greycaster Posted July 24, 2017 Share Posted July 24, 2017 I have just checked my also air top suspension and both units look deflated but the pressure is still showing 2 bar. Does anybody know what's going on. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 25, 2017 Share Posted July 25, 2017 What you’ve not said is whether you’ve inspected the “Air Top” units in the past and they looked different. As you’ve confirmed that there is a 2.0bar air-pressure in the air-bellows units, I’m not sure that there is actually something ‘wrong’ with them. If you scroll through the photos on this link https://live.staticflickr.com/6038/6322398220_a0d279db43_b.jpg you’ll find 4 photos of an AL-KO “Air Top” system fitted to an Auto-Sleepers “Stratford” panel-van conversion. The first 3 photos show an air-bellows with the vehicle jacked up and no weight being placed on the bellows, whereas the 4th photo is of an air-bellows after the vehicle is back on its wheels and weight has ‘squashed' the bellows. The 4th photo https://live.staticflickr.com/7028/6633816733_3dae07d4b3_b.jpg looks pretty similar to yours. Link to comment Share on other sites More sharing options...
MikeJJ Posted July 25, 2017 Share Posted July 25, 2017 Just went outside to take a look at my "Air-Top" units, which are also set at 2bar. They looked somewhere in-between, not as low as yours and not as high as the pictures of unloaded axle. They felt hard. The axle loading on mine (from weighbridge printout) is approx. 2100kg on a Maxi chassis. Do you have excessive load or maybe you have a different spec of Air-top????? Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 25, 2017 Share Posted July 25, 2017 The photo provided in the original posting seems to indicate that the leaf-spring below the air-bellows unit is ‘flat’, suggesting that - if the air-bellows unit were not there and the original ‘spring-assister’ were in place - the suspension would resemble the photo below. If that’s the case, and if the motorhome would sit level with the spring-assisters present, fitting air-bellows units that had an overall length when inflated that was longer than the spring-assister when compressed would cause the vehicle’s rear end to rise. However, with no details of what make/model of motorhome greycaster owns, comparing like-with-like requires a crystal-ball. Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted July 25, 2017 Share Posted July 25, 2017 Still driveable to me.Maybe a combination of leaf and air. Check the full rear suspension. And always check your driving height on the rear at different loads. And made a record on it. Link to comment Share on other sites More sharing options...
MikeJJ Posted July 25, 2017 Share Posted July 25, 2017 Derek, I can see the "flatness" in the leaf spring you describe and that is quite different to the curvature which I have in the leaf springs on mine. My rear axle is loaded to 2100kg with the rating capacity of 2500kg. The Air-Top were factory fitted by Fiat. Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted July 25, 2017 Share Posted July 25, 2017 Interesting is to know when these airtops are at their internal bump stops and how the bellow looks than. Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted July 25, 2017 Share Posted July 25, 2017 I doubt that fiat sevel fits any of these but i cant be wrong. Link to comment Share on other sites More sharing options...
