Air Suspension

[4petedaniel]

I was at the Malven show last week and one of the exhibitor was selling air suspension kits for diy installation on Motorhomes.

I am interested if any one has had experiance of fitting them and if it was worth the effort.

[Patricia]

Had Air-Rides fiitted professionally at a show years ago - well worth the money especially cornering. My m/home is on a Fiat but not sure that they can be fitted to a Mercedes on an Alko chassis. Know nothing about DIY but they took a long time to fit them with at least two blokes.

[Guest JudgeMental]

I have fitted these kits twice when I had a demountable camper on a number of 4x4 trucks. I am not mechanically minded but its straight forward when you have the correct tools.

 

If you have a long overhang and tend to load to the limit, you will notice the difference

[Melvin]

I fitted the kit to my Autotrail Cheynne 660, early this year, It was very easy to fit taking a couple of hours.

 

My motorhome has a long overhang and I notice the difference. I set the air pressure to 60 psi.

[Brian Kirby]

I have recently fitted Firestone Driverite (sic) semi-air (their terminology) helper springs to our Hobby Van, which is on the Mk 7 Transit FWD chassis. 

After several thousand miles, and a couple of minor grounding incidents, I decided this was desirable merely to raise the tail of the van.  Ours has a longish rear overhang, and is a "garage" layout, so tends to accumulate weight behind the rear axle.  Although the axle is well within its limits (weighbridge!), the accumulation of load at the rear causes the rear to squat, while the front remains relatively unaltered.  The van thus adopts a somewhat tail down stance, which, with the long overhang, leaves it prone to grounding. 

The air suspension units, inflated to 3 Bar (7 Bar permissible) have lifted the rear by approximately 25mm.  The kit was supplied for DIY fitting and, apart from the usual awkward access beneath the van, was not especially difficult to install.  All was completed within a day.  I have installed the simplest version, with one air inflater on each side: each air spring being individually inflated, no built in pump, no manometer.  The chassis was slightly raised with a jack to allow removal of the original bump-stops, the wheels remaining fitted, and fully in contact with the ground, throughout the whole process until final tightening of the fixings.  On a subsequent run of about 100 miles unladen, there was little difference in how the van felt to drive - which was fine, since it has always been OK unladen. 

I should add that the van has never been a general concern to drive, except for an initial a tendency to "tramline" down irregularities on the road, corrected by reducing the front tyre pressures to suit their relatively light loading.

Given that your van is based on the RWD chassis, and appears to have a relatively shorter rear overhang than ours, I am a little surprised that you feel the need to augment the rear suspension.  I realise that the rear kitchen tends to make it relatively tail heavy, but it is a longer wheelbase than ours, so should balance better.  You have not said why you feel the rear needs assistance, but I do wonder if you have weighed the axles fully laden, to see whether loading is, in fact, the problem?

[4petedaniel]

Brian Kirby - 2009-08-22 4:05 PM

I have recently fitted Firestone Driverite (sic) semi-air (their terminology) helper springs to our Hobby Van, which is on the Mk 7 Transit FWD chassis. 

After several thousand miles, and a couple of minor grounding incidents, I decided this was desirable merely to raise the tail of the van.  Ours has a longish rear overhang, and is a "garage" layout, so tends to accumulate weight behind the rear axle.  Although the axle is well within its limits (weighbridge!), the accumulation of load at the rear causes the rear to squat, while the front remains relatively unaltered.  The van thus adopts a somewhat tail down stance, which, with the long overhang, leaves it prone to grounding. 

The air suspension units, inflated to 3 Bar (7 Bar permissible) have lifted the rear by approximately 25mm.  The kit was supplied for DIY fitting and, apart from the usual awkward access beneath the van, was not especially difficult to install.  All was completed within a day.  I have installed the simplest version, with one air inflater on each side: each air spring being individually inflated, no built in pump, no manometer.  The chassis was slightly raised with a jack to allow removal of the original bump-stops, the wheels remaining fitted, and fully in contact with the ground, throughout the whole process until final tightening of the fixings.  On a subsequent run of about 100 miles unladen, there was little difference in how the van felt to drive - which was fine, since it has always been OK unladen. 

I should add that the van has never been a general concern to drive, except for an initial a tendency to "tramline" down irregularities on the road, corrected by reducing the front tyre pressures to suit their relatively light loading.

Given that your van is based on the RWD chassis, and appears to have a relatively shorter rear overhang than ours, I am a little surprised that you feel the need to augment the rear suspension.  I realise that the rear kitchen tends to make it relatively tail heavy, but it is a longer wheelbase than ours, so should balance better.  You have not said why you feel the rear needs assistance, but I do wonder if you have weighed the axles fully laden, to see whether loading is, in fact, the problem?

