800 series 5 ton axle vs 900 series

[IHCBigJohn]

I am planing on using a pair of 5 ton rockwell axles on a project truck of mine (truck is rated for 24000lbs currently), but I have heard bad things about the brakes on both series... that the 800 series air over hydraulic are not strong enough, and that the 900 series air brakes are too strong and have caused lots of accidents. The truck will be driven up to, but not over 65mph. Openions? Thanks!

 

[drgreg]

My 809 series brakes work fine.

 

[jcappeljr]

I run 53" tires on my 5 ton m817 dump,she stops fine.

 

[IHCBigJohn]

Most of the people I hear saying the 800 series brakes suck are the people putting them under pickup trucks and such. I have kind of wondered if maybe they werent working because they might have hooked them to the brake system on the truck rather than the air over setup. I will be using the 16r20 xzl's as well.

 

[R Racing]

My M813 stops great even with a heavy load. I wonder if there missing the extra preasure needed to actuate them ?

 

[IHCBigJohn]

Thats kind of what I was thinking. Something else to consider though is that my truck already has airbrakes, so while more expensive, the 900 series would be less work to install, but I have heard that something like 34% of the vehicular related accidents in the military were somewhat due to the 900 series brakes being too strong. That they are not "supposed" to drive them over like 46 mph. If I used them would I have to worry about hitting the brakes too hard? If I went with the 800 series I would probably buy a whole chassies for parts and sell / scrap what I dont need. Maybe going so far as to just swap my cab over and change the engine/tranny out.

 

[LanceRobson]

Hello John

The only drawback to properly maintained M809 brakes is that they are single circuit brakes and any major leak will cause the complete loss of braking.

The issues with the M900 trucks was that the brakes are sized to stop a fully loaded truck and to do it from maximum speed. Also, the truck has a quite high center of gravity. The trucks are rarely run anywhere near their max weight so the brakes had a pronounced tenancy to lock up especially on reduced traction surfaces. The problem was (and is) aggravated by operators smashing the pedal as hard as they can and not releasing it when the brakes lock up.

Add in the tendency to roll over when pushed hard into a turn or in a crash and they can be deadly if you do not operate them in a professional manner.

The issue was mostly rectified by the retrofitting of anti-lock brakes. Still, as a matter of fitness for purpose tactical vehicles will always have a shorter wheelbase, more ground clearance and the resulting higher center of gravity than a civilian on-road truck of comparable carrying capacity.

The bottom line is that if your truck has straight air brakes you probably want the M900 axles and you can find threads on the site that get into the gear ratio (that info might be in the TM, too).

It is worth noting that the axles and it's brakes are not designed to stop the rated weight at 65 MPH. You'll want to check the speed rating of the tires as well. I'm not sure if the 16.00R20s are rated for 65 MPH.

Good luck.

Lance

 

[Derrickl112]

Supersingles were also a reason why the 900's had alot of accidents.

 

[IHCBigJohn]

I already have the rest of the gearing and such worked out. A not so mildly hopped up 8.3 cummins with a eaton tx14607b trans, spicer 8341 aux with OD. How much torque can a 2.5 ton t-case handle BTW?

Anyway, where would be a good place to look at how to set myself up with ABS?

 

[Derrickl112]

watch these ABS vs Non ABS video clips


http://www.steelsoldiers.com/5-ton-up/46227-m939-a1-a2-abs-vs-non-abs-trucks.html

 

[M813A1]

Well as Lance Robson said the 900 series brakes are no different then a commerical truck style air brake and that they are to strong for an empty truck and are setup for a heavly load truck !! I would consider using the 800 series axle and use the Hydra Boost unit from a Ford F350 Superduty or Chevy 4500 to get enough power to work the brakes on the 800 series axle !! If you use just the vacuum it will not be strong enough to work the large 800 brakes without the the booster !! And like Derrick shyowed that the 900 series truck with the air brake has a prtoblem with the super singles and the air brakes and it causes the large tire to lock up easliy and the tire starts to bounce a bit and loose of control happens !!

 

[Squirt-Truck]

900 series axles use wedge lock actuators and they are maintenance intensive and not nearly as predictable as "S" cams. The hydraulic 800 series are just fine with enough boost.

