Tyre pressures Autotrail Mohican

[CarolMaria]

Please can anyone tell me what tyre pressures to use on our new Autotrail Mohican - Fiat Ducato base? We are getting conflicting advice from the dealer & the handbook.

Many thanks - Carol

[rupert123]

CarolMaria - 2009-11-28 11:53 PM

 

Please can anyone tell me what tyre pressures to use on our new Autotrail Mohican - Fiat Ducato base? We are getting conflicting advice from the dealer & the handbook.

Many thanks - Carol

 

Carol, this questions crops up again and again. Neither Fiat or Autotrail will be able to tell you. You will have to get the van weighed and when you have axle loads email the tyre maker with your tyre size and axle weights, they will give you recomended pressures.

[Derek Uzzell]

CarolMaria - 2009-11-28 11:53 PM

 

Please can anyone tell me what tyre pressures to use on our new Autotrail Mohican - Fiat Ducato base? We are getting conflicting advice from the dealer & the handbook.

Many thanks - Carol

 

What pressures does the dealer recommend and what's the advice in the handbook, please?

 

 

[Syd]

rupert123 - 2009-11-28 11:59 PM

Carol, this questions crops up again and again. Neither Fiat or Autotrail will be able to tell you. You will have to get the van weighed and when you have axle loads email the tyre maker with your tyre size and axle weights, they will give you recomended pressures.

 

Admitedly we have a caravan but I have tried emailing ALL of the tyre manufacturers for a difinitive tyre pressure for the caravan but every single one of them has replied that they were unable to help in this instance and for me to contact Tabbert.

[rupert123]

Syd - 2009-11-29 11:32 AM

 

rupert123 - 2009-11-28 11:59 PM

Carol, this questions crops up again and again. Neither Fiat or Autotrail will be able to tell you. You will have to get the van weighed and when you have axle loads email the tyre maker with your tyre size and axle weights, they will give you recomended pressures.

 

Admitedly we have a caravan but I have tried emailing ALL of the tyre manufacturers for a difinitive tyre pressure for the caravan but every single one of them has replied that they were unable to help in this instance and for me to contact Tabbert.

 

Well Syd that may be the case but i have always got a response with M/H. There are several charts around that will give you pressures but to be accurate you will still need to know the loaded axle weights, I cannot think their is any other way.

[Tomo3090]

I went to a local tyre fitters with my Cheyenne and they looked it up on their computer and made the correct adjustments for me there and then for nowt.

[peterjl]

hi

 

on my autotrail the tyre presures are on a plate just inside the passenger door.

 

similalry on my last hobby they were on a plate inside drivers door.

I emailed data to the tyre manufactures who confirmed the pressures.

 

Peter

[rupert123]

peterjl - 2009-11-29 1:37 PM

 

hi

 

on my autotrail the tyre presures are on a plate just inside the passenger door.

 

similalry on my last hobby they were on a plate inside drivers door.

I emailed data to the tyre manufactures who confirmed the pressures.

 

Peter

 

These are the tyre pressures for the base vehicle, not for a loaded camper van.

[EJB]

Base vehicle pressures are often plated as 80PSI. However this is the highest safe pressure that allows for all situations and legally lets FIAT etc off the hook.

My MH pressures are 55 and 50PSI recommended by the tyre manufacturer after a weighbridge check and a 2 minute phone call.

Even a telephone call with the plated maximum axle loads to the tyre company will give a more sensible answer.

 

[Solwaybuggier]

EJB - 2009-11-29 2:23 PM

 

Base vehicle pressures are often plated as 80PSI. However this is the highest safe pressure that allows for all situations and legally lets FIAT etc off the hook.

My MH pressures are 55 and 50PSI recommended by the tyre manufacturer after a weighbridge check and a 2 minute phone call.

Even a telephone call with the plated maximum axle loads to the tyre company will give a more sensible answer.

 

Sadly I'm not sure that's true any more - I did all of this and got pressures for weighbridge weights from Michelin of 55/50 psi. Van runs much better at this than at 80 psi.

 

But I think I've subsequently read on another forum that VOSA have leant on (OK, "advised"!) tyre manufacturers and they are upping the recommended pressures to usually 80 psi.

 

Can anyone else recall this?

[Brian Kirby]

Solwaybuggier - 2009-