What are the two tires on the back of Cement trucks for?

Question

I've always wondered why there were two tires on the back of cement trucks.. anyone know the reason?

Answer 1

SUPPORT FOR THE TROUGH POURING THE CEMENT TO PROPER LOCATION

Answer 2

That is called a "booster", the laws regulate how much weight can be carried on the 3 axles of the truck. By lowering the "booster" and using the hydraulic rams to push down on the road the 2 booster tires can carry some of the weight. This allows the truck to legally carry more concrete per load. That is why you see the booster wheels in the "up" position sometimes, the truck is either empty or not carrying a full load so the extra capacity is not needed.

Good question!

Answer 3

a greater load to carry, more wheels to carry the load.  

Answer 4

I'm an automotive engineer and the reason is to carry the heavy weight of the truck, and by the way it can be seen also at any other big trucks like gas trucks...etc

also there is another reason which is the main reason that it increases the traction force, and what is the traction force?

it's the ability to transfer engine torque and translate it to a drag force through the wheel contact with the road

that's why in some racing cars like porsche the wheel width is big just to increase the ability to transfer the high torque of the engine to translate it to acceleration and speed

another reason is to make the motion safer, increases stability

so in brief:

1- To increase the traction

2- To increase the stability

3- To overcome the weight of the truck with load