thebishbus Posted July 25, 2017 Share Posted July 25, 2017 The air pressure and the appearance must depend on number of leaves in the spring , the third photo has two leaves , the second has only one leaf , you cannot tell with the first photo. Brian B.. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 26, 2017 Share Posted July 26, 2017 MikeJJ - 2017-07-25 3:36 PM Derek, I can see the "flatness" in the leaf spring you describe and that is quite different to the curvature which I have in the leaf springs on mine. My rear axle is loaded to 2100kg with the rating capacity of 2500kg. The Air-Top were factory fitted by Fiat. Mike May I ask which make and model of motorhome you own, please? I’ve looked through all your postings but - having established that your vehicle has a Fiat Ducato X290 ‘maxi’ chassis, was obtained in July 2015, has the ‘cup holder’ cab storage fitment, has Michelin tyres and is not a panel-van conversion - I can’t find any means to identify the motorhome converter or the model. Nowadays (as far as I’m aware) AL-KO markets “Air Top” air-bellows units only for Fiat Ducato, Peugeot Boxer or Citroen Relay/Jumper vehicles/chassis and (again as far as I’m aware) there is only a single one-size-fits-all bellows variant, although an “Air Top” kit will differ according to whether the vehicle/chassis is an X250/X290 or the earlier X230/X244. Unlike some other makes of bellows-unit, (apparently) there are no heavier-duty bellows for heavier weight chassis - irrespective of whether the vehicle is a Ducato ‘light’ or a Ducato ‘maxii’, it’s seemingly the same air-bellows unit. Like Monique, I’m doubtful that Fiat will have fitted the “Air Top” system to your motorhome - it’s more likely that the motorhome converter has done this. Auto-Sleepers fits “Air Top” as standard to some of their motorhomes, but that’s part of the conversion process. I think that (years ago) Benimar used to fit air-bellows units as standard to some of their models, but I wasn’t aware of any converter except A-S doing this nowadays. I note that greycaster simultaneously asked about this on the Autosleepers Owners Forum (his motorhome evidently is an A-S Warwick XL) http://www.autosleeper-ownersforum.com/t21975-alko-air-top and the consensus there seems to be that, on an A-S Warwick with around 2.0bar pressure in the bellows, the bellows will resemble the one in graycaster’s photo in the original posting on this forum-thread. Link to comment Share on other sites More sharing options...
MikeJJ Posted July 26, 2017 Share Posted July 26, 2017 Derek, Yes I need to add details, just as you have - but only worked it out yesterday! The motorhome is a 2017 Pilote P746C with the option of the Maxi chassis. For all low-profile m/h fitted with 16" wheels Pilote require the fitment of the Alko "AIR-TOP" in order to provide adequate clearance under wheel arches when fully loaded. As you, I was also surprised about the fitment of the air-top but contacted Pilote who confirmed that they receive the cab/chassis complete from FIAT and make no alterations themselves. After having collected the m/h I read the dated (Oct 2016) FIAT Certificate of Conformity and that states the chassis upgrade. The FIAT CoC predates the Pilote Certifcate (Feb 2017) as expected. I suppose FIAT could have subcontracted the fitment to a garage around the corner!!!!!! Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 26, 2017 Share Posted July 26, 2017 Fair enough - if the Fiat CofC shows the AL-KO “Air Top” system then (as Pilote told you) the system will have been fitted by Fiat. According to the Fiat database my Rapido has ’non standard paintwork’, so it’s clear that motorhome converters can specify (at least to some degree) changes to the basic specification. Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted July 26, 2017 Share Posted July 26, 2017 This is very strange. That pilote P746C assume the light which can be with 16 wheels has no wheel arch to accomade them. And using a alko airtop to line up. But i have seen this on pilotes in the simplist forms in our club. A wheel arch not able to fit 16 wheels W/O a airtop You are kidding. Link to comment Share on other sites More sharing options...
