NDCC Tire Design --> Obsolete and Unsafe?

[M1075]

Found this on www.globalsecurity.org when looking for info on 5 tons...

The nondirectional cross country (NDCC) tire design on the M939 basic truck was engineered for cross-country applications prior to World War II. Changes in vehicle speeds, road construction, mission requirements, as well as advances in tire technology have made this NDCC bias tire obsolete and unsafe. This modification will change the tires from the current bias ply NDCC tire to a radial tire designed for on/off road. Recent improvement in radial tire design will provide better traction and mobility, which will enhance system safety.

 

[maddawg308]

I agree. The NDT and NDCC are great for offroad traction, and were top notch for their day. However, most know that modern tire tread designs provide better traction off road and on. They are not really unsafe off road, but on road they are far from safe at modern road speeds, mostly in wet conditions. The older tires just don't contact the ground much, they have a small "footprint". When you have to brake in wet conditions, the bigger the footprint, the better. NDTs and NDCCs will slide like all get out in wet conditions.

 

[TheBuggyman]

Second that.
Sometimes the good 'ole days just were not that good, tire technology being one area of vast improvement.

 

[JDToumanian]

Nothing about my 40-year-old deuce is safe 'by modern standards'... single-circuit braking, no shoulder belts, no impact energy absorption features or, perhaps most importantly, no rollover protection. But I like it just the way it is!... If Bill Gates offered to 'spare no expense' in upgrading my truck to include all these modern safety improvements for me, I would politely decline the offer.

I haven't driven my deuce in the rain yet, but I'm sure I'd agree that the wet traction leaves something to be desired. To a large extent that can be compensated for by planning ahead and driving carefully. Changes in vehicle speeds? I can still only go 55, and that isn't enough speed to cause even my rotten old tires to fly apart.

Maybe the Global Security article was suggesting that NDCCs were unsafe for some of the newer, faster trucks?

Regards,
Jon

 

[cranetruck]

Of course, all tires have a speed rating, even new radial off road heavy lug tires have a rated speed limits of 50 or 60 mph.
The Michelin super singles are not that great on wet pavement either, from what I have read, and with weaker sidewalls not the best choice for rough terrain either IMHO.

I sipe my tires for better wet pavement traction and use chains for mud and snow, where no tire, regardless of tread, bias or radial, new or old design can do well. The CTIS is not a final solution either.

Off road, if the tire spins, you have lost traction.
Used correctly, the deuce with NDCC's can be safe.

(This should stir up some arguments. )

 

[cranetruck]

What's really unsafe are worn tires. How good is a 40,000 mile tire at, say 35,000 miles?

 

[clinto]

Although the article is correct, a good (responsible, thoughtful and intelligent) driver can overcome quite a few engineering, manufacture and obsolete deficiencies.

 

[RF202]

Traction is governed some, by tread design, but most of a tire's traction comes from its ability to conform to the ground. Just as in braking, it's all about how much of the tread face contacts the surface, be it asphalt or dirt. If you look at a heavy radial truck tire, properly inflated, on uneven ground, from the rear, you will usually see that a portion of the tread does not contact the ground. A radial, for the most part, is designed for long wear life on the tread and high temperatures. It does not have as much strength in the sidewalls as the older bias ply tires. There may well be some exceptions to this, but it applies to the vast majority of radial truck tires. Military radials are probably the ONLY exception. We ran 11:20's on the rear of our civilian trucks for years, and never had any problems. Offroad traction was unmatched. In fact, the old NDCC's perform a lot like ag tractor tires.

 

[mtech]

Obviously new tires/designs are not always the answer. If you recall the issues that Firestone had a couple years ago. I haven't experienced anything like that with the NDCC's on my deuce.

 

[ARMYMAN30YearsPlus]

I think a big part of this is that we transporters are now seeing more combat related attacks than a lot of the infantry armor teams. Go figure I have been screaming this for over 25 years that we needed better protection and capability in the trucks we drive for the Army. In Iraq and Afghanistan a big part of getting through safely is by driving like a bat out of H. Drivers try to drive as fast as they can to get through areas safely. We outfitted all of our M 915 tractors with radials on one mission back in 86 and they got better milage and less flats from that point on.

