Steel Soldiers::Military Vehicles Supersite - View Single Post - M939/A1/A2 ABS vs. Non-ABS Trucks

BKubu · 01-10-2010, 08:44

Quote:

Originally Posted by ida34

I drove the deuce, an M925 with Michelin super singles towing a M198 howitzer and a M977 HEMTT. I drove the M925 on the march into Iraq during the first gulf war. We did not have ABS and due to problems with the brakes on the M198 we never used the trailer brakes. The M198 weighs in at about 15,500 lbs. The truck was loaded with a couple of thousand pounds of people and equipment. I never had a problem with locking the brakes up. I had a few high pucker stops but never locked them up. Some were panic stops. The march was in darkness only using PVS-7 NVGs with blackout drives and chemlights on the tubes of the howitzers. The goggles cut our depth perception and when the truck in front stopped it was hard to see. This was on a road cut in the desert a few hours earlier by the engineers.

I think a lot of the problem lies with the air brakes on the 900 series. The older air over hydraulic brakes of the deuce and the 800 series were hard to lock up and when you went from driving these vehicles to driving a 900 series there was a steep leaning curve as to brake input from the driver. I don't remember the same problem with the M977 and IIRC it also has full air brakes. I was always looking for the brakes to lock up on the M925 but I attributed the touchy feeling of the brakes to the 15,500 lbs howitzer pushing it with no brakes. I am sure the air brakes ability to lock the brakes caused a lot of my personal caution also.

What year did the ABS MWO come out?

BTW I did drive the M925 while empty and did not lock it up at all either.

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Thanks, Chuck, for this great post. I was reading this thread and planning to post some of these same thoughts. The brakes on this truck were designed to stop heavy loads and there is no question that they are better than what is found on the older trucks. The trucks were designed to be driven with a load and the brakes were designed to stop that load. Without a load, one needs to be careful to avoid locking up the brakes (without ABS, that is). You don't need to hit the brakes as hard as you can to get the vehicle to stop quickly and without locking the brakes (again, non-ABS truck). The problem, I believe, lies with the fact that many of the guys driving these trucks don't have experience driving vehicles with air brakes and don't really know how much pressure you have to apply to get the truck to stop. I was one of these inexperienced drivers, but two guys with hundreds of thousands of miles in over the road trucks explained how to drive a truck with air brakes. They do not really work like the brakes in your deuce, Unimog, or earlier 5 ton. Sure, the pedal is basically the same and the theory is the same, but the pressure required to stop a truck, even fully loaded, is different. I now have hundreds and hundreds of hours in both ABS equipped trucks and non-ABS trucks and I have never had a problem. Just as Chuck stated, I have had panic stops where people pulled out and stopped in front of me when I was driving at 50 mph. The truck stopped without any issues, the brakes never locked and I was able to maintain control. Basically, the ABS idiot proofs the truck. If you are aware of your surroundings, drive defensively, reduce your speed in bad weather, and avoid standing on the brake pedal, you should be fine. I currently own non-ABS and ABS M939 series trucks and I drive them the same way. To me, the ABS simply allows the driver to think less. Sure, it is a great safety item that I wish were on all of my trucks...who wouldn't?!?!