Dually truck vs cab chassis truck

[brendonv]

Anyone know the difference between a dually truck and a cab and chassis (with duals) truck? Particularly ford? Is the dually axle wider?

Found a nice rig but not sure my dump bed will work on it. I wanna say the dually frame is wider too, like a pickup frame.

 

[woodworkingboy]

I believe with the same make, the axles are the same width, but the brake drums are wider and set in further with dual rear wheels. Duals can handle more weight....theoretically twice the amount, tires last longer, and you can drive with one flat.

 

[lumberjack]

Cab and chassis have a standard 34" wide frame. Pickups don't.

Both have dual rear wheels, Jay.

 

[Dave Shepard]

Typically a dually pickup will be wider than a chassis cab, but I think on 450 and up trucks they are all the wider stance.

 

[brendonv]

Figured so, found a low mile clean dually reg cab. But my dump body won't swap. Bummer. Next!

 

[woodworkingboy]

Carl's correction, so sorry for the misinformation.

 

[lumberjack]

The 450 can come either way, afaik the 550 is only chassis.

The difference is frame width. Usually on all makes, if it came factory with a pickup bed it's not a cab and chassis. It's not uncommon to put a pickup bed on a cab and chassis by the end user.

 

[Al Smith]

I' m thinking around 34" is about standard or used to be for a heavy ton and a half like a chip hauler size .

Tom picked up a dandy one ton Ford diesel side drop dumper this winter plus my neighbor landed a '02 Ford gasser for little of nothing with an 8 foot dumper .If I get a chance I'll measure the frame width .

 

[brendonv]

Chassis cabs are 34 al, I have one. The guy is measuring the dually pickup frame for me, but I do think they are about eight inches wider.

 

[RopeArmour]

I see that cab and chassis is usaually a level frame front to back and
the other steps down from the cab to box.
Mine needed to be built up with few supports to take a dump box.

 

[brendonv]

FWIW, the frame is about 5" wider on a dually pickup compared to a dually cab and chassis. The guy measured for me.

 

[Evan Sussman]

I believe with the same make, the axles are the same width, but the brake drums are wider and set in further with dual rear wheels. Duals can handle more weight....theoretically twice the amount, tires last longer, and you can drive with one flat.

This just came up in conversation with a friend recently. He adamantly stated that dual wheels do not increase your capacity. Your axle is the limiting factor, and usually it's the same axle, unless someone bought the axle upgrade. You do however benefit from increased stability, reduced tire wear, more traction, and a backup tire if one blows. If you look on the side of a truck tire I've usually seen two ratings, one for single and one for dual. Notice it isn't twice the capacity when used as a dually.

 

[Pelorus]

I think you end up with less traction with duals.

 

[lumberjack]

I've yet to see a single tire that would fit on my F550 that would have a 6800lb rating, thus it has dual rear wheels. No point in designing an axle to take more weight than the tires can handle. Thus you have different axles/configurations in a SRW F350 and a DRW F350/550.

I don't understand your point regarding tire weight ratings in single vs dual applications.


How do you end up with less traction? I'd say it's situationally dependent.

 

[Evan Sussman]

I've yet to see a single tire that would fit on my F550 that would have a 6800lb rating, thus it has dual rear wheels. No point in designing an axle to take more weight than the tires can handle. Thus you have different axles/configurations in a SRW F350 and a DRW F350/550.

I don't understand your point regarding tire weight ratings in single vs dual applications.


How do you end up with less traction? I'd say it's situationally dependent.

RE:traction, situation dependent makes sense, definitely more rubber on the ground on pavement, and your weight is spread out on soft ground. how would it be worse? if I wasn't clear, I meant I thought dually would be better traction.

RE: weight capacity, my tires say "3042lbs single, and 2778 dual" so I just meant it's not quite twice the capacity. As I think about it lumberjack, I think you're right, my friend must've had something else in his head, or is just wrong. What's your first name lumberjack? I'm Evan.

 

[lumberjack]

My traction comment was towards Pelorus. I would figure in icy conditions that duals, which have a lessor contact pressure, would do worse than a higher loaded single.

Regarding the weight capacity, usually there's a 5-10% difference. This difference is in part to increase the safety factor of the dual assembly as the tires rarely share the load evenly. Picture a road with an exaggerated crown, for example.

Sometimes a specific configuration of an axle's build (for example a GM 14 bolt) could be rated at a higher figure (say 10klbs), but in a SRW it's impractical to have tires to carry that load. Thus the axle is derated to suit the application and the tires commonly available for it.


I'm Carl Rutherford, pleased to meet you.

 

[Pelorus]

All things being equal, I think duals will provide better flotation = less ground pressure = less traction. If you are a swamp logger flotation might be more of a concern.

 

[brendonv]

Singles are better in snow than duals.

 

[lumberjack]

The coefficient of friction side of traction is irrespective of psi loading. However, higher contact pressures promote a mechanical interface between the tire and the surface. On a smooth, dry surface with equal weight and tires, there's no advantage SRW or DRW.

 

[CurSedVoyce]

add several thou and I bet that changes.....

 

[lumberjack]

Not if it's the same weight on the dually or srw. This is all theoretical in that it's situationally dependent, and excluding ice, largely unimportant from my perspective. It's more common for my trucks to sink in than it is for them to spin on top of the ground.

 

[Evan Sussman]

Pleased to meet you too Carl.

I was just reading a thread after searching the web about this question. It seems to be totally situationally dependent. Personally I think/feel like for my need of getting into and out of peoples yards the duallys are more suitable. For off roading when you can get through the slop to hard ground the singles are gonna be better. Most of the time I just wanna be in 4low creeping out and avoiding the spin, but I could see how single would definitely be better on ice.

 

[Evan Sussman]

http://www.steelsoldiers.com/showthread.php?34368-Traction-Super-Singles-or-Duals

Here's the thread, its an interesting read.