Bop Posted July 26, 2017 Share Posted July 26, 2017 Evening All, Can someone tell me what the life expectancy of an air top unit is before it needs replacing. Cheers, Andrew Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 27, 2017 Share Posted July 27, 2017 monique.hubrechts@gm - 2017-07-26 4:41 PM This is very strange. That pilote P746C assume the light which can be with 16 wheels has no wheel arch to accomade them. And using a alko airtop to line up. But i have seen this on pilotes in the simplist forms in our club. A wheel arch not able to fit 16 wheels W/O a airtop You are kidding. According to recent Pilote”Pacific”-model price listings available on-line, AL-KO “Air Top” has been an option for the Ducato camping-car chassis, but NEEDED to be specified for low-profile designs built on a 4250kg chassis. It is also stated that, if 16”-diameter wheels (steel or Fiat alloy) were specified as an option, the “Air Top” system MUST also be specified. What this comes down to is, if one ordered a Pilote “Pacific”-model motorhome that will have 16”-diameter wheels (optional on a Ducato ‘light’ chassis; standard on a Ducato ‘heavy’ chassis) “Air Top” became mandatory for that vehicle. Which is what MikeJJ has said above... Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 27, 2017 Share Posted July 27, 2017 Bop - 2017-07-26 8:35 PM Evening All, Can someone tell me what the life expectancy of an air top unit is before it needs replacing. Cheers, Andrew As far as I’m aware there are no actuarial data available regarding the life-expectancy of air-bellows units, whether they be AL-KO “Air Top” ones or other makes. Unless the bellows itself becomes damaged, the unit should last for a long time. The rubber the bellows is made of won’t last forever of course, but a 10 years minimum life should be a reasonable expectation. The bellows of Dunlop air-assist units is replaceable, but if the bellows used on other makes fails/gets damaged, I believe the complete unit needs replacing. Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted July 27, 2017 Share Posted July 27, 2017 This is very interesting to our pilote drivers in our club. They think it was a promotional item. On the other end how critical and burden on the pressure on the bellows are specified in the manual in regards to wheel arch? What i know is that the light as one leaf and the heavy two, apart from the lighter in weight ceramic leaf option. In case of airtop the fiat bump stop is removed and sits in the bellow, nobody believes that but it is. Alko rear axle is very clear on this they have for every ride height setting a wheel arch drawing and tyre dimension given to the builders. They even sell wheel arches to them. But that is alko not sure how fiat CCS chassis works that way to fit their suspension. Be also aware that wheel off sets have influence on track. How much uneveness can you correct on the rear whit the bellows at a site? Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted July 27, 2017 Share Posted July 27, 2017 The Track- record on motorhomes i read during the last years being alko looks different. In case of a air top failure bellow can you drive? Link to comment Share on other sites More sharing options...
MikeJJ Posted July 27, 2017 Share Posted July 27, 2017 I did contact Pilote to ask if they could give me advice on wheel arch clearance or a recommendation of air pressure in the bellows. I was told they couldn't advise. As it is standing at 2 bar pressure and 2100kg load, I have approx. 8cm clearance between the top of the tyre and the underside of the wheel arch. Changing the pressure between 1.5 bar and 2 bar seems to make very little difference. I haven't tried raising the pressure to the max of 3bar. Maybe I should when I have a spare moment. Going back to "Greycaster's" original question maybe he should try a range of pressures to see the effect. In the ALKO manual (p11 of Installation manual) it does say that for test purposes only the unit can be tested at up to 5 bar to establish if there is any leakage but advise no higher than 3bar in normal operation when installed on a motorhome. Link to comment Share on other sites More sharing options...
Brian Kirby Posted July 27, 2017 Share Posted July 27, 2017 Don't know if this will help, but when I fitted air assistance to the rear of our Hobby, I adopted the following method to set the air pressure. First, with the van unladen, I measured and noted the distance from the underside of the rear "bumper" to the ground. Once the air assisters were fitted, I inflated them to their minimum recommended pressure. Then, with the van fully laden for a trip, and with it standing in the same place as before the air assisters were fitted, I inflated the two bellows evenly until they reinstated the unladen clearance between u/s of rear bumper and ground, and noted the pressure. Due to the small volume of the assisters, this was easily accomplished with no more than a few strokes normal bicycle pump on each side. This gave excellent results in terms of ride and sway and, by reinstating the unladen ride height, eliminated any further instances of grounding. Link to comment Share on other sites More sharing options...
