What does CTIS offer that you can't do "by hand"?

[cranetruck]

Simple question, really, or is CTIS just another result of the "push button/let the computer do the thinking" mentality?

A related question, is there a provision to manually air up/down the tires, like in a second valve on each tire?

 

[CUCVFAN]

RE: What does CTIS offer that you can

Well, given than CTIS ws first available on the DUKW, I would say not. The computer has just been adapted to make it easier for an 18-year old soldier/marine to think about the mission and not worry about his tire pressures. Just pick an appropriate terrain and get moving. It ain't perfect, but I think it's a wonderful feature (when it works... ).

 

[crusty]

RE: What does CTIS offer that you can

When there is the potential for sniper fire, being able to adjust pressure "on the fly" is a huge advantage..

 

[BKubu]

RE: What does CTIS offer that you can

With all this said, the CTIS has to work to be relevant. While I love the M939A2 series of trucks, the CTIS is junk. I've owned four M939A2 series trucks and NONE of them had working CTIS!!! I have a friend who has had multiple M35A3s and none of them had working CTIS!!! The Russians have had CTIS on some of their trucks since the 60s, I believe, and I've heard it was a bullet proof system, unlike ours.

 

[cranetruck]

RE: What does CTIS offer that you can

Keep in mind that the time to inflate/deflate is not much different from doing it manually...figure 15 to 20 minutes.

 

[jasonjc]

RE: What does CTIS offer that you can

What cucvfan said plus the fact that you do not have to stop. You see/know that you are coming up on soft/hard stuff push the button for the typ of road and keep on rolling. You don't have to stop and wast 30min or more getting out a hose and going from tire to tire with the bad guys watching you.

 

[CUCVFAN]

RE: What does CTIS offer that you can

Yeah, but you're driving while they are inflating/deflating...

Edit... Jasonjc beat me to it...

 

[cranetruck]

Re: RE: What does CTIS offer that you can

.....The Russians have had CTIS on some of their trucks since the 60s, I believe, and I've heard it was a bullet proof system, unlike ours.

Based on some posts on this forum (I'd have to do some searching), they have their share of problems with it also, but it is more manually oriented and it still takes a lot of time.

 

[jasonjc]

RE: Re: RE: What does CTIS offer that you can

I drove M939A2's in the Army and never had any prlombles with the ctis. Now I did drive alot and these were new trucks at the time. I'm thinking at least 4-6 different that I drove plus all the other ones in the units. Is it age getting to them or did they improve it for the wost????

 

[cranetruck]

RE: Re: RE: What does CTIS offer that you can

Does the CTIS require specific maintenance? How important is the air dryer to the health of the valving? Is there a manual override (=separate system for doing it the old fashioned way)?
Airing up/down on the fly is certainly a plus.

 

[BKubu]

RE: Re: RE: What does CTIS offer that you can

I have spoken to a guy in the NC AR NG who got several fresh M923A2s/M925A2s straight from a complete overhaul and he said he could not get one of the trucks' CTIS to work. He said they plug them off so the inspecting officers THINK the CTIS is operational, but it is not. I also heard this same tale from a member of the NJ AR NG when Joe Young and I were visiting with a friend of his who was a motor pool mechanic. To be fair, I have never torn into any of the CTIS to see why they did not work. I really need to do that.

 

[Jones]

RE: Re: RE: What does CTIS offer that you can

The CTIS controller is marked; "-CAUTION- Do not change CTI setting when cornering or wheels are slipping. Damage to driveline may result". So unless you're planning on driving in a straight line on a firm surface while the CTIS does it's thing, you're buggered. And since the controller is wire technology there's no way to change settings if the electronic part of it goes out.
Just remember: "New and improved", usually isn't either.

 

[rmgill]

RE: Re: RE: What does CTIS offer that you can

oshkosh has it on their MTVR and they show it being used while climbing a grade where the driver needs more traction. How does it work on their trucks?

 

[Joaquin Suave]

I'll throw my $.02...

First-off there is nothing computerised about CTIS. It is basically an electrically controlled valve "system" that has preset values (highway, cross-country, sand, emergency, & run-flat). The system has the ability to output a value for the transmission to "read" so that the Allison won't shift into higher gears then safe to drive at that tire pressure.

The REAL strength of the CTIS is the run-flat! I've heard that it was designed to keep 1 TIRE inflated (at all pressure values) with a 1" bullet hole in the side wall!

