Why are lorries sometimes driven with one set of wheels raised ?
Answers:
In order to meet the government axle loading requirements when they are heavily loaded they have to drop down the extra axle and drive on more wheels. When they are not as full they pickup that axle to avoid wear on those wheels.
I always thought they were the spares.
there is no weight on the lorry
and it saves on wear and tear on the tyres aswell
i think its for two reasons
as spares and for overload
It depends on how much weight the lorry is carrying. If has a heavy load then it will need to put down the extra wheels.
Fuel economy
just because they are only used when the lorry is full and needs a better weight distribution
Saves tyre wear!
These lorries or trucks are built for very heavy payloads,
so they need the extra axle and wheels to support the load
and not damage the vehicle and the road surface. When
fully laden the extra axle is lowered to distribute the weight
and relieve the pressure of all the wheels. When empty,
the extra axle and wheels are not needed and would only
waste and have a shorter life, so they are lifted. Also you
should consider that the extra axle, will only increase drag
and increase fuel consumption if not lifted. A further
consideration would be a road tax relief when the extra
axle is up.
Lorry Tyre's are expensive. Without a load, the wheels are retracted to save wear and tear and of course money. It is also better for the environment and makes the vehicle more maneuverable.
unloaded it doesnt need all the wheels to spread the load. and if you had to buy tyres, you'd want to keep them off the roads for as long as you could.
an average HGV can go thru tyres in 50000 miles, or less, and your lorry does, 350000 a year, as its never allowed to go cold. and each tyre is around 200 quid.
It is to do with Road Tax. It is cheaper to tax a vehicle with 6 axles running at 44 tonnes than it is for 5 axles. The reasons for this is that the load is more spread out over 6 axles than 5. Therefore less damage to the road. When the vehicle has dropped his load and is running back empty. The extra axle can be raised, thus saving tyre wear and increasing fuel economy!
They are attached to overload springs. When the load is light or the truck is empty, the wheels will rise up enough to clear the road surface. When loaded, the weight will bear down lowering the wheels permitting them to carry part of the load.
If the lorry is unladen - to save wear on the tyres especially when cornering and to reduce fuel consumption (by increased friction) - they raise the wheels using a built in system. if fully laden the extra wheels spread the load and help with grip etc.
To save tyre wear when they are unladen
Heavy trucks with multiple axals need all the wheels on the ground when they are loaded to carry the weight safely but this causes tyre wear and truck tyres are expensive so to save money on tyre wear one or more axals are lifted off the ground when the vehicle is empty.!
The wheels are raised to reduce fuel consumtion and tyre wear.
The rear suspension geometry characteristic is also changed by this action to allow less shock absorber reaction, reducing wheel bounce when unladen , which improves roadholding and handling.
to preserve the tyres
To save on tyre wear.
Nobody seems to notice but lorries with multiple axles really tear up the roads as one set is being dragged round against the other.
You should have seem the loading yard of our works when it was hot and the tarmac soft they piled it up in heaps!
RoyS
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