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Compressors and air suspension


Sundowner

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Posted

When we bought our Adria Compact, the only thing that I did not like about it, was the lack of a spare wheel. I soon rectified this, and the peace of mind, knowing that there was one safely strapped behind me in the garage (bike shed), was well worth the considerable amount of money that it cost.

 

However, the silver lining of all this is the compressor supplied instead of the spare wheel, is very useful for pumping up my bike tyres. It will of even more use, if I upgrade my rear suspension, by fitting one of the several air assist suspension units advertised.

 

I have read the threads on this forum, with great interest, but am having difficulty in deciding which particular system to go for.

 

Can anybody please give me some of the pros. and cons. of the various makes avaiable.

 

As always, looking forward to reading any opinions posted,

 

Many thanks in advance (hopefully!)

 

I've just realised, that the hard ride is another thing that is not quite perfect!

Posted

Yes, some air bag systems do not come with the compressor as standard. Most of them can have a compressor fitted together with the change over valves and a pressure gauge or even two.

 

The cost of the fitted dedicated compressor makes me wonder if it is just as easy to use a decent 12v truck style portable compressor and you can always blow your tyres up with it as well. It is a lot cheaper to do it that way.

 

I am going to have a pair of air units installed next year before I go off on my travels, I have not decided which ones yet, although they all seem to do the same job I think.

 

I have also considered a small pressure vessel (tank) to pump up using a garage compressor and then using this to pressurise the air bag system as required.

 

Hope it helps, any more questions just ask away.

 

H

Posted

Hi Hallii,

 

Thanks for the prompt response, I think you must have been replying while I was still editing my posting!

 

As you can now see, I have a good Fiat supplied compressor with a built in gauge, and am now wondering if I can do without the supplied gauges and make do with the two valves and the schrader connection.

 

rgds. sundowner

Posted

I had a "basic" Dunlop air assistor kit fitted to our Chausson(..no gauges or pump) and as I had visions of me tinkering with the ride height all the time,I fully intended to "upgrade" it at later date..but to be honest,having now used it for probably best part of a year,I now just don't see the need to.

I just leave it at the one "setting"(approx 40 psi)..and as the valves are located just inside the wheelarch,they're easy enough to access,whilst you're checking the rear tyre pressures.

(..and I now just adjust ours' with our old foot pump..as our 12v pump was a bit of a faff about ..by the time I'd unravelled it and threaded the lead through opposing windows..I can be all finished and packed away with the footpump ..)

 

Okay,maybe if the vehicle has a long rear overhang and ferries are used a great deal,then perhaps the ride height may need adjusting more often and I could then see a possible need for an onboard/plumbed-in compressor but in our case(..and I suspect the case for a good many others),an onboard compressor would just be a "boys-toys gadget".. (lol)

Posted

Hi Ernie,

 

I fitted a Dunlop Aux Air System to our Merc based AT early last year and have found it be excellent ever since. Like Pepe I too do not have gauges or compressor and simply inflate both valves to around 40psi when I check tyre pressures before a trip. I find they lose 2 or 3psi over a couple of weeks so do not require checking other than before a trip.

I use either a foot pump or a bicycle 'Joe Blow' Track pump to inflate and they never take more than a couple of pumps to get them up to pressure.

Our system came from Marcle Leisure and I can thoroughly recommend them for product knowledge and helpfulness.

 

Also, and the main reason for fitting the system, the ride is very much improved with far less body roll and swaying on cornering or in high winds.

 

HTH,

Keith.

Posted

Just to add to my earlier post..I did fit a pair of Grayston coil spring assistors to our previous van(a Pug X250 Compass 120 coachbuilt )..and to be fair,they also worked really well..lifting it about 30mm+ at the wheelarch and firming up the body-roll.

Really easy to fit,about an hour max(..in short,after bolting on a couple of base-plates,they just slip over the orignal "doughnut" bumpstops).

 

Obviously not adjustable but around half the price of no frills,air set up and probably more than up to the job of a PVC...

Posted

Hi there,

 

Thanks to your responses and advice. I appear to be on the right track and the fact that both pepe and keith, are happy with the Dunlop system, confirms my own thoughts that that is the way to go.

 

However, my problem is that, although I am well within the allowable rear axle weight, and on inspection when parked, there is still a reasonable gap between the springs and the "bump stops", the ride is hard, and appears to be bouncing off the "bump stops" more than is to be expected.

 

I am aware that on our previous van, an '08 Twin PVC, the "bump stops" were designed to be part of the suspension, but am not certain if this is the case with the Compact.

 

What I am trying to do is improve the quality of the ride, ie take away the harshness, without raising the ride height.

 

My years of experience driving HGVs, tells me that the difference between cart springs and full air suspension is incomparable, I am hoping that by replacing the "bump stops" with the air assist system, I can replicate the same difference.

