If you drop the trailer suspension and drive with it lowered, does it reset itself if you go over a certain speed?
Only reason I ask is I delivered to a place last night and had to go under a 13’9" bridge (quite a wide 4 line railway bridge) with a 13’6" trailer. I did the delivery and just to be safe (with me being new) I decided to dump the air out of the unit and trailer to drive back under it with the assumption that the trailer will be more susceptible to bounce with it being empty. When i pulled over to reset it all I found the trailer had already reset itself, hence the original question ^^^^^^
EDIT - I didn’t know whether it was something I’d done or whether it reset itself.
It depends if the handle valve has an automatic or manual reset function fitted both look the same unless you know what you’re looking for in the way it’s plumbed in only way to tell is testing it really.
Manual version - you push the handle in and then move left or right to raise or lower. The trailer won’t reset to normal ride height unless you physically pull the handle back out again
Automatic reset version - this version operates exactly the same but uses a feed, from usually the red line*, to automatically pop the handle back out again, when the line pressures up, in case the driver forgets. If it operates in this way and you want to go under a bridge, or some distance say without it automatically resetting, the first option is to drop the red line and do so on shunt. The 2nd option, more likely if there’s some fault with the ride height/air suspension system and you need to over-ride it for a long distance is to clamp the airline going to the handle that would normally cause it to pop out, tie wrapping the handle in the pushed in position may also be an option.
*They don’t always take the feed from the red line so this can’t be assumed in all cases, best to test a bit first to establish for sure.
Forgot to say this is all on trailers without EBS. On new trailer with EBS as mentioned it’s based on wheel speed and controlled electronically, the speed it resets at will have been set at manufacture usually and can vary it pops the handle out itself the same way.
AS has been said, the newer ones do but I wouldn’t rely on it so check it anyway.
OOhhh look at you, newbie being careful, fair play to you sir!
Just to add, I went under a 4.3m bridge with a 4.27m trailer there recently, I dropped the unit suspension but not the trailer, the old bomb bay doors do tighten a bit as you creep under!
Yeah, normally I don’t bother if it’s close just in case & will go round via a different route but I had to go under that one basically so just got on with it.
More important is remembering to drop the unit tag axle on a empty(ish) Scania especially if close to height, must be about the highest tractor unit out there with tag raised, they go up about 3"…wish i had another 3"…
Juddian:
More important is remembering to drop the unit tag axle on a empty(ish) Scania especially if close to height, must be about the highest tractor unit out there with tag raised, they go up about 3"…wish i had another 3"…
Is it the same for the tag axles aswell then? I know on the mid lifts they raise it by 3". Don’t think I’ll ever get to use a tag axle.
Juddian:
More important is remembering to drop the unit tag axle on a empty(ish) Scania especially if close to height, must be about the highest tractor unit out there with tag raised, they go up about 3"…wish i had another 3"…
Is it the same for the tag axles aswell then? I know on the mid lifts they raise it by 3". Don’t think I’ll ever get to use a tag axle.
Sorry Tarrman, i meant the mid lifts, call 'em all tag axles for some reason too bloody old to change now…
Silver_Surfer:
Yeah, normally I don’t bother if it’s close just in case & will go round via a different route but I had to go under that one basically so just got on with it.
I had a choice, I was at a cross roads junction, my delivery was about 50 meters past the 13’ 9". To my left was a 14’ something bridge and to my right was a small residential street. A u turn would of been very difficult so I decided what the hell and hoped to god I’d set my height right
Juddian:
More important is remembering to drop the unit tag axle on a empty(ish) Scania especially if close to height, must be about the highest tractor unit out there with tag raised, they go up about 3"…wish i had another 3"…
Is it the same for the tag axles aswell then? I know on the mid lifts they raise it by 3". Don’t think I’ll ever get to use a tag axle.
Sorry Tarrman, i meant the mid lifts, call 'em all tag axles for some reason too bloody old to change now…
I should imagine they both go up about the same for what I’ve seen of the likes of the biomass drivers. Tag/mid lift, same thing (dons tin hat ).
Juddian:
More important is remembering to drop the unit tag axle on a empty(ish) Scania especially if close to height, must be about the highest tractor unit out there with tag raised, they go up about 3"…wish i had another 3"…
Is it the same for the tag axles aswell then? I know on the mid lifts they raise it by 3". Don’t think I’ll ever get to use a tag axle.
Sorry Tarrman, i meant the mid lifts, call 'em all tag axles for some reason too bloody old to change now…
I should imagine they both go up about the same for what I’ve seen of the likes of the biomass drivers. Tag/mid lift, same thing (dons tin hat ).
Disconnect the ABS line and it will stay in “low run” mode
Silver_Surfer:
AS has been said, the newer ones do but I wouldn’t rely on it so check it anyway.
OOhhh look at you, newbie being careful, fair play to you sir!
Just to add, I went under a 4.3m bridge with a 4.27m trailer there recently, I dropped the unit suspension but not the trailer, the old bomb bay doors do tighten a bit as you creep under!
Generally only if there’s an electrical connection to the back of the handle it’ll be an auto-reset at whatever speed the trailer’s been programmed at.
If something’s knackered and you need to travel with the suspension manually altered above that speed unplug this wire from the handle. Easy to spot as everthing else going to and from will be airlines.