So if I was dodging bullets in my LMTV...I'd think that CTIS was some pretty cool SH*T!
But since i'm not dodging bullets...I think its a TOTAL PAIN IN THE *SS!

I've so tired of having to look at Libelula with one flat tire that I cut some big blocks that I can put under the axles then deflate the CTIS to the emergency setting and lowering the truck onto the blocks.

A couple of months ago, an SS member pointed out that the "way to go" was to just get the CTIS wheel covers, put them on, and be happy you didn't have the real thing!

If you study some of the big "cammion" class trucks at the Dakar rally you will see that a lot of trucks have abandoned the thru-alxe CTIS for break-away hoses on the outside of the wheel. In a non-military enviornment, that system makes WAY more sense.

 

[M1075]

I have had nothing but positive experience from the CTIS on the PLS. It has proven to be easy to use and reliable (so far). It greatly increases traction when needed. The only time I have stuck the PLS was when I failed to use the CTIS. Moving 90,000# around offroad and in the mud can be a sticky situation!

A turn of the switch and a press of the start button is all it takes, on the move. Here is a pic of the controls. Note there is a manual overide switch and also lights to indicate things are functioning properly or if you are in an overspeed situation for a given setting. There is some serious air drying equipment on the PLS.

On the PLS, the CTIS controller also controlls the air actuated inter-axle and intra-axle lockers. Basically, the lockers are engaged as needed to match the terrain you are on. Pretty much a dummy proof system. Just touch "D" for drive on the transmission selector, and choose a CTIS setting for the terrain. Skinny pedal after that!

 

[cranetruck]

For comparison, here are the M35A3 CTIS controls.

 

[M813rc]

I looked at the CTIS controller on a Russian BTR-152 armoured truck once. It was between the front seats and looked like a critter from Alien, or a lobster gone wrong, being a mass of valves and hoses and controllers. Basically, there was a large central thing (highly technical term) to which a separate control lever and all the associated plumbing, including a small gauge, for each wheel were attached. Very crude, but probably quite effective.

Cheers

 

[Alredneck]

First alot of the trucks in our motorpool that had CTIS had them blocked off cause they were to much of a pain to keep runnin right. ( 900 series ) The FMTVs seemed to work a little better but run flats have nothing to do with CTIS a run flat is inside the tire, it is a solid rubber type material used with 2 piece combat rims only. Humvees used to have metal ones and now are using a rubber style also but look different than the ones in the big trucks. You can rip a whole sidewall off and keep goin with run flats, the saying is something like 30miles at 50mph or 50mile at 30mph whatever! You can go a long ways and get back to base with out having to change tires on the side of the road in a hostile country. And its sad cause poorly trained leaders are still having soldiers stop and change tires. You can do your 8hr mission then get back to base and do it in the safe confines of the FOB A-HOLES!( For those out there! ) Whats the world coming to? Beats me, Captain

 

[bigbee]

ours worked great

In my guard unit, the 900 series 5 tons with CTIS had the CTIS disabled when I first got there because of problems with the brake system which would cause the truck to flip nose over. Once the trucks were set with ABS, the CTIS was fixed.

In our training, we emphasized that the CTIS was automatic on the increase air mode--if you sustained a speed over that rated for the inflation level, the tires would air up. EXCEPT in the Emergency mode, where all of the air is pumped into the tire with no pressure as long as the truck is running. We would drop the pressure one step when we were hauling troops, and maintain a slower pace. I rode in the back once with a troop trying to keep up with Humvees on a two track. NOT GOOD!

All in all, CTIS on the 900 series for me was a positive.

EDIT:
And, oh, yeah. There is a way to use the manual hose from the trucks air system like the other 5 tons and deuces. It's just that the valve is on the back of the wheel/tire and to get it from almost flat (20 psi) up to highway pressure (80 psi) can take nearly an hour. And you're reaching/leaning over a tire on a running truck or on the ground underneath. Running from a larger, shop compressor would probably be quicker, but not by much. That's on the rears. Never had to manually air up a front.

 

[CUCVFAN]

Re: ours worked great

...problems with the brake system which would cause the truck to flip nose over.

Man, I must be mis-understanding this statement? Please elaborate.

I'm pretty sure it had more to do with the engine stalling on a panic stop and inexperienced drivers sliding into vehicles and killing people or losing control of the truck and killing or hurting themselves. There is no amount of traction that those two front tires could generate to cause that truck to flip over forward. That can't be what you meant?