I’ve forgotten, not dropped the trailer since Feb! 
Winseer:
For split couplers, having that “few inches of settle” squish you against the A frame because the damned thing can still roll (red air line not pulled first/red brake not applied first) is NOT good is it?
When split coupling you should have trailer brake applied, well you should have it applied on all coupling operations. If your trailers roll under these circumstances, then they need defecting. 
green456:
cieranc:
Winseer:
Also, when taking air lines OFF, the yellow line removal tends to see some “settle” from any pumped-up suspension.Can’t get me head around this.
Why does the air suspension drop/settle when you pull the yellow line?
The yellow line only supplies the service brake.The suspension and the brakes are seperate systems, and the suspension system takes it’s feed from the red airline.
winseers getting confused with his red and yellow, hes thinking about working tax credits and jobseekers allowance
You’ve obviously not driven a large enough variety of trailers to ever have one “settle” on pulling the yellow air line. Or maybe you never operate the pump-up handle in the first place for it to settle down from? - Knocked any stuff over on the very rear of the trailer recently? Heavy loads have a tendency to hard-bounce around all over the place when the springs are bending back the wrong way you see… The suspension should be set according to the load and balance of the trailer. Sounds like such niceties are not within the driver’s general knowledge domain. Vosa spot checks even go through the trouble of climbing under the trailer to see if your springs are unevenly bent (among other things) - let alone bending the wrong way!
As for the other flannel - I’ve signed on for a total of 9 weeks in the past 25 YEARS so don’t give me that crap about unemployment spongeing. I bet there’s plenty of others who got no work on agencies this last jan/feb season as well, but doubtless they were too ‘superior’ to sign on, and therefore didn’t get their stamp paid. Go figure! 
All the yellow line does though is control the service portion of the trailer spring brake chambers either from brake pedal depression or secondary brake (first portion of the parking brake throw before it clicks on).
I don’t bother with the yellow one
4whatitsworth:
I don’t bother with the yellow one
I do but once noticed I hadn’t whilst having a walk around whilst the tank was filling with diesel at the services. 
Own Account Driver:
4whatitsworth:
I don’t bother with the yellow oneI do but once noticed I hadn’t whilst having a walk around whilst the tank was filling with diesel at the services.
It’s when you stop for diesel and you notice the trailer ain’t there youve got to worry 
Winseer:
cieranc:
Winseer:
Also, when taking air lines OFF, the yellow line removal tends to see some “settle” from any pumped-up suspension.Can’t get me head around this.
Why does the air suspension drop/settle when you pull the yellow line?
The yellow line only supplies the service brake.
The suspension and the brakes are seperate systems, and the suspension system takes it’s feed from the red airline.You’ve obviously not driven a large enough variety of trailers to ever have one “settle” on pulling the yellow air line. Or maybe you never operate the pump-up handle in the first place for it to settle down from? - Knocked any stuff over on the very rear of the trailer recently? Heavy loads have a tendency to hard-bounce around all over the place when the springs are bending back the wrong way you see… The suspension should be set according to the load and balance of the trailer. Sounds like such niceties are not within the driver’s general knowledge domain. Vosa spot checks even go through the trouble of climbing under the trailer to see if your springs are unevenly bent (among other things) - let alone bending the wrong way!
Maybe I’m just thick, but I’ll ask again, how does the yellow suzie / service brake have any bearing on the air suspension?
By pump-up handle do you mean the COLAS valve?
I’m also unsure as to how you bend an airbag the wrong way. Unlike steel springs, they only go one way, the piston goes inside the bag, slightly arched.
I’m just curious (I’m obviously not as experienced with such things as I thought I was), but how do you set the trailer according to load and balance of the trailer?
My understanding is:
Steel suspension you don’t have a choice,
Air suspension you set the COLAS valve to it’s default (which automatically finds its proper level),
Oil suspension you use an air-over-oil pump shoved into a barrel of Tellus to pump some more oil in.
As for the jibe about the dole, just don’t bite
4whatitsworth:
I don’t bother with the yellow one
i turn my tap on, on the blue line for my red diesel! 
works a treat! 
Ok so I’ll ask this same question from a different approach.
Red suzie applied - Air in the trailer for suspension, and air in the chambers to hold the spring brake off.
Yellow suzie applied - Air to the service brake diaphragm when footbrake in cab applied.
Trailer park brake on - Air exhausted from chambers so spring brakes apply.
Trailer park brake off - Air from red suzie allowed back into chambers to hold spring brake off.
If the trailer is at rest with the red suzie disconnected (or red suzie connected and park brake applied), there is no air supply to the chambers. Therefore, all the braking effort is made by the chamber springs.
If the footbrake is applied in the cab, then air is sent (via the yellow suzie) to the service brake side of the diaphragm. So Spring brake AND service brake applied.
