2006-07-12 03:25:05 · 12 answers · asked by Anonymous in Cars & Transportation ➔ Other - Cars & Transportation
Those trucks have what is known as "drop axles", There are weight limits on the highway, and trucks can not exceed that total weight. There is also a limit as to how much weight can be on any one axle. These weight limits are to keep the roads from being damaged.
The driver can raise or lower the extra axle, depending on the amount of weight they are carrying. If the truck is empty, or has a light load, they keep the axle up. If it is fully loaded they lower the axle, to spread the weight over more axles, and avoid being the axle weight limit!
2006-07-12 03:55:30 · answer #1 · answered by fire4511 7 · 4⤊ 1⤋
To allow it to be loaded. Each set of axles and wheels (up to a point) allows more weight to be carried by the vehicle. Of course having the tires on the ground constantly means wear and tear on the tires, so it makes sense to have them off the ground until they are needed. You will find them on garbage trucks for example, as they load on their route and reach a certain weight, the extra wheels will be used to help support the load.
2006-07-12 03:31:13 · answer #2 · answered by oklatom 7 · 0⤊ 0⤋
Has to do with the number of axles and wheels on the ground. They only crank down the wheels when they need it to legally carry the load.
2006-07-12 03:31:22 · answer #3 · answered by Anonymous · 0⤊ 0⤋
they are extra axles for use when more axles are needed to stay within legal load limits as determined by state laws depending on total gross weight some states allow heaver total gross weights depending on the number of axles also some secondary roads require more axles to carry the same loads ( especially in winter months with freezing and thawing of roadways) the axles are operated by air bags which can be raised or lowered by the operator with air controls and pressure Gage in cab of truck
2006-07-12 08:45:15 · answer #4 · answered by louise m 3 · 0⤊ 0⤋
When the weight reaches the amount required for the extra wheels they are used
2006-07-12 03:29:22 · answer #5 · answered by George O 1 · 0⤊ 0⤋
They lower to the road for a heavier load, but they raise them up to save on toll roads where they charge per axle. Save some tire wear and tire friction too for MPG when not needed as well.
2006-07-12 03:31:26 · answer #6 · answered by rkfire 3 · 0⤊ 0⤋
I think just as a spare. You know that the wheels can blow out (mostly depending on the quality/miles driven). The spares allow them to keep on truckin. HAHAHA I crack myself up....you didn't catch that did you? Keep on truckin....the song....never mind.
2006-07-12 03:29:28 · answer #7 · answered by lilsedalemami 3 · 0⤊ 0⤋
extra heavy loads
2006-07-12 03:29:33 · answer #8 · answered by jay 7 · 0⤊ 0⤋
they are adjustable and can be used when the truck is very heavy... notice they are usually on dump-trucks and the likes...
2006-07-12 03:29:41 · answer #9 · answered by Jonny Propaganda 4 · 0⤊ 0⤋
they are for times when the trucks carry heavier loads
2006-07-12 03:28:42 · answer #10 · answered by Anonymous · 0⤊ 0⤋