Air Assisted Rear Suspension & Handbrake

 
 
 
 
 
 
essjay
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Air Assisted Rear Suspension & Handbrake

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Posted: 06.08.2019  ·  #1
I have just fitted the Dunlop air assisted rear suspension to my Knaus which is on a Ducato x230 Maxi chassis and the handbrake cable cover seems a bit short.

When I pumped the bags up to 80psi to check for leaks, the cable was so tight against the bottom of the leaf springs I couldn't move it. Dropped down to 40psi and there's a little slack but still seems shorter than I like. Down to 30psi and as with 40psi there's a little wiggle room but at 30psi the benefit of the bags is hardly noticeable.

Anyone else have this issue that fitted the air bags instead of bumpstops?


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 06.08.2019  ·  #2
I only ever run mine at


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 06.08.2019  ·  #3
I had factory fitted air suspension and it was 25 psi too but that is possibly different to a retro fit like yours


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 06.08.2019  ·  #4
I keep mine at about 2 bar. Approximately 29 psi. Only put more in them to rise the rear if necessary


essjay
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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 06.08.2019  ·  #5
Thanks for the input.... I guess my question is more to do with the handbrake. On your vans at 30psi, how tight is the handbrake cable to the bottom of the leaf springs? One one side of the van there's space but rubbing on the left side. I wonder has someone fitted a shorter handbrake cable cover.

BTW. At 30psi, the van seems just about level as it was sagging at the back (26 year old leaf springs)


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 07.08.2019  ·  #6
BTW, when I had them fitted on my 1999 X230, he pumped them way up to show me how they worked. I subsequently ran them at 23 which put the springs back in shape.
However, he didn't adjust the load sensor which obviously hadn't been need for many, many years. A few weeks later the load sensor failed and I had zero brakes. I think he wrenched the sensor out of its slumber and the seal was too tired to cope.
A weak point on the X230 is that the load sensor is common to both brake lines and you lose the lot!


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 07.08.2019  ·  #7
I think it is called the brake compensator and mine was part number 1315251080. Just so you can see if you have it fitted.


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 07.08.2019  ·  #8
Trying to put a bit of clarity on air assistance suspension, as most motorcaravans are built on van chassis cabs and to get the stability and in some cases upgrade to a greater carrying capacity as well they have to add air bellows between the chassis and normal spring suspension. This operates as a rule of thumb around 2 bar /25psi to 30 psi. You have a light laden valve (compensator )mounted above the rear axle which senses a light load and turns down the rear brakes so you dont skid the rear wheels. As the caravan conversion makes the vehicle run at near max it should be adjusted to max to keep the brakes efficient, (personally I dont think it is needed on a motorhome conversion and taken off, any comments?). The handbrake is adjusted to 3 or 4 clicks from off to on. This is achieved by adjusting the rod or cables underneath so the back wheels spin freely when off and lock up when the handbrake is on. Some converters moved the handbrake angle to let the drivers seat rotate thus reducing the efficiency, I took the mechanism off and returned the bracket back to its original mounting and got a better handbrake You can increase the air pressure to 4 bar to lessen tail drag to say board or unload from a car ferry ramp if it is very steep or remove a rear tyre say for a puncture ,it lifts the bodywork up and give more clearance


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 08.08.2019  ·  #9
Basically you are saying that the airbags are fooling the compensator valve into thinking that the motorhome is carrying a lighter load and the rear brakes are not operating correctly? If so that sounds dangerous. Should the airbags be let down when the van is presented for a test?


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 08.08.2019  ·  #10
A few years ago when I fitted mine


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 08.08.2019  ·  #11
Interesting topic. I have a question about these but I don't want to jump in yet and change the topic slightly, I'll wait my turn when you are all sorted ;)


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 08.08.2019  ·  #12
Yes Chausson It does not hurt to let the suspension down a little for the test as you are putting more load on the light laden valve, which is on the older models like mine is a rod from the rear axle with a spring on it .


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Air Assisted Rear Suspension & Handbrake

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Posted: 08.08.2019  ·  #13
On older vans with a constant load the valve freezes in a in a set position with a very short stroke .
So it will work if more weight is added to the van ( lower to the ground ) but will not operate pass the position it has been in for years ( if the body is raised )
I discovered this when after replacing 12 year old rear shocks, I had a break imbalance .
I stripped it out and cleaned all the linkage and freed up the piston rod got full travel in both directions. Works grand since.

Advise . if doing an aftermarket fit of air assist, check if you have a valve, its obvious ( a block with brake pipes attached and a leaver system connected to the axle.) And make sure it is operational .


essjay
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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 08.08.2019  ·  #14
Yes my van has the LSV (load sensor valve?) and it was pretty much siezed in position. Not sure it even matters on a camper as its constantly loaded.

Concerned now that it could let go and I'd lose brakes.

Back to the handbrake. Can it be adjusted to give more slack to the cable cover under the leaf springs?

And just to note, I'm not looking to raise the an but to level it. After 26 years it was sagging at the back and the bags have now just levelled it.


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 09.08.2019  ·  #15
Quote by essjay
Back to the handbrake. Can it be adjusted to give more slack to the cable cover under the leaf springs?


instructions as to whats req


JonMac46
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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 09.08.2019  ·  #16
Agreed it is constantly loaded, but blowing the airbags up will have probably caused it to move for the first time ever! It took about a month before mine leaked and I lost the brakes. The AA man identified it and I drove at 1mph to the garage 200 yards away. The ordered the part and sorted it.


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Re: Air Assisted Rear Suspension & Handbrake

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Posted: 09.08.2019  ·  #17
On the Fiat/Peugeot/Citreon range before they changed the cab about 2006 you have handbrake cable running to a central steel rod running down the center of the underfloor, this has fluted curved end which the cable from the rear wheels run and must have a bit of grease in the flute to let the rear brake cable equalize . The rear brake shoes must be correctly adjusted and move freely before you adjust anything else.


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