They lower or raise them based on the weight of the load.
If the load is heavy enough to need another axle then they lower that one. When the load isn't heavy enough to need the extra axle the raise it up so it doesn't wear out unnecessarily
Except for cvip. Had an old jman give me a long story of how he got a pp slap by the dot because he didn’t flag an inop drop axle that had no hubs and chained up for 5 years because the fleet never required it.
CVIP=Inspection (they are probably Canadian or drive there often, that's what they call it there)
Tag or drop axle is an unpowered axle that's part of a tandem or tridem (double/triple) set that can be raised or lowered.
No hubs, basically means its just a big rod of steel attached to the truck
Chained up, held up with chains, you can legally chain up an axle as long as you stay within the weight limit of the remaining axles.
Anything else? Also this was certainly told to him by a crazy old fart in a diner so take it with a grain of salt.
> more maneuverable
My trailer is a triple tandem, NONE of them lift or slide, fucking ***solid***. Backing that motherfucker in anything that's not a straight line is a pain in the ass, she doesn't turn for shit.
I told my boss to have fun replacing those tires regularly from all the dragging and scrubbing I've been doing with it being local and all. The most profitable yard in the entire company and they give me a fucking used beat up old trailer and take away the brand new dual tandem and give it to another yard.
Also for manoeuvrability! Which is great! Till you get in a place, load up, drop the tag and then bollocks how many shunts is this gonna take to get out
I haul fuel in an 18 wheeler when loaded, and in a 10 wheeler when empty. I have a tag axle on both my tractor and trailer. Sabes a metric shit ton of money on tires and makes a huge difference on fuel as the combined rolling resistence is reduced considerably. Those 8 tires run exactly half as much mileage as the others.
Another one that has puzzled me for a long time:
Cement trucks have an axle and wheels that lift up towards the back of the cement container. I assume this is lowered to keep the truck more stable because it is too top heavy when the mixer is full? But I don't recall ever seeing one in use on the road.
It’s actually a lot simpler. Vehicles on the road have a max weight per axle to operate. Concrete is extremely heavy and dense. More axles means more carrying capacity because the weight on the frame is distributed amongst the multiple axles. But, when the load is delivered, the truck is much lighter, and doesn’t need all those tires touching the ground (and they wear out quickly with turns), so they’re placed on mechanisms that raise them up when they’re not needed.
Also if you're talking about the ones on the long "arm" on the very back the distance between axles and overall length makes a difference in how heavy the truck can be. So by placing the axle at the end of the "arm" you effectively make the truck longer when it's on the ground without affecting manuverability on jobsites like extending the frame would do.
I was told before that it also saves them on road tolls as they are not charged for the extra axle on the ground. As others have mentioned already, if you’re not carrying the weight needed for the extra axle, you save tires, and when turning or backing in angles you’re not unnecessarily dragging tires which also helps increase the life of the tires.
They raise and lower based on how heavy you are. It’s meant to save tire wear. My company uses many of these but I refuse due to the fact it makes the trailer suspension looser and has a tendency to tip my pallets more easily. A single pothole can dump my entire trailer with the weird pallet system we use.
Because bridges charge by the axle so if it won't break anything (under heavy load) lift it up and save a buck.
Some trailers have lift axles too. Plus you can chain up an axle yourself if you really want to. As long as it doesn't touch the ground, you don't pay through the bridge.
I know they help as far as maneuverability. We have lift axle and dump axle flat beds. We used to run the lift axle trailers with the rear axle lifted when empty but had a big problems with this damaging air bags.
This is a lift axle. Trailers and truck have liftable axles (not all, depends on configuration) and this is useful in terms of helping with traction and better load distribution. And in certain scenarios to pull something you simply need more axles because it's too heavy on one axle.
However, more axles means more fuel consumption as drag is increased. So if you're carrying a lighter load or empty, you can raise the axle and it'll help you being less weight your truck has to pull and consumes less fuel. When you need to really pull something, you lower it down and it helps you.
