I’m just wondering why you see some units (mainly tankers) with a tiny lift axle wheel? I’ve been told by a driver that its simply a weight saver, but a tanker only fits x amount in it weather you shed weight elsewhere or not, can anyone shed any light on it just out of interest
they save a bit of weight, they also make room for larger fuel tanks.
someone on here once said to a women that they were stabilisers for new drivers. it still cracks me up. 
The lighter the truck and trailer the more cargo you can carry.
Or am I missing something?
It is simply a weight saver, but to say that a tanker only fits x amount in is missing the point. Liquids and amounts carried are governed by specific gravity (sg), so, a 36000 ltr tanker filled with eg Acetone would gross at 42 to 44 tonne (a quick guess btw) whereas 36000 ltrs of Nitric acid would have the same vehicle grossing off at over 60 tonne! ( again a quick guess for example). It is worth bearing in mind that on many (but by no means all) occasions tankers are loaded to max out their weight, so 500kg shaved off an axle is 500kg more (paying) payload.
A full tank of polystyrene granules weighs less than a full tank of milk powder.
It`s surprising how many tanker firms have small lift axles to increase payload, then go down the big engine, donkey engine route.
dowahdiddyman:
It`s surprising how many tanker firms have small lift axles to increase payload, then go down the big engine, donkey engine route.
i used to drive a unit with a smaller mid lift and pull tankers that had donkey engines, the customer owned the tanks and spec’d them that way for flexibility of easily getting a unit to do deliveries if needed.
and the the unit was spec’d that way for bulker work originally anyway!
Ah I understand it now! It always baffled me 
Derf:
A full tank of polystyrene granules weighs less than a full tank of milk powder.
what weighs more. A ton of lead? or a ton of feathers?
limeyphil:
they save a bit of weight, they also make room for larger fuel tanks.
someone on here once said to a women that they were stabilisers for new drivers. it still cracks me up.
gotta try that on someone!!
Sometimes they r also specced that way to fit the blowing equipment on the side of the chassis aswell as a larger fuel tank
Derf:
A full tank of polystyrene granules weighs less than a full tank of milk powder.
No it doesn’t!
Milk powder weighs 449kg/m3, and Polystyrene granules weigh between 550 and 670 kg/m3 depending on grade.
If by Polystyrene you mean EPS, the stuff your new washing machine comes packed in, that is carried in unexpanded form, in Octobins, its never moved expanded. It doesn’t go in tanks because the Pentane gas within the granules, which makes them go pop when heated leaches out all the time and makes it highly volatile. This puts it under ADR but also means that even carried under Nitrogen, it would be potentially very exciting to try blowing it under pressure.