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I've wondered about this for years


Alpo

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One of y'all must know.

 

See the truck.

kenworth-t880-dump2_11175480.jpg

 

It is a ten-wheel truck. Two rear axles with dual wheels.

 

But notice, in front of the rear axles there is another wheel. This wheel is not on the ground, but is about six inches off the ground.

 

Are these wheels (there's one on each side) bolted to the chassis, and are spare tires? That kinda makes sense, except there are many other ten-wheelers running around without spares, and I've never seen a semi with a spare. I figgered if a big truck had a flat they called a wrecker. I know I'd hate to try to jack up a dump truck with 20 yards of sand in it, to change a tire. :unsure:

 

Or are they attached to a fourth axle, and they are only on the ground when there's a REAL heavy load in the truck? Kinda like wheelie wheels - they're up in the air until you NEED them?

 

And if neither of these idiotic ideas are their purpose, why are they there?

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They are for weight, they have hydrolics to raise and lower them

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Oh my Gawd. I researched this very question four days ago.

 

i think I have been alpo’d.

 

they have some kind of air bladder support so that inflating it puts the wheels on the road and allows them to meet weight regulations which are most important when crossing bridges.

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They allow the truck to carry a heavier load. I don't remember all the rules but each axle can only carry so much weight and that weight has to be spread across a certain area. There is a minimum distance required between each axle based on how much weight it is carrying.

On the truck I drove on the farm the 3rd axle was controlled by air pressure and was behind the driving tandem axles instead of in front. In addition to raising and lowering the amount of weight it was carrying could be adjusted as well. 

 

State and federal laws dictate how many and the configuration.

 

Here is a cement truck with a hydraulically controlled one in transition from use to stowage.

Image result for 3rd axle on cement truck

 

This one is the extreme

Pusher axles and the

 

Here is a good write up: Lift Axle Considerations

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Come on guys!  Those wheels are fakes.  The laws concerning how much weight a truck can carry are based on the number of axels. An extra axel will allow you to carry X number of more pounds per trip.  More pounds per trip, the more money in the truckers pocket. Many times the axels are merely chained to the truck body.  If you look at the tires, they are very small and never intended to touch the ground.

The concrete truck with the wheels out behind uses those wheels to carry a longer chute when necessary to get the mix into a tight job site.

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4 hours ago, Marshal Mo Hare, SASS #45984 said:

Oh my Gawd. I researched this very question four days ago.

 

i think I have been alpo’d.

 

they have some kind of air bladder support so that inflating it puts the wheels on the road and allows them to meet weight regulations which are most important when crossing bridges.

 

I have the same problem now, I have wondered the same thing as Alpo.................................................................  should I go speak to a doctor?

 

We now have a new Wire term- To be Alpo'd, To have privately considered a conundrum that has been, or soon is, posed publicly by Alpo. The inference being your conundrum is somewhat bizarre or worrying, but at least you kept it to yourself until outed by Alpo..   

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I always thought they were just used  to carry extra wheel nuts, in case you got a flat tire or two,  out on the vacant highway,

and lost one or two, while changing the tire. That said, you should see the size of those jacks they use. 

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5 hours ago, Marshal Mo Hare, SASS #45984 said:

Oh my Gawd. I researched this very question four days ago.

 

i think I have been alpo’d

Hangin' around me is rubbin' off.

 

'Fore you know it, you'll be droppin' Gs, sayin' Y'ALL, and misspellin' FIGURE.

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Another reason is for tax purposes. Owner pays more when 12 wheels are down than 10. At least in some states and yes Fed regulations designate how much weight you can carry per axle on the vehicle. When he hits the weight regulated for the two rear axle's he can lower the extra two wheels on the single axle and legally haul more weight per load. Thus he makes more money per haul since he is allowed to haul more load.

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4 hours ago, Noz said:

Come on guys!  Those wheels are fakes.  The laws concerning how much weight a truck can carry are based on the number of axels. An extra axel will allow you to carry X number of more pounds per trip.  More pounds per trip, the more money in the truckers pocket. Many times the axels are merely chained to the truck body.  If you look at the tires, they are very small and never intended to touch the ground.

The concrete truck with the wheels out behind uses those wheels to carry a longer chute when necessary to get the mix into a tight job site.