 

rgds. Sundowner

Posted

We also fitted Dunlop Air Suspension this year. Makes for a much better ride, we bought a compressor from Maplin (It has built in gauges) Bought the equipment from Marcle, and had it fitted at Adams Morley,(Portsmouth) who do our servicing.

PJay

Posted
Am I right in assuming your van is on a Fiat chassis? If so so air springs will not help from what you say you are looking to soften the ride, air systems stiffen up soft suspension the Fiat set up is very firm the only way to soften the ride would be to replace the existing rear springs which I would of thought is not a practical option.
Posted
Sundowner - 2011-09-28 8:07 AM

 

Hi there,

 

Thanks to your responses and advice. I appear to be on the right track and the fact that both pepe and keith, are happy with the Dunlop system, confirms my own thoughts that that is the way to go.

 

However, my problem is that, although I am well within the allowable rear axle weight, and on inspection when parked, there is still a reasonable gap between the springs and the "bump stops", the ride is hard, and appears to be bouncing off the "bump stops" more than is to be expected.

 

I am aware that on our previous van, an '08 Twin PVC, the "bump stops" were designed to be part of the suspension, but am not certain if this is the case with the Compact.

 

What I am trying to do is improve the quality of the ride, ie take away the harshness, without raising the ride height.

 

My years of experience driving HGVs, tells me that the difference between cart springs and full air suspension is incomparable, I am hoping that by replacing the "bump stops" with the air assist system, I can replicate the same difference.

 

rgds. Sundowner

 

Your Adria's ride characteristics will relate to a large degree to the 'strength' of the vehicle's rear springs and the inflation-pressure of its tyres. Although there is air-space beneath the bump-stops and the springs when your motorhome is parked, you are speculating that this space disappears when the vehicle is being driven and it's probable that's indeed so. If you want to confirm how much the bump-stops are contributing to the harsher-than-you-like ride, then the simple answer is to remove them temporarily and see what the result is. If the ride quality improves dramatically, then installing air-bellows should be worthwhile. If the ride quality is little different with no bump-stops, then fitting air-bellows is unlikely to help.

 

As you've got air-space below the bump-stops on your Adria, I'm tempted to think its rear springs are pretty strong. I'm also guessing that (as it's Ducato-based) your Adria has 'camping-car' tyres and, if that's true, then you MIGHT be using high inflation-pressures that MIGHT be usefully reduced if your motorhome's normal axle-loadings are well below their permitted maxima. Realistically you can't do anything about the springs, but if you are using higher-than-necessary tyre-pressures on a relatively lightly-loaded vehicle, then the ride quality will inevitably suffer. So, before you go down the air-bellows route, I suggest you weigh the vehicle and confirm its fully-laden axle-loadings.

 

If you do decide to fit air-bellows, then the Dunlop kits (which have repairable bellows-units) are probably as good as any (and better than many) regarding quality and ease of fitting. But don't expect air-assistance to provide the 'magic carpet' ride that's obtainable from a full air-suspension system.

 

(It's perhaps worth adding that, of all the light commercial vehicle chassis used as the basis for motorhomes, received wisdom is that the Ducato chassis produces the firmest ride. The up-side of this is that the Ducato's firm ride equates to good handling.)

 

Posted
lennyhb - 2011-09-28 9:03 AM

 

Am I right in assuming your van is on a Fiat chassis? If so so air springs will not help from what you say you are looking to soften the ride, air systems stiffen up soft suspension the Fiat set up is very firm the only way to soften the ride would be to replace the existing rear springs which I would of thought is not a practical option.

 

 

Hi Lenny,

 

Yes, it is a medium wheelbase Fiat chassis with a 2 metre rear overhang. It weighed off with 170kgs. spare capacity on the back axle. This was fully laden with my bicycle plus a heavy electric trike in the garage.

 

When I used the van to move some family possesions, it was probably near it's max. rear axle weight.

This, of course, showed up in the van's handling, roadholding etc., but resulted in a noticeable smoother ride. Perhaps the springs were resting on the bump stops, rather than bouncing off them?

If this is the case, maybe airbags would illiminate the impact between the springs and the bumpstops.

 

rgds. Ernie

Posted

I really don't think fitting air units will help as the hard ride is due to the very stiff springs Fiat fit. You could try as Derek suggests removing the bump stops and see if there is any difference.

 

It is possible as you have a heavy load in the garage behind the axle you are getting a pendulum effect on rough roads causing the bump stops to bottom out, looks like taking them off is the way to find out.

Posted
Derek Uzzell - 2011-09-28 9:20 AM

 

Sundowner - 2011-09-28 8:07 AM

 

Hi there,

 

Thanks to your responses and advice. I appear to be on the right track and the fact that both pepe and keith, are happy with the Dunlop system, confirms my own thoughts that that is the way to go.

 

However, my problem is that, although I am well within the allowable rear axle weight, and on inspection when parked, there is still a reasonable gap between the springs and the "bump stops", the ride is hard, and appears to be bouncing off the "bump stops" more than is to be expected.

