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[Too many Kubotas]

Anything heavy can be a biotch in sand, and much more so with duals.

My light Jeep with oversize tires at 1 psi on the other hand...

 

[Renze]

My light Jeep with oversize tires at 1 psi on the other hand...

You better have beadlocks then, or risk spinning the rim in the tire.
10 psi is the lowest i went with tractor pull. Tires on the rims for a decade so they dont slide easy.

And does the middle of the tire still touch the ground or is it running on the sidewall stiffness, instead of air ?

 

[WinterDeere]

Anything heavy can be a biotch in sand, and much more so with duals.

My light Jeep with oversize tires at 1 psi on the other hand...

I don't get it. Duals suck in snow, but for the opposite reason. In sand, you want minimal PSI at the contact area, which is exactly what duals would give you. How could they be worse?

Snow, you want the opposite, maximum PSI so they cut thru and grip the ground beneath. This is why tall skinny tires usually perform best in snow, and duallys are a nightmare.

 

[bcp]

In sand, it isn't so much the duals themselves, but the HEAVY truck they are attached to.

Bruce

 

[Too many Kubotas]

You better have beadlocks then, or risk spinning the rim in the tire.
10 psi is the lowest i went with tractor pull. Tires on the rims for a decade so they dont slide easy.

And does the middle of the tire still touch the ground or is it running on the sidewall stiffness, instead of air ?

No, never did care for beadlock wheels. And yes, the tires would turn on the wheels. Especially the right rear.

At first I repositioned them on the wheel, but then realized that it was much quicker to just swap them side to side and letting them go back to (and a bit past) where they should be.

The tires were marked relative to the valve stems so it was easy to see where they should be.

That was with bias ply tires, usually slightly tuned with a grooving iron for even better conformability, so a rather large contact patch was the result.

 

[Too many Kubotas]

I don't get it. Duals suck in snow, but for the opposite reason. In sand, you want minimal PSI at the contact area, which is exactly what duals would give you. How could they be worse?

Not that I fully understand how it really works, but let's say that you have a pair of duals with 5" wide tread each.

In theory that should equal a single 10" wide tire, but it doesn't. Far from it.

Learned that lesson very quickly the first time hitting the beach with a dually, with the same camper and flat towing the same Jeep as I had been with an otherwise basically identical single wheel GM crew cab.

Yes, now the skinny fronts worked against me, but it was sketchy even in 4WD. The SRW was a 2WD with oversized tires and really didn't give me any problems.

 

[BigBlue1]

I've heard that called out before in off-road discussions that duals make things worse in sand. I don't know the 'why' of it, but it appears to be the case.

 

[WinterDeere]

Yes, now the skinny fronts worked against me, but it was sketchy even in 4WD.

I was thinking this, while posting that prior comment, and it has to be the only valid answer. You want minimal PSI when on sand, your finding lower tire pressure helps is the very proof of that, and duals increase that potential lower range even more than singles, when on sand or snow. It has to be the fact that you've got floating duals in rear, while skinnies digging in up front, that is the confounding factor.

 

[bcp]

Back in the 60's in the Army, there were two versions of 6x6 truck chassis. IIRC, one had dual 9x20 tires and the other had single 11x20 tires. I was told the singles were for better off-road performance.

Bruce

 

[BigBlue1]

I was thinking this, while posting that prior comment, and it has to be the only valid answer. You want minimal PSI when on sand, your finding lower tire pressure helps is the very proof of that, and duals increase that potential lower range even more than singles, when on sand or snow. It has to be the fact that you've got floating duals in rear, while skinnies digging in up front, that is the confounding factor.

From discussions I've heard about it I don't think that's it at all. For some reason duals tend to dig themselves in faster in sand. I'm no expert and all I have to share is hearsay from folks who are 'experts', such as on Matt's Off Road Recovery who operate in those conditions all the time. But what I've heard from those folks contradicts this idea.

 

[ning]

Back in the 60's in the Army, there were two versions of 6x6 truck chassis. IIRC, one had dual 9x20 tires and the other had single 11x20 tires. I was told the singles were for better off-road performance.

