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Air Suspension on Hymer MLT


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We have a 2015 Hymer MLT 580 and are having problems with grounding of the straps on the grey water tank.

Of course both the dealer and the manufacturer have not heard of anyone else with the problem. Is there anyone out there who also encountered this? We are not new to motorhoming and have 10 years experience and two previous (Knaus) vehicles.

We are considering fitting air assist suspension ourselves.

Is this the most practical option or has anyone any other advice?

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Photos of a Hymer 580 MLT show that the model’s rear overhang is substantial with no significant upwards-angling toward’s the vehicle’s rear




so there is plenty of potential for grounding


This long MHFacts 2011 discussion about grounding may be of interest




Anti-grounding rear rollers are mentioned (examples on following links)






but these may not be effective as it’s the straps of your waste-water tank that are grounding.


You could fit stronger springs to the rear suspension (or ‘helper’ springs) but probably your best bet would be to fit an air-assist (air bellows) system. You could then control the motorhome’s rear ground clearance so that it’s adequate to prevent grounding, but not so high that the vehicle is excessively nose-down or the rear springing becomes so stiff that ride-quality is badly affected.

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Hi Clive,


How heavily laden is your Hymer?


Or more importantly what is the loading on your rear axle?


My first port of call would be to visit a weighbridge and get an overall weight and, more importantly, a separate rear axle weight. Make sure you get a ticket with these weights accurately recorded.


Then compare this with the vehicles VIN plate for max axle loadings and see where you stand. If you are obviously well below the stated max figure then I would return to the selling dealer (assuming you bought it new) and state that the MH is 'Not fit for purpose' and see what they have to say.

If you cannot safely operate within the stated axle max weights then my opinion is that it is not fit for purpose and would expect the dealer and/or manufacturer to make right any design fault.


You have paid a lot of money for this MH and should not have to spend more to make it usable.


My opinion only and you are free to take or leave my suggestions.


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I agree with Derek. I have reservations (not based on personal experience) about fitting rollers. First, the overhang is likely to be supported on a chassis extension. Second, that chassis extension is likely to have been designed to take a load from above, whereas the rollers, if they come into contact with the ground, will impart a load from below. Third, grounding contact is not always gentle or progressive: an unseen sleeping policeman, an entry from a drive or very minor road (campsite entrance for example), or even just driving off a parking space can result in a quite sharp change in level that can drop the tail of a van quite sharply (as can at times the inside track of a steep uphill hairpin bend).


We fitted air assistance to the rear of our last van (FWD Transit based), after a couple of incidents where the tail grounded and it improved general stability, reduced roll, improved rear ground clearance, and was a general all-round success. So, air assistance would be my choice. I fitted no pump, and the two air springs were individually inflated so that no air was displaced from side to side to help counter roll (may be useful on a Merc base :-)). The pressure to raise the tail of the laden van to the level at which it sat when empty was quite low and took only a few strokes of a conventional bicycle pump to achieve. So, simple, effective, and at quite reasonable cost.

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We had a Hymer 544 on a low alko chassis that used to ground [driver side external locker] when going over kerbs or when exiting right from the local fuel station. We only went over a kerb once - to park - and we stopped turning right out of the fuel station. Problem solved. Our current van doesn't ground but has rear semi air suspension. Even when we used one of the highest pressures, the rear of the van doesn't rise that much.


So in what circumstances does the MLT ground? I'd certainly get the van axles weighed to see whether either are overloaded and whether there is a big difference between front and back axles [which may in extreme circumstances affect adhesion of the front wheels]. SV Tech has a calculator on its website that enables you to see what happens when you add weight to the rear. You might find load redistribution helps [we moved some heavier stuff from the garage to the underfloor lockers at the front].


According to the Hymer website, the 580 has a payload of 530kg [3,500kg model] but as we have found with our current Hymer, that soon begins to disappear when UK specs and other accessories, such as a spare wheel, are fitted. It also seems to have a large garage, which presumably has a loading restriction [think yours is 350kg], which houses the heavy gas bottles.


My son hired a Peugeot Boxer commercial van on a low Alko-Chassis. It had plastic/nylon running skis bolted to the rear of the chassis that curved around the end of the chassis. These protected the chassis when grounding.


Does the van ride level when fully loaded?


I'd also take the opportunity to check out the tyre pressures by contacting the tyre manufacturer with your axle loading figures.

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Air bags may not raise the rear much without unreasonably high pressure, they just replace the bump stops and have a similar dimension.

Would larger tyres make a difference? If they are standard 215/70/15 then van tyres are available up to 225/75/15. I think this would give you about an inch and a half, and therefore more at the rear.

