Is there any any advantage to running a 6x2 tag over a 4x2 if you don’t need the weight? Our place is speccing a unit for 30k ltr tankers (tri-axle front lift and rear steer) on farm work and have been told by a sales rep that the best config for the tractor would be 6x2 tag but I’m not seeing it. I get that a 6x2 tag will turn on a sixpence with the tag up but we don’t need the weight. Wouldn’t a 4x2 be better with a short(ish) wheel base if such a thing exists? What am I missing that a 6x2 tag will do in our use case that a 4x2 won’t ? 
Axle weight distribution.
Wildy:
Axle weight distribution.
Elaborate please.
When fully loaded you can easily end up overweight on drive axle even if gross weight is within limits. What is maximum weight you’re carrying in 30k litre tanks?
With the 6 wheel tag unit, beware the 5th wheel position if pulling a shortish tank. Especially rear of chassis and trailer legs.
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If you want manoeverabilty then you’re right a short unit is best, and having a longer chassis with an axle hanging off it will give more unit tail swing if you’re in a really tight spot.
Cheaper tax for 6 axle 44 ton, than 5 axle 40 ton isn’t it? With 6 axles the gross is higher, but so is the tare, but you do get a couple of ton payload bonus if you need it.
If running max weights you will have more weight tolerance with a 3 axle unit, but if the tank has the pin and axles all in the correct place then the weight imposed onto the tractor should not over load it, if it’s a monocuve.
If you’ve got a multi pot tank you should be able to load more to the rear for a 2 axle tractor, or load more to the front for a 3 axle.
Diesel is 832grams per litre. So 30,000 litres is not far short (Ok 40kg short) of 25 metric tonnes.
However, water is 1000grams (ok, 1kg) per litre (it’s the reason the metric system is easy) so 30,000 litres of water are 30 metric tonnes.
Not a clue how much proper farmyard slurry weighs though 
probably a ZB load 
Advantage of a tag axle over over a 2 axle or mid lift unit as the rep says is manoeuvrability, as when down and up with the 5th wheel behind the drive axle, will push the front of the trailer out resulting in a wider turning circle, where as a 2 axle and mid lift with the fifth wheel in front of the fifth wheel will pull the front of the trailer in when turning, resulting in a smaller turning circle, which could mean getting round or not getting round farm buildings in a tight yard.
weeto:
Advantage of a tag axle over over a 2 axle or mid lift unit as the rep says is manoeuvrability, as when down and up with the 5th wheel behind the drive axle, will push the front of the trailer out resulting in a wider turning circle, where as a 2 axle and mid lift with the fifth wheel in front of the fifth wheel will pull the front of the trailer in when turning, resulting in a smaller turning circle, which could mean getting round or not getting round farm buildings in a tight yard.
I don`t see that.
The amount of trailer hanging out the front is dependent upon the trailer pin position, surely?
A short 4 wheel unit will not have the unit chassis swinging out, as a tag will with rear axle raised.
Franglais:
weeto:
Advantage of a tag axle over over a 2 axle or mid lift unit as the rep says is manoeuvrability, as when down and up with the 5th wheel behind the drive axle, will push the front of the trailer out resulting in a wider turning circle, where as a 2 axle and mid lift with the fifth wheel in front of the fifth wheel will pull the front of the trailer in when turning, resulting in a smaller turning circle, which could mean getting round or not getting round farm buildings in a tight yard.I don`t see that.
The amount of trailer hanging out the front is dependent upon the trailer pin position, surely?
A short 4 wheel unit will not have the unit chassis swinging out, as a tag will with rear axle raised.
It has nothing to do with what’s in front of the pin, it’s where the pivot point is, on a tag it’s behind the drive, you turn left, the trailer will will carry on going straight longer resulting in less cut in at the rear of the trailer, on a 2 axle unit pivot point is in front of the axle, you turn left, the pivot goes left straight away, pulling in the trailer rear earlier.which you don’t really want in tight yards.
weeto:
Franglais:
weeto:
Advantage of a tag axle over over a 2 axle or mid lift unit as the rep says is manoeuvrability, as when down and up with the 5th wheel behind the drive axle, will push the front of the trailer out resulting in a wider turning circle, where as a 2 axle and mid lift with the fifth wheel in front of the fifth wheel will pull the front of the trailer in when turning, resulting in a smaller turning circle, which could mean getting round or not getting round farm buildings in a tight yard.I don`t see that.
The amount of trailer hanging out the front is dependent upon the trailer pin position, surely?
