another gear for the highway. The 16:00s essentially gave me that taller ratio. It cruises very well at 63 mph unloaded (I know, I know about the tire speed limit, but that's a rating for full load, right?) and has no trouble pulling about 20,000 lbs of payload (flatbed trailer, swamp buggy, 5 four-wheelers, ice, guns, kids, dogs) in 1-4. I like 4th for WOT at 55mph with the buggy and trailer because it keeps me more in the loaded speed range of the tires and it keeps my EGTs lower than the same speed in 5th.

I'm frequently in deep sugar sand or water with my truck and loaded buggy-trailer, and the 16s just handle it he terrain better and I still have plenty of power. I like the highway feel, too...not as bumpy as the 14s. I did balance them with Dynabeads though and the 14s were not balanced.

Plus, the 16s just look better! (In my humble opinion)

 

[Suprman]

Do they dyna beads affect the ctis function?

 

[RobertoGatos]

It is adjustable via a computer program. Which is available for download online. If you could only find the Y cable that plugs in between the harness and controller you would be all set. This cabłe was only sold in combination with a controller upgrade package.

Is it possible to swap the controller from a wrecker into a cargo truck for the higher on road inflation? Is the software the only difference? Nothing mechanical? Would like my tractor to have higher pressure when loaded.

 

[spook]

Suprman, I debated on that issue for a long time as I was prepping to swap the tires. I finally decided (hoped!) that since the fill-air from the CTIS is generally going to be coming into my tires (I rarely deflate for sand, cross country, etc.) it would keep the beads blown out of the CTIS tubes. Also, I felt the CTIS valves are remote enough from the fill-orifice in the wheel rim to keep the beads from making the long trek through the orifice and up the tube and supply hose to the valve at the hub. I've been running the 16:00s with the beads for about 9 months now and so far, so good.