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Brock - 2015-12-19 1:32 PM..................So in what circumstances does the MLT ground? I'd certainly get the van axles weighed to see whether either are overloaded and whether there is a big difference between front and back axles [which may in extreme circumstances affect adhesion of the front wheels]. ....................

It's rear wheel drive, John, on a Merc 313 chassis, no AlKo.


But, it is a good question, especially in relationship to the waste water tank mounting position which, in view of the long rear overhang and garage, may be amidships rather than at the rear. I assumed it would be the tail that caught, but possibly not.


I'm surprised you and Bill found you didn't get much lift from air assistance. I didn't try to raise the rear overall, but just to reinstate the rear ride height of our Hobby Van back to its unladen value when the van was fully laden. It did this with ease, just compensating for the rear sag that affected the van.


The MLT looks very similar to the Hobby Van in side profile, with a long rear overhang behind a relatively short wheelbase. I would therefore expect it to place a large proportion of its not very generous (in standard form) payload onto its rear axle. The Merc conversions have always seemed to me to be rather softly sprung, and to wallow and roll rather more than others. Possibly it is very close to its maximum permissible rear axle load with the front relatively lightly loaded, leading to a nose up stance and a reduced ground clearance at the rear. Just depends where the tank is, and where it is grounding.

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Brian, I thought Hymer had moved to using the Merc's low-frame cab chassis [similar to Alko] and not the standard Merc chassis.


Twemlow will know where his tanks are located and can tell us. If they are between the axles, I can't see how semi air on the rear will help - assuming it can be fitted. If the waste tank is behind the rear axle, then rear air will help ensure the van is level but the driving characteristics may change if the van slopes to the front to give increase ground clearance for the waste tank.


Twemlow should be able to work out how high is tanks are from the floor, where they are in relation to the axles, and then draw a little diagram to show what angle will cause grounding. Then he can assess how realistic the angle is for his usage.


I'm very pleased with my Goldschmitt rear semi air suspension. It has sorted out the problems I had with the rear. Like you, I use it to level the ride but one occasion, I used it to level the van at the rear on site.




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Although Mercedes does offer a ‘low frame’ ladder chassis for Sprinter, I believe the Hymer MLT range uses the standard Mercedes chassis. The tyre size is 235/65 R16 and the only realistic tyre-size alteration to increase ground clearance would involve a change to 225/75 R16. If all four tyres were replaced this should (in principle) increase ground clearance by about 17mm and the vehicle’s overall gearing by about 4.5%.


Travelword is currently advertising several Hymer MLT 580 motorhomes and the photos (example below)




reveal that the waste-water tank is located (as one might expect with a RWD motorhome) directly behind the vehicle’s rear axle. There’s a large garage behind/over the waste-water tank and heavy loads in that garage will directly affect the ground clearance below the tank. It’s likely that the straps of the waste-water tank only ground infrequently (on traffic-calming humps, for instance): if that’s so even a relatively small increase in the beneath-tank clearance should be beneficial.


Fitting auxiliary air springs to the Hymer’s rear springs seems the logical approach, but care should be taken when selecting the system. ‘Semi air’ systems come in various flavours, with air-bellows that differ regarding dimensions and specification. Some research will be needed to ensure that the most suitable product is chosen and it would be worth discussing the issue with specialists like VB-Airsuspension




and Travelworld, who market Mercedes-based Hymers and should be familiar with Goldschmitt systems






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Clive (Twemlow),


I see that you have logged on to the forum a couple of times since posting your original question so please could you do us the courtesy of replying to some of the questions asked...


ie, Is your Hymer on a Merc with Low or Standard chassis?

What tyre size are you currently running?

Is your waste water tank immediately behind your rear axle?

Have you ever weighed your Hymer?


The answers to these, and other questions asked through the thread, will help forum members answer your query to the best of their abilities.


Maintaining 'Radio silence' will not help either side!




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Our Rimor Sailor was on a Merc 313 chassis, and it had the most horrendous overhang at the rear, I don't remember the exact dimension but I do recall checking it and finding that it was spot on the permitted 60% without the towbar which took it over.

The overhang was supported on a square tube subframe which appeared to be bolted to the rear of the chassis, and it must have extended the chassis by about 5 feet.

I have to confess that my imagination would run riot during those dark nights when I couldn't sleep, but it gave not the slightest cause for concern during the years we had it, but at various times it did hit the ground pretty hard.

We had air assistance on it and I think we inflated it to around 4.5 bar, which kept it level but didn't stop it grounding at every opportunity.

One dark night somewhere in France, whilst trying to locate an Aire, we tried to do a U turn in a carpark entrance, not realising it had a practically Alpine slope on it, and lifted the rear wheels almost clear of the ground, leaving us with no traction. By inflating the suspension to over 7 bar we managed to get enough grip to extract ourselves without any damage, but the airbags started to leak, we repaired them with the leak stuff that goes in through the valve, worked a treat.