 

I am aware that on our previous van, an '08 Twin PVC, the "bump stops" were designed to be part of the suspension, but am not certain if this is the case with the Compact.

 

What I am trying to do is improve the quality of the ride, ie take away the harshness, without raising the ride height.

 

My years of experience driving HGVs, tells me that the difference between cart springs and full air suspension is incomparable, I am hoping that by replacing the "bump stops" with the air assist system, I can replicate the same difference.

 

rgds. Sundowner

 

Your Adria's ride characteristics will relate to a large degree to the 'strength' of the vehicle's rear springs and the inflation-pressure of its tyres. Although there is air-space beneath the bump-stops and the springs when your motorhome is parked, you are speculating that this space disappears when the vehicle is being driven and it's probable that's indeed so. If you want to confirm how much the bump-stops are contributing to the harsher-than-you-like ride, then the simple answer is to remove them temporarily and see what the result is. If the ride quality improves dramatically, then installing air-bellows should be worthwhile. If the ride quality is little different with no bump-stops, then fitting air-bellows is unlikely to help.

 

As you've got air-space below the bump-stops on your Adria, I'm tempted to think its rear springs are pretty strong. I'm also guessing that (as it's Ducato-based) your Adria has 'camping-car' tyres and, if that's true, then you MIGHT be using high inflation-pressures that MIGHT be usefully reduced if your motorhome's normal axle-loadings are well below their permitted maxima. Realistically you can't do anything about the springs, but if you are using higher-than-necessary tyre-pressures on a relatively lightly-loaded vehicle, then the ride quality will inevitably suffer. So, before you go down the air-bellows route, I suggest you weigh the vehicle and confirm its fully-laden axle-loadings.

 

If you do decide to fit air-bellows, then the Dunlop kits (which have repairable bellows-units) are probably as good as any (and better than many) regarding quality and ease of fitting. But don't expect air-assistance to provide the 'magic carpet' ride that's obtainable from a full air-suspension system.

 

(It's perhaps worth adding that, of all the light commercial vehicle chassis used as the basis for motorhomes, received wisdom is that the Ducato chassis produces the firmest ride. The up-side of this is that the Ducato's firm ride equates to good handling.)

 

Hi Derek,

 

Thanks for your response, much food for thought!

 

I am a bit hesitant about driving without the bump stops in place, even experimentaly. I have visions of excessive lean when cornering, without them.

 

As I said, when responding to Lenny, the ride seems noticeably smoother when loaded nearer the rear axle's max. capacity. As my normal running weight gives about 170 kgs. spare capacity the harsh ride could be caused by the springs bouncing off the bumpstops. Inserting air bags could possibly cushion the impact between the springs and the bumpstops If I do go down this route, Dunlop appears to be the favoured and possibly the cheapest option

 

Before doing anything else, I will experiment with the tyre pressures.

 

Incedentally, when I bought the van, as part of the deal, the GVW was uprated from 3300 kgs. (with axle weights of 1750 and 1900 kgs.) to 3500 kgs.

 

Much to my surprise, when the replating certificate eventualy arrived the rear axle had also been uprated to 2000 kgs. I checked with SV who issued the certificate, and was told this was OK. I do however, still use the original 1900 kgs. in all my calculations - for my own peace of mind!

 

Thanks for your advice,

 

rgds. Ernie

Posted

Depends what actual chassis your vehicle started life as, the 3500kg chassis are down rated 3850kg chassis could be why you have a 2000kg rear axle loading. To re-plate a 3500kg Chassis to 3850kg is just a paper exercise.

 

My van is on a 3500kg chassis and on rough roads (particularly in Belgium & Ireland) the ride is very harsh almost unbearable at times, unfortunately it is a characteristic of the vehicle but on the plus side the handling is superb.

Posted
lennyhb - 2011-10-02 9:18 AM

 

Depends what actual chassis your vehicle started life as, the 3500kg chassis are down rated 3850kg chassis could be why you have a 2000kg rear axle loading. To re-plate a 3500kg Chassis to 3850kg is just a paper exercise.

 

My van is on a 3500kg chassis and on rough roads (particularly in Belgium & Ireland) the ride is very harsh almost unbearable at times, unfortunately it is a characteristic of the vehicle but on the plus side the handling is superb.

 

 

Hi Lenny,

 

I'm pretty sure that my vehicle started life with a 3300kg. chassis - 15" wheels, rather than 16", and at my request ,it awas replated to 3500kgs. This of course was also a paper exercise.

 

By coincidence, it was on a 3 week trip around Southern Ireland that I decided to try and improve the ride!

 

I am however, following Derek's advice, and experimenting with the tyre pressures. Early results seem to be quite encouraging.

 

Thanks to Derek, you Lenny and everybody else who showed an interest, it looks as though you could be saving me a considerable amount of money!

 

rgds. Ernie.

 

 

 

 

 

 

 

 

 

 

 

 

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