ferd Posted March 31, 2012 Share Posted March 31, 2012 Just had air suspension installed on a Ford Transit Hobby. Any advice on the best pressure to run on would be welcome. Link to comment Share on other sites More sharing options...
Guest peter Posted March 31, 2012 Share Posted March 31, 2012 Start off with 40 psi and see how you go. Link to comment Share on other sites More sharing options...
Keithl Posted March 31, 2012 Share Posted March 31, 2012 Ferd, I'd agree with 40psi as a starting point too. That's what we run the Dunlop system on our Merc at. Keith. Edit, What system have you fitted and did it not come with a recommendation on pressure? Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 31, 2012 Share Posted March 31, 2012 I'm somewhat surprised you've felt the need to add air-assistance to the rear suspension of your relatively compact and lightweight 2008 Hobby Siesta Exclusive T-555 FS, as I've never considered it worthwhile on my longer Transit-based Hobby built on a similar 3.75m wheelbase chassis. Perhaps you are carrying something heavy (like a scooter) on the back, or perhaps my 2005 motorhome has heavier-duty rear springs than yours. What inflation-pressure proves best will depend on what air-assistance 'kit' has been fitted and the load that's being placed on the motorhome's rear axle. I'd tend to start lowish (say 20psi) and work up if you feel that's insufficient. Might also be worth knowing what rear tyre pressures you are using as, if they are high and you also use a high pressure in the air-bellows, you could end up with a pretty harsh ride. Link to comment Share on other sites More sharing options...
ferd Posted March 31, 2012 Author Share Posted March 31, 2012 I would agree with your comments but I found that the the Hobby tended to sway rather a lot and gets a buffeting by lorries and crosswinds all of which I find disconcerting. I'm hoping that the air suspension will go some way to overcome this. I do not carry anything excessively heavy but I did find the original suspension soft. It's a Dunlop system which has been fitted and does have recommendations but I thought I would seek some advice from these excellent forums. Thanks for all the advice. Link to comment Share on other sites More sharing options...
Brian Kirby Posted March 31, 2012 Share Posted March 31, 2012 I'll tell you what I did. I measured the distance from ground to the underside of the rear bumper with the van completely unloaded. Then, with it fully loaded, I increased the pressures, equally on each side, until the rear bumper was back where it had started. So, quasi-scientific, as opposed to suck-it-and-see! :-) I fitted the air-ride assisters mainly to prevent occasional grounding as ours, in which nearly all added load falls upon the rear axle, has a lenghty rear overhang. Re-setting the rear ground clearance in this way has worked for us, no grounding since, general improvement in stability down uneven roads, and noticeably reduced yawing around roundabouts. Link to comment Share on other sites More sharing options...
George Collings Posted March 31, 2012 Share Posted March 31, 2012 Brian, I have no details of how the braking system on your Transit deals with variation in rear axle loading but on most vehicles the ride hight is used to alter the front to rear braking bias. Using the air to maintain ride height can mislead any load sensing eqipment. Have you taken this into consideration. If not there is the possibility that your rear brakes are not providing the optimum braking effort. This could lead to increased breaking distance in an emergency stop or front brake fade on long descents. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 31, 2012 Share Posted March 31, 2012 ferd - 2012-03-31 11:43 AM I would agree with your comments but I found that the the Hobby tended to sway rather a lot and gets a buffeting by lorries and crosswinds all of which I find disconcerting. I'm hoping that the air suspension will go some way to overcome this. I do not carry anything excessively heavy but I did find the original suspension soft. It's a Dunlop system which has been fitted and does have recommendations but I thought I would seek some advice from these excellent forums. Thanks for all the advice. There's an advert for a 2010 version of your Hobby Siesta here: http://tinyurl.com/cymtwjn I notice from the side-on view (photo 2) that this has single-leaf rear springs (like Brian's "Van"), whereas the rear springs of my 2005 T-600 are double-leaf. This difference may be significant as my motorhome - despite an extra 0.38m of rear overhang - does not suffer unduly from 'lorry buffeting'. It will react a bit to strong cross-winds, but that's really to be expected. Some people seem completely unconcerned by such