It there is no footbrake applied, no air down the yellow suzie, so still spring brake applied.
I just can’t see how, if the red suzie is already removed, the removal of the yellow suzie can have any effect on the (already set) spring brakes.
Yellow suzie/service brake has no involvement with the spring/emergency brake.
Can anyone point out where my logic fails?
I think there are/were some makes of units that pressurise the service brake when the parking brake is clicked on in the cab. When you disconnected there might be some movement in the trailer as the braking went from the stronger service application to weaker spring, nothing to do with suspension though.
I do occasionally manually fiddle with air suspension ride height, rather than leave in default, if there’s reasonable amount of difference in fifth wheel height to what the default setting is based on.
Yeah I get that mate, but if that’s the case you’re going from spring brake PLUS service brake to spring brake only.
If the trailer moves with spring brake effort only, then there’s something seriously wrong.
I can’t see how it has anything to do with the suspension.
Then again, I’m just a thick fitter
Airbags are the more modern trailers. Over the years I’ve picked up all kinds of knackered old things from here and there (eg tiphook), but having verified the MOT is ok, one then proceeds and takes in the learning curve of things that may well be seen very rarely these days.
Examples:
(1) Ratchet trailer brake on trailer
(2) Blue airline socket on trailer. (I’ve not put anything on one of those since driving leyland roadtrains in the early 90’s!)
(3) Composite Springs rather than airbags on trailer brakes
(4) No power steering on tractor and trying to pull a modern trailer (!)
and of course
(5) No ABS connection.
If you don’t connect the yellow airline, see what happens when you try stopping sharpish when running downhill with a full load on… If the service brake had no purpose, it would be omitted. I wouldn’t recommend only connecting red unless you intend shunting across the yard, and that’s it. I wouldn’t be leaving the yard without the yellow on when loaded that’s for sure!
Has anyone else ever taken a yellow airline off and noticed a sharp escape of air alongside a sudden “settle” in the trailer?
It seems to happen to me when I’m dropping a fully loaded trailer (with some air suspension in it) onto a bay. Red off first, but on pulling off yellow, there’s definately a sharp settle and a louder release of air than when taking the red one off sometimes…
At places like Langdons, you’ll find each depot has different height loading bays requiring the suspension to be raised/lowered according to where it is for example. I’ve had this happen on both their trailers, and nagel ones, so I don’t think it’s dependent upon the trailer.
As for balancing the trailer/load, you’ll have a grounding risk if you sometimes don’t alter the suspension when traversing certain cambers and inclines in yards and both haulier and customer alike. A close-coupled fridge with a level gradient can turn nasty if you try going down an access ramp without pumping the rear suspension up for example - although this time we’re talking about rear tractor axle rather than the trailer.
inform.wabco-auto.com/intl/pdf/8 … 573-08.pdf
This is an interesting link for insomniacs
Winseer:
Airbags are the more modern trailers. Over the years I’ve picked up all kinds of knackered old things from here and there (eg tiphook), but having verified the MOT is ok, one then proceeds and takes in the learning curve of things that may well be seen very rarely these days.Examples:
(1) Ratchet trailer brake on trailer
(2) Blue airline socket on trailer. (I’ve not put anything on one of those since driving leyland roadtrains in the early 90’s!)
(3) Composite Springs rather than airbags on trailer brakes
(4) No power steering on tractor and trying to pull a modern trailer (!)
and of course
(5) No ABS connection.
Sorry mate, my mistake for assuming we were discussing vehicles used this century
None of that list has anything to do with the yellow line affecting the suspension.
Winseer:
(3) Composite Springs rather than airbags on trailer brakes
Airbags on trailer brakes ■■? You’ve lost me completely now.
Winseer:
If you don’t connect the yellow airline, see what happens when you try stopping sharpish when running downhill with a full load on… If the service brake had no purpose, it would be omitted. I wouldn’t recommend only connecting red unless you intend shunting across the yard, and that’s it. I wouldn’t be leaving the yard without the yellow on when loaded that’s for sure!
No-one’s questioned the use of the yellow line, that’s your service brake. Of course it has a purpose, of course you need it. Who said you don’t? The only people who don’t use the yellow line drive Terbergs.
What I can’t get my head around is your statement “I remove yellow line and the trailer moves”.
Winseer:
As for balancing the trailer/load, you’ll have a grounding risk if you sometimes don’t alter the suspension when traversing certain cambers and inclines in yards and both haulier and customer alike. A close-coupled fridge with a level gradient can turn nasty if you try going down an access ramp without pumping the rear suspension up for example - although this time we’re talking about rear tractor axle rather than the trailer.