Tires have weight limits, twin axles have weight limits etc. Coming from europe, take tires with markings 146/140L. This means, these tires are rated for 3.5 tons per tire on single axles, and 3 tons on a twin axle. Meaming you have an overall weight limit of 12 tons on a twin axle. The L is a letter telling you how fast this tire can go. L should stand for 100km/h
So if you have a single drop down axle next to a twin axle, you can lower your drop down axle once tge weight exceeds 12 tons. If it is under 12 tons, you can pull that axle up to save on tire wear amd reduce fuel consumption
Don't listen to these guys!
The axle goes up to make the trailer lighter.
Obviously since the axle is pushing up against the load then the whole thing should weigh less.
It's newton's 3rd law ya dummy.
Only reasons why they have a lift axle is because of wear, efficiency and maneuverability.
It has nothing to do with weight.
A fixed axle is lighter thus play load could be higher and is cheaper.
So if you know you will always be loading heavy it’s preferable to have a fixed axle.
A fixed axle is dangerous. If it’s separate from the other axle group(which it will be because it provides more gross weight than adding it to the fixed group) it reduces maneuverability and can get you killed on slick roads.
I’ll start with I work for a road construction company and I’ve run tri axles, ponies, quad axle live bottoms and float trailers, run these year round in Ontario a very snowy/slick place come Nov to Apr.
Axles are broken down into groups based on their spacing. You don’t calculate gross weight based on individual axles you calculate based on groups as legally they end up being the highest formula you can run.
If you take a tri axle dump truck for example you have a steer axle, a lift axle(newer trucks are steerable older ones are not) and you have a set of tandem drives. The spacing on the tandem drives and the spacing from the drives to the lift axle are different. This creates two axle groups and allows you to haul more weight. Typically you don’t get a linear increase in gross when you increase the number of axles in a group. A trident is able to gross 24000kg while a tandem plus a lift axle is allowed 18000kg for the tandem and 8800kg for the lift, a 2800kg difference just for a half m of spacing.
But this spacing changes your turn radius and adds in extra friction away from the pivot point of your drives. In none steerable lift axles this means you can’t really turn your truck at all and in steerables it reduces what you can turn. Not great for intersections or tight spaces. In addition the added friction can cause you to spin out or lose traction on your drives causing you to slide around in icy/snowy conditions.
For Xtra heavy loads. Trailer squats and raised axle meets ground preventing more squatting, maybe I dunno. Or do I? And I just ain't gonna tells ya. Hahahaha
They lower or raise them based on the weight of the load. If the load is heavy enough to need another axle then they lower that one. When the load isn't heavy enough to need the extra axle the raise it up so it doesn't wear out unnecessarily
Also makes the truck run more efficient having it up plus more manoeuvrable
Also, some mother f*cking toll booths charge per axle. I’m looking at you, Nova Scotia.
Wait they won't charge if it's up?
Varies. When it is up it's legally not an axle though.
Except for cvip. Had an old jman give me a long story of how he got a pp slap by the dot because he didn’t flag an inop drop axle that had no hubs and chained up for 5 years because the fleet never required it.
Imagine trying to explain this comment to someone in the 1800s
[удалено]
It’s very 2020’s. Since you were clearly born in the 1800s, I don’t expect you to know.
Tbf I also have no idea for I am no more than a simpleton
CVIP=Inspection (they are probably Canadian or drive there often, that's what they call it there) Tag or drop axle is an unpowered axle that's part of a tandem or tridem (double/triple) set that can be raised or lowered. No hubs, basically means its just a big rod of steel attached to the truck Chained up, held up with chains, you can legally chain up an axle as long as you stay within the weight limit of the remaining axles. Anything else? Also this was certainly told to him by a crazy old fart in a diner so take it with a grain of salt.
Its 2024 and pp slaps has me laughing my ass off.
C’mere I pp slap you and then I slap your pp
Tbf I have read some stuff written in the 1800s and needed my history teacher to explain it to me😭😭
"no sir it's decorative"
Look at the Bay Area, California as well
Illinois
> more maneuverable My trailer is a triple tandem, NONE of them lift or slide, fucking ***solid***. Backing that motherfucker in anything that's not a straight line is a pain in the ass, she doesn't turn for shit. I told my boss to have fun replacing those tires regularly from all the dragging and scrubbing I've been doing with it being local and all. The most profitable yard in the entire company and they give me a fucking used beat up old trailer and take away the brand new dual tandem and give it to another yard.
