Learning trucks! Single axle vs tandem or double axle truck?

salespitch1100

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Feb 13, 2015
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Sorry if this is like asking if a Corvette has a V8 in it or not but what are the main differences between single vs tandem or double axle semis? I already used the forum search and google just gives me a bunch of for-sale websites.

How much does a single axle truck weigh usually? Just the truck

What is the max weight a single axle can successfully haul? What the math and paper says is usually not the real world result, you know

Do single axle trucks get better MPG than tandem? Im guessing yes since they are lighter but Im still learning trucks.

What are the normal work applications for single axle trucks? I noticed the difference in HP in some single axle trucks are big, like 330 vs 425 so it looks like theres some variety to this.

Im trying to figure out if we can move away from tandem double axle trucks to single. Small operation, we haul just dry freight locally in regular 53 foot trailers so total axles would be 4. Sometimes the max freight weight is 30-40,000lbs Thanks forum members.
 
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Injun

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Single-screw trucks are most often used in hauling doubles or pup trailers.

Tandem axles can be used for almost everything except some oversize/overweight loads. My drive axles each have a capacity of 20,000, which gives me 40,000 capability. I won't load more than 34,000 on my drives, which is pretty standard.
 
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salespitch1100

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Single-screw trucks are most often used in hauling doubles or pup trailers.

Tandem axles can be used for almost everything except some oversize/overweight loads. My drive axles each have a capacity of 20,000, which gives me 40,000 capability. I won't load more than 34,000 on my drives, which is pretty standard.

Thanks for your reply Injun. So that 20,000lbs per drive axle = 40,000 lbs plus 20,000 for the truck plus 10,000 for the trailer comes out to 70,000 lbs

Sooo if a single axle truck has a gvw of up to 65,000lbs, trailer weighs 10,000 to 12,000 and if the truck weights about 20,000, that means it can haul up to 35,000lbs? How can a single drive axle haul that much?
 
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Injun

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Thanks for your reply Injun. Is that 20,000lbs per axle for all axles behind the very first axle on your truck? That would be 4 axles x 20 = the 80,000lbs?

Sooo if a single axle truck has a gvw of up to 65,000lbs, trailer weighs 10,000 to 12,000 and if the truck weights about 20,000, that means it can haul up to 35,000lbs? That comes out to 17,000 per axle? Is my math ok here?
For legal weights, it's 12,000 on steers, 34,000 on each set of drive and trailer tandem axles.

It gets a little more complicated for spread axle trailers, but not much.
 
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salespitch1100

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I don't know what a single-screw can haul. I have no experience there.

Thanks. I edited my post right before you replied. I'll have to do more searching but if its close to 12,000lbs per steer and 20,000lbs for a single drive axle = 32,000lbs + 34,000 tandem trailer axle = 66,000 lbs, pretty much the max GVW.

So my question has become, how much does a single axle "screw" cab truck weigh?

I'll need to verify of course. Any other input is welcome!
 
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Duck

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why some other trucks has double axle and some don't?
Single drive axle tractors are for hauling pup trailers. Sometimes they pull full length 53 footers but they're light or empty.

You can legally only put 20,000 lbs on a single axle, and only if the axle & tires are rated for it. (they usually are, if it's a drive axle).

If you've got 30-40k in freight weight, unless it's all in the tail, you'll be over 20k on the drive axle. So keep the twin drive axles. Not just for legal reasons but because the equipment simply can't handle it & it's unsafe.

I pulled a loaded 53 footer with a single screw tractor once. It didn't feel safe. I could feel the tire sidewalls flexing & knew if I had a blowout, it would potentially jackknife easily.


That being said, most yard jockey trucks have a single drive axle, but move fully loaded 53 footers around all day, every day.

This is because they remain on private property and don't go very fast. In their case, they're constantly making tight turns while backing trailers into spaces in the yard,which is easier to do with a single drive axle.
 
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gearjammer

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another way to go is with a drop axle in place of one of the drive axle's which would then give you the capability same as a regular tandem and the versatility of raising it when not needed saving fuel, sometimes tolls, maintenance costs ect.
I have had two trucks with this set up and loved it
 
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The setup with a liftable axle, on a 3 axle tractor, is what is most common here in Scandinavia, as to tandem configurations.

There's 2 variations with each their forces. You can have the liftable axle in front of your traction axle (we call that a Pusher axle), with or without additional steering. The pro's for this setup is that it's easier to load your steering axle to max load, and when driving empty, or a light load with the axle lifted, the ride is more steady, hence a longer distance between the axles. What speaaks against this setup - you don't have to much weight on your drive axle for driving in winter conditions.

The other option, is to have the liftable axle at the very rear, (we call that a Bogie axle) this axle doesn't come with steering. You can have it with double mounted tires, or with super singles. I have this setup on my truck, and prefer it to the Pusher axle, because I drive for 6 - 8 months a year in severe winter conditions, and the Bogie axle configuration, applies roughly 2 - 3 Metric Ton more pressure to the traction axle, when empty, and the Bogie axle is lifted. Also, the Bogie axle truck can vitually turn on a plate, since the kingpin is set behind the traction axle. In extreme conditions, fully loaded, I can forcelift the Bogie axle, and my Traction axle then applies roughly 20 ton to the ice or snow, this has to be used with caution, since the steering becomes VERY light ;)

I won't go too much into weights and such, since our weight limits are different from yours in the US.
You see my setup on the picture below, 1 metric ton = 2204 Lbs
Front axle 8 ton, traction and Bogie axle 18 ton, and the 3 axles on the trailer may weigh 24 together.

I hope the above made a little sence to you ;)
 
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