air ride systems

[fesspark]

For those that remember my early requests for info on my Burstner nexxo 55 hard ride problem I have decided to leave the double springs on and go for air ride asstd; system. Can anyone inform me as to the system I need and what co; fit at your home address,mine being Dawlish Devon. fesspark.

[George Collings]

Try here.

 

http://www.airide.co.uk

[Derek Uzzell]

I think you will find that combining your double rear-springs with air-assistance will make your motorhome’s hard ride worse not better.

 

If you had one of the double springs removed (as was suggested as a possibilty in an earlier thread) and then fitted air-assistance you might find an improvement, but adding even more spring resistance (which is what air-assistance does) is counter-productive.

 

On your own head (or backside!) be it...

[thebishbus]

Hi. I think it will depend on whether or not your rubber spring assist units are in contact with your springs. If they are not in contact, air assist will not help, but if they are in contact it may. My Hymer has double leaf springs and the rubber assist units were in contact with the springs. I fitted basic Dunlop air assist units from Marcle Leisure . I had to experiment with air pressure for between hard ride or rolling and found that 20 to 25 psi to be a good compromise.

Brian B.

[Derek Uzzell]

This is the July 2014 forum thread in which fesspark originally mentioned his 2014 Burstner 690G’s harsh ride

 

http://www.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/burstner-nexxo-690G-55-2014-model-problems/35380/

 

The 690G “55” model is relatively compact (6.89m long) and built on a Fiat Ducato 35 ‘Light’ chassis with 3.8m wheelbase and 15” wheels. The tyres are likely to be 215/70 R15CP “VancoCamper”. An example is detailed here

 

http://www.southdownsmotorhomecentre.co.uk/burstner-nexxo-t690g-55-special-edition-motorhome.html

 

This model is unusual as the chassis maximum authorised weight is uprated as standard from its more normal 3500kg to 3850kg. In fesspark’s case, his 690G has apparently been ‘down-plated’ and UK-registered with a chassis-weight of 3500kg.

 

I don’t know exactly what measures were taken to raise the 690G’s chassis-weight from 3500kg to 3850kg. In the July thread fesspark said "...The company I purchased the vehicle from has offered to look at it and maybe remove 2 of the red secondary springs...”. In this thread he refers to “double springs”.

 

It has been known for motorhomes with leaf-spring rear suspension to be fitted with secondary coil springs to increase the spring rate, but I’m guessing that the 690G has just been fitted with the Ducato twin-leaf -spring option.

 

A photo of this set-up is included in this 2010 thread

 

http://www.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Autotrail-Tracker-suspension-on-X250-3-ltr-/19900/

 

and it’s worth noting the comments about harsh ride quality continuing even when tyre pressures have been reduced to 65psi.

 

As Brian Kirby advised in the July 2014 thread, if improving the ride quality is high priority, the initial approach should be to experiment by weighing the motorhome and selecting tyre pressures that are the minimum that can be used safely.

 

If that doesn’t change things for the better, the next step might to be to remove temporarily the rubber spring assisters and see how that affects the ride quality. As thebishbus says, if the spring-assist units are in hard contact with the springs and their removal significantly softens the ride, then fitting air-assistance may well help - as was the case with his Hymer.

 

I can’t see that fitting air-assistance would do any harm, but if the rubber spring assisters (see 2010-thread photo) are currently not providing much resistance, it shouldn’t do a great deal of good either.

 

The first thing to do, though, is to make sure that inflation pressures are not unnecessarily high for the loads being placed on the tyres.

[rinty]

My first post on here.

I would agree with Derek, I cannot see how adding extra springing (eg air ride) could make an already firm ride softer without taking away some of the existing resistance.

I was considering fitting the Dunlop units from Marcle myself to help reduce rolling in corners, however after checking with my insurers (Comfort) and being advised that if I fit them myself I will have to send in full details of the modification and incur a 25% premium loading (£200+) as opposed to a £15 administration fee to note the policy if I have them fitted "professionally". Apart from the cost it is a lot of hassle to travel and have them fitted.

I have decided not to bother until my insurance comes up for renewal and I can get some alternative insurance quotes.

Makes you think about all the diy mods done on motorhomes.

[Uncle Bulgaria]

I had Dave Newell Leisure Vehicle Services fit the Dunlop air assistance units to my Ford Transit based Hobby. Before fitting there was about 2 to 3 inches of clearance between the rear axle and the rubber "bump stops". With the air assistance unit fitted I'm using them at 40 psig. This has raised the rear for the motorhome by about 2 inches but has also made the rear suspension more compliant. I guess this is because the load on the rear axle is now distributed between original leaf springs and the additional air springs. I'm now running the tyres at the Ford recommended maximum pressure of 69 psig for the rears and the ride comfort is (subjectively) better than when I used a laden weighbridge determined figure of 58 psig prior to having the air assistance units fitted. The slight downside is a tail up stance which requires the more frequent use of levelling ramps.

