Uprating motorhome...tyre implications

[peter21]

Hi all

 

The current maximum axle loadings on our motorhome (front 2100 kg, rear 2400 kg, total 4500 kg) limits the amount of gear we can stow in the garage so we are planning to uprate the rear axle to 2600 kg max by fitting air assist suspension units on the back axle, (after discussion with SVtech). This will not increase the total all up weight allowed, which stays at 4.5 tons.

 

Current tyres are michelin agilis camping, rated 116, which means that the maximum load is 1250 kg, i.e. less than the 1300 kg which the uprated back axle will be able to carry (1300kg for each side).

 

We are considering replacing the back tyres only, with Hankook RA18's, which will carry the increased weight required. The front tyres are low mileage, low age (5000 miles, less than a year), so do not need to be replaced.

 

Is there likely to be a problem in mixing tyres front to back like this? It is not possible, we are told, to get the Michelin agilis camping tyre in a load rating higher than 116.

 

Also, I don't think that the hankooks are mud and snow rated, but we are told that this is not important for a non driven axle (the motorhome is front wheel drive).

 

Thanks in advance for any comments/advice.

[Keithl]

Hi Pete,

 

A bit more info is needed to give you an answer.

 

What is base vehicle and does it have ABS and/or traction control?

 

What size are current tyres and what do you propose to fit in their place?

 

Do you have a spare and if so what size do you plan to carry in the future? Remember in some countries it is illegal to run odd size tyres on the same axle so you will really need to carry 2 spares if you use odd tyres front to rear.

 

HTH,

Keith.

[colin]

Those max axle loads are for a Ducato Maxi chassis I guess same as ours.

 

Using different tyres front to rear is not a problem in the UK, not sure about europe, but I have driven around europe on different size tyres front to rear.

Where you may come unstuck is front traction, do you know the actual loaded axle weights front to rear and what putting an extra 200kg in rear will do to that baleance?

 

p.s. have you had a previous up plating from SV tech to 4.5t? as usualy the chassis is only rated to 4.005t

[Airstream]

Hi,

Lots of Sports/Supercars have larger rear tyres than fronts and all "spacesaver" spares are smaller than the other tyres fitted and are legal on both axles all over the EU?

Ray

[peter21]

Thanks for comments.

Keith..Base vehicle is concorde credo emotion, fiat engine, alko chassis.

Currently all tyres 225/75R/16CP

I wouldn't change tyre size, just make...

No spare...there is a temporary inflation pack with some sort of sealant but no good of course if major blowout and I had always planned to get roadside assist service in event of puncture.

I just need to get a bit more load carrying capacity on back axle tyres, and don't want to dispense with good tyres on front if not necessary.

Peter

 

[Derek Uzzell]

peter21 - 2014-02-06 6:33 PM

 

Also, I don't think that the hankooks are mud and snow rated, but we are told that this is not important for a non driven axle (the motorhome is front wheel drive).

 

Hankook Vantra LT RA18 tyres ARE M+S-marked.

 

I can't see any problem doing this. It's legal in the UK and - to the best of my knowledge - will be legal elsewhere.

 

I'm not certain about the legality of mixing (on the same axle) same-size tyres with different load indexes if, say, a spare wheel were fitted. As Keith says, to address that scenario two spare wheels would be required.

[peter21]

Thanks Derek..that's helpful. I was hoping in the event of a blow out you could specify the replacement tyre the call out guys would fit?.....no point in them fitting an illegal tyre and I guess this point would be easy to argue with whichever company you pay to provide the breakdown cover. We don't carry a spare tyre.

 

Colin...No...the base chassis is an alko, 4.5 ton rated, and cannot according to SVtech be uprated total weight wise....only the back axle loading can be increased. And good point about front axle traction which I hadn't thought about. There is probably a minimum weight specification for the front axle somewhere..........(I know the max is 2.1 tons).

[Brian Kirby]

What you describe is unusual, in that the MAM you refer to is the sum of the two axle maxima.