 

[emr]

the brakes on the 939 series is not the reason for the accidents, the accidents started after the A1 series put the 1400s on . and the drivers were driving highway speeds in excess of 50 that had the accidents in everything I read and heard of here that is the truck co. the 250th , that put more miles in the gulf wars than any other units in these trucks and have the citations to prove it, , they went to antilock brakes and a max speed in these trucks of 40 mph, and that all but stoped the accidents, they were ALL driver error, NOT the brakes being to strong, wear did U hear that? the 809 series brakes are actually just fine for the truck they are on and never had any types of failures in any bulk fashion at all, hobby guys get to thinking they must not be good because they are a single system actually they worked fine for many many years in all climates and all types of environments. the air brakes are superior for sure, but that just makes sense. many units with the 939s went to the G177s duel set ups for cargo because duels are more stable loaded and handle much better on road , the BIG off road type tires are just that, and were driven past there ability by the average drivers in service.OH I have spent many miles and hours in both trucks and they are just fine when driven like they were meant to be, rugged and reliable.U mention u heard they were not supposed to be driven over 46 mph, this also is an opinion of someone, there was no speed restriction on these trucks untill after the rash of accidents when the 1400s were out in large numbers on the road, then the speed restriction was and IS 40 mph and stands today. thats all fact. also like the clip shows and i think we all know ABS brakes are superior to all others, but there are ways to drive both, If u were to brake the ABS and the standard the same steady pressure u will see big difference IF U are an experienced driver and know your truck and your brakes and know how to properly handle and brake standard brakes the difference although still there would NOT be as severe. good luck.

 

[Nonotagain]

From my reading of the accident reports on M939 series trucks the main cause was placed on in-experienced drivers, then the Allison transmission then lastly the dual tire configuration.

The MWO required a reduction in speed on all vehicles until the ABS brake modules were installed as well as the super single tires.

 

[spicergear]

Well as Lance Robson said the 900 series brakes are no different then a commerical truck style air brake and that they are to strong for an empty truck and are setup for a heavly load truck !! I would consider using the 800 series axle and use the Hydra Boost unit from a Ford F350 Superduty or Chevy 4500 to get enough power to work the brakes on the 800 series axle !! If you use just the vacuum it will not be strong enough to work the large 800 brakes without the the booster !!

Gents...not to keep picking a wound but hydro boost is not really where we should be looking. Hydro MAX is the system that should be looked at. The International S1700, those monster 4x4 trucks with the dually pick up bed, etc use the Hydro MAX system. Big tires add more rotating mass and leverage over the brakes than what most people think. I mentioned in another post about contacting a hydro boost company then being turned to hydro max. What I didn't post was that I tried hydro boost on my truck first. Tried a large piston master cylinder for volume of fluid moved...but the larger the master cylinder piston, the more force it takes to push the fluid because of the surface area. It didn't work well. Then I tried a smaller piston master cylinder and it worked better as I could get the truck to lock up the tires on dirt but would just come to a slow roll on asphalt and not even think of being good enough. After speaking to the hydro boost people and going over the details they mentioned Hydro Max.

I set off looking up info on that system and was really impressed with the information turning up. Has something like triple the brake multiplication power compared to the hydro boost system and has a piston size that moves enough fluid easily for all 6 wheel cylinders on my 18,000lb crane truck. The system I used was from a late 90's S1700 International truck and that system had a GVWR of 43,000lbs.

Braking is REALLY important due to liability. In going over details with the hydro boost poeple...it was something like that system would be performing at like 80-90% of it's total capacity for average braking with not much to spare for emergency and my trial and error with the system proved it.

Some of the Ford medium duty trucks (like those with the 3208's) ran the hydro max. It has the same number of parts (pump, lines, booster, MC, etc) as a boost system but its way bigger.

 

[IHCBigJohn]

So basically 900's will be just fine as long as I dont panic brake or drive like a male donkey?

 

[IHCBigJohn]

Wonder what kind of brakes these guys have. They are running an 18.5L diesel putting out 850 hp, 16 speed auto, and top out at 120! (I think I also remember that they are running 14r20 michelins)
[media]http://www.youtube.com/watch?v=lUj6VQTVndU[/media]

 

[Vintage iron]

thanks for that clip Big John. holy crap!

 

[quickfarms]

Air brakes feel different in the pedal than fluid brakes. The air brake pedal does not push back and get hard like a fluid brake pedal. Air brakes take some getting used to for some people but they stop great.

Since your truck already has air brakes I would keep it that way. It would be less work.

 

[jcappeljr]

Awesome video..