 

Hope this experience helps.

 

[Brian Kirby]

Now I'm puzzled! :-) 40psi seems a bit of a high pressure for these units. How was this arrived at? Can't remember exactly what, bit I'm sure I ran ours at lower pressure, and the van sat pretty well level when laden.

 

May I make a suggestion? Unload the van completely, and let the air-rides right down. Then measure the height of the rear bumper from the ground. Re-load the van fully (the absolute lot!) and again measure the height as above. Then, re-inflate the air-rides a bit at a time until the rear sits at the same height above ground with the air-rides deflated and the van empty. Go for a ride, and see how it handles. If all is OK, reduce the tyre pressures back to those you were using before the air-rides were fitted. If yours is anything like ours, you should find this gives the best of both worlds with a more compliant ride coupled with reduced body-roll on roundabouts and sharp bends. Can't promise, but it definitely worked with our "Van".

[Keithl]

Brian Kirby - 2014-08-20 5:32 PM

 

Now I'm puzzled! :-) 40psi seems a bit of a high pressure for these units. How was this arrived at? Can't remember exactly what, bit I'm sure I ran ours at lower pressure, and the van sat pretty well level when laden.

 

Brian,

 

From my experience with the Dunlop system 40 psi is about right. These systems are rated to 101 psi, see below.

 

Quote Section 5.6 of installation instructions...

 

"Spring Inflation

Once installation of the air assist kit is complete, inflate the springs via

the inflator console taking careful note of the following...

 

Maximum and Minimum Pressure

 

Maximum Pressure 7.0bar Minimum Pressure 0.5bar

 

Do not exceed 7.0bar (101psi), which is the recommended

maximum charge pressure for the air springs.

The springs may be deflated if the vehicle is to be stored for a

lengthy period without use, but a pressure of at least 0.5bar

(7.25psi) should be maintained at all times in order to avoid

possible compression damage to the springs."

 

I have actually just increased ours to 45 psi to see if I can tell the difference.

 

Keith.

[Brian Kirby]

Hi Keith.

 

I didn't mean that the pressure was high in relation to air-ride systems, but possibly a bit high for air-rides on a Hobby Van.

 

To explain: our Hobby Van was, in essence, the same as Uncle Bulgaria's and was also Transit based. Ours "wallowed" at the rear, especially on roundabouts, mainly due to its longish rear overhang, exacerbated by the fact that, because of its layout, nearly all added load fell upon the rear axle. For example. Unladen: front 1,260kg, rear 1,420 (46 - 54). Laden: front 1,310, rear 1,970 (40 - 60). I'd be a bit surprised if the laden loads on Uncle Bulgaria's axles are significantly different in proportion.

 

This also caused some tramlining at the recommended tyre pressures. Reducing pressures to Continental's databook pressures for the actual loads greatly reduced, but did not eliminate, the tramlining. I also had a couple of instances of the tail "grounding", one on a steep uphill hairpin, and decided sommat had to be done!

 

So, I fitted Firestone DriveRite units to the rear, and did as described above to arrive at a starting pressure. I found this virtually eliminated the remaining tramlining, but also the roundabout wallowing as the air units acted to resist roll.

 

A possibly significant difference between the Transit and the Ducato is that the FWD Transit has a permissible rear axle load of 2,250kg, whereas the equivalent Ducato is limited to 2,000kg. As you can see from our laden figures above, the rear axle limit was never in jeopardy. So, given the Transit's harder rear springs, I'd be surprised if Uncle Bulgaria's Dunlop units were fitted to eliminate any more than wallowing on roundabouts, and possibly occasional grounding, such as we experienced. I'd anticipate lower pressures for a Transit than for a Ducato, because its stiffer rear springs will cope with more of the load.

 

He says the tail now sits high, whereas ours was more or less level (on balance slightly nose down) when the units were inflated as I described. However, this never caused us levelling problems as described (in fact it was an advantage to be exploited when siting), leading me to surmise that Unlce Bulgaria's air-rides are inflated above what is strictly necessary. IMO, the only way to find out, would be to experiment with lower pressures.

[Derek Uzzell]

Brian Kirby - 2014-08-21 11:56 AM

 

...our Hobby Van was, in essence, the same as Uncle Bulgaria's and was also Transit based...

