CTIS question

[cubdriver55]

I am wanting to do away with the CTIS system on my M35A3. I have read about it here on the forum but there seems to be some different ideas on just what to do to disable the system and fix the tires so they do not go flat all the time. Can the valves be fixed without breaking down the tires or do they have to be broken down and remounted? Thanks Steve

 

[autigers35a3]

If I was going to take mine off I would contact Erik @ Eriks miltary supply in CA. before I turned a wrench. He knows how to do it and has the plugs and seals you will need.
Someone will probably post a link very soon where this topic has already been discussed.
They always do when a A3 question gets posted... Good luck.

 

[Rustygears]

If I wanted to disable my A3 CTIS, I would remove the plastic tube & fitting connecting the wheel valve to the fill stem in the rim on each wheel. I would then use a plumbing reducing fitting to adapt the 3/8 stem pipe thread to a standard 'schrader' valve - the same type of valve used on tires. I think the schrader valve is 1/4 inch pipe fitting. You can get that valve at any car parts store for a couple of bucks. Then you refill the tire through the fitting. There is no need to remove or cap any of the remaining CTIS plumbing.

With that said, your issues with leaky tires is most likely NOT due to the CTIS wheel valves. 99% of the leaky tires are due to failure of the rubber grommet sealing the fill stem to the inner rim half. They rot & shrink, then leak. Unfortunately, to replace it you must split the rims and dismount the tire. The grommet is a couple of bucks from Erik. Labor is a solid few hours work with an engine hoist and a hefty impact wrench. There's a few posts on the topic and step by step instructions. Or you could pay a reputable heavy equipment tire shop to do it. There was a post last weekend from a poor soul who paid $$ for an obviously unskilled facility to do it. Frankly, I enjoy doing it myself because I know it's done right and I can PM everything else on the wheel -o ring, rust, threads, etc. at the same time so I fix it just once.

I'll bet that by replacing the grommet, you have no more leaks and the CTIS can stay stock, regardless if you use it or not. I had 4 of 6 wheels losing air - some fast & some slow. All 4 were fixed by installing new grommets and o rings.

 

[CobraCDR]

Given the cold weather up where you are (and the fact that the CTIS is suppose to be turned off in the cold - see below), I could see not wanting to keep it. However, I agree with Rustygears, might just be easier to cap it and leave it attached and just not use it than to rip everything off.


From TM 9-2320-386-10:

The CTIS should be deactivated during operation in extreme cold, 0° to -65°F (-18° to -54°C). Extremely cold temperatures can cause air seals located at each wheel to fail.

 

[dezert ratt]

If I was going to take mine off I would contact Erik @ Eriks miltary supply in CA. before I turned a wrench. He knows how to do it and has the plugs and seals you will need.
Someone will probably post a link very soon where this topic has already been discussed.
They always do when a A3 question gets posted... Good luck.

Thumbs up. Now I know a local place to get parts after I pick up my deuce in january!

 

[Rustygears]

Erik is a good guy and is located in San Marcos or Vista as I recall. He is super prompt and super helpful. He carries all the little A3 specialty bits like grommets and o rings at a reasonable price. Nice guy. All the construction water truck guys use him for parts. That's how I originally found him.

 

[dezert ratt]

Thats good to know. the mv group seems pretty small in ca compared to the other states, its nice to see we have some good resources around here

 

[glcaines]

Ditto on what Rustygears said about the valve stem grommets causing most air leaks. Ditto also on Erik's. He is honest and prompt about shipping and has a lot of A3 stuff.

I would recommend leaving the CTIS stuff on and simply not use it. You don't want to use it anyway because the highway setpoint is 45 PSI which is too low and it is much better to run your tires at 55-60 PSI where the truck handles much better. Don't go over 60 PSI because the wheels are red-lined at 60 PSI.

 

[Rustygears]

Gary is right on the money regarding CTIS - it looks cool, keeps the unique A3 features, but unless you offload continuously, sucks for highway. I have mine all rebuilt, but turn it off and manually inflate each wheel to 55 psi. Since I've rebuilt the rims for leaky grommets, etc. there's virtually no maintenance to keep the tires at 55, even when sitting for weeks at a time.

 

[AceHigh]

I did like Rusty, got the system working pretty well. I had the tires up at 50-something and was heading to Lowes. Decided to turn it on running down the interstate, heard it venting the excess air.

