rooster63 Posted December 9, 2020 Share Posted December 9, 2020 I am shortly to take deliver of a new camper van (used but new to us) and it has been fitted with air suspension. Not sure if there will be a manual or how knowledgable the hand over dealer will be but can anybody give me any advice as how you know it is at the correct pressure? I have got a fairly weighty cycle carrier and 2 electric bikes so there are times when the load on the rear axle will be about 70kg heavier. Do I need to alter the pressure depending on whether I am carrying the bikes or not? Or do I set it for the heaviest load (and how do I know it is set correctly?) and leave it at that? Link to comment Share on other sites More sharing options...
Keithl Posted December 9, 2020 Share Posted December 9, 2020 The first thing you are going to need to know is the make of the air suspension kit, possibly AirRide, Dunlop, Firestone or ??? Keith. Link to comment Share on other sites More sharing options...
rooster63 Posted December 9, 2020 Author Share Posted December 9, 2020 Until I pick the van up I won't know so maybe come back to this question then. The reason I've posted the question now is I don't know how knowledgable the dealer will be and there are a lot of things to find out as the new van is very different to our old van. Link to comment Share on other sites More sharing options...
Keithl Posted December 9, 2020 Share Posted December 9, 2020 OK Come back when you have the van. In the meantime I would suggest checking there is at least some pressure in the system before driving as certainly the Dunlop system I have advises against driving with no pressure in the system as this can result in damage to the air bellows themselves. I would suggest a pressure of 40 - 50 psi as a starting point. You say you plan on carrying a 'fairly weighty cycle carrier and 2 electric bikes' on the back but will you have sufficient reax axle load to cope? You will need to visit a weighbridge to check before proceeding. The weight of the carrier plus bikes will add more than its own weight to the rear axle with the difference being transferred from the front axle. The SV Tech website has a useful tool to calculate the effects of adding a load... http://lda2.svtech.co.uk/design?type=type1 Keith. Link to comment Share on other sites More sharing options...
webby1 Posted December 9, 2020 Share Posted December 9, 2020 Just as a little aside about air suspension. The van is in storage at the moment.............hey let's all hope it won't be for too long. I wonder whether folk keep their air suspension inflated......................or is it just like keeping tyres inflated Hmm have I answered my own question :$ :$ Link to comment Share on other sites More sharing options...
Brian Kirby Posted December 9, 2020 Share Posted December 9, 2020 Keithl - 2020-12-09 12:41 PM......................... In the meantime I would suggest checking there is at least some pressure in the system before driving as certainly the Dunlop system I have advises against driving with no pressure in the system as this can result in damage to the air bellows themselves. ....................................Keith. As did our Firestone Driverite system. I'd suggest asking the dealer well before you go, so that if any owners manuals etc are missing, they can get them from the previous owner. You may also need to find out how the system is inflated/deflated to adjust the pressure. Ours was very simple, manually inflated with a cycle pump. Others are automated, yet others have built in pumps that are manually switched with a pressure gauge to show pressure. In terns of establishing the best pressure, what I found worked best was to completely unload the van, deflate the air bellows (this assumes air assisted, not full air), and measure the height of a central, fixed, point (such as the centre of the rear bumper) above ground. This should approximate to the van state when delivered new. Then, with the van unmoved, load it fully (as in absolutely fully, as you will use it with everything and everyone on board) and then inflate the bellows until the rear lifts back to the same height as when unladen, and note the pressure. Then drive it around and see how it feels on the road, and adjust the pressure up or down in small increments (keeping notes) until satisfied. You should only need to follow this procedure once. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted December 9, 2020 Share Posted December 9, 2020 Based on rooster63's recent earlier postings, I'm guessing that the motorhome in question is a 2013 Timberland Destiny. There is some on-line evidence that the 'semi-air' addition to the rear suspension would have been fitted as standard by Timberland as part of the conversion process, so Timberland might be able to advise on the system's manufacturer and there might be guidance in the Timberland handbook regarding air-pressure. This 2016 forum thread covered the same ground: https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Help-please-air-suspension-psi-/42255/ (30psi is probably a good starting point, but it really depends on what tyres are fitted, what type pressures are chosen and how firm a ride is desired when the motorhome if in its normally loaded condition.) Link to comment Share on other sites More sharing options...
