Hi, I’ve known it for a while and as I sit here waiting I thought about it again.
If I push in and push down my handbrake it feels like it releases the trailer brakes. Which I don’t understand, first I thought it released the unit brakes so you could split couple.
So does anyone know the reasoning behind this.
Also I told another driver who has been driving for 20 years and he never knew about it so I guess it isn’t used much.
Just tried it and can indeed report that something does happen. Quite what I’m not sure but the truck moved an inch. So that’s me happy now.
Isn’t the parking brake supposed to be a progressive brake (rather than all-on or all-off) so that it can be used as a secondary brake in case your service brakes fail? Perhaps you’re sensing the first stages of it starting to release the brakes slightly, and that the trailer ones are a bit more sensitive than the unit ones?
MrFlibble:
Isn’t the parking brake supposed to be a progressive brake (rather than all-on or all-off)
All the trucks that i have driven, it’s been basically an all or nothing brake, from what i can tell, not really into stuff getting thrown through the windscreen, to test further
you can use them just the same as a brake pedal… progressively…
even the electronic ones such as fitted in the new volvo’s and renault’s, just be careful first time you try it…
The op isn’t on about using the handbrake progressively, he/she is talking about when you’re stationary with the handbrake applied you can push the lever in and down and then hear a release of air. Well, on the Actros that happens.
Certainly on a merc pushing it down after the usual stop releases the trailer brakes - it explains in the manual that its so you can test the unit brakes are holding the whole outfit OK. I used to do it once I’d stopped to let it level out.
If im closing an extender i sometimes use the first couple of inches on the handbrake to apply the trailer brakes only, suppose it works the opposite way round as well
It is only on units which apply the trailer brakes when the unit brakes are in park. Pushed in and down it does release the trailer brakes. The purpose is so that the driver can check whether the unit parking (spring) brakes are capable of holding the combination on a hill on their own.
Oh right I see. Just something I come across and didn’t understand. I still don’t think it’s a part of the that won’t be used.
Good to have a understanding of what it is used for though.