A short 4 wheel unit will not have the unit chassis swinging out, as a tag will with rear axle raised.It has nothing to do with what’s in front of the pin, it’s where the pivot point is, on a tag it’s behind the drive, you turn left, the trailer will will carry on going straight longer resulting in less cut in at the rear of the trailer, on a 2 axle unit pivot point is in front of the axle, you turn left, the pivot goes left straight away, pulling in the trailer rear earlier.which you don’t really want in tight yards.
Assuming the front of the unit is in the same place, close to a wall maybe, then with a short unit and the 5th wheel in front of the drive axle, then the pin will be further forward before a turn commences.
I don`t see that you gain anything?
Tag motor gives you more room for error on axle weights, obviously whenever loaded near a DVSA wagon or weighbridge that tag will be down
Also gives you better drive axle grip because fitfh wheel behind the drive axle, in effect lifting the steer axle appreciably.
Downside slightly choppier ride with tag motor.
Juddian:
Tag motor gives you more room for error on axle weights, obviously whenever loaded near a DVSA wagon or weighbridge that tag will be down
Also gives you better drive axle grip because fitfh wheel behind the drive axle, in effect lifting the steer axle appreciably.Downside slightly choppier ride with tag motor.
Quite agree with that.
Years ago I used to spec tag lift tractor units, back in the F10, Scania 3 series days. It gave great manoeuvreability and you could put loads of weight over the drive, but they were a pain getting stuck in motorway tram lines. Empty they were a ■■■■ ride and keeping them in a straight lines at times was difficult.
The main problem with them is the fifth wheel load is imposed outside the wheelbase, making them less stable than a midlift or 4x2.
Doing more driving over that last couple of months I’ve been amazed that the tag axle is being specified a lot more, but on more standard vehicles. Stick them on a farm tanker or tipper, fine, but on general haulage? Really?
Wait until it tips over on a roundabout, people will be flocking back to mid lifts in droves.
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Interesting discussion. Thanks for your comments.
To add to my earlier post, after some investigations and questioning they are no longer considering a 4x2 as we’d be weight restricted on the tanks. I’m not up to speed on the litreage in milk tankers to put you at 44 tonne but if my beer mat calculations are right I reckon that 30,000 litres would put it overweight and the max we could fit in whilst staying legal would be around 28,500 litres? Does that sound about right to you tank guys?
There’s talk now of it not doing the farms but instead doing trunking picking up from Leicester and Wrexham so we don’t have to pay transport from other companies. Given the tanks are unbaffled and 6x2 tags having a bit of reputation for a lively ride, it sounds like it could be a bit of a handful at speed. The last 6x2 tag I drove was on springs and it’s fair to say the ride was… unpleasant. What is the ride like on air? It will be a Scania R series most likely.
I wouldn’t get too concerned about instablity, wouldn’t be anywhere near as bad as a typical modern car transporter (which also has the coupling outside the tractor or prime mover’s wheelbase) because a semi trailer’s axles are at the back not like a car transporter drag nearer the centre line, so that tail wagging the dog syndrome due to insufficient weight imposed on the tractor won’t be an issue, and you don’t see tag axled motors littering the carriageways on their side, the ones that go over regularly are bulk waster/wood shaving high sided motors but that’s stupid driving failing to take account of high centre of gravity issues, and containers.
You can’t really spec a motor till they’ve decided what they’re going to do with it.
If its going to be a trunker, then a 6 x 2 makes more sense (apart from lack of wet drive axle grip, wheelspin can be a pita), most makes can be ordered with small mid lift for weight advantage…note new gen Scanias are heavy beasts if weight saving is an issue.
If its going to be a farm collector, i’d prefer a tag both for maneuverability and grip, not just on the farm but for winter times on untreated roads that extra weight on the drive axle will make a lot of difference to getting around…obviously if you have a front lifter on the trailer that helps shift some weight onto the tractor too when empty or lightly loaded whatever design chosen.
If you have input to spec and it’s going on farms, suggest fitting the rear window in the cab to help blind siding in poorly lit tight places, whether you’d want that window in for trunking based work only you know the sorts of places it would be going to, i see lots of rear and even nsr windows perma covered by curtains so maybe i’m the only bugger bothered these days about good direct visibility helping to avoid damage where possible.
Ride quality with a short wheelbase tag will always be worse than a longer mid lift, especially when empty, the new gen Scania at least in mid lifter guise is a vast improvement over the previous model for ride and general comfort and quiet.
I drove a 2 month old R450 tag unit only a couple of months ago. The ride was far better than I expected.
