Traction: Super Singles or Duals?

[Scout]

Which have the lowest ground pressure and/or best traction (I understand the two are not always the same thing). While I like the aggressive look of super singles, it make the truck really tall to load, and I can't decide if the larger diameter and width of the super singles offsets the effect of the rear duals on ground pressure.

 

[papercu]

Titan is a supplier of NDT military tires. Wayne
Titan International | America's Best Since 1898

 

[DMgunn]

If you are referring to of-road conditions, and if we can apply what I've learned from too many years of working in the mud with tractors, and playing in it with mud trucks, I have come to one conclusion..........

The more square inches of rubber, the better. The most rubber on the ground, whether it be width or length (from airing down or increasing diameter) will equal the best chance of success. On soft vegetation or crop residue, you have a very thin layer on top of the ground that is like an elastic fabric almost. As long as you don't break through that very delicate layer by too much g.p. or by tearing it with throttle, you will stay on top. I like duals because of the decrease in ground pressure, and the consequent decrease in sink-ability - seems like the space between the tires will add a bit of phantom flotation, but if you do break the surface, that space quickly fills with mud, then the tread follows, and soon you have too much mud, and no cleaning action. In that case, super singles are better, assuming the same overall size of contact patch (good luck finding a single that wide). Maybe you could approximate it with the combination of more height AND more width. Then you also gain clearance at the diffs......

The guys that favor narrow tires "to get to the bottom" have never wheeled in North Dakota clay, where there is no bottom. I've seen 20.8-42s (over 5' tall) go over 2/3 under ground level with no end in sight - thank God some people know when to stop trying to get out....

Traction is a function of tread pattern, contact pressure, and of course how many axleshafts are driven....a combination that excels in ice is going to look very different from something that works in mud.

Now that I've written a small novel..................

 

[11Echo]

For soft or loose soil you want the widest footprint/lightest lbs per sq. in. tread surface you can get for flotation.



For hard surface or ice you want the most lbs per sq.in. tread surface you can get for optimum traction.




For real sloppy, deep mud conditions you need wheel speed and luck.



Maybe dualls in rear and a super single in front for more choices.



YMMV

 

[jeep thing]

well i have direct comparison ,in my backyard with dual it sank to the axels,the same spot with the 52's it walked right through

 

[cranetruck]

From the TM 9-8000:

Drawbar pull = Tractive factor multiplied by the weight on powered wheels

So, increase your pulling power by increasing the weight (as long as the gearing is low enough to turn the wheels)....

 

[StrykerPez]

Another thing to consider is the actual tire tread. I'd rather have a single tire with aggressive tread than dual NDTs.

 

[BKubu]

I believe the military did testing in the 50s and found that the singles performed better off-road. For whatever reasons, they stuck with the duals for the most part for the next 30 years. I have not read the report, although I believe David Doyle has a copy. I have been told that this is one of the reasons the military went back to the singles in the 80s. I am sure there are applications (like those stated above) where the singles would not perform as well as the duals, but I am betting that the singles outperformed the duals in more situations than the reverse. Otherwise, why would the military have switched? This assumes the military makes decisions based upon good intel, though.

 

[TheBuggyman]

I agree totally with DMgunn. BUT, the singles do perform better off road in my ACTUAL experience. The Camoplast belted farm tractors with their lower PSI will always be able to work sooner after a rain than the rubber tired machines but any farmer will tell you that the rubber tired machines will pull harder at the drawbar. So what gives? I think that the more modern radial tire on the super single trucks is just a better design that will float fairly well and deliver better tractive force than a NDT. And maybe someone can figure out the PSI/tire on duals vs 14R20 or 16R20. I bet that the difference is not that great. The amount of rubber on the ground is sustantial with the bigger singles. After all, a NDT is crowned which would seem to allow the tire to sink easily into the mud where a super single tread is almost flat to the ground to start with........

Just my opinion....

 

[emr]

It is a fact that singles Perform better off road, BUT Duels are by far the better set up for a cargo truck when loaded, now this is the same truck with the same weight and drive train, apples to apples...these tests were done before WW2 and again through out the early history of the US Army, simply put the single tire does not have to use up power and traction to widen the track made by the front tires.it is that simple...now as for the types and treads of said tires, all have a give and take, low air pressure is your all around BEST friend anywhere. NOW I will also say the driver is at least as important as the tire. wide tire sand, narrow tire mud and snow.are very basic rules, In the Mud in the Rains of Aberdeen past, the M37s Jeeps/Mutts and aired down deuce trucks out performed ALL other trucks that tried to pull others out, the Hummers did TERRIBLE with those wide tires in that very very SLIMY mud. Now the little Toyota or other type 2 wheel drive little light pickups with the cheapest narrowest tires cut right thru and left almost everybody in the dust, but they were not towning anything either,there are alot of factors out there ,but the basic rules as above are the best way to start out and learn from there, ..Randy...oh i just saw above the thought the NDT was crowned would sink? actually the NDT will air down to 15 PSI and be actually awesome and knurle overa and thru most as good as most other tires out there, now if one wants to try to run highway tire pressure , well that is when they get stuck, I call that driver error...Randy again...

 

[silverstate55]

I believe the military did testing in the 50s and found that the singles performed better off-road. For whatever reasons, they stuck with the duals for the most part for the next 30 years. I have not read the report, although I believe David Doyle has a copy. I have been told that this is one of the reasons the military went back to the singles in the 80s. I am sure there are applications (like those stated above) where the singles would not perform as well as the duals, but I am betting that the singles outperformed the duals in more situations than the reverse. Otherwise, why would the military have switched? This assumes the military makes decisions based upon good intel, though.

