The friendly 'dumb' truck questions thread

[Koyaanisqatsi]

Inspired by the same thread in the biker section, which has proved to be very helpful, I thought I'd try starting a truck equivalent. For every question, no matter how small, I'm sure there will be a helpful answer.

I'll kick off by saying that we've just got a new artic unit which is 6x4, double drive with a tag axle and 80ton fifth wheel with a huge loader crane on it. Having not driven one before (tag axle, that is), what are the pros and cons of a tag axle rather than midlift? I assume much better turning circle (when empty at least), but need to reverse under trailers with the axle / air down otherwise the rear mudguards scrape against the greasy underside of the trailer? Any other tips?

And why do all the scrap / recycling lorries have a taglift, is it simply for manoeuvrability around tight sites?

[Stussy]

Tags are better for rough terrain or where more traction is needed, and as you said, better turning circle with it lifted. Mid is better for long distance as it’s more stable.
As for backing under a trailer, it’s worth lowering the air regardless of which type it is, then lifting it once the 5th wheel is under and the hitch up

[Smint]

Tags for maneuvering and grip.
Tags can be an issue with older and shorter (ie urban) trailers due to fifth wheel position.
Downside of tags are typically a worse ride when empty, though in reality the really short wheelbase tractor units of the 70s were the worst boneshakers one could hope to experience, a modern tag unit offering limo ride quality in comparison to those.

6 x 4 is interesting, presumably drive is disconnected from the rear axle when in the raised position?

Edited by Smint on Saturday 30th August 22:35

[Its Just Adz]

Smint said:

Tags for maneuvering and grip.
Tags can be an issue with older and shorter (ie urban) trailers due to fifth wheel position.
Downside of tags are typically a worse ride when empty, though in reality the really short wheelbase tractor units of the 70s were the worst boneshakers one could hope to experience, a modern tag unit offering limo ride quality in comparison to those.

6 x 4 is interesting, presumably drive is disconnected from the rear axle when in the raised position?

Edited by Smint on Saturday 30th August 22:35

At my previous job we had 6x4 Volvos, used for landfill work.
So yes, the drive from axle 2 disconnected somehow when the tag was lifted.
They were brilliant off road.