rooster63 Posted December 9, 2020 Author Share Posted December 9, 2020 Thanks for all your help, sorry if I sound pedantic about things but the main reason I have changed the van is that I was always uncomfortable that our old van didn’t have a passenger air bag as a few years ago my wife had a very serious car accident which undoubtedly she wouldn’t have survived if the car she was in hadn’t had air bags. I want to make sure that any vehicle we drive in is as accident proof as can be. I know that worn shock absorbers or springs, incorrect tyre pressures can all affect handling so just want to make sure that the air suspension is set up correctly so that handling isn’t compromised. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted December 10, 2020 Share Posted December 10, 2020 rooster63 - 2020-12-09 8:36 PM ... just want to make sure that the air suspension is set up correctly so that handling isn’t compromised. Although it would be possible for someone unfamiliar with the type of semi-air system fitted to your motorhome to treat it ‘incorrectly’, this would really just involve under or over inflating the air-bellows. The air-bellows will have an inflation-pressure ‘window’ (say 15psi to 100psi) and, provided that the user stays within that window, the bellows themselves should not be damaged. But - as I said in my last posting - there are a several variables that affect the choice of pressure depending on why the motorhome has been fitted with a semi-air system (eg, to address weakened rear springs, to cope with significant changes in the load that the vehicle carries, to improve stability in windy conditions, etc.) so some effort needs to be made by the users to select the pressure that is most suitable for their requirements. The following links are to user manuals for semi-air systems by Drive-Rite and AirRide https://www.motorhomeairsuspension.com/wp-content/uploads/2016/11/semi-air-um-dr.51.016000-rev3.pdf https://airride.co.uk/air-suspension-explained/set-up-of-basic-kit/ The AirRide link indicates that the inflation ‘window’ of that system is 20psi-100psi and the following advice is given HOW DO I SET THE RIGHT PRESSURE? To begin with, leave the vehicle at 100 PSI and go for a drive; ideally on a combination of both bumpy back roads and smoother main roads. After you have a feel for the vehicle, stop safely and drop the pressure by 10 PSI. Repeat this until you get to 20 PSI (provided you can drop that low without grounding). We strongly advise taking notes of each pressure and how it feels on both roads and corners. Ask yourself: - What is the handling like? - What is the ride quality like? - What are the load support and stability like? - Does the motorhome bounce or crash? After this you will have a good indication of what pressure is needed to drive. The perfect pressure may be different on main roads and back roads and you will probably have to make some sort of compromise. Leave a note in the vehicle of what pressures you decide work best as it can be hard to remember years later, or for a new owner to know (we provide free stickers if you email your name and address.) As a general rule, most leaf-spring motorhomes would need between 50 and 80 PSI. Coil-spring or torsion-bar (AL-KO) vehicles can be very different. If you’re not sure which kind of spring you have, e-mail us and we’ll ask for some pictures to try and work it out for you. That guidance is probably as good as any... Link to comment Share on other sites More sharing options...
Deneb Posted December 10, 2020 Share Posted December 10, 2020 Fiat provide the following specifications for the X250/X290 Ducato in unladen condition. I would imagine the other Sevel vans would be identical. Measured on a level surface, from ground to load floor at rear doors: Light chassis: 545mm Heavy chassis: 555mm (560mm for 6.3m extra-long body) The idea of air suspension is to return the ride height to its normal position with the vehicle in laden condition. That should retain the best stance for handling and available suspension travel without being unduly harsh. The pressure required in the system will obviously depend on the load being carried at any given time. I use to have air-assist shock absorbers on my tow cars many years ago, and the setting advice was similar. Ditto with the air systems fitted to our Range Rover accident tenders. My Ducato PVC on a light chassis with twin leaf rear springs has never required more than 20 psi in its air suspension. If carrying rear mounted bicycles, or on a coachbuilt van with a longer rear overhang and a garage or similar rear storage space, the pressure required is likely to be somewhat higher. Link to comment Share on other sites More sharing options...
Hans Posted December 10, 2020 Share Posted December 10, 2020 Air suspension in the first place is to get a softer ride in your jingle jangle motorhome. The Citroen Ds hydro pneumatic is the best example. Like a Aircraft landing on his feet's But the heck you can change driving height. and parking height too.. And axle weights. If your air bellows leak you are a stranded duck. (lol) (lol) Link to comment Share on other sites More sharing options...
Derek Uzzell Posted December 11, 2020 Share Posted December 11, 2020 The two attached photos are of the rear suspension of Ducato panel-van conversions - one with single-leaf springs and the other with twin-leaf springs. Fitting a semi-air system will involve removal of the orange components (spring assisters) replacing them with air-bellows. In the 1st photo the spring assister looks well squashed and fiting a semi-air system should be beneficial: in the 2nd photo the spring assister is much more extended and a semi-air system might be unnecessary. (I’ve no idea how ‘loaded’ the PVCs were when the photos were taken...) If an air-bellows of a semi-air system fails, the effect will depend on how important a part the bellows was playing. If the bellows was supporting a lot of weight, the effect should be significant and visually obvious: if it were only supporting a relatively low weight, a driver might not notice the failure. But only in extreme cases should a bellows failure make the vehicle undrivable. A semi-air system is not a panacea for rear suspension-related problems. And if a motorhome’s load is to vary significantly (eg. by occasionally transporting a motorbike on a rear carrier) or a motorhome’s rear ground clearance needs to be temporarily increased (eg. when embarking on a ferry) it would be sensible to include an electric air-compressor in the system so that the pressure in the bellows can easily be matched to the load or circumstances. Link to comment Share on other sites More sharing options...
