M925A2 CTIS Question

[rcb]

Greetings All !!
I recently received my newest, a M925A2 Fire Departmentized !! The super singles and the CTIS units on the wheels were all removed. Standard split rims were installed. Until I locate all missing CTIS pieces, is there a safe way to disconnect/cap the CTIS system to drive the truck or should I just wait until I obtain all CTIS pieces and reinstall with the super singles ??
Thanks...
Bob

 

[emmado22]

They did you a favor by removing the CTIS stuff.. It never works correctly... I wouldnt worrry about it....

 

[BKubu]

I agree with Mark...don't bother with the CTIS stuff. This comes from someone who currently owns two M925A2s and has owned an M936A2 and an M932A2. The CTIS NEVER works! Plus, those CTIS parts are very hard to find and very expensive. Get ready to bend over...I'm serious. I've been quoted $1000/wheel! If you want it to look right, just get the rock guards for the front wheels and call it a day. EVERYTHING that was CTIS-related was replaced on both of M925A2s and it still does not work properly. I wanted it all to be new...that's just how I am with my trucks...but I am not saying it made any sense.

 

[BKubu]

Also, the correct super single rims are getting scarce because the deuce guys and M809 guys want them. Expect to pay for them, too.

 

[gringeltaube]

... The CTIS NEVER works!....

We have heard the same kind of complains regarding the M35A3... Specifically, what is it that fails? Hub internal seals, wheel valves or electronics???

G.

 

[BKubu]

I have never torn into the CTIS system to see what was not working. Basically, the CTIS stuff was missing on my truck so we replaced it. I wil add that the in-cab computer sometimes fails. There is also a main valve behind the shift tower that also often goes bad.

 

[justsomeguy]

If I were you I would find the stuff even if it doesn't work and just put a valve core in the tire. It'll look complete, I'll guaranty 90% of the military does the same thing. What I found was, that when it works properly the C series cannot build enough boost to make the horsepower to turn those big tires(in emergency/runflat). I have never seen the computer go bad, pneumatic controlers do go bad although rarely, usually it's in the wheel valves (getting the tubes to line up and hold air) and rarely is it the seals in the hub. It is not that complicated of a system just a pain to get working correctly. On the M35A3's it's the bearings and seals.

 

[justsomeguy]

Sorry, back to your oringinal question just put a plastic plug in the hole at the axle flange so dirt and water will not get inside the hub. Make sure the port for hose is on, this one is on the back side of the brake backing plate. The holes allow the air to pass from a passage drilled in the axle houseing up to a cavity created by two seals and then to the hole drill in the hub. The system works kinda like a crank with oil and the hole drilled in the crank. If you do not plug them you could allow water and dirt in the cavity and over time it could cause problems. The system is just one big 6 legged spider up to the wheel valves, the computer just uses the pneumatic controller to moniter the air pressure in the lines. The wheel valves are what allow a blown tire not to deflat all of the other tires. There must be some pressure in the tire in order for the CTIS to fill a tire. If you have one completely flat it will not inflate it untill your have like 5 psi in it. That is not a exact number just a guess. The is three other valves (one per axle) that do the deflating job never had a problem with those valves.

 

[gringeltaube]

After finding and studying the A3 parts manual I'm hoping to find the appropriate seals (and valves) to try to retrofit a std. deuce front axle. To bad if those seals are the weak link in the systems chain. The bearings look to be std.
I think that a kind of poor man's dash controlled "TIS" at least at front, would be a great improvement for all those running on super single wheels and tires.
No electronics, just a flip switch, pressure regulator w/gauge and the air lines to the knuckles and...!

Gerhard

 

[BKubu]

JUSTSOMEGUY: I wish you were closer...I'd try to bother you to help me track down my CTIS problems! I think the problem he is going to have is, first, finding all of the CTIS stuff and, second, the cost. I called a place in GA...can't recall the name of the place, but I believe it was down the street from SECO...and they quoted me $1,000 for the parts to do one wheel!

 

[steelsoldiers]

I was fortunate enough to own a 923A2 that had a fully functional CTIS. It didn't work when I first got it because the left front hub had been disassembled and some parts were missing. I replaced a couple of seals and a wheel valve and the system worked like a gem. They really could stand a higher volume auxiliary air compressor to power the CTIS. The interesting this is that there is a hard line that diverts turbo boost from the turbo to the intake on the air compressor. That is why the manual suggests holding the tranny in a lower gear so that the turbo build more boost and assists the air compressor in refilling tires.

The blow-down valve above each axle can also get gummed up. There is a rubber flapper on the end of the valve to help keep dirt and water out. They can rot and fail allowing muck to get to the valve, which can cause it to stick open or closed.

 

[Joaquin Suave]

They did you a favor by removing the CTIS stuff.. It never works correctly... I wouldnt worrry about it....

CTIS is a 100% PITA. I paid something like $200. for the inline air filters ( in the wheel assembly). Each one is about the size of my thumbnail.

 

[NightOwl]

I was fortunate enough to own a 923A2 that had a fully functional CTIS. It didn't work when I first got it because the left front hub had been disassembled and some parts were missing. I replaced a couple of seals and a wheel valve and the system worked like a gem. They really could stand a higher volume auxiliary air compressor to power the CTIS. The interesting this is that there is a hard line that diverts turbo boost from the turbo to the intake on the air compressor. That is why the manual suggests holding the tranny in a lower gear so that the turbo build more boost and assists the air compressor in refilling tires.

The blow-down valve above each axle can also get gummed up. There is a rubber flapper on the end of the valve to help keep dirt and water out. They can rot and fail allowing muck to get to the valve, which can cause it to stick open or closed.

My m923a2 CTIS is working pretty well so far. Just got my truck from GL. I think my whole truck was just rebuilt so I may have all new parts. I have only run in HWY mode so far. It sure would be nice to have pressure gauges like my old H1 Hummer had.

 

[chadande]

For reference here are the CTIS pressures:

 

[gottaluvit]

So how long (approximately) does it take to air down the tires from highway mode to cross country?