behaviour: other people (like me) don't care for it at all - it depends on one's fear-threshold I guess. I can't say the level of my Hobby's cross-wind movement bothers me greatly and I'm not sure it would be easily curable. I use 4.0bar for the rear tyre pressures and would rate the general ride quality as firm but not harsh - certainly not soft. Given the design and interior layout of your Hobby model (and of mine), grounding at the rear will never normally be an issue. It's probable too that (unlike Brian's shorter wheelbase, garage-equipped "Van") there won't be a disproportionally-large amount of weight on the rear axle when your motorhome is fully loaded. Brian's technique of measuring the under-rear-bumper ground clearance and adjusting the bellows-pressure accordingly sounds like the best way forward to begin with, but if your Siesta currently rolls unpleasantly when cornering, you may have to increase the bellows-pressure a good deal to obtain sufficient roll-stiffness to effectively combat body-sway during spirited driving. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 31, 2012 Share Posted March 31, 2012 George Collings - 2012-03-31 2:12 PM Brian, I have no details of how the braking system on your Transit deals with variation in rear axle loading but on most vehicles the ride hight is used to alter the front to rear braking bias. Using the air to maintain ride height can mislead any load sensing eqipment. Have you taken this into consideration. If not there is the possibility that your rear brakes are not providing the optimum braking effort. This could lead to increased breaking distance in an emergency stop or front brake fade on long descents. George I believe that all Transit Mk 6 and Mk 7 vehicles have ABS as standard. Certainly the 2004-onwards Transit chassis used by Hobby all have ABS. Unlike earlier non-ABS-equipped Transit models, there's no ride-height-based load-sensing feature to bias front/rear braking proportionate to rear-axle loading. In an emergency, whether you've got a bag of feathers or a half-tonne of gold bullion stored above the rear axle, you just stamp on the brakes and pray that the electronic magic of ABS will optimise your braking and save your bacon. Link to comment Share on other sites More sharing options...
ferd Posted March 31, 2012 Author Share Posted March 31, 2012 That Hobby in the photograph is sitting higher at the rear than mine before the suspension kit was fitted. Mine is a 2008 plate second hand and was used to towing a small car in its previous ownership. Don't know if that makes a difference or not. Link to comment Share on other sites More sharing options...
Mel B Posted March 31, 2012 Share Posted March 31, 2012 ferd - 2012-03-31 11:43 AM I would agree with your comments but I found that the the Hobby tended to sway rather a lot and gets a buffeting by lorries and crosswinds all of which I find disconcerting. I'm hoping that the air suspension will go some way to overcome this. I do not carry anything excessively heavy but I did find the original suspension soft. It's a Dunlop system which has been fitted and does have recommendations but I thought I would seek some advice from these excellent forums. Thanks for all the advice. Hi ferd ... welcome to the mad house! :-D We had air suspension (Air Ride) fitted on our previous van (Mk 6 Transit Twin RWD Rimor Sailer 645TC at 7.14m) and have had it put on our current van (Mk 7 Transit FWD Chausson Flash 04 at 5.99m). We found with the Rimor that it dramatically improved the ride and handling, reduced the 'wash' effect from passing lorries and buffeting from strong winds. Although our Chausson wasn't anywhere near as badly affected we still noticed the lack of air suspension so had it put on soon after we bought it and it has definitely improved things so you will cetainly notice how beneficial it is on your van ... you just need to remember that you're in a motorhome and not a racing car! :D Link to comment Share on other sites More sharing options...
EMS Posted March 31, 2012 Share Posted March 31, 2012 We had air suspension fitted to our Hymer Van a transit, the ride was better without the bump stops thumping. The strange effect is, when cornering around a large roundabout the body slowly tilts(slowly as the two air bags have been left with the airlines connected) then on leaving the roundabout the tilt slowly goes back to the correct position. This effect would be eliminated if the airline connected that connects the two airbags was turned of. The Van is very much more comfortable, staying stable when there are side gusts or when passing large lorries. We run at a pressure of 35psi this seems a good compromise, the van is about 3 tons. Link to comment Share on other sites More sharing options...