Hello, newbie here; but I was in the USMC in the 80s & early 90s, when the switch-over from NDTs to Super Singles occurred. The big reasons (from what I was told at the time) for the late switch-over were cost & technology. The SS were newer high-performance radials, and the technology for these just didn't exist back in the 50s/60s for these large of truck tires. And the military is pretty price-sensitive, especially considering the massive quantity of truck tires the Armed Forces go through every year, the NDTs presented quite a bit of savings.

Through the 70s Goodyear & Michelin were able to bring about large truck radials that could handle heavy loads on- & off-road, and bring the prices down to affordable levels that made the switch-over cost-effective for the military.

Although, I do remember right after the USMC switched to SS on their 5-tons, there were a rash of on-road accidents, especially on wet roads. One resulted in a civilian fatality in North Carolina, and almost deep-sixed the entire SS switch-over for the Marine Corps. The truck driver was facing a court-martial as well, but IIRC the charges were eventually dropped due to changes the USMC agreed to incorporate with SS on hard surfaces. Or something to this effect; I don't recall all the exact details since it happened around 20 years ago.

 

[BKubu]

SILVERSTATE55, thank you for your post. While there are a lot of guys on this list with a lot of knowledge about these trucks, it is great to hear from someone with military experience who actually used these vehicles in service. There are others on here, too, who have served and there are also many were in the USMC. FRANKUSMC, HALFTRACK and others are either still in the Corps or have served previously. I'd like to welcome you aboard and ask that you chime in whenever possible with your input!

 

[atankersdad]

I can only add that my yard has deeper ruts in it from the singled radials that the truck with the NDT duals. It is real evident of the tracks and depth and who was the culprit vehicle.. I have never been off roading in either so I have no input from that perspective.

 

[KaiserM109]

I was gonna stay out of this one, but finally got sucked in.

I grew up off roading in Western Colorado and ALWAYS favored NARROW tires. Then I moved to the Eastern Slope and found out that “ALWAYS” isn’t always right.

The difference was that all of the high country off-roading I used to do involved a couple inches of slime over top something hard. In that situation narrow tires could dig down through the slime and found something to grip. I have a pushed in front fender on my ’69 Bronco from a wide set of tires that slid off the road under those conditions.

On the Eastern Slope there is a lot of ground where there is no end to the soft stuff and you need to float on top. Then wide or as much rubber surface as you can get is best. Something else I discovered is that wide tires in loose rock often do better because they are more likely to find something to grip.

As far as NDT tires go, they are probably the best tread you can get for sloppy mud. I saw them do some amazing things in Vietnam. BUT on slick roads they are dangerous. In the winter of ’73 we had to bring several trucks down from the mountains in bad snowy conditions. I was driving a 5 ton tractor pulling a lowboy with a D8 dozer loaded. We wound up parking all the equipment at the side of ClearCreekCanyon and riding home in civilian vehicles because someone was going to wind up in the creek. We could not control the trucks at all.

As soon as I have the money and tires bubble up on my priority list, I will own a set of singles that are NOT NDT.

 

[tjcouch]

I don't have alot of experience . . . but that won't stop me from my $0.02.

1. It seems the military is switching to singles . . there has to be a reason.
2. It seem the OTR truckers are switching to singles. . " " " " " .
3. At the Steel Soldiers Rally in FL, I walked my truck with singles through the entire "mud bog.", a beautifully restored, stock M35 with dual NDTs did not do well in the mud at all.

So what is the answer? Is there one? . . . I don't know . . . may it is "go with what looks best" in your eye.

Consider that is the most common application of your truck . . . mud? street? cargo hauling off road? cargo hauling on road? Authentic static display?

 

[Scrounger]

There is no one answer to the question. As already stated it depends on what you are striving for. Every tire and every setup has plusses and minuses.
I think one of the biggest reasons the military has gone to the single tire is for the central tire inflation system. It is easier to control the tire pressure from behind the wheel than getting out, airing down the tires, then getting out and airing them back up. I know we would rather take the risk of getting stuck than going thru the effort when I was in. As already posted there is stability issue with singles that has resulted in a lot of injuries. There was a program in place to try and “solve” it.
Super Singles have become more prevalent on OTR equipment the past few years. The reasons are primarily due to cost. Super Singles when replacing duals result in a weight savings of a couple thousand pounds. That means that much more cargo without going over 80K. There is also a slight decrease in rolling resistance, especially around corners that increases fuel mileage. How ever when one is driving in the rain Super Singles will hydroplane before duels. And if one gets a flat you are on the side of the road whereas with duels one can limp to safety.
The answer is what you want to do with it and decide accordingly.

 

[Gamagoat1]

Ina a word......COST

 

[emr]

Alot of awesome input, this is a good MV truck thread...

 

[Parker2]

As said before it depends on what your driving on. I work alot in sand and know from experience that duals are superior in sand.

 

[flighht2k5]

A quote from a Unimog brochure.

"Single Tires. For anywhere and everywhere. Unlike the normal four-wheel drive trucks with twin tires fitted on the rear axle, the Unimog has four single tires. The rear wheels always run in the compressed tracks created by the front wheels, which offer higher traction and lower resistance."