Anyone know what the air pressure is when
connecting the air lines just trying to workout
the force needed to connect them.
I read that for the trailer 105 psi is recommended but
85 psi is ok. also when searching the net I read that the
low buzzer sounds at 60 psi but there was a fatal accident
when a truck had a air leak and rolled at 70 psi.
I’m not sure I understand the question. Realistically, you don’t need any pressure to connect the lines. Some Daf’s tend to be a PITA because they also have a pressurised Service Line.
However, once stopped, if you repeatedly pump the brake pedal and exhaust any residual pressure in the tanks, then both the red and yellow lines will connect with minimum effort. It just means that you then have to sit for a couple of minutes, or so, whilst the pressure builds back up.
Your air pressure gauge should tell you the pressure the truck has built up and that’s the force you’ll be trying to overcome when connecting the Susie’s.
The emergency spring brakes should come on when your air pressure gauge drops into the red section which on a DAF is about 5 or 6, which I think is Bar.
When you drop a trailer and pull the park brake on
I think I seen somewhere 87 psi applies the trailer
brakes. what I was wondering when connecting the
air lines from the unit to trailer would that 87 psi be
the reason why it takes some effort pushing the air
lines on.
Basically the more air pressure in the tanks the more pressure needed to connect the line.
As for the reply about brakes coming on @ about 80lbs per sq. inch this no longer applies as all new trailers from about the early eighties or so were fitted with spring brake chambers which as soon as there is no air to push the spring in the chamber back off, the brakes come on with the full force of the spring chamber.
Put simply (without being condescending) when you pull / push the “Parking Brake Switch / Button” you are then releasing the air in the spring chamber in the same way as you would do with the red line removed the only difference being that with the "park brake " applied when you couple the red line for safety the trailer brakes stay on so the trailer stays put instead of running down the road or off the back of the unit.
I can,t understand what the point is about a truck rolling over with 70PSI in the air tanks as if I remember from my fitting days (many moons ago) I seem to remember that when the buzzer came on the (then) regs stated that you should have had at least 4 full pressure applications of the brake before losing your brakes obviously things and regs (thankfully / hopefully) have moved forward.
Ahh! now theres a handy little tip i never thought of & may make auqward susies easier & please correct me if im wrong.
If i pump the pedel & drop & switch off the motor then it will be easier for me to connect the red air line ?
robntl:
If i pump the pedel & drop & switch off the motor then it will be easier for me to connect the red air line ?
You should always switch of the engine when coupling, not only can it make it easier to couple the air lines but it can also go a long way in avoiding those amber ABS warning lights on the dash.
Another point in favour of turning the engine off. I witnessed an incident where a driver with an automatic left it in drive after doing the tug test but forgot to put the park brake on so when he attached the red airline the vehicle actually ‘drove away’ rather than just rolling. Rolling is bad enough but driving could be so much worse, luckily he whipped the red line back off and stopped it.
You got it in one with that one Robntl it is easier to connect the red line with no pressure in the tanks but if you are changing trailers on a regular basis (say 4/5 times a day) it gets a bit tiresome dropping air every time you change trailers.
another thing on this one if your yard has shunters they won,t be to impressed every time they pick up a trailer you have dropped with no air in the tanks!!!
Yeah!!!
Sod the shunters 
Some & not all of em just look at you as if your slowing em down & dont wanna help when you ask pollitly.
Oh & Coffee I always turn off the motor when connecting its the way I was taught & I stick to that riggorously. On my second day as a class one driver I picked up a VOSA leaflet that was all about EBS ABS lines im sure youve probably seen it or know the consiqueses of not connecting it but it went on to state that conecting it whilst the engine was runing Damages the ECU & volvo ecu’s are temporamental enough.
What have just learnt from this topic next time i pick up a trailer im gonna try pumping the pedal & drop the presure b4 I carry out my usual routine switch off walk around blah blah blah!!!
Split coupling is a regular thing for me so pressure is partially low anyways but depending on wheather its a 6 or 4 legger may make it easier rather than struggle & push my roids out trying to get the red line on.
robntl:
…may make it easier rather than struggle & push my roids out trying to get the red line on.
Thanks for that image, I was hoping to have a kip later but I think that nightmare image may have put an end to that. 
Years ago when I last did Class One (no remarks about Scammell couplings please! ) there were shutoff taps on the red lines. Is there any reason (apart from the obvious one of cost) why they were discontinued?
gnasty gnome:
Years ago when I last did Class One (no remarks about Scammell couplings please!
As far as I know it was down to the obvious one.
Ah the old days, shut off taps and blue air lines - good yet simple times.
gnasty gnome:
Years ago when I last did Class One (no remarks about Scammell couplings please!
Elf and safety mate!
drivers cannot be trusted to turn on the taps. It comes as second nature like pulling your zip up
I use palm couplings, never need to use gloves and never have to struggle to connect or make them seal. If it is good enough for all Europe and the United States, why does the UK have to be the odd man out again
I seem to remember the regs were changed a few years ago to comply with Euro regs. as they think that we are a bunch of idiots who can,t be trusted to turn a tap on or off safely! 
I heard it was because they were incidents where the Susie’s got wrapped around the taps and turned them off. No idea if its true but sounds possible on some combinations
DAFMAD:
I heard it was because they were incidents where the Susie’s got wrapped around the taps and turned them off. No idea if its true but sounds possible on some combinations
Not knowing what them days were like i can’tcoment but as for suzzies wrapped around each other & in a tangled mess I find every day i spend 10 mins untangling them, yet when I leave the truck at th end of shift they are al lined up & untangled.
Why ? I know they just tangle for no reason but it dont take much to keep em tidy.
Coffeeholic:
Ah the old days, shut off taps and blue air lines - good yet simple times.
And the “Dead man’s handle.” An additional hand control lever, tucked away behind the seat somewhere, that applied only the trailer brakes and the steer axle brakes.
I never managed to work out the ‘logic’ behind that one. But probably good for tight corners at speed.
Krankee:
Coffeeholic:
Ah the old days, shut off taps and blue air lines - good yet simple times.And the “Dead man’s handle.” An additional hand control lever, tucked away behind the seat somewhere, that applied only the trailer brakes and the steer axle brakes.
I never managed to work out the ‘logic’ behind that one. But probably good for tight corners at speed.
And the seperate trailer brake was invented to save owner drivers money relining brakes when pulling ferry trailers 
Wheel Nut:
And the seperate trailer brake was invented to save owner drivers money relining brakes when pulling ferry trailers
Mine went by the name of ‘The Allport Brake’.
And the seperate trailer brake was invented to save owner drivers money relining brakes when pulling ferry trailers
Yeah, I remember them, they reckon they stopped them because they couldn’t get the ABS to work with them. 
Anyway, going back to the Blue Susie, which was supposed to be an auxiliary, but did anyone have any trailer that the blue actually did something useful on apart from making the trailer brakes stick on temporarily ?