Bop Posted July 28, 2017 Share Posted July 28, 2017 Derek Uzzell - 2017-07-27 9:12 AM Bop - 2017-07-26 8:35 PM Evening All, Can someone tell me what the life expectancy of an air top unit is before it needs replacing. Cheers, Andrew As far as I’m aware there are no actuarial data available regarding the life-expectancy of air-bellows units, whether they be AL-KO “Air Top” ones or other makes. Unless the bellows itself becomes damaged, the unit should last for a long time. The rubber the bellows is made of won’t last forever of course, but a 10 years minimum life should be a reasonable expectation. The bellows of Dunlop air-assist units is replaceable, but if the bellows used on other makes fails/gets damaged, I believe the complete unit needs replacing. That sounds like a very fair estimate Derek. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 28, 2017 Share Posted July 28, 2017 The AL-KO pressure gauges used with the “Air Top” product read from 0bar to 5bar, with 0bar-to-1bar and 3bar-to-5bar in red sections of the gauge and 1bar to 3bar in the green section. It can reasonably be assumed from this that AL-KO considers under-1bar to be too low and over-3bar to be too high. The “Air Top” system allows the rear suspension’s springing to be adjusted by a vehicle’s owner/driver to match the load being placed on the vehicle’s rear axle. Just like tyre pressures, there will be no optimum pressure for the air-bellows - if a motorhome’s rear end sags badly when fully loaded (as Brian’s Hobby did), increase the pressure in the bellows until it does not; if it does not sag, there’s no overwhelming reason to increase the pressure beyond minimum. In Mike’s case, if the air-bellows at 2bar inflation-pressure are significantly augmenting the leaf-springs when there is a rear-axle loading of 2100kg, lowering the pressure will lower the motorhome’s rear and increasing the pressure to 3bar will lift it. However, if the air-bellows at 2bar inflation-pressure are NOT significantly augmenting the leaf-springs when there is a rear-axle loading of 2100kg (which seems quite likely given the double leaf-springs fitted to Mike’s Pilote) lowering the pressure will not lower the motorhome’s rear end, though increasing the pressure to 3bar will raise it. As “Air Top” bellows can safely be inflated to 3bar, greycaster could increase his Warwick’s pressures from 2bar to 3bar as an experiment. Similarly Mike could do the same. Playing about with air-bellows pressures can be considered as suspension ‘tuning’ and - to some extent at least - what pressures are chosen are down to driver preference. As 2bar is in the middle of the ‘green’ range, it’s a good starting point. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 28, 2017 Share Posted July 28, 2017 Bop - 2017-07-28 9:22 AM Derek Uzzell - 2017-07-27 9:12 AM Bop - 2017-07-26 8:35 PM Evening All, Can someone tell me what the life expectancy of an air top unit is before it needs replacing. Cheers, Andrew As far as I’m aware there are no actuarial data available regarding the life-expectancy of air-bellows units, whether they be AL-KO “Air Top” ones or other makes. Unless the bellows itself becomes damaged, the unit should last for a long time. The rubber the bellows is made of won’t last forever of course, but a 10 years minimum life should be a reasonable expectation. The bellows of Dunlop air-assist units is replaceable, but if the bellows used on other makes fails/gets damaged, I believe the complete unit needs replacing. That sounds like a very fair estimate Derek. It’s not an estimate, it’s an educated guess. Link to comment Share on other sites More sharing options...
MikeJJ Posted July 28, 2017 Share Posted July 28, 2017 As an experiment this morning I took a number of readings at different pressures to see what the change would be. To confirm Derek's analysis: lowering the pressure (from 2bar to min 1bar) really did not make a lot of difference in the height of the vehicle at the rear axle, say 4-5mm. In fact between 1bar and 3bar the total lift amounted to 2cm. But at 0bar pressure the bellows were still nowhere near as compressed as shown in Greycaster's first photo - so I can understand his concern. This would suggest that his bellows are in fact configured to do much more work than the mine in supplementing the leaf spring (and/or that his leaf springs have weakened over time). So I would draw a couple of conclusions: Firstly at my "relatively" low axle loading, 80-85% of its rating, the air-top are making little difference and that suggests that Pilote's statement of just maintaining clearance under the wheel arch at full load (and max pressure) does make sense. But even at a maximum of 3bar the bellows are only adding about 6% extra load capacity. Secondly, these are all static measurements and in a dynamic situation, taking account of body roll and bumps etc, the air-top could be acting in a significant non-linear way significantly stiffening the springing on an upward jolt when under high load. The pity is that I was unable to get any information from Pilote as to what they must have observed during their own design/testing which caused them to stipulate the addition of air-top bellows. (or maybe, as Monique suggested, it was all marketing?) Link to comment Share on other sites More sharing options...
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