Keithl Posted March 31, 2012 Share Posted March 31, 2012 EMS - 2012-03-31 8:40 PM We had air suspension fitted to our Hymer Van a transit, the ride was better without the bump stops thumping. The strange effect is, when cornering around a large roundabout the body slowly tilts(slowly as the two air bags have been left with the airlines connected) then on leaving the roundabout the tilt slowly goes back to the correct position. This effect would be eliminated if the airline connected that connects the two airbags was turned of. The Van is very much more comfortable, staying stable when there are side gusts or when passing large lorries. We run at a pressure of 35psi this seems a good compromise, the van is about 3 tons. EMS, All the instructions for various makes of air suspension that I have read say that the interconnecting valve(s) should be closed after inflation to prevent this 'Cross talk'. I suggest you re-read your instructions or contact the supplier to check if you should be closing the valve(s) on yours as this is a dangerous condition and I doubt is the system where designed to be used in this way. Keith. Edit to reply to George, The Dunlop system has 2 variants for with or without ABS. As we do not have ABS the kit included a bracket to locate the biasing valve at it's 'fully loaded' position and (from memory) a warning that this bracket must only be used on MH's over a certain weight and not on vans. Link to comment Share on other sites More sharing options...
George Collings Posted March 31, 2012 Share Posted March 31, 2012 Derek Uzzell - 2012-03-31 2:48 PM George Collings - 2012-03-31 2:12 PM Brian, I have no details of how the braking system on your Transit deals with variation in rear axle loading but on most vehicles the ride hight is used to alter the front to rear braking bias. Using the air to maintain ride height can mislead any load sensing eqipment. Have you taken this into consideration. If not there is the possibility that your rear brakes are not providing the optimum braking effort. This could lead to increased breaking distance in an emergency stop or front brake fade on long descents. George I believe that all Transit Mk 6 and Mk 7 vehicles have ABS as standard. Certainly the 2004-onwards Transit chassis used by Hobby all have ABS. Unlike earlier non-ABS-equipped Transit models, there's no ride-height-based load-sensing feature to bias front/rear braking proportionate to rear-axle loading. In an emergency, whether you've got a bag of feathers or a half-tonne of gold bullion stored above the rear axle, you just stamp on the brakes and pray that the electronic magic of ABS will optimise your braking and save your bacon. Derek. ABS Is superb at preventing wheel locking where brake force exceeds the available tyre grip but that is dependent upon axle loading. If the brake effort is insufficient for the axle load and available tyre grip the ABS will not operate , the ABS will operate on the other axle preventing locking, however maximum retardation will not be available increasing stopping distances. In prolonged braking either from high speed or more likely long descents if there were no rear axle load compensation the front brakes would be doing most of the work and front fade become a real posibility. Some air bag kits do provide a bracket to reposition the load sensing unit on non ABS equipped vehicles. The load sensors used to be hydraulic and could be quite complex, some modified brake line pressure taking into account that heavy braking tranferred weight off the rear axle but that this effect was much less during moderate braking . I saw somewhere that on some vehicles this is now done electronically probably in conjunction with the electronic stabity control sytem that corrects driver error during cornering by applying appropriate levels of braking to individual wheels but I am not up to speed on the latest developments. Air bag alterations to ride height might still be critical fi the sensors tell the computers porky pies. Link to comment Share on other sites More sharing options...