Where do you go where you can ground out a fridge trailer? This isn’t what you were talking about, you said:
Or maybe you never operate the pump-up handle in the first place for it to settle down from? - Knocked any stuff over on the very rear of the trailer recently? Heavy loads have a tendency to hard-bounce around all over the place when the springs are bending back the wrong way you see… The suspension should be set according to the load and balance of the trailer. Sounds like such niceties are not within the driver’s general knowledge domain
Only time I’ve managed to ground a trailer out was coming across the number 2 Prairie at Lackenby with a 4 axle Nooty, the ground was rough as hell and I had to lift both ends of the trailer up to stop it bottoming out.
And when you were referring to air suspension ‘settling’, can you explain what you mean by the springs bending back the wrong way? I still don’t understand how an airbag can bend the wrong way.
ashbyspannerman:
I’ve forgotten, not dropped the trailer since Feb!
I bet your fifth wheel is bone dry then!
Paul
You’ve got airbags and brake springs around the trailer axels. The springs come in two types - composite (the old fashioned leaf springs) which act as suspension, and the coiled ones inside the brake assembly, keeping the brakes on unless air is pumped into them. Two different springs in the same area.
Then there’s what I call the airbags… One might act as resovoir for the brakes (like the metal airtanks) and the other as suspension for the axel. Two different kinds of airbag. I’m not an engineer, so only have a layman’s knowledge of the bits involved. Maybe the paintwork holds up the axel, and the number plate light helps braking action - what do I know?
Grounding a Fridge:
Maybe I’m using the wrong term. You go down a ramp with a close-coupled fridge, and the very bottom of the ramp, the trailer tips forward and either scrapes the legs (despite them being wound up) or tips the top of the fridge compressor into the aerofoil on the cab… I dunno the term for the latter event, so I’ll just refer to the scraping the legs bit that I reckon is called “Grounding”. Both events can occur at the same venue though. Pumping up the rear tractor axel prevents both at least.
“Settle” - If you have a fully pumped up trailer, and you are dropping it on a high bay (hence leaving it pumped up in the first place!) then after taking the red line off, there is “give” when taking off the yellow one. It occurs to me that taking off the red one CAN’T be purging all the air from the trailer, otherwise it would “settle” when taking the RED line off!. Air is left in the trailer (keeping it pumped up), and some I think escapes when taking the yellow line off that’s all I think I’ve been observing here. 
Winseer:
You’ve got airbags and brake springs around the trailer axels. The springs come in two types - composite (the old fashioned leaf springs) which act as suspension, and the coiled ones inside the brake assembly, keeping the brakes on unless air is pumped into them. Two different springs in the same area.
Then there’s what I call the airbags… One might act as resovoir for the brakes (like the metal airtanks) and the other as suspension for the axel. Two different kinds of airbag. I’m not an engineer, so only have a layman’s knowledge of the bits involved. Maybe the paintwork holds up the axel, and the number plate light helps braking action - what do I know?Grounding a Fridge:
Maybe I’m using the wrong term. You go down a ramp with a close-coupled fridge, and the very bottom of the ramp, the trailer tips forward and either scrapes the legs (despite them being wound up) or tips the top of the fridge compressor into the aerofoil on the cab… I dunno the term for the latter event, so I’ll just refer to the scraping the legs bit that I reckon is called “Grounding”. Both events can occur at the same venue though. Pumping up the rear tractor axel prevents both at least.
“Settle” - If you have a fully pumped up trailer, and you are dropping it on a high bay (hence leaving it pumped up in the first place!) then after taking the red line off, there is “give” when taking off the yellow one. It occurs to me that taking off the red one CAN’T be purging all the air from the trailer, otherwise it would “settle” when taking the RED line off!. Air is left in the trailer (keeping it pumped up), and some I think escapes when taking the yellow line off that’s all I think I’ve been observing here.
Suspension airbags are known as Spring Bellows or possibly Air Springs, they are certainly not a reservoir for the brakes.
Composite means made of two or more materials. Leaf Springs are made from steel as are single spring bows.
Airtanks or reservoirs are made from steel or aluminium and hold the air from the engine driven compressor.
The brake assembly you speak of are called brake actuators or airpots. Yes they have a coil spring inside to either apply or hold off the brakes, depending on your age 
The suspension and brakes are two separate systems and have no relation to each other except feeding from the same compressor.
Winseer:
I’m not an engineer, so only have a layman’s knowledge of the bits involved. Maybe the paintwork holds up the axel, and the number plate light helps braking action - what do I know?
You know enough to make patronising comments such as:
Winseer:
You’ve obviously not driven a large enough variety of trailers to ever have one “settle” on pulling the yellow air line… Sounds like such niceties are not within the driver’s general knowledge domain.
Or rather, you think you do. From what you’ve posted in this thread so far, it’s quite clear that what you think you know and what you actually do know are completely seperate entities.
The only time I have known a trailer to settle is when you run a fridge in electric mode on the bay. We have a paddle you must move to plug it in, this applies the trailer brakes. When you unplug it and move the paddle back, the now loaded trailer drops a good few inches.