We inflated ours with the cheap and tatty Chinese made 12 volt vacuum cleaner/compressor which we have had for years, and which we still use for the tyres on our present van.


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The following advert includes a photo of the VIN-plate of a 3500kg-chassis version of a Hymer MLT 580




The standard tyre-size of a MLT 580 is (as I said earlier) 235/65 R16 and the tyre normally factory-fitted seems to be Continental’s “VancoFourSeason”. (There is an on-line advert showing an MLT 580’s wheel that allows the tyre-size to be read and the chunky tread pattern suggests that the tyre was 'all-season' type.)


I can’t see it being significant whether an MLT 580 is built on a standard or ‘low-frame’ Sprinter chassis, as it’s the clearance beneath the waste-water tank’s straps that matters in this instance. However, the MLT 580’s wheelbase of 3665mm indicates that a standard chassis is used.


There’s no doubt about where an MLT 580’s fresh-water and waste-water tanks are located - both are rearward mounted above/behind the rear axle. This is commonly stated in on-line reviews of the motorhome (Hymer saying the tanks are deliberately positioned there to optimise weight distribution, but suggesting that travelling with full tanks is not recommended) and photos clearly show the waste-tank’s drain-outlet protruding behind the right rear wheel.


Although this Hymer model’s wheelbase-length is not generous for a 6.98m motorhome and there’s a fairly long rear overhang as a result, photos give no real clue that the waste-water tank might ground. Hanging, say, a scooter on a rear-carrier, or heavily loading the rear garage, could be expected to reduce ground clearance beneath the vehicle’s rear bumper, but Clive has not mentioned rear-bumper-grounding being a problem.


Clive’s inquiry asked if anyone else had experience of this problem. The Hymer MLT range was introduced quite recently and are not cheap, so it’s likely that currently there are few in the UK. The chances are slim then that a member of this relatively small forum will own an MLT 580 and will be able to comment based on ownership experience. It might be more productive for Clive to inquire on the larger forums (ie. MotorHomeFacts and MotorHomeFun) - though I couldn’t find anything Hymer MLT-related on either.


As Clive is not a motorhome ‘newbie’ and has referred specifically to the waste-water tank’s straps grounding, it seems fair to assume that the ground clearance beneath the straps is not large and - if that’s the case - this should be visually obvious. It’s not unreasonable to believe that the dealer who sold Clive his Hymer has not had (or heard of) similar complaints about grounding as the number of MLT 580s in the UK will be quite small. It’s possible that the problem is peculiar to Clive’s motorhome or to the 580 model’s specification when Clive’s motorhome was built, but that seems unlikely.


I’m guessing that Clive has asked the dealer who sold him the Hymer to resolve the tank-strap grounding problem, but this approach has been unsuccessful. A more aggressive stance (as suggested by Keithl) might get some action and, perhaps, an agreement that ‘air assist’ be fitted to the rear suspension at no charge to Clive. As fitting an ‘air assist’ system appears to be the best (perhaps the only realistic) approach to increase clearance beneathe the tank-straps, it really boils down to who will pay for it.

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Thanks for all the interest shown in our problem – far more than the manufacturer or the dealer!

To answer the points raised -

Weights – On the weighbridge the van as delivered (including ½ tank diesel, 20 kgs of fresh water and two full calor lites) was 3,160 kgs, 1340 front and 1820 rear.

Plated weights 3880/1800/2430

Adding passenger, bikes and everything ready to go was 3480. The garage maximum load stated 250 kgs and our actual garage load is 120 kgs.

Tyres – Are as has been pointed out 235/65/16 All Season

Waste Tank – Positioned just behind rear axle and extends 1.52 m. The total rear overhang is 2.2 m.

The rear strap has 200 mm ground clearance. The mid strap 188 mm.

The chassis is said to be a Mercedes Sports Safety chassis

I’m attempting to also post a photograph showing the waste tank and the straps. The problem is that on grounding the rear strap tears away and on the first occasion the centre strap bent severely.


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I'm new to this and didn't manage to get the photo posted - I'll try again.

As mentioned previously neither the dealer nor the Hymer will acknowledge there is a problem with the positioning of the grey water tank nor the fact that the straps run across the vehicle so are inclined to tear away even when just scraping the ground. The rear strap is only attached by 4 self tapping screws and can in no way actually supporting the grey water tank.

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The forum is currently 'Broken' and no-one can post photos. See the tread on Motorhome Matters for details.


I am afraid that my earlier view still stands, your new MH is 'Not fit for purpose'!


My next suggestion would be to contact someone like Trading Standards, Citizens Advice or possibly the legal team of the RAC, AA or possibly the CC or C&CC if you are a member, to get advice on how to approach the dealer to get a resolution.