Bruce

Part of this is likely not getting rocks stuck between the duals

 

[Too many Kubotas]

You want minimal PSI when on sand, your finding lower tire pressure helps is the very proof of that, and duals increase that potential lower range even more than singles, when on sand or snow. It has to be the fact that you've got floating duals in rear, while skinnies digging in up front, that is the confounding factor.

Never did bother with airing the tow vehicle down.

It was much quicker to leave in Drive, then hop in the Jeep and push it out. That was one (the only?) advantage of flat towing.

 

[RobertN]

I've heard that called out before in off-road discussions that duals make things worse in sand. I don't know the 'why' of it, but it appears to be the case.

TrailMater does ok. Rory does better on the rock, but TrailMater and Ol' Blue do run in the sand.

He's more the exception than the rule though.

 

[masscity]

I worked in the mud for 29 years, the dual wheels on Ready Mix trucks were much better in mud than the single fat tires.

Don't remember about sand.

I operated a P&H 215 Crane mounted on a (CCC) Crane Corporation Company 10 wheel truck with front wheel drive.

I learned the best way to back up in sand was to pick a speed, 2/3 to full throttle and don't change the speed and it prevents

hopping.

 

[Jstpssng]

It's actually super easy with one of those vehicles. Just shut the traction control off and have fun

The problem is that over 30 mph, GM products turn it back on again.

 

[garry1p]

In the AF fire department our water tanker had dual rear axles with dual tires and all wheel drive, the crash trucks had dual rear wheel axles single tires all wheel drive.
These vehicles are heavy and the water tanker would go off road in sand or mud where the crash trucks could not go.
In fact the only time we almost got stuck in the tanker it would have taken a large bulldozer to haul it out.

 

[Too many Kubotas]

In the AF fire department our water tanker had dual rear axles with dual tires and all wheel drive, the crash trucks had dual rear wheel axles single tires all wheel drive.
These vehicles are heavy and the water tanker would go off road in sand or mud where the crash trucks could not go.

There's more to it than if a vehicle has tandem axles and singles or tandems with duals. A lot of other things factor in.

When getting my M936, which should have duals, I specified 14R20 singles instead, knowing damn well that otherwise (at best) I'd leave deep tracks...or get stuck.

The seller recommended against it in a crane application for stability reasons, but when I explained that I'd rather deal with less lateral stability than getting 40,000 lbs. stuck, they agreed with my choice.

 

[Renze]

From discussions I've heard about it I don't think that's it at all. For some reason duals tend to dig themselves in faster in sand. I'm no expert and all I have to share is hearsay from folks who are 'experts', such as on Matt's Off Road Recovery who operate in those conditions all the time. But what I've heard from those folks contradicts this idea.

Carrying ability, especially off road on low air pressure, has little to with tire width, but with air volume.
We used to have a tractor on 12.4-36 tires, with add-on duals.
Our later one had 16.9-30 which are the same height, yet 50% wider. They had the same load capacity as the 12.4-36 on duals.

Also modern tractors, when you go over 200hp tractors dont use the wide ratio 650/65R42 anymore, but 650/85R38, higher sidewall gives more air volume, gives more flex, thereby a larger contact patch and more carrying capacity.

Single tires have high sidewalls, and therefor are better in bellying out over a large contact patch, by making contact to the ground over a longer length, without increasing the amound of mud the tire has to displace to get along.

Here in Holland we run dumptrucks on supersingles all around, even the fixed axle. 11.5 ton allowed when the axle has permanent drive and is more than 6 feet spaced from the next axle, with a max GVW of 50 ton.

When you create ruts, you have less resistance with all wheels in the same track. With a conventional 8x8 you run a track with your front axles, then your tandem duals push a new rut in the soil on both sides of the front axle rut. Displacing soil causes resistance.

Heres a Tatra 10x10 with a legal gross of 50 ton, in dredger sand. Since these became available, more and more people choose supersingles on dumptrucks.

 

[masscity]

In Detroit, the reason they were going to fat singles is that mud and rocks don't get jammed in between the duallies.

 

[Renze]

In Detroit, the reason they were going to fat singles is that mud and rocks don't get jammed in between the duallies.

Another added benefit. When driving a dually in deep mud, it takes a quarter mile before the last mud is slung from between the duals. Nowadays with people sueing whenever they slide off the road during harvest season, (instead of driving careful) its an important argument for wide singles.