Got to Lowes, turned off CTIS, turned off the truck and heard air hissing out the exhaust valve. I started thinking about sitting in the lot with all the tires flat.

Turned the truck back on, CTIS on and aired up the tires. The system worked fine then. I can say my heart was pumping!

 

[CobraCDR]

The joy of the CTIS on the deuce (and the other military vehicles), it is a little unnerving to hear it keep doing stuff when you're not directly controlling it. It takes a bit to get used to and trust in the equipment knowing what's normal.

 

[Ma Duce]

Well we recovered another truck today.

My friend Roger bought one of the 109s out of Sparta on the last auction. So we went up to get it.

On the way home following the truck I saw that the rear diff was hopping constantly. So I took it to be flat spots on the tires and that maybe withe some miles and time they would work themselves out.

Well after 250 miles they were still hopping. Several times I pulled out from behind and ran up on the truck. Both rear axels were doing this. And what I was able to see, was that the shimmy, shake or hop -- whatever you want to call it was syncronised witht he CTIS gear spinning with the wheel.

So it appears that the wheels are not completely balanced with all that extra weight on them.

So after wathcing this run today, and with my truck having different low tires every couple of days -- yes I know it mught be the groments, I am thinking about removing the CTIS completely from the wheels and the truck. . . .

 

[motomacguyver]

I had my CTIS stuff off the wheel and weighed the components at the grocery store.

The cover 3.57 lbs
The counter weight 2.82 lbs
The wheel valve with fittings and hoses. 1.75 lbs
4 lug nuts 1.38 lbs
4 regular nuts .45 lbs.

So if we figure (guess) 75 % of the cover weight (because it is pie shaped and most of the mass is at the outer edge)

2.6775 lbs
valve assm. 1.75
lug nuts 1.38

equals 5.8075 lbs.

minus 2.82 lbs for the counter weight

leaves a 2.9875 lb imbalance.

So, if you replace all of the lug nuts on the CTIS side of the wheel with regular size nuts (JUST THE ONES THAT HOLD ON COVERS OR VALVES). Than put all the lug nuts on the other side. That should get the imbalance down to around 2/3 of a pound. Still heavy on the wheel valve side though.
I think car guys use weights in 1/4 ounce increments or less. (for comparison) This is the very first thing I would do to help tame the wobble. The A2 guys probably don't have wobble due to NO CTIS

 

[3dAngus]

I was fascinated with the concept of CTIS when I first heard of it. I honesty believe it was a good design by good engineers in a lab with good intentions. They should hr ave had a dirty soldier by their side.

The water and grease, grit buildup in the air tanks will always provide contaminants that will ruin a CTIS system. Or, I should say, my opinion is....

CTIS was designed for a clinical environoment IMHO. Not for 4 or 6 wheelling through mud and water. Knowing what I know now, even as much as I love the concept, I would disconnect it because I simply do not need high maintenance on a high maintenance machine, which all deuces are.

I bought some Orings with intentions of making an effort to repair to original condition and no longer need them. I think I have six if it helps anyone. PM me if in need, and good luck with the project. I just turned CTIS off and pumped up the tires with the glad hand to 50-55 lbs. , front and back tires. Worked fine.

 

[Ma Duce]

If I switch to HEMMITT rims, CTIS is irrelevent to the truck.

I want something short of a daily driver, but a bobbed truck I can run around in when I want to without having to worry about filling all my tires and such before I run.

I think the CTIS was a great concept. Just to many hurdles to overcome.

 

[1 Patriot-of-many]

If either of you guys want to ditch the CTIS, let me know I'd like to have spare CTIS parts for my truck.

 

[Ma Duce]

Will do. When I start the bobber project, keep an eye out for the thread and remind me.

 

[Rustygears]

If either of you guys want to ditch the CTIS, let me know I'd like to have spare CTIS parts for my truck.

Ditto here too! I fix the manifold and wheel valves.

 

[1 Patriot-of-many]

Ditto here too! I fix the manifold and wheel valves.

Great.... competition to drive up the prices

 

[glcaines]

The whole CTIS system is very simple. Unless the diaphragm us ruptured, there is no reason to replace a wheel valve. The wheel valves normally only malfunction if the CTIS seals in the axle have failed and let differential lube enter them from the hollow stud. They are extremely easy to dismantle and clean. You don't need any written instructions - it would be hard to screw it up. The small o-ring can normally be re-used, but can also be replaced if needed. However, be sure not to lose it.