So what about this guy?:wacko:

sld-HH_232_75T.jpg

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10 hours ago, Alpo said:

One of y'all must know.

 

See the truck.

kenworth-t880-dump2_11175480.jpg

 

It is a ten-wheel truck. Two rear axles with dual wheels.

 

But notice, in front of the rear axles there is another wheel. This wheel is not on the ground, but is about six inches off the ground.

 

Are these wheels (there's one on each side) bolted to the chassis, and are spare tires? That kinda makes sense, except there are many other ten-wheelers running around without spares, and I've never seen a semi with a spare. I figgered if a big truck had a flat they called a wrecker. I know I'd hate to try to jack up a dump truck with 20 yards of sand in it, to change a tire. :unsure:

 

Or are they attached to a fourth axle, and they are only on the ground when there's a REAL heavy load in the truck? Kinda like wheelie wheels - they're up in the air until you NEED them?

 

And if neither of these idiotic ideas are their purpose, why are they there?

If it helps it is a new truck...They might advertising it to show how it will look in its surrounding...Does this give you the answer?

 

Texas Lizard

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They are training wheels for new drivers.  Actually they are used to carry more weight as has been said.  I have driven a four axle tractor a few times, have pulled three and four axel trailers a bunch.  The three axel trailers had three axels with duals, the four axel trailers were like the three axels with a drop axel on the back.  In this part of the country a standard three axel tractor and two axel trailer can gross 80,000 Lbs.  With a three axel tractor and four axel trailer I could go 95,500 Lbs.

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I work for company that builds straight-truck bodies, Class 4 thru 7.  These are the rental and delivery box and flatbeds.

The term that we use for the auxiliary axle is a tag axle.  Most are lowered or raised by hydraulic control on the back of the cab.

They are there to carry heavier loads.

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Strange, all the drop axles I have any experience with used air bags.  There is a switch in the cab to lower or raise, the regulator to control the pressure is outside so the driver can't change the "ground pressure" going over a scale.  The auxiliary axle behind the drivers or trailer axles is indeed a tag, but what to call one in front off the drivers... that's why I just refer to them as drop.

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On 1/4/2019 at 10:31 AM, Alpo said:

One of y'all must know.

 

See the truck.

kenworth-t880-dump2_11175480.jpg

 

It is a ten-wheel truck. Two rear axles with dual wheels.

 

But notice, in front of the rear axles there is another wheel. This wheel is not on the ground, but is about six inches off the ground.

 

Are these wheels (there's one on each side) bolted to the chassis, and are spare tires? That kinda makes sense, except there are many other ten-wheelers running around without spares, and I've never seen a semi with a spare. I figgered if a big truck had a flat they called a wrecker. I know I'd hate to try to jack up a dump truck with 20 yards of sand in it, to change a tire. :unsure:

 

Or are they attached to a fourth axle, and they are only on the ground when there's a REAL heavy load in the truck? Kinda like wheelie wheels - they're up in the air until you NEED them?

 

And if neither of these idiotic ideas are their purpose, why are they there?

 

did note they have mud flaps in front and behind the raised wheel

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Very common on trash trucks.

They will 'drop' when the trucks axle weight sensors say to, or can be controlled by the driver.

They do steer a bit when turning.

Drove many rigs with'em when haul'n for Uncle Sugar.

OLG

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On 1/4/2019 at 8:33 AM, The Shoer 27979 said:

They are for weight, they have hydrolics to raise and lower them

What he said.

 

Hang on a sec...you have wondered this for years and are just now getting around to asking? Are you feeling all right? :D

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That's exactly it.

 

I'll see or read or hear something, and think, "I wonder...", which causes that to get stuffed in a folder in the I WONDER file, in the corner of my brain.

 

Occasionally I'll think of it again, and the file folder gets pulled, and another copy of I WONDER gets put in it.

 

Some of them file folders been in there twenty, thirty years or more, and have a couple dozen I WONDERs stuck in them. But I just ain't got 'round to checking.

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Around  Ohio, they are called cheater axles. Heard of an outfit in Michigan that hauled steel. They had a huge bow built in the flatbeds and when they drove by the patrol, they would just raise the air tags.

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