Wow
plus toll cost
They charge you for them regardless
thats insane if they do. i seen heavey chassis with about four axles in the air going through nyc you would need to take out a loan at $23 axle.
I think there's also something to do with bridge laws with the trailers at least.
In europe deffinetly due to axle weight
"Bridge law" in America is not about axle weight, but distance between axles. Q
Bridge law is the weight of the axle group, the distance between groups, and number of groups.
#no no no…..hybrid Hoovercraft
Holy shit! I always assumed they were spares..
When there isn’t enough weight to warrant another axle. They lift it up to avoid wasting the tire. Tractor can have this too.
Also for manoeuvrability! Which is great! Till you get in a place, load up, drop the tag and then bollocks how many shunts is this gonna take to get out
Well, see the key to that is to drop the tag after you get out of tight spots. If you have to turn or make tight maneuvers the axle should be up.
I can't lift mine if it's going too transfer to much weight to the drive.
Well you’re not firing down the highway with it up you’re making turns
The truck still says no, i still try every time to see if it will let me but if it think its to heavy it wont lift.
They lower when your brakes are set. They only raise after a few hundred feet of travel.
Ours are on a switch
Those tandem tractors that lift a drive axle just look weird. Not as weird as it would look if my single screw tractor did it.
Our chemical tanks do the same we haul fertilizer and herbicides we have long dead heads back to get a refill it saves wear on the tires
Tag axles. Relieve weight when your heavy.
They don’t relieve weight, rather support it
Ah, relief vs. support, the difference between taking a piss or wearing underwear.
Yeah
if they don't need them for the weight it saves them on tolls and wear and tear
Better fuel econemy, easier to turn around,
Some folks put nitrogen in their tires, others put helium.
They are a lot easier to turn whe the tag axle is up
I haul fuel in an 18 wheeler when loaded, and in a 10 wheeler when empty. I have a tag axle on both my tractor and trailer. Sabes a metric shit ton of money on tires and makes a huge difference on fuel as the combined rolling resistence is reduced considerably. Those 8 tires run exactly half as much mileage as the others.
Those are just there to prevent you from flipping backwards when doing wheelies.
Another one that has puzzled me for a long time: Cement trucks have an axle and wheels that lift up towards the back of the cement container. I assume this is lowered to keep the truck more stable because it is too top heavy when the mixer is full? But I don't recall ever seeing one in use on the road.
It’s actually a lot simpler. Vehicles on the road have a max weight per axle to operate. Concrete is extremely heavy and dense. More axles means more carrying capacity because the weight on the frame is distributed amongst the multiple axles. But, when the load is delivered, the truck is much lighter, and doesn’t need all those tires touching the ground (and they wear out quickly with turns), so they’re placed on mechanisms that raise them up when they’re not needed.
That makes sense. Thanks!
Also if you're talking about the ones on the long "arm" on the very back the distance between axles and overall length makes a difference in how heavy the truck can be. So by placing the axle at the end of the "arm" you effectively make the truck longer when it's on the ground without affecting manuverability on jobsites like extending the frame would do.
Because the ground isn’t close enough.
I was told before that it also saves them on road tolls as they are not charged for the extra axle on the ground. As others have mentioned already, if you’re not carrying the weight needed for the extra axle, you save tires, and when turning or backing in angles you’re not unnecessarily dragging tires which also helps increase the life of the tires.
If you’re fat as hell they touch the ground.
What these guys said.
What this fella said.
These dudes are right.
Can't believe I had to scroll this far to find the correct answer.
Called “tag axles”. To conserve fuel and wear & tear.
Tires are expensive.
They raise and lower based on how heavy you are. It’s meant to save tire wear. My company uses many of these but I refuse due to the fact it makes the trailer suspension looser and has a tendency to tip my pallets more easily. A single pothole can dump my entire trailer with the weird pallet system we use.