Mel B Posted March 31, 2012 Share Posted March 31, 2012 Keithl - 2012-03-31 9:00 PM EMS - 2012-03-31 8:40 PM We had air suspension fitted to our Hymer Van a transit, the ride was better without the bump stops thumping. The strange effect is, when cornering around a large roundabout the body slowly tilts(slowly as the two air bags have been left with the airlines connected) then on leaving the roundabout the tilt slowly goes back to the correct position. This effect would be eliminated if the airline connected that connects the two airbags was turned of. The Van is very much more comfortable, staying stable when there are side gusts or when passing large lorries. We run at a pressure of 35psi this seems a good compromise, the van is about 3 tons. EMS, All the instructions for various makes of air suspension that I have read say that the interconnecting valve(s) should be closed after inflation to prevent this 'Cross talk'. I suggest you re-read your instructions or contact the supplier to check if you should be closing the valve(s) on yours as this is a dangerous condition and I doubt is the system where designed to be used in this way. Keith. EMS, I'll second what Keith says - the valves should be closed and therefore 'sealed' from being able to allow the air to flow between them. Link to comment Share on other sites More sharing options...
ferd Posted April 1, 2012 Author Share Posted April 1, 2012 I was told by the garage to keep the valves closed. Link to comment Share on other sites More sharing options...
George Collings Posted April 1, 2012 Share Posted April 1, 2012 Air suspension raises the ride height and the vehicles centre of gravity but if the units on each side are coupled they do not contribute roll stiffness as the air just pumps from side to side. Disconnection gives additional roll stiffness more than combating the effects of the higher centre of gravity. Link to comment Share on other sites More sharing options...
cronkle Posted April 1, 2012 Share Posted April 1, 2012 Mel B - 2012-03-31 10:57 PM Keithl - 2012-03-31 9:00 PM EMS - 2012-03-31 8:40 PM We had air suspension fitted to our Hymer Van a transit, the ride was better without the bump stops thumping. The strange effect is, when cornering around a large roundabout the body slowly tilts(slowly as the two air bags have been left with the airlines connected) then on leaving the roundabout the tilt slowly goes back to the correct position. This effect would be eliminated if the airline connected that connects the two airbags was turned of. The Van is very much more comfortable, staying stable when there are side gusts or when passing large lorries. We run at a pressure of 35psi this seems a good compromise, the van is about 3 tons. EMS, All the instructions for various makes of air suspension that I have read say that the interconnecting valve(s) should be closed after inflation to prevent this 'Cross talk'. I suggest you re-read your instructions or contact the supplier to check if you should be closing the valve(s) on yours as this is a dangerous condition and I doubt is the system where designed to be used in this way. Keith. EMS, I'll second what Keith says - the valves should be closed and therefore 'sealed' from being able to allow the air to flow between them. My system is Airide. I was told that the valves should be open to equalise the pressure between the two sides. The website says the same - http://www.airide.co.uk/airide_operating_instructions.pdf I run my van, a Mark 7 Transit FWD at 38 psi ish Link to comment Share on other sites More sharing options...
George Collings Posted April 1, 2012 Share Posted April 1, 2012 I can understand the Airide instructions to open the taps to equalise pressure after using the sytem to level the van but not the bit about damaging the gauges because the air has nowhere to go. The highest pressures would occur when the vehicle negotiated something like a speed hump at excessive speed ( anyone not got the T shirt). There the suspension including the airbags is fully compressed and may well hit the bump stops, it would take some very hard cornering to compress one side so much. Baffled (but not silenced) in south Devon Link to comment Share on other sites More sharing options...
cronkle Posted April 1, 2012 Share Posted April 1, 2012 George Collings - 2012-04-01 4:14 PM I can understand the Airide instructions to open the taps to equalise pressure after using the sytem to level the van but not the bit about damaging the gauges because the air has nowhere to go. The highest pressures would occur when the vehicle negotiated something like a speed hump at excessive speed ( anyone not got the T shirt). There the suspension including the airbags is fully compressed and may well hit the bump stops, it would take some very hard cornering to compress one side so much. Baffled (but not silenced) in south Devon I just looked at my system and I think what they are driving at is that the guage is in the airway between the schrader valve and the taps. This is a gap of about 2.5cm and as that section is mostly casting the gauge would be the weakest point and therefore likely to be damaged first if trying to inflate the system with the taps shut. If I remember correctly one of the other reasons for balancing the system was to make sure that both sides did the same thing if one of the airbags suddenly deflated. EDITED: to add 'if trying to inflate the system with the taps shut.' Link to comment Share on other sites More sharing options...
