Two daft truck/lorry questions
Discussion
Hi guys
I have 2 questions if I may
1) The really big trucks on the road will often have 6 wheels on the trailer, I only normally see 4 of them in contact with the road with the other pair normally the front pair lifted off the ground, why are they there
2) Coming back from a meeting today around the M25 I saw a truck with 2 cabs on its bed, one was
facing the rear and looked quite funky with modern lights and all in white, the other had parts covered up and was covered in the black and white camp stuff that car makers use to try and disguise new models, are they as secretive about trucks too?
I have 2 questions if I may
1) The really big trucks on the road will often have 6 wheels on the trailer, I only normally see 4 of them in contact with the road with the other pair normally the front pair lifted off the ground, why are they there
2) Coming back from a meeting today around the M25 I saw a truck with 2 cabs on its bed, one was
facing the rear and looked quite funky with modern lights and all in white, the other had parts covered up and was covered in the black and white camp stuff that car makers use to try and disguise new models, are they as secretive about trucks too?
powerstroke said:
Yes !!!volvo merc etc dont want daf scania seeing what they are up to or the truck buyers seeing a new model before they have got rid of the old models just like cars.
2 The axles are lifted to save fuel and reduce wear on empty or lightly loaded trailers.
2 The axles are lifted to save fuel and reduce wear on empty or lightly loaded trailers.
Cheers I think these were Fords, they didn't have badges on but there was a whacking great oval hole where a badge should go
Ah makes sense cheers
Nickyboy said:
Container trucks possibly?
The trailer splits in 2 so 2 20ft containers can be dropped for unloading at the same time
It could be, but more likely a standard 3+3 combination imho. As mentioned you can raise them via a button on the side of the trailer. If the tractor unit is a 3 axle one then usually the non-driven axle at the back can be raised via a button in the cab. It's a slightly better ride, corners better if the tractor unit axle is raised and saves on fuel/wear. The trailer splits in 2 so 2 20ft containers can be dropped for unloading at the same time
^ in the case of a tag axle, yes..
Most 6 leg units in the UK have a lift axle which is the middle one which lifts when running light.. The drive axle is the furthest back.
They're pretty keen on us running with the lift up.. IIRC you can be at 40T before the axle automatically drops. If you run with them down light or more so lots of manoeuvring in tight yards etc you can scrub a set of middle tyres off in a few weeks!
Most 6 leg units in the UK have a lift axle which is the middle one which lifts when running light.. The drive axle is the furthest back.
They're pretty keen on us running with the lift up.. IIRC you can be at 40T before the axle automatically drops. If you run with them down light or more so lots of manoeuvring in tight yards etc you can scrub a set of middle tyres off in a few weeks!
philmots said:
The drive axle is the furthest back.
Not always, Phil.. 
Most of the fleet-y type artics here in the UK have a pusher axle (what we usually refer to as a mid lift) but you can also spec them with a tag axle which is behind the driven axle and often steers and/or lifts too.Scania with tag axle for illustration purposes.
Sorry for causing confusion. I realise there's an option for a tag axle with drive being the middle.
From my last post.....
[quote=me]^ in the case of a tag axle, yes..[\quote]
They're just very rare compared to a middle lift..
Always seem to be on trucks that you'd see on more off road use. Like the Biomass Stobart ones. I've not driven one so can't comment on their behaviour other than they must have an uber tight turning circle when lifted.
From my last post.....
[quote=me]^ in the case of a tag axle, yes..[\quote]
They're just very rare compared to a middle lift..
Always seem to be on trucks that you'd see on more off road use. Like the Biomass Stobart ones. I've not driven one so can't comment on their behaviour other than they must have an uber tight turning circle when lifted.
philmots said:
r causing confusion. I realise there's an option for a tag axle with drive being the middle.
From my last post.....
. Ride tends to be rather choppy vs a conventional mid lift layout because of the short wheel base with the tag raised, though. 
From my last post.....
me said:
^ in the case of a tag axle, yes..[\quote]
They're just very rare compared to a middle lift..
Always seem to be on trucks that you'd see on more off road use. Like the Biomass Stobart ones. I've not driven one so can't comment on their behaviour other than they must have an uber tight turning circle when lifted.
Yes they do, can turn them on a sixpence They're just very rare compared to a middle lift..
Always seem to be on trucks that you'd see on more off road use. Like the Biomass Stobart ones. I've not driven one so can't comment on their behaviour other than they must have an uber tight turning circle when lifted.
. Ride tends to be rather choppy vs a conventional mid lift layout because of the short wheel base with the tag raised, though. philmots said:
Is there any other reason for that layout though other than the turning? Any traction benefits?
We have a handful of 4x2 and they make it a lot easier in very tight places.
Honesty don't know Phil! Only driven a couple (both on plant work) and to be honest never really paid any attention to it. Don't quote me but I think the 5th wheel is generally nearer to the middle axle on a 6 legger than the back axle so maybe there are some traction benefits? We have a handful of 4x2 and they make it a lot easier in very tight places.