Remember you only have legal redress with the dealer and NOT Hymer as you paid your money to the dealer.


PS Did you buy on finance? If so notify the finance company immediately of your problems as you also have redress with them if things get worse.



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This is the advice Will gave to me on how to post a picture. It worked for me. I was able to size the photo using Photoshop Elements/Save foe web.


I'm not familiar with your photo systems so……….. assuming you have chosen your picture and sized it (not necessary) you should be able to see what size in kbts it is by mousing the pointer over the picture icon. 100kbts is the maximum permitted for uploading, if it's over then reduce it. (or start again)


You must have a way of exporting or sending your picture to a 'named folder'. If you name the folder 'desktop' it should be seen on the screen with ITS OWN NAME that you have given it (John Jim Jack etc) You can name the folder 'Pictures' and it will go to your pictures folder.


On forums … type your message … scroll down the page and you will see 'attach a file after posting' tick the box … tick submit which will post your message only… you will now see a window that says 'choose file' click on it … find your named picture on desktop or in pictures … click on the icon with the picture you have named (once or twice not sure) … this should then be sent to the forum system, if successful the forum will say so, if not it will say unsuccessful … If this occurs I start all over again as I've made an error somewhere. It all works very well but as you know it will only do what you tell it and in the right order !… have a go… I'm not IT literate and do these things by trial and error and have a very very short memory span … The same method applies with the small picture under your name … Will



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Twemlow - 2015-12-21 11:14 AM


I'm new to this and didn't manage to get the photo posted - I'll try again...



As has already been advised, the “Attach a file after posting” feature normally employed to post photos is currently non-functional. This (plus some work-arounds) is mentioned in these discussions on the “Motorhome Matters” forum:






Assuming that the 200mm/188mm strap clearances you’ve quoted are with your motorhome in normally-loaded ‘holiday’ condition I feel you may have difficulty persuading anyone that this is genuinely inadequate, though I understand completely what you are saying regarding the damaging effect grounding can have on the straps that support the tank.


My current Rapido motorhome has its (uninsulated) waste-water tank in a similar position to your Hymer’s and is held by simple steel straps. But there’s plenty of clearance under the tank and I don’t anticipate having the type of grounding problems you’ve experienced. (Besides which, with the Rapido, any obstacle in the road high enough to hit the tank’s underside would smash into the lower-to-the-ground rear axle first.)


Replacing the Hymer’s present rear tyres with a different size would almost certainly conflict with the Mercedes warranty and would potentially complicate tyre-rotation and carrying a spare wheel. And (as I said earlier) the most ‘lift’ you’d get would be around 17mm.


Unless the dealer/Hymer is prepared to modify the tank’s support-system so that it’s less vulnerable to grounding, adding 'air-assist' would be the logical technical approach. This might in fact benefit the vehicle’s handling and, if air-assist results in the motorhome riding a little tail-up, I believe that won’t have any realistic negative impact on the vehicle’s on-road behaviour.

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Thanks again for all your comments - keep them coming.


Obviously I had hoped there would be another Hymer MLT owner noticing my post and having a similar problem. This would then back-up my complaint to the dealer.


Apart from the problem highlighted it is otherwise an excellent motorhome and suits us down to the ground! We have travelled 10,000 miles in it since we purchased new in April this year.


If I were able to post the photo you would then see how the problem is exacerbated by transverse straps.


If we don't get any further with the dealer then we will most probably go down the air suspension route.


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Fantastic, thanks very much for that link Robinhood.


Amazing how neither the Dealer (very near to you) nor Hymer said they had heard of our problem before and that even if any modifications were done to the model they would not necessarily by applied retrospectively. Hymer are saying that they are happy with the clearance with the Motorhome and that there is no repair that they would recommend for this as the tolerance is OK.


Dirk stuck in Sweden does not seem to agree as the struts were hanging off his tank

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  • 4 weeks later...

Welcome to the Out&AboutLive forums, Stu.


Assuming that the “grounding” that occurred when you drove on/off a ferry mirrored Clive’s (Twemlow’s) experiences - with the underside of the waste-water tank’s enclosure hitting the ground - you will now be in a position to draw the attention of your dealer to this discussion and to the complaints made on the German-forum link provided by Robinhood in his posting of 21 December 2015 3:46 PM.


(I also note that a 2014 pro-mobil review of a pre-production Hymer MLT-560 mentioned that the installation of the rear-mounted fresh- and waste-water tanks in a heated and insulated box, together with the long rear overhang, resulted in limited ground clearance.)


What response you get from your dealer will largely depend on how prepared you are to push the issue and whether there is clear evidence of the grounding having significantly damaged the waste-water tank’s ‘box’ as happened in Clive’s case.

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