 

My understanding, from press reports and Southdowns web site, is that the ex works MAM for the Credo Emotions was 4,250kg, not 4,500kg. This suggests that the MAM has already been increased by 250kg. This should show on the vehicle plate. Do you have the full vehicle history?

 

Base is Ducato Maxi 3.0 litre comfortmatic, plus alko chassis. The Credo Emotion 763L (reviewed in Which Motorhome August 2010) had a not inconsiderable payload of 940kg.

 

My main question is whether SVTech have consulted AlKo UK regarding this work? The AlKo chassis are quite finely engineered to minimise weight, so I would have expected some input from them regarding the uprating of the rear axle. The additional load will stress more than just the rear suspension, it will also add stress to the AlKo axle, its mountings, and through them, the AlKo chassis itself. Is this upgrade using an AlKo air assistance kit? I assume SVTech will carry out the work, and issue a new plate to show the 2,600kg rear axle loading? Before doing this, I think I would verify that AlKo have no reservations.

 

Have you checked Concorde's load limit for the garage? There will be one!

 

My second question is regarding the wheels. I understand that alloys were standard supply. Has their load carrying capability been verified. With a design axle load of 2,400kg there would have been no need to specify wheels for 2,600kg, so will they take it?

 

Also, if you do suffer a flat, it is quite likely that, even at your existing rear axle load, the tyre will be terminally mangled before you have the vehicle safely parked for a wheel change. It is also possible that the alloy rim would become damaged to the extent that a new tyre could not be fitted to it. So, there is a realistic prospect that you would need a new tyre, and not a repair, and possibily a replacement wheel. Outside the UK (especially France), it seems fitters may not fit different tyres across axles so, if your van is shod with Hankook RA18 tyres, they will fit only Hankook RA18 replacement, or will insist on fitting a pair of a differnet make. I don't know how readily available Hankooks of that specification are across Europe, but wonder if it might be worth investigating this and being prepared to select a tyre that is more commonly available?

[Robinhood]

Brian Kirby - 2014-02-07 1:03 PM

 

What you describe is unusual, in that the MAM you refer to is the sum of the two axle maxima.

 

My understanding, from press reports and Southdowns web site, is that the ex works MAM for the Credo Emotions was 4,250kg, not 4,500kg. This suggests that the MAM has already been increased by 250kg. This should show on the vehicle plate. Do you have the full vehicle history?

 

....snip.....

 

 

....the reasonably recent price list here:

 

http://www.southdownsmotorcaravans.co.uk/pdf/southdowns-2013-concorde-credo-pricelist.pdf

 

.......indicates that an ex-factory MAM of 4500kg is probably correct.

 

The remaining questions are all valid, however (though given SVTech's experience I would suspect they have the AL-KO questions covered. I would certainly want to be checking out the design weight of any alloy wheels though!)

 

 

 

 

[peter21]

thanks for the detailed replies.

Brian ...the MAM and axle maxima are correct ...the alko leaflet and chassis plate agree. It is an alko AMC45H chassis.

We have the full vehicle history and there has not been a previous uprating.

I have spoken to SVtech again, they are happy with the dunlop air suspension units we are fitting and were quite sure that the factory supplied wheels would be well able to handle another 100 kg each.

There is a plate giving a 250 kg max load for the garage but this has not taken in to account the larger leisure batteries (2 160ah) which have been fitted, and a weigh bridge visit showed we were very close to the back axle maximum with not much luggage in the garage.

I don't have a feel for tyre availability on the continent. We mainly visit France and Spain. Another tyre option is Continental Vanco all seasons...a bit pricy at £180 each...not sure if these are more easily found than Hankooks.

 

[Derek Uzzell]

A Michelin Agilis Camping 225/75 R16 tyre's 116 Load Index indicates an axle-loading maximum of 2500kg.

 

Uprating Peter's motorhome's rear axle maximum from 2400kg to 2500kg would allow another 100kg of 'stuff' to be stowed in the garage, allow the present tyres to be retained and (with luck) might allow the uprating to be carried out without the (expensive) addition of suspension air-assistance.