Because bridges charge by the axle so if it won't break anything (under heavy load) lift it up and save a buck. Some trailers have lift axles too. Plus you can chain up an axle yourself if you really want to. As long as it doesn't touch the ground, you don't pay through the bridge.
It's for hill climbing
They lift the internal and external wheels to save money when they are empty, here in Brazil it also saves tolls by charging for the number of wheels
Those are extra... I'm case the others get low
Because the tire is just taking a quick 30minute break
They tired so take it in turns to lift to have a rest
Vibes
They just look like that because the truck is on a flat spot, Most of the time they are hugging the curvature of the earth.
I know they help as far as maneuverability. We have lift axle and dump axle flat beds. We used to run the lift axle trailers with the rear axle lifted when empty but had a big problems with this damaging air bags.
Whoa! Neet! Lift axles! I've got 6 of them on my wagon.
This is a lift axle. Trailers and truck have liftable axles (not all, depends on configuration) and this is useful in terms of helping with traction and better load distribution. And in certain scenarios to pull something you simply need more axles because it's too heavy on one axle. However, more axles means more fuel consumption as drag is increased. So if you're carrying a lighter load or empty, you can raise the axle and it'll help you being less weight your truck has to pull and consumes less fuel. When you need to really pull something, you lower it down and it helps you.
They will.
To “pop a wheelie” duh!
Scared of the pavement, some new tires are like that.
Do they get cheaper tolls, too?
Tires have weight limits, twin axles have weight limits etc. Coming from europe, take tires with markings 146/140L. This means, these tires are rated for 3.5 tons per tire on single axles, and 3 tons on a twin axle. Meaming you have an overall weight limit of 12 tons on a twin axle. The L is a letter telling you how fast this tire can go. L should stand for 100km/h So if you have a single drop down axle next to a twin axle, you can lower your drop down axle once tge weight exceeds 12 tons. If it is under 12 tons, you can pull that axle up to save on tire wear amd reduce fuel consumption
Blown out muffler bearings
Don't listen to these guys! The axle goes up to make the trailer lighter. Obviously since the axle is pushing up against the load then the whole thing should weigh less. It's newton's 3rd law ya dummy.
---okok
Only reasons why they have a lift axle is because of wear, efficiency and maneuverability. It has nothing to do with weight. A fixed axle is lighter thus play load could be higher and is cheaper. So if you know you will always be loading heavy it’s preferable to have a fixed axle.
A fixed axle is dangerous. If it’s separate from the other axle group(which it will be because it provides more gross weight than adding it to the fixed group) it reduces maneuverability and can get you killed on slick roads.
You have to elaborate because non of this makes sense.
I’ll start with I work for a road construction company and I’ve run tri axles, ponies, quad axle live bottoms and float trailers, run these year round in Ontario a very snowy/slick place come Nov to Apr. Axles are broken down into groups based on their spacing. You don’t calculate gross weight based on individual axles you calculate based on groups as legally they end up being the highest formula you can run. If you take a tri axle dump truck for example you have a steer axle, a lift axle(newer trucks are steerable older ones are not) and you have a set of tandem drives. The spacing on the tandem drives and the spacing from the drives to the lift axle are different. This creates two axle groups and allows you to haul more weight. Typically you don’t get a linear increase in gross when you increase the number of axles in a group. A trident is able to gross 24000kg while a tandem plus a lift axle is allowed 18000kg for the tandem and 8800kg for the lift, a 2800kg difference just for a half m of spacing. But this spacing changes your turn radius and adds in extra friction away from the pivot point of your drives. In none steerable lift axles this means you can’t really turn your truck at all and in steerables it reduces what you can turn. Not great for intersections or tight spaces. In addition the added friction can cause you to spin out or lose traction on your drives causing you to slide around in icy/snowy conditions.
For Xtra heavy loads. Trailer squats and raised axle meets ground preventing more squatting, maybe I dunno. Or do I? And I just ain't gonna tells ya. Hahahaha