I agree with John though my truck is a 1970 I will upgrade things like lights and other safety issues but since my tires are in good shape the tread design just will stay the same and as Clint said drive safely and defensively and in 99% of the time you will be all right. Thank God that we do not face IED's like we did in Iraq they blow the whole safe driving technique out the window.

 

[Westech]

I have a set of the XL'S on my deuce and there great off road but even on dry roads there not much better then the old NDT'S. I had it out in the cold wet raid we got here last week and the XL'S were just as bad as the NDT'S. Face it kids if you dont have tires made for the road, there going to suck.

 

[jkelly66]

I sipe my tires for better wet pavement traction and use chains for mud and snow, where no tire, regardless of tread, bias or radial, new or old design can do well. The CTIS is not a final solution either.

What is sipe and how do you do it?

 

[cranetruck]

Tire siping is best done by hand, takes about 15 minutes/tire. The cuts are 1/4 inch deep and the rubber gets a better grip on wet pavement and even ice. The idea came from Sperry deck shoe patent in the 1940's.

I have about 5,000 miles on my siped tires, but very little on wet pavement, so I can't report on that. The wear appears to be about the same as without siping. The front tire shown in the 3rd image has been siped, just hard to see.

 

[Lax]

I have always thought the sipeing (sp?) the NDTs would be a very good compromise. The thing that makes the older NDTs bad is that bar that runs down the center of the tire. Any snow, ice or water on the road and the only thing really touching the road is that bar. Wow that is scary! If the bar was deeply siped wouldn't that help a lot? Just asking.

As far as safe driving goes. Everyone says they will be safe. No one says they are going to go out and get in an accident today! That is why they are called accidents. It's easy to say but not so easy to do.

I once had a car, a very little car, stop short in front of me on a city street in the rain down hill. I could not hear if the tires were sliding when I locked em up over the high pitched screaming of terror that sounded really close. In an hour or two when my hart slowed down again I realized that the little girl screaming in the cab with me was me!

I knew it sounded close. She must have had bad breath too because shortly after that the cab smelled really really bad and I need to to change my pants.

 

[cranetruck]

Lax, the contact area is not just the center portion, but extends to the edges of the tire. I have another image which shows the contact area after a long highway run better, but this picture shows the area dust/dirt covered.
The tire is 1100-20 and the pressure is 70 psi. Tire load is about 4,000 lb.
The typical "scalloping" of the outer edge on the front tires is an indication of the width of the contact area.

 

[steelsoldiers]

I read that article too. I think a lot of the problems with the NDCC tires on the new 915 5-tons etc... has to do with top-speed, air brakes, and unsafe following distances. It seems that quite a few of the fatal accidents in the 915's stemmed from drivers following too close, convoy slowing rapidly in front of the closely following truck, resulting in panic stop with air brakes, resulting in tire lock-up, engine stalling whick killed the power steering, which led to poor evasive control and roll-overs. The newer 915A2 trucks have 14R20 lugged super singles plus ABS. The ABS has prevented most lock-up/stalling issues and has greatly reduced the problem. Even with that, many units enforce a 45mph top speed, down from 65mph to try and prevent fatalities. Can you speak to that effect in your unit David?

 

[OPCOM]

Driving my heavied deuce on road in the rain soon convinced me to use semi-truck steer-tires. The behavior difference between NDCC and a good on-highway radial with a tube is phenominal, (as well as about $125/tire assuming finding 11.00x20's new for $175)

 

[Lax]

 

[cranetruck]

I'm not sure what whould make a "phenomenal" difference in performance, since I'm quite happy with my fronts, no shimmy at any speed, truck runs smooth and straight when I momentarily let go of the steering wheel, good on and off road performance. Got thousands of miles to prove it.

I do not keep my rear axles coupled on the highway, now that makes a BIG difference in turning radius and ease of steering and tire wear.

In any case, just happen to have a picture of Patrick's fronts here. BTW, he runs dual 1100 NDCC's in the rear.

Dang, a locking interaxle differential from day one would have been so much better, there has to have been one made, every commercial truck has it...

 

[cranetruck]

Here is Patrick's great looking rig (that's Peter, aka Opie, in the back during their visit a couple of months ago).