There is a recent article here about the different types, and current trends:
Captain_Amateur:
There is a recent article here about the different types, and current trends:
Interesting article, thanks.
Gaffer has today hired an 2019 R450 topline 6x2 tag so will see how it goes later this week when it comes. He’s wanting to trial doing trunking with it first and so a tri-axle non-steer 30k ltr tank has been sourced. Truck will be no good for farms with the height of the cab down the lanes so not sure why he’s got a tag.
Well yes it is an interesting article, but from the way its written those not in the know could imagine the mid lift is stuck down at full weight imposed permanently.
I drive mid lift, in practice soon as i’m off the road i press the weight transfer button to take all the weight off said mid lift, yes i know i’m in a minority and yes i have heard umpteen times ‘‘i don’t pay for the tyres’’ 
, they forget all the extra strain tight turning puts on the chassis and suspension, they’ll be the same lemmings who describe tyre ripping U turns because they never learned how to blind side reverse, the same crew who need several attempts to reverse in somewhere tight when its wet due to wheelspin triggering TC and cutting power same time as auto clutch disengages, because they don’t know how to transfer weight from the lifter, and don’t know the reason why the driver can turn off TC/ASR.
Some mid lifts (MAN definately and Daf’s i’ve driven) will actually lift the mid lift completely off the ground fully loaded (weight transfer button, NOT axle lift button), and it will stay there until you cancel the weight button or travel above 20mph when it will automatically drop if loaded.
Dafs especially with small mid lift wheels loaded heavy it looks like the wheels are trying to bend under the chassis on tight turns if you don’t transfer weight, goodness knows what’s being worn faster than needed suspension wise if you ignored the tyre abuse.
It should be noted not all makes have the ability for the driver to transfer weight on at least some models, some Ivecos and Mercs i’ve used the driver has no input over the mid lift at all, barrell of laughs they’ll be on slippery roads
R420:
Interesting discussion. Thanks for your comments.To add to my earlier post, after some investigations and questioning they are no longer considering a 4x2 as we’d be weight restricted on the tanks. I’m not up to speed on the litreage in milk tankers to put you at 44 tonne but if my beer mat calculations are right I reckon that 30,000 litres would put it overweight and the max we could fit in whilst staying legal would be around 28,500 litres? Does that sound about right to you tank guys?
There’s talk now of it not doing the farms but instead doing trunking picking up from Leicester and Wrexham so we don’t have to pay transport from other companies. Given the tanks are unbaffled and 6x2 tags having a bit of reputation for a lively ride, it sounds like it could be a bit of a handful at speed. The last 6x2 tag I drove was on springs and it’s fair to say the ride was… unpleasant. What is the ride like on air? It will be a Scania R series most likely.
I used to drive a tag axle Scania (can’t remember the exact model) with a rear steer trailer for Farm milk collections - for that particular set up 26650 litres of milk would get me up to around 44 ton. But different types of milk have different weight. 
There is a milk weight scale (per litre) somewhere online.
Torkey:
R420:
Interesting discussion. Thanks for your comments.To add to my earlier post, after some investigations and questioning they are no longer considering a 4x2 as we’d be weight restricted on the tanks. I’m not up to speed on the litreage in milk tankers to put you at 44 tonne but if my beer mat calculations are right I reckon that 30,000 litres would put it overweight and the max we could fit in whilst staying legal would be around 28,500 litres? Does that sound about right to you tank guys?
There’s talk now of it not doing the farms but instead doing trunking picking up from Leicester and Wrexham so we don’t have to pay transport from other companies. Given the tanks are unbaffled and 6x2 tags having a bit of reputation for a lively ride, it sounds like it could be a bit of a handful at speed. The last 6x2 tag I drove was on springs and it’s fair to say the ride was… unpleasant. What is the ride like on air? It will be a Scania R series most likely.
I used to drive a tag axle Scania (can’t remember the exact model) with a rear steer trailer for Farm milk collections - for that particular set up 26650 litres of milk would get me up to around 44 ton. But different types of milk have different weight.
Thanks. 26650 seems low? Milk density is between 1.022 to 1.036 kg per litre depending on the type of milk, so call it 1.03 for round numbers. 28500 litres would be roughly 29355 kg. Talking to a driver of one of our subbies, he drives an FM12 globetrotter cab with standard 6x2 mid lift config and standard tri-axle non-steer trailer on alloys and reckons he can squeeze in 28500 and still be legal. Our R450 is the big cab (do they still call them Toplines?) and specced with all sorts of extra tat too, so that’s going to eat into the payload for sure. Will have to find out where the local scales are and run it over and see what the tare is.