Just for a giggle..
Most steering lift axles are physically connected in some way, Iveco has some dodgy electronic pump system. This is what happens if you try to go lock to lock fully freighted, say whenever you are trying to do a stupidly tight maneuver with lots of pedestrians watching or holding up traffic
Most steering lift axles are physically connected in some way, Iveco has some dodgy electronic pump system. This is what happens if you try to go lock to lock fully freighted, say whenever you are trying to do a stupidly tight maneuver with lots of pedestrians watching or holding up traffic
4key said:
Just for a giggle..
Most steering lift axles are physically connected in some way, Iveco has some dodgy electronic pump system. This is what happens if you try to go lock to lock fully freighted, say whenever you are trying to do a stupidly tight maneuver with lots of pedestrians watching or holding up traffic
I just put my fingers in my ears when I saw that Most steering lift axles are physically connected in some way, Iveco has some dodgy electronic pump system. This is what happens if you try to go lock to lock fully freighted, say whenever you are trying to do a stupidly tight maneuver with lots of pedestrians watching or holding up traffic
philmots said:
^ in the case of a tag axle, yes..
Most 6 leg units in the UK have a lift axle which is the middle one which lifts when running light.. The drive axle is the furthest back.
They're pretty keen on us running with the lift up.. IIRC you can be at 40T before the axle automatically drops. If you run with them down light or more so lots of manoeuvring in tight yards etc you can scrub a set of middle tyres off in a few weeks!
The Axors we run with a non steering mid lift also have issues with the wheel bearings failing on the lift axle due to too much manoeuvring with the axle dropped.Most 6 leg units in the UK have a lift axle which is the middle one which lifts when running light.. The drive axle is the furthest back.
They're pretty keen on us running with the lift up.. IIRC you can be at 40T before the axle automatically drops. If you run with them down light or more so lots of manoeuvring in tight yards etc you can scrub a set of middle tyres off in a few weeks!
4key said:
The trick i found, is not to stop. If you are always moving it doesnt trip over itself. Not so easy when you have to do a couple of shunts on a slope to reverse through a gate
I'll always remember trying to reverse a 40ft rear steer curtain side trailer without locking the axle first. Much chuckling from all the onlookers stood in the yard.. 
I have 2 more if I may (I should explain I have a new job which involves regular client visits so I am spending a lot of time stationary on various motorways around the UK)
So today I was about 10 cars back from a lorry that essentially shat one of its rear tyres all over the place, cue lots of heavy braking as people tried to avoid the huge section of tyre left on the road and we all stopped to allow the driver to nip across and grab it from the 3rd lane where it ended up
It was the tyre from his trailer and he made it onto the hard shoudler, as I continued my journey I noticed other bits of lorry tyre on the hard shoulder in various places, so are lorry tyres a bit s
t? Or is it we only notice these bits cos they are huge and it seems more often as there are loads of lorries
Also years ago I saw on a technology program of some sort a device a guy had invented that was a frame with 2 small wheels when a lorry slammed on the brakes this dropped down and seemed to act as a sort of anchor reducing the stopping distance massively they were projecting this would be fitted to loads of trailers and would stop a lot of accidents but I have never seen one since
Anyone know what I am talking about?
Feel free if these questions are getting boring to tell me to do one I just find it all facinating
So today I was about 10 cars back from a lorry that essentially shat one of its rear tyres all over the place, cue lots of heavy braking as people tried to avoid the huge section of tyre left on the road and we all stopped to allow the driver to nip across and grab it from the 3rd lane where it ended up
It was the tyre from his trailer and he made it onto the hard shoudler, as I continued my journey I noticed other bits of lorry tyre on the hard shoulder in various places, so are lorry tyres a bit s
t? Or is it we only notice these bits cos they are huge and it seems more often as there are loads of lorriesAlso years ago I saw on a technology program of some sort a device a guy had invented that was a frame with 2 small wheels when a lorry slammed on the brakes this dropped down and seemed to act as a sort of anchor reducing the stopping distance massively they were projecting this would be fitted to loads of trailers and would stop a lot of accidents but I have never seen one since
Anyone know what I am talking about?
Feel free if these questions are getting boring to tell me to do one I just find it all facinating
anonymous said:
[redacted]
Trailer tyres take a lot of abuse from bad drivers and neglect :- Drivers that don't take corners and turns wide enough resulting in the trailer tyres being compressed against the kerb and smacking them into the kerb face and over the top. From what I've seen most truckers have absolutely no mechanical sympathy whatsoever for the truck or trailer.
- Drivers screwing the trailer round on its axis in tight yards through sheer laziness. Especially bad when the trailer is fully loaded. On a 44 tonner each trailer tyre will be supporting nearly 4 tonnes of weight.
- Drivers neglecting to check the tyre pressures. This is probably the biggest factor in blow outs.
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