A question for Lorry Drivers!

Oracle · 20 Mar 2006 at 11:34

What are the wheels on the trucks (and sometimes the trailers), full wheels, that are raised up into the arches.

Can you tell me what they are for and in what circumstances they might be used.

Is it an axle load soultion?

Thanks

kaiowas · 20 Mar 2006 at 11:36

Oracle said:
Is it a axle load soultion?

Thanks

Yup. They're retracted whenever possible to reduce rolling resistance and therefore running costs but can be lowered to the ground when you've got a heavy load.

Oracle · 20 Mar 2006 at 11:36

are they driven? Or just rolling!?

kaiowas · 20 Mar 2006 at 11:41

Oracle said:
are they driven? Or just rolling!?

Pretty sure they'd just be freewheeling

Sputnik II · 20 Mar 2006 at 13:24

Oracle said:
What are the wheels on the trucks (and sometimes the trailers), full wheels, that are raised up into the arches.

Can you tell me what they are for and in what circumstances they might be used.

Is it an axle load soultion?

Thanks

What you are refering to is quite often known as the 'drop axle', It's to prevent the Front and rear axle on the tractive unit from being overloaded when either the trailer is 'nose heavy' or when carrying the maximum permissible weight.
They are used because when your running empty or below maximum weight they can be raised to save fuel and tyre wear. Also gives better traction on the drive axle in the case of a 6x2 config.
Quite often they are 'twin steers' which reduces both turning circle and tyre wear. DAF twinsteers lock in the straight position at around 30MPH to improve stability. I've not seen or driven one that has a driven drop axle but, I'm in the understanding that they do exist.

Treefrog · 20 Mar 2006 at 14:33

Lifting one axle also makes it easier to steer from what R124/LA420 told me IIRC

Sputnik II · 20 Mar 2006 at 14:44

Treefrog said:
Lifting one axle also makes it easier to steer from what R124/LA420 told me IIRC

Yes, thats very true but, not always possible as the axle won't lift if the vehicle has a heavy load on it or is 'nose heavy'.

Scania · 20 Mar 2006 at 18:05

Sputnik II said:
Yes, thats very true but, not always possible as the axle won't lift if the vehicle has a heavy load on it or is 'nose heavy'.

Many HGV's will allow you to briefly raise the "lift axle" to help in situations of poor traction, however, some indeed don't!

Note the middle axle lifted in this picture, as the truck was empty.

The Scania R124/420 for example, will lower the axle if its detects the weight is too high, alas, it won't automatically raise once the load is lighter, which is certainly a manouverability issue.

The more axles a vehicle has, the heavier its load carrying ability, when my rigs empty, I can lift the middle axle on the 'unit and the first axle on the trailer, this reduces drag (as they are not driven) and helps fuel consumption.

Oliver · 20 Mar 2006 at 18:50

What wheels are driven on a lorry?

great advice · 20 Mar 2006 at 18:53

Oliver said:
What wheels are driven on a lorry?

The ones on the tractor (the cab on the front).

Sputnik II · 20 Mar 2006 at 19:05

Oliver said:
What wheels are driven on a lorry?

On a rigid the rear wheels and on an artic the rear axle of the tractor unit. (answer based on a 4 wheel rigid and 4 wheeled tractor unit 4x2)

Scania · 20 Mar 2006 at 19:08

Sputnik II said:
On a rigid the rear wheels and on an artic the rear axle of the tractor unit. (answer based on a 4 wheel rigid and 4 wheeled tractor unit 4x2)

Sometimes the rear axle of a tractor, sometimes the middle, depending on the configuration / type.

Some HGV's have all wheel drive on the tractor units, but, such kit is rare, expensive and prone to eating transmissions!

I'm yet to see a trailer with driven wheels........

Oliver · 20 Mar 2006 at 19:29

Oh right. I wouldn't have thought that would provide enough grip really but obviously it must!

Sputnik II · 20 Mar 2006 at 19:29

R124/LA420 said:
Sometimes the rear axle of a tractor, sometimes the middle, depending on the configuration / type.

Some HGV's have all wheel drive on the tractor units, but, such kit is rare, expensive and prone to eating transmissions!

I'm yet to see a trailer with driven wheels........

Ok, yes some weird Scania units (6x2) have centre drive axle's with lifting rear axles. but, then I did say answer based on a 4x2

Off topic,does your Topline have the fold flat gear lever? I used to have a topline in the late '90s just wondered if they still have it. I miss the look on peoples faces as the bottom step folds down when you open the door.

Scania · 20 Mar 2006 at 19:42

Sputnik II said:
but, then I did say answer based on a 4x2

Soz mate, missed that detail , as per usual!

Sputnik II said:
Off topic,does your Topline have the fold flat gear lever? I used to have a topline in the late '90s just wondered if they still have it. I miss the look on peoples faces as the bottom step folds down when you open the door.

The step scares quite a few people!

Yes, the current 4 Series Toplines have the folding gear lever, both on the "W" reg's we have and the "04" reg.

FWIW, I prefer the feel and splitter layout of the earlier models.

Sputnik II · 20 Mar 2006 at 19:51

The topline I had was a 'w' reg with a 3 over 3 plus splitter transmission.

Scania · 20 Mar 2006 at 20:02

Sputnik II said:
The topline I had was a 'w' reg with a 3 over 3 plus splitter transmission.

Thats the configuration I prefer, certainly streets ahead of the DAF XF I'm currently stuck with.

Sputnik II · 20 Mar 2006 at 20:12

R124/LA420 said:
Thats the configuration I prefer, certainly streets ahead of the DAF XF I'm currently stuck with.

I'm not a DAF fan either for what its worth. Recently I've driven a few DAF CF's, I don't mind the 4 over 4 'box its just a good job its got the splitter cos they haven't got the power to go up a whole gear at a time