 

I suspect that Uncle Bulgaria’s Hobby Van’s rear suspension differs from yours.

 

Earlier Vans had long hollow ‘rubber’ spring assisters that spanned the complete distance between the chassis and the top of the leaf-spring. This was later changed, with the spring assister being replaced by a much shorter genuine rubber bump-stop, resulting in a substantial air-gap between the bump-stop and the leaf-spring beneath it. (Presumably the strength of the leaf-spring was altered to match.)

 

I’ve looked through Uncle Bulgaria's earlier posting that mention his Hobby, but haven’t been able to find how old the vehicle is. However, the statement that "Before fitting there was about 2 to 3 inches of clearance between the rear axle and the rubber "bump stops”” strongly suggests that it has the later arrangement.

 

You have stated why you chose to fit air-assistance units, but it might be worth knowing what the objective was in Uncle Bulgaria’s case.

 

I also note that he says that, having had air-assistance units fitted and having increased the tyres’ inflation-pressures from 58psi to 69psi “...the ride comfort is (subjectively) better...” Logically the air-assistance units must have increased the ‘strength’ of the rear springing and increasing the tyre-pressures must have made them less resiliant regarding damping out road-surface imperfections. Nevertheless, it’s perfectly possible for a vehicle to feel more ‘comfortable’ after such modifications have been made. It really depends on why those changes have been made and how ‘uncomfortable’ the vehicle was in the first place.

 

Fesspark’s July posting said about his Nexxo “...when I ride over cats eyes,or road joints the noise and banging from the rear is unbearable...” This sounds like what one might reasonably anticipate from a relatively-light Fiat Ducato-based coachbuilt motorhome with beefed-up rear springs and ‘camping-car’ tyres run at a high inflation-pressure. It’s not the type of harsh ride one would expect from a motorhome based on a FWD Ford Transit (generally accepted as being softly sprung) using larger-diameter ‘commercial’ tyres and lower pressures. So, even if air-assistance units are helpful for certain FWD Transit-based motorhomes, just fitting them to Fesspark’s Nexxo won’t automatically solve the rough-ride problem.

 

[MHTECH]

Drive-rite are a good product try www.peterboroughmotorhomes.co.uk they fit the systems

[Brian Kirby]

Derek Uzzell - 2014-08-21 3:37 PM..............I suspect that Uncle Bulgaria’s Hobby Van’s rear suspension differs from yours.

 

Earlier Vans had long hollow ‘rubber’ spring assisters that spanned the complete distance between the chassis and the top of the leaf-spring. This was later changed, with the spring assister being replaced by a much shorter genuine rubber bump-stop, resulting in a substantial air-gap between the bump-stop and the leaf-spring beneath it. (Presumably the strength of the leaf-spring was altered to match.)

 

I’ve looked through Uncle Bulgaria's earlier posting that mention his Hobby, but haven’t been able to find how old the vehicle is. However, the statement that "Before fitting there was about 2 to 3 inches of clearance between the rear axle and the rubber "bump stops”” strongly suggests that it has the later arrangement.

 

You have stated why you chose to fit air-assistance units, but it might be worth knowing what the objective was in Uncle Bulgaria’s case.

 

I also note that he says that, having had air-assistance units fitted and having increased the tyres’ inflation-pressures from 58psi to 69psi “...the ride comfort is (subjectively) better...” Logically the air-assistance units must have increased the ‘strength’ of the rear springing and increasing the tyre-pressures must have made them less resiliant regarding damping out road-surface imperfections. Nevertheless, it’s perfectly possible for a vehicle to feel more ‘comfortable’ after such modifications have been made. It really depends on why those changes have been made and how ‘uncomfortable’ the vehicle was in the first place.

 

Fesspark’s July posting said about his Nexxo “...when I ride over cats eyes,or road joints the noise and banging from the rear is unbearable...” This sounds like what one might reasonably anticipate from a relatively-light Fiat Ducato-based coachbuilt motorhome with beefed-up rear springs and ‘camping-car’ tyres run at a high inflation-pressure. It’s not the type of harsh ride one would expect from a motorhome based on a FWD Ford Transit (generally accepted as being softly sprung) using larger-diameter ‘commercial’ tyres and lower pressures. So, even if air-assistance units are helpful for certain FWD Transit-based motorhomes, just fitting them to Fesspark’s Nexxo won’t automatically solve the rough-ride problem.

Ah! So we need to hear again from Uncle Bulgaria.

 

Re Fesspark's hard ride, the only way I can imagine air-rides working with his installaton, is if the air-rides, which are more compliant than a cart spring, take some of the load off the cart springs.

