2006-10-11 03:48:26 · 20 answers · asked by Anonymous in Cars & Transportation ➔ Other - Cars & Transportation
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.
2006-10-11 03:51:56 · answer #1 · answered by Rich Z 7 · 0⤊ 0⤋
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.
2006-10-11 10:54:52 · answer #2 · answered by Ricky 6 · 0⤊ 0⤋
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.
2006-10-11 10:59:56 · answer #3 · answered by Julian E 1 · 0⤊ 0⤋
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.
2006-10-11 10:56:30 · answer #4 · answered by Mike D 3 · 0⤊ 0⤋
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!
2006-10-11 10:58:40 · answer #5 · answered by Turbot Face 2 · 0⤊ 0⤋
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.
2006-10-11 10:51:43 · answer #6 · answered by tracey c 2 · 0⤊ 0⤋
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
2006-10-11 13:42:36 · answer #7 · answered by Roy S 5 · 0⤊ 0⤋
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.!
2006-10-11 11:02:42 · answer #8 · answered by Anonymous · 0⤊ 0⤋
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.
2006-10-11 10:58:44 · answer #9 · answered by Anonymous · 0⤊ 0⤋
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.
2006-10-11 11:40:12 · answer #10 · answered by anthony e 2 · 0⤊ 0⤋