Mel B Posted April 1, 2012 Share Posted April 1, 2012 I've just read the instructions in the link where they say: "It is not normally necessary to leave both taps closed, we have had owners do this and forget to re-open them before attempting to inflate the system, this is likely to damage the gauge, as the air has nowhere to go" IMV I suspect they don't mean for BOTH taps SHOULD be OPEN, but ONE tap can be OPEN and ONE tap should be CLOSED, this would prevent any damage to the gauge if someone tried to inflate it but shouldn't affect the handling and wouldn't allow the air to move from one side (closed) to the other (open). Below is an extract from the instructions: Link to comment Share on other sites More sharing options...
cronkle Posted April 1, 2012 Share Posted April 1, 2012 Mel B - 2012-04-01 4:38 PM I've just read the instructions in the link where they say: "It is not normally necessary to leave both taps closed, we have had owners do this and forget to re-open them before attempting to inflate the system, this is likely to damage the gauge, as the air has nowhere to go" IMV I suspect they don't mean for BOTH taps SHOULD be OPEN, but ONE tap can be OPEN and ONE tap should be CLOSED, this would prevent any damage to the gauge if someone tried to inflate it but shouldn't affect the handling and wouldn't allow the air to move from one side (closed) to the other (open). Below is an extract from the instructions: I think the first sentence of your quote from the pdf. confirms what I was told - the taps are provided to allow each side to be inflated to different pressures to aid leveling when parked. I have had some success with this as a technique. Link to comment Share on other sites More sharing options...
Keithl Posted April 1, 2012 Share Posted April 1, 2012 EMS & Cronkle, I think the best course of action for both of you would be to phone AiRide and ask them to clarify the situation and then post the answer on this thread. I think you are reading too much into the instructions and what you should actually be doing is opening both valves to level the system then closing ONE to prevent what I would call 'Cross Talk'. I await the answer from AiRide with interest. Keith. Link to comment Share on other sites More sharing options...
cronkle Posted April 1, 2012 Share Posted April 1, 2012 Keithl - 2012-04-01 5:51 PM EMS & Cronkle, I think the best course of action for both of you would be to phone AiRide and ask them to clarify the situation and then post the answer on this thread. I think you are reading too much into the instructions and what you should actually be doing is opening both valves to level the system then closing ONE to prevent what I would call 'Cross Talk'. I await the answer from AiRide with interest. Keith. hi Keith Thanks for your concern but I am fairly clear about what I was told on installation and in subsequent conversations with Airide. I posted because people were being quite definite about the taps being closed. This was not consistent with what I had been told by Airide. It is not how I interpret the pdf. I would also point out that the pdf does not say that the taps cannot be closed - you just need to remember that they are closed when you come to re-pressurise the system. The pdf. implies/states that the taps are only there as a leveling aid when parked. Therefore a system used whilst on the move could consist of a system without taps. I agree with you in that my advice for others who are not sure would be to contact the manufacturers who, after all, have a legal duty to give accurate and responsible advice. Link to comment Share on other sites More sharing options...
Keithl Posted April 1, 2012 Share Posted April 1, 2012 Cronkle, I'm sorry to keep disagreeing but I knew I had seen somewhere that you should NOT drive with both valves open and have just found it. It is on the Marcle Leisure website page for Dunlop Gauge Assemblies, here... Link and I quote below... "After inflating your system, always close the valves, and only open one at a time when you wish to check the pressures. Keeping the valves closed prevents air passing from one side the vehicle to the other which can happen when cornering or travelling along roads with an adverse camber." And "Always close the valves" was in BOLD but didn't copy. Once again I think a call to AiRide would be in order to clarify their understanding. Keith. Link to comment Share on other sites More sharing options...
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