 

The alternative (changing the rear tyres and adding air-assistance) gains only an extra 100kg of weight-carrying capability at the rear axle, but adds cost and significant complication.

 

While recognising that a Concorde Credo Emotion is an expensive motorhome (so the cost of uprating the rear axle to 2600kg may not be an issue) I definitely wouldn't do what Peter is planning unless it were absolutely unavoidable.

 

My very first priority would be to get a spare wheel and tyre to carry in the motorhome. There's every chance that, in the event of a puncture that damages a tyre beyond repair, a breakdown company won't be able to match immediately the make/pattern of the damaged tyre, whether the latter be Michelin Agilis Camping or Hankook Vantra LT RA18. And, of course, if you do have a spare wheel and tyre, a breakdown company will be able to make a rapid wheel change at the roadside, rather than need to transport the motorhome somewhere to await provision of whatever replacement tyre can be found.

 

(Realistically, the chances of a breakdown company locating quickly a Continental Four Season tyre are even lower than for a Michelin Agilis Camping or Hankook RA18.)

[Keithl]

Peter,

 

I may have found a simpler answer for you after looking at a Conti tyre information leaflet.

 

Against 225/75R16 C is given 2 options of load ratings,,,

 

First at Speed rating 'R' (106 mph) is a Load Index of 116

 

Then against a Speed Index of 'P' (93 mph) is 118

 

These different SI have different pressure/load requirements but at SI 'P' they can carry an axle load of 2,640 kg which is what you are after.

 

As I expect you never run your MH at anywhere near 93 mph they will be perfectly suitable and far easier to obtain.

 

I will try and find a link to the Conti brochure but if I can't then send me a PM with an email address and I'll send you a pdf copy.

 

Keith.

 

Edit Link didn't work :-(

[Brian Kirby]

peter21 - 2014-02-07 2:27 PM

 

thanks for the detailed replies.

Brian ...the MAM and axle maxima are correct ...the alko leaflet and chassis plate agree. It is an alko AMC45H chassis.

We have the full vehicle history and there has not been a previous uprating.

I have spoken to SVtech again, they are happy with the dunlop air suspension units we are fitting and were quite sure that the factory supplied wheels would be well able to handle another 100 kg each.

There is a plate giving a 250 kg max load for the garage but this has not taken in to account the larger leisure batteries (2 160ah) which have been fitted, and a weigh bridge visit showed we were very close to the back axle maximum with not much luggage in the garage.

I don't have a feel for tyre availability on the continent. We mainly visit France and Spain. Another tyre option is Continental Vanco all seasons...a bit pricy at £180 each...not sure if these are more easily found than Hankooks.

Robin's find of the Concorde price list (thank you Robin) confirms that the information I got from the Which Motorhome article was wrong, or has been superceded. It also confirmed that the 3.0 litre engine, the auto transmission, and the alloy wheels are optional extras. Possibly the mag had a fully loaded version to test.

 

I was going to suggest the conti VancoFourSeason 2 tyres, but they have disappeared from the Conti website and from their 2013/14 Technical databook. So, I phoned Conti to ask what they now recommend instead. Caused a bit of puzzlement at first, but they 'phoned back and confirmed the tyre is still in production, and in stock in UK, in the 225/75 R 16 10PR 121/120 R version (plus others). They had no idea why the tyre seemed to have disappeared! As you say, quite a bit more expensive. It is unstated in the databoook, but the tyre carries M+S designation on its sidewall, but not the snowflake.

 

I had two of its predecessor fitted to the front of our Hobby because it was tail heavy, and the traction on the front became very poor on grass or wet/greasy roads. They were very slightly noisier than the standard Vancos, but barely detectably so, but the wet grip was noticeably improved. I was very pleased with them overall.

[Keithl]

Peter,

 

Further to my earlier post you can download the Conti Technical brochure for Cars & Vans from Here and the info I referred to is on Pages 76-77. Load Index and Speed Index details are on page 8.