Deneb Posted December 11, 2020 Share Posted December 11, 2020 Derek Uzzell - 2020-12-11 8:21 AM If an air-bellows of a semi-air system fails, the effect will depend on how important a part the bellows was playing. If the bellows was supporting a lot of weight, the effect should be significant and visually obvious: if it were only supporting a relatively low weight, a driver might not notice the failure. But only in extreme cases should a bellows failure make the vehicle undrivable. Sorry, I would have to disagree with that Derek. The original "bump stop" / spring assister unit is clearly touching the contact plate on the spring in both of your pictures. That is by design, as it is intended, as you correctly identify, to be a spring assister and not just a bump stop to restrict suspension movement at the limit of spring compression. The purpose of the spring assister has even confused MOT testers and has been the subject of an advice notice and entry in the Matters of Testing journal in the past to make them aware that contact between the spring and assister is intentional by design, and should not have been regarded as a reason for rejection under the old MOT test criteria. So the orange spring assister is clearly an integral part of the suspension system. When air assist suspension kits are fitted, the air bellows normally takes the place of the original composite assister cone and allows for a more variably adjustable rate of resistance and progression of movement in spring compression. If the bellows on one side were to fail, the extent to which it might affect the static stance of the vehicle would depend on its laden condition, and may not be obvious with an unladen van, but I would expect it to result in some degree of leaning to one side on a motorhome where the weight of the habitation conversion already takes up a considerable amount of the original base vehicle's payload capacity. But in any case, it will have a detrimental affect on the handling of the vehicle. Again, how much might depend on its laden condition, but also on the severity of any steering or other input by the driver. The complete deflation of an airbag would likely result in its irreparable damage or disintegration over a relatively short period of time, as well as allowing full suspension deflection beyond the original design limit imposed by the original composite assister. It would also be regarded as a defect under the DVSA Categorisation of Defects criteria for enforcement. If the bellows or any part of the air system was visible damaged and considered likely to fail, but had not actually done so, it would be regarded as a dangerous defect under the criteria. If it had failed (in the wording of the manual, was "displaced/damaged/fouling other components/seriously deteriorated or leaking air") it would fall within the criteria of an immediate prohibition on the vehicle being driven on a road until the fault had been rectified. So whilst I realise you may have meant that a failed bellows might not physically prevent you driving the vehicle, it would legally do so and could have serious repercussions in the event of an accident or other incident where the suspension was deemed to have been defective before the incident, especially if regarded as a contributory factor. As an aside, I once prohibited a Sevel van where a missing conical assister cone had been replaced by a lump of 4x4 timber jammed between the axle and chassis rail, and lashed around the axle tube 8-) Link to comment Share on other sites More sharing options...
arthur49 Posted December 11, 2020 Share Posted December 11, 2020 In that first photo the semi air suspension needs adjustment! The bellows are out of alignment - they should be vertical in all directions, not offset 8-) 8-) Link to comment Share on other sites More sharing options...
Keithl Posted December 11, 2020 Share Posted December 11, 2020 arthur49 - 2020-12-11 1:58 PM In that first photo the semi air suspension needs adjustment! The bellows are out of alignment - they should be vertical in all directions, not offset 8-) 8-) That's because it is not air assisted, it is the standard fit Fiat spring assistor. Basically a very large bump stop with progressive compression. Keith. Link to comment Share on other sites More sharing options...
arthur49 Posted December 11, 2020 Share Posted December 11, 2020 Keithl - 2020-12-11 2:46 PM arthur49 - 2020-12-11 1:58 PM In that first photo the semi air suspension needs adjustment! The bellows are out of alignment - they should be vertical in all directions, not offset 8-) 8-) That's because it is not air assisted, it is the standard fit Fiat spring assistor. Basically a very large bump stop with progressive compression. Keith. Ah! So it is ...... :$ :$ Link to comment Share on other sites More sharing options...
witzend Posted April 21, 2021 Share Posted April 21, 2021 rooster63 - 2020-12-09 11:27 AM Do I need to alter the pressure depending on whether I am carrying the bikes or not? Or do I set it for the heaviest load (and how do I know it is set correctly?) and leave it at that? Usually a case of how you want the ride there should be a gauge start of mid range and adjust to suit 15 to 20 psi suits mine Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.