Gap between cab and trailer

UK PROFESSIONAL DRIVERS FORUMS THE UK PROFESSIONAL DRIVERS FORUM (INTERACTIVE)
1

When the 5th wheel is “moveable” how do you judge the correct gap between the trailer and the cab :question:

If the gap is too short when turning am i going to take the back corners of the cab off :question: but what if the gap is too long :question: what effects if any does this have :question:

does this makes sense :question:

Dave

2

if you get the gap to close the first thing that is likely to happen is you take the rear lights off the unit as they hit the landing gear and front of the trailer hitting the back of the cab. it is also difficult to connect the airlines, which is why you see some connect the airlines before the fifth wheel engages. I think 0.5 metre clearence is ok, but I always do a couple of small turn and get out and have a look to see if anything is about to make contact. The main thing about a close coupled trailer is it looks nice and tidy :smiley:
Big gaps use fuel, becuase the overall length is longer it makes getting into tight spots more difficult and could mean you are over length, but mainly it don’t look as good :smiley:

3

Dave L:
When the 5th wheel is “moveable” how do you judge the correct gap between the trailer and the cab :question:

You don’t “judge”, you get out and look to make sure that you don’t bury the front of the trailer in the back of the cab.

If the gap is too short when turning am i going to take the back corners of the cab off :question: but what if the gap is too long :question: what effects if any does this have :question:

If the suzi sockets on the trailer don’t clear the suzi sockets on the unit then it’s too close. As a general rule, the trailer is close enough when you can just squeeze in the gap between the trailer and the unit but can’t actually do anything other than stand there.

If the gap is too long you’ll get 3 things:

  1. Horrible drag and horrendously poor fuel consumption
  2. Terrible handling as all the weight will be sitting on last few foot of the unit which will result in very light steering.
  3. Terrible drag up hills.
4

Also if you are running on only 5 axles and you have the 5th wheel right back, you risk overloading the drive axle!!

5

Rough guide is that you need 9 inches from the air-deflector 'round the cab, or 18 inches from the cab wall. That’s what I’ve always gone on, and never yet had a problem…:wink:

It is always worth pulling away slowly with full lock on, then getting out and havng a peek if you’re not sure, though… :open_mouth:

6

There isnt a measurement you can use. You have to check everything for clearance.

Some trailers will have a sloping chassis at the front and will dig into the chassis rails on a unit as you turn up a hill or on a junction.

Ferry trailers are the worst for this, because you may only ever see one like it. Italian trailers are notorious for having deep chassis and deep pins.

7

You have also got to be careful it don’t end up over max permissable length. In most cases with a 45ft (13.5) ish trailer, its got to be bleeding close.