 

Keith.

[Brian Kirby]

The defeatist reply, I suppose, would be to review all that stuff, to see what can be omitted or how it could be redistributed, to bring the rear axle load back within its factory limit. Cheapest remedy of all! :-D

[globebuster]

Surely ,if you do go down the route of carrying a spare [i do, and wouldn't be without one] you will pretty much negate your potential 'upgrade' - if carried aft of the rear axle.

[Derek Uzzell]

Tyres potentially suitable for a motorhome in 225/75 R16 size are marketed with a Load Index (LI) of 116, 118 or 121. These LIs represent ‘single wheel’ axle-loading maxima of (respectively) 2500kg, 2640kg and 2900kg. As Peter plans to uprate his Concorde’s rear-axle maximum to 2600kg and exploit that loading during normal operation, it would be logical to use tyres with an LI of 121.

 

The Concorde’s existing tyres are Michelin Agilis Camping tyres (CP-marked) with an LI of 116. 225/75 R16 CP-marked tyres from Continental and Pirelli also have a 116 Load Index, which means that any tyre with a LI above 116 will need to be C-marked (ie. be a ‘white van’ tyre) rather than be a tyre aimed specifically at the motorhome market.

 

Many motorhome nowadays are marketed with no spare wheel. For some of these vehicles carrying a spare wheel would be impracticable, but I’m sure that few people would be blind to the implications of driving a motorhome with no spare wheel. Similarly, I’m confident that, if a motorhome has the capability to carry a spare wheel easily (in a ‘garage', say) most people would think that doing so would be a sensible move.

 

Plainly (as globebuster observes) the weight of a spare wheel (30kg?) carried in Peter’s Concorde’s garage would erode some of the load-carrying benefits obtained by uprating the rear-axle loading from 2400kg to 2600kg. But, even if, say, 60kg of the extra 200kg were lost because of the ‘leverage’ of the weight of the spare wheel in the garage, it would still be worthwhile in my view.

 

Some of the discussion above has involved speculation about how obtainable a replacement tyre might be if Peter’s motorhome had a puncture or tyre failure.

 

Peter has said that he mostly visits France and Spain and in those countries I’d guess that Continental and Michelin C-marked tyres should be reasonably easily obtained (though not necessarily immediately obtained). Continental’s Vanco-2 and Michelin’s Agilis+ C-marked tyres are both available with an LI of 121 (though neither is M+S-marked).

 

If the Concorde’s rear tyres were replaced and a spare wheel were carried, it would be sensible to fit the spare wheel with the same make/pattern of tyre as the rear tyre replacements. This would mean that, in the event of a front-wheel puncture and the spare wheel being fitted, the front axle would carry different makes of tyre and that those tyres’ LI would differ.

 

The obvious solution would be to bite the financial bullet and replace all of the Concorde’s present tyres, not just the rear tyres. Choosing Hankook’s RA18 (M+S) pattern would probably be cheaper than choosing Continental or Michelin brands, and it MIGHT be easier to obtain Continental or Michelin tyres abroad (though a quick check of French on-line tyre suppliers indicates that 225/75 R16 RA18s are available.)

 

As I said earlier, I wouldn’t consider driving this size of motorhome without a spare wheel when it’s evident that carrying one is technically easily achievable.

 

I’d also want to be absolutely certain, before playing about with suspension and tyre changes, that the weighbridge readout that revealed that the motorhome’s rear-axle loading was near its 2400kg limit was accurate.

[peter21]

Thanks again to all for the most helpful replies to this thread. (Incidentally we did weigh the vehicle twice; the second weigh bridge agreed).

We have now had Dunlop air suspension assist units fitted and we were very impressed by Phil McNally of Rhino Installs, who drove up to Cumbria, through the rain and snow, to fit the units quickly and efficiently, at a very good price. And saved us the diesel we would have needed to take the vehicle to another fitter.