i am looking for some advice regarding sliding 5th wheel. I recently drove a truck where the 5th wheel had been moved as close to the back of cab as possible? 1 of our other drivers said that it should be as far back as possible from cab in the bad weather as it will put more weight onto the drive axle, i am not sure on this. My boss has agreed with this other driver and is going to have all 5th wheels moved as far back from cab, in my opinion i would think this may overload drive axle if carrying heavy load and therefore have positioned mine centrally so the weight is distributed.
ant2503:
i am looking for some advice regarding sliding 5th wheel. I recently drove a truck where the 5th wheel had been moved as close to the back of cab as possible? 1 of our other drivers said that it should be as far back as possible from cab in the bad weather as it will put more weight onto the drive axle, i am not sure on this. My boss has agreed with this other driver and is going to have all 5th wheels moved as far back from cab, in my opinion i would think this may overload drive axle if carrying heavy load and therefore have positioned mine centrally so the weight is distributed.
He is correct in what he’s saying…but you’re correct on what you’re suggesting…So what advice are you seeking? 
I was really wanting to know really the best position to have it in as i wouldn’t want to be running overweight on axles. What position do most other people run, if you were struggling for traction could you not press the weight transfer button.
Has the boss realised the impact this will have on his fuel bill? 
Coffeeholic:
Has the boss realised the impact this will have on his fuel bill?
I wouldn’t have thought it’d make any difference really as the engine still has to move the same weight??
Adam_Mc:
Coffeeholic:
Has the boss realised the impact this will have on his fuel bill?I wouldn’t have thought it’d make any difference really as the engine still has to move the same weight??
You think wrong in that case, it makes a big difference and it’s not about weight but about airflow over and around the vehicle. The smaller the gap between the back of the cab and the front of the trailer the better the fuel consumption.
Adam_Mc:
Coffeeholic:
Has the boss realised the impact this will have on his fuel bill?I wouldn’t have thought it’d make any difference really as the engine still has to move the same weight??
It’s the airflow disruption that causes drag that would be the problem.
You are correct as far as axle weights are concerned, other considerations would include the handling of the vehicle as you have now taken the load from the steering axle, and also the vehicle may now be over length the U.K limit for an articulated truck being 16.5 meters.
mrpj:
Adam_Mc:
Coffeeholic:
Has the boss realised the impact this will have on his fuel bill?I wouldn’t have thought it’d make any difference really as the engine still has to move the same weight??
It’s the airflow disruption that causes drag that would be the problem.
When you say the airflow…you mean the size of the gap between the trailer and the tractor unit? Thats easy to understand…but I thought he was talking about weight on the axles making the difference.
ant2503:
I was really wanting to know really the best position to have it in as i wouldn’t want to be running overweight on axles. What position do most other people run, if you were struggling for traction could you not press the weight transfer button.
You could, or if you can dump air from the drive axle if you don’t have a weight transfer button. If it’s a 6x2 lift the axle first then dump air from the drive.
Adam_Mc:
mrpj:
Adam_Mc:
Coffeeholic:
Has the boss realised the impact this will have on his fuel bill?I wouldn’t have thought it’d make any difference really as the engine still has to move the same weight??
It’s the airflow disruption that causes drag that would be the problem.
When you say the airflow…you mean the size of the gap between the trailer and the tractor unit? Thats easy to understand…but I thought he was talking about weight on the axles making the difference.
I wasn’t commenting on the weight on the axles. I was wondering if the boss realised his decision to slide all the 5th wheels back as far as possible was going to result in higher fuel bills when there are other ways of dealing with traction problems that don’t involve risking axle overloads, overall length issues and possible handling problems. Seems a bit drastic to run round permanently with the wheel back as far as possible when you can get going by other temporary means such as dumping air, lifting axles and using weight transfer switches.
I agree coffeeholic, there are other ways and i have never had many problems before with traction, but my boss is 1 of them people if someone says something to him he totally agrees and thats that dont seem to have mind of his own.
easiest way is ring the dealer and ask him where it should be , on a twin steer i usually have it about midway between the lift and drive axle, i could have it a bit further forward to lessen the gap as coffee so rightly says, but i dont like crane drivers throwing 45ft boxes at me and bouncing them off the back of the cab, in the position mines in it will still lift the middle axle for traction with about 20 ton on
close coupled is a pain in the ■■■ , let him move them back he’s paying the bill … 
Depends on what sort of trailer. We pull powder tankers and our sliders are between the rear axles. One other thing, if the sliders are moved back as far as they will go watch it around around corners as the steering will be rather light! 
ant2503:
I agree coffeeholic, there are other ways and i have never had many problems before with traction, but my boss is 1 of them people if someone says something to him he totally agrees and thats that dont seem to have mind of his own.
Your driving it so it’s up to you where you have it unless you can get the vehicle on a set of scales to measure individual axle weights it’s just guess work.
It slides for a reason, but there are various legalist things that need to be considered, turning circle, overall length, axle weights and headlight aim.
When you get all these right, you have to consider whether you can couple the suzies, do the landing legs clear the rear lenses? and if there is a high fuel tank or a saddle tank for the hydraulics, does the trailer clear it as you drive up an incline?
If the trailer is an airflow, teardrop type or fitted with other aerodynamic aids and your boss sets the slider to the rear position then he needs a serenade with a brass wind instrument
Coffeeholic:
I wasn’t commenting on the weight on the axles. I was wondering if the boss realised his decision to slide all the 5th wheels back as far as possible was going to result in higher fuel bills when there are other ways of dealing with traction problems that don’t involve risking axle overloads, overall length issues and possible handling problems. Seems a bit drastic to run round permanently with the wheel back as far as possible when you can get going by other temporary means such as dumping air, lifting axles and using weight transfer switches.
The term “woolly steering” springs to mind
Guess many of this company’s drivers are going to have a sharp learning curve in the term “understeer.” Hell, they won’t even go in straight line down a motorway.
- don’t they look daft so far back… just like pulling a tandem
Best practice is to have it closer to the cab rather than further away due to reduced fuel consumption the smaller the gap between the cab and the front of the trailer, this can make a BIG difference. I prefer pulling trailers where it’s nearer the cab as the combination is shorter and it turns tighter, you just have to watch the front of the trailer sticking out when you turn, many a wall or security gate post has been retired due to drivers not checking this during a turn. I just close couple if the trailer is to near the back of the cab to get between, not a problem.
I am surprised that moving the trailer back would put more weight on the back axle, I would have thought the opposite would be the case as their would be more of the load over the back axle the further forward the trailer.
One final imortant point as well, if the fifth wheel is all the way back it looks crap It will handle like a pig as well with vague steering. I have the fifth wheel dead centre in between the two rear axles. Seems a good compromise.
Oh just be careful if its been moved as close to the cab as possible to pull curtains and boxes if you go to pull fridges as BANG! erm boss…
Also as Coffee says if its close to the cab, make sure the rear lenses on the unit clear the landing legs/winding handle on a full turn or you can take them all out.
Silver_Surfer:
Also as Wheel Nut says if its close to the cab, make sure the rear lenses on the unit clear the landing legs/winding handle on a full turn or you can take them all out.
Fixed that for you.