 

To do this the rear of the van would need to be raised by the air-rides, so that the cart springs were allowed to partially relax. It seems just possible that having relaxed the cart springs and transferred the resulting load to the air-rides, the combined effect might be a bit softer - but I wouldn't want to bet on it, or to spend my money to find out. :-)

 

If the rear is presently that hard, although more costly, I would think the best result would be gained by removing the cart springs altogether and installing full-air units at the rear. Ultimately, this may not be that much more costly than removing leaves each side and then installing air-over units in tandem with the remaining cart spring, as both options would presumably have to be professionally installed to maintain the permitted rear axle load as on the VIN plate, and that labour won't come cheap.

[artheytrate]

My last van was a new 2011 Auto Roller 100 on the mk7 Ford Transit, it was low on the back from new and wallowed terrible on bends and roundabouts. I fitted the Dunlop system which I bought from Marcle leisure and after fitting it I found that 30-35 psi was sufficient and the rear of motorhome had risen approx. 4"s, driving it was totally different it was a pleasure to drive.

When we ordered our new 2014 Auto Sleeper Broadway on a Peugeot chassis I asked for air suspension to be fitted before we picked it up, they fitted air rides and now our van is low on the front and we also use levellers more when parked up, but this is also a pleasure to drive with no rolling or wallowing, I pressurise this one at 15 psi.

 

John.

[Uncle Bulgaria]

A little more explanation / detail in response to Brian's questions. My Transit base was manufactured in May 2011. As Derek surmises the rear axle had simple plastic bump stops to limit vertical movement of the rear axle, with a normal gap of between 2 to 3 inches between the rear axle and the bump stop. My laden axle loads are very similar to those quoted by Brian - front 1350 Kg, rear 1950 Kg. This rear axle load includes the addition of a spare wheel mounted on a carrier at the rear of the vehicle (mounted on a frame that bolts to the mounting points provided for a tow bar on the chassis rear extensions).

 

The Hobby Van has a longish rear overhang and I wanted to achieve the objectives of improving the rear ground clearance (to reduce the chance of grounding when boarding ferries) and counteract the effect of the spare wheel mounted at the rear of the vehicle, and also to increase the roll resistance and reducing sway when being passed by, or passing, coaches and other high sided vehicles. I've not experienced the "tramline" problem reported by Brian, but that may be due to the choice of tyres. Fitting the air assistance springs has achieved all these objectives, although they were never particularly problematic . I've tried various bellows pressures, and I can sense little difference between 30 and 40 psig. The Transit chassis rear suspension has always felt relatively soft compared with the Ducato base I had on a Burstner. Adding the air assistance units has, as I say, subjectively further improved this. It's certainly no saloon car ride, but the crashing and banging is much reduced. My choice of tyre pressures has been guided by the observation that I do not find much difference in ride comfort between a weighbridge determined value of 58 psig for the rear axle and the Ford handbook figure of 69 psig for a maximum rear axle load of 2250 Kg, and I'm running 300 Kg below this limit. As I can't feel the difference in ride comfort I've opted for the Ford handbook figure on the basis that it is safer to be over-inflated, for the actual load, than under-inflated. The Transit tyre is also a 16 inch with a 75 section and I think this combination of diameter and aspect ratio is, in part, responsible for the less harsh ride, even at maximum recommended tyre pressures. The recommended maximum pressure for the front tyre is only 50 psig for a maximum axle load of 1750 Kg. The tail-high stance is barely noticeable and certainly not enough to need levelling ramps on a level pitch. The one effect I have noticed is that with the motorhome unladen, so probable weighing around 2800 Kg, the rear end will really bounce when driven over a speed hump at more than walking pace, and the difference between the fully laden and unladen response to speed humps is more noticeable with the air assistance springs than before I had them fitted.

 

All in all, I've found the air assistance springs have brought a useful improvement to ride comfort and overall vehicle dynamic behaviour.

 

Richard.

[Brian Kirby]

Thanks for this, Richard. Interesting. Perhaps there is a bit more difference between the rear suspension on yours, and that on ours, than the mere omision of the longer polymer spring assisters ours had in favour of conventional bump stops. The assisters can be seen on the attached pic.

 

My guess is that the spring rating was also modified, and this, plus ours being slightly more tail heavy, plus possibly having a slightly higher centre of gravity (high bed vs low bed?), and having different belows, probably accounts for the differences. Ours definitely gave a better ride with lower tyre pressures but, hey, if you find no difference between the Ford/Hobby recommendation and the lower Continental recommended ones, why change what works! :-)