Hi Brian I am look at the prospects of fitting a scooter on the rear and I suspect that this will cause it to ground on inclines also I get feed up when being passed by lorries at speed causing me to have to fight for control, as I believe that it would be more stable with air suspension

[Guest JudgeMental]

 

E biking not working out Peter?

 

We had a great summer away with ours.......

[Brian Kirby]

4petedaniel - 2009-08-22 4:35 PM  Hi Brian I am look at the prospects of fitting a scooter on the rear and I suspect that this will cause it to ground on inclines also I get feed up when being passed by lorries at speed causing me to have to fight for control, as I believe that it would be more stable with air suspension

In that case, I would first do two things.  

1  Fully load, with everything you normally carry, including passengers, and get its overall weight, and the loads on both axles, from a weighbridge, to see how much free load you have on the rear axle in running trim.  Don't forget the load on the axle will increase by more than the weight of the carrier plus the scooter.

2  With those fully laden axle loads, check how close you are to Ford's permitted maximum at the front as well.  If as I suspect, you are well below the maximum, you may gain some advantage by reducing front tyre pressures to match actual load.  As said many times before, note the make, size, speed rating, and type of tyre fitted, and then contact the tyre manufacturer for their advice.  You may find that reduced pressures give increased stability. 

Having said that, I don't think you should be having so acute a problem as you describe with trucks.  I normally cruise at around 65MPH, so a little faster than most trucks are permitted to travel and, although there is a bit of a push as we pass them, I have never felt I had to fight for control.  I assume you are cruising at below 60MPH to be overtaken by so many and, at this relatively lower speed, would have expected your van to remain relatively stable.  The only things that consistently wobble ours are tankers, which just seem to have strange slipstreams.

Eddie's (judgemental) is a Luton bodied RWD Transit.  I wonder if he gets pushed around by the trucks?

[Guest JudgeMental]

Brian Kirby - 2009-08-22 5:34 PM

Eddie's (judgemental) is a Luton bodied RWD Transit.  I wonder if he gets pushed around by the trucks?

 

 

Brian, mine is a FWD with probably one of the largest luton/overcab's available. The rear overhang is not bad ( van 6.6 m long) compared to some.... and overall it handles very well, overtaking never a concern really.....

 

I push on, 70 + mph most of the time. Only time I don't like the handling is when overweight (not often *-) ) and carrying bikes on rear rack. So I normally carry bikes in garage. Have never considered air necessary with this van but if I was towing I would fit it :-D

[4petedaniel]

JudgeMental - 2009-08-22 4:58 PM

 

 

E biking not working out Peter?

 

We had a great summer away with ours.......

 

E bike great Can't lift it on and off the bike carrier. though. too heavy

[Guest JudgeMental]

 

Noticed your other threads, have you checked you have the spare payload for a rack and scooter/awning/TV/solar panels etc.........why I avoid shows to much temptation! *-)

[4petedaniel]

JudgeMental - 2009-08-22 10:20 PM

 

 

Noticed your other threads, have you checked you have the spare payload for a rack and scooter/awning/TV/solar panels etc.........why I avoid shows to much temptation! *-)

[4petedaniel]

4petedaniel - 2009-08-22 10:34 PM

 

JudgeMental - 2009-08-22 10:20 PM

 

 

Noticed your other threads, have you checked you have the spare payload for a rack and scooter/awning/TV/solar panels etc.........why I avoid shows to much temptation! *-)

 

Proberly not I will be visiting the weighbridge soon

[Derek Uzzell]

4petedaniel

 

These are a couple of earlier threads relating to 'air assistance' that it would be worth you reading:

 

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=10020&posts=25

 

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=9716&posts=14

 

Historically, DIY kits have been based around 'throw away' Firestone-made air-bellows, but kits with Dunlop-made repairable bellows are now available. See article in MMM August 2009, page 227, and

 

http://www.marcleleisure.co.uk/store/air-suspensions-c-58.html

 

The Marcle Leisure (ML) website carries plenty of useful information about installation procedures and it might be worth asking ML if they can provide you with a copy of the instructions appropriate to your Transit chassis as the fitting method is likely to be much the same whatever make of kit is involved.

 

I'm not confident that the 'kit-to-Transit-chassis' data on ML's website is completely accurate, and it should be noted that the kits do vary according to the year and type of chassis. In some cases drilling and/or metal-cutting/grinding may be needed to allow the air-bellows units to be installed, but I don't know if that will be so with your Amethyst (I'd guess probably not.)

 

You'll almost certainly need to raise your motorhome's rear chassis to gain sufficient clearance to fit the air-bellows units and you'll need to establish how best to do this. Jacking directly beneath the rear axle (which is probably what Ford recommends for wheel changing on RWD Transits) won't work, and I suspect that the standard Ford-supplied jack may not be 'tall' enough to reach the chassis rails or spring eyes..

 

Driver sensitivity to the effect of windy weather or vehicle overtaking will, in my opinion, have much to do with a driver's Fear Threshold. As a rule of thumb, FWD motorhomes seem to have better straight-line stability than equivalent-design motorhomes that are RWD. My 1996 RWD Transit Mk 5-based Herald Templar wasn't too bad regarding overtaking large vehicles, or being overtaken by them, but I disliked driving it in strong winds. My present FWD Hobby is significantly better, though its low profile shape (versus the Herald's overcab design) probably helps.

 

If you've got a low Fear Threshold (and I readily admit to having one), there's a natural tendency to attempt to correct a motorhome's perceived waywardness immediately it occurs (ie. "to fight for control"). In practice, such losses of directional stability are normally very transitory, and you are better off letting the vehicle recover itself rather than trying to control the movement by sawing at the steering wheel. It takes a helluva lot of aerodynamic disturbance to knock a large motorhome genuinely out of control, and it's evident from the way White Van Man can blast along motorways seemingly oblivious to weather or traffic conditions that motorhome-size/shape vehicles are nowadays pretty stable.

[Derek Uzzell]

Brian Kirby

 

I think your Transit Mk 7-based Hobby's rear suspension may differ from that of my Mk 6-based version.

 

According to my 2005 Transit Owner's Guide, the rear springs of a 350 Series FWD panel van (all these FWD platform-cab chassis are essentially panel vans shorn of their tin roof, sides and rear) have a circular rear 'eye' beneath which the standard jack can be securely positioned when raising the vehicle to change a wheel. However, my Hobby's rear springs have an eye-shape that prevents the jack being secured to it and, to change a rear wheel, I have to jack close to the front of the rear spring. Are your Hobby's rear springs like that?

 

A bump stop is normally a shaped lump of 'rubber' fixed to a vehicle's chassis with an air space between the bottom of the bump-stop and the top of the rear axle. What my Hobby has is a substantial slightly barrel-shaped chunk of cream-ish flexible plastic - about 9cm maximum diameter and 18cm in length - that extends from the chassis underside right down to the upper surface of the rear axle. There is no air space between the plastic component and rear axle, even when the motorhome is at its lightest operating weight, and it's plain that the component must be assisting the rear leaf springs at all times.

 

The arrangement is rather like that shown on

 

http://www.timbren.com/timbren-application-guides/application-pdfs/FRTRNSA.pdf

 

but the plastic component carries a Ford marking, so presumably it isn't a special fitting added in the Hobby factory.

 

The lower end of the plastic 'assister' sits on (but isn't attached to) a circular metal plate welded to the top of the axle, while the assister's upper section is enclosed within a shroud fixed to the chassis underside. I don't know how the shroud + plastic assister are attached to the chassis as I've never attempted to remove them. Don Browning's comment about fitting air-assistance to his Transit Mk 6-based Eura Mobil suggests that the shroud may be welded to the chassis, but who knows?

 

Could you say, please, what the arrangement was on your Hobby, as I'm pretty sure you'd have said if it had been difficult to remove the bump stop?

[Brian Kirby]

Derek Uzzell - 2009-08-24 9:08 AM Brian Kirby I think your Transit Mk 7-based Hobby's rear suspension may differ from that of my Mk 6-based version. According to my 2005 Transit Owner's Guide, the rear springs of a 350 Series FWD panel van (all these FWD platform-cab chassis are essentially panel vans shorn of their tin roof, sides and rear) have a circular rear 'eye' beneath which the standard jack can be securely positioned when raising the vehicle to change a wheel. However, my Hobby's rear springs have an eye-shape that prevents the jack being secured to it and, to change a rear wheel, I have to jack close to the front of the rear spring. Are your Hobby's rear springs like that?

Hello Derek

From what you say, the rear springs are not the same on the Mk7.  It has a rectangular section axle "U" bolted to a single leaf spring, some of which will be visible in the attached picture (next section).  Our 'Enry's jacking arrangement is, in my view, pure Heath Robinson (that is to say Zany, but would probably work!).  A large, purpose made, (embossed Ford) aluminium block is provided upon which to sit the scissor (1,600Kg max capacity!) jack.  The jacking point is stated to be the rear spring shackle, which disconcertingly is the swing shackle - so bound to pivot forward as the spring relaxes on lifting.  I also noted that there is no proper location for the jack head, and that the jack head has only a slight depression to keep the spring "knuckle" in place.  This, I do not trust!  Jacking alongside a busy road, with HGV slipstreams rocking the van, while it teeters on top of such a jack with one wheel off just feels too close to suicide!  Anyway, Ford (but maybe Hobby?) do not provide a spare wheel, just a can of gunk and a 12V pump (with an electric lead that won't reach the offside rear wheel from the 12 socket in the cab - so, yes, it was well researched!) so I can't see how they thought the jack was to be used!  I digress: but in short I bought a Halfords 4 tonne hydraulic bottle jack (£16!) and have carried out surgery to the jack housing so that this now fits in lieu of the scissor job!

A bump stop is normally a shaped lump of 'rubber' fixed to a vehicle's chassis with an air space between the bottom of the bump-stop and the top of the rear axle. What my Hobby has is a substantial slightly barrel-shaped chunk of cream-sh flexible plastic - about 9cm maximum diameter and 18cm in length - that extends from the chassis underside right down to the upper surface of the rear axle. There is no air space between the plastic component and rear axle, even when the motorhome is at its lightest operating weight, and it's plain that the component must be assisting the rear leaf springs at all times. The arrangement is rather like that shown on http://www.timbren.com/timbren-application-guides/application-pdfs/FRTRNSA.pdf but the plastic component carries a Ford marking, so presumably it isn't a special fitting added in the Hobby factory. The lower end of the plastic 'assister' sits on (but isn't attached to) a circular metal plate welded to the top of the axle, while the assister's upper section is enclosed within a shroud fixed to the chassis underside. I don't know how the shroud + plastic assister are attached to the chassis as I've never attempted to remove them. Don Browning's comment about fitting air-assistance to his Transit Mk 6-based Eura Mobil suggests that the shroud may be welded to the chassis, but who knows? Could you say, please, what the arrangement was on your Hobby, as I'm pretty sure you'd have said if it had been difficult to remove the bump stop?

Most of the answer will come, I think, from the attached photo.  This component is undoubtedly a spring assister.  It is of some sort of dense plastic foam and is hollow down the centre.  If just the chassis is lifted, so that the base of this foam assister is about 25mm above the "saucer" on the axle, it is then possible to pull the assister firmly sideways, and it eventually comes away from its top housing without damage.  All can be re-fitted if necessary! 

The "saucer" is welded to the axle: it does not need removal to fit the Driverite kit, as it serves to locate the bottom air spring mounting.  The top mounting of the foam assister is held in place by a single, vertical, central, bolt, into a captive nut on the underside of the chassis rail.  Bit of grunting here and there, but surprisingly easy and relatively bloodless!

[bob b]

You gotta touch up the damaged underseal on the chassis rail Brian !

[Derek Uzzell]

Brian

 

Thanks for that information.

 

The 'spring assisters' on your Hobby Van pretty much match those on my T-600 FC motorhome (I think the shroud designs may differ marginally). I felt that the assister's top mounting would be bolted to the chassis and (remembering that, for air-bellows to be fitted to some earlier Transits required chiselling off the bump-stop mounting bolt) hoped that Ford would have used a rational attachment technique.

 

However, a major difference between our vehicles' rear suspensions is that mine has twin-leaf rear springs. The lower leaf is full length and, at each end, passes through a rubber block that links it to the upper leaf. These blocks mask the spring eyes/shackles, meaning that, to locate the standard scissors-jack for wheel changing, you have to position it on the spring itself. You can't position it near the rear end of the spring (where it would be most effective) because the leaves curve sharply upwards there, so it has to go just behind the front rubber-block connector. This position places a lot of load on jack and spring, but there's no alternative. When I had the rear tyre valves fail, the French breakdown guys used a trolley-jack beneath the front rubber-block connector, which made me wince mentally, but seemed to do no harm.

 

To gain the required 'lift' for the jack, 3300kg and 3500kg FWD Transits need the aluminium block you mention. It's normally stored within the well of the spare wheel which, of course, means that, before beginning to jack up the vehicle's rear wheels, you first have to lower the spare to fish out the block. My block now lives beneath the motorhome's bed. Ford does have the good grace to mention the aluminium block (and its storage within the spare wheel) in the Owner's Guide booklet, but we all know that few people bother to study handbooks.

 

Not long after I bought the Hobby, I wrote to Ford(UK) saying that it was virtually impossible to change a wheel on my vehicle using the standard Ford-supplied tools and that I believed this would be true for many motorhomes constructed on the Transit FWD platform-cab chassis. I don't think my complaint did an atom of good though.

 

I'd like to see a Top Gear challenge where a pairing of a Ford and Hobby engineer were tasked to change a rear wheel on a same model/same specification Hobby motorhome as mine. They'd have to use just the Ford tools and have 10 minutes to fully complete the job. Every extra minute taken would earn each of them five savage lashes from a long whippy cane wielded vindictively by the Stig. In fact, this test could become a mandatory requirement for Eurozone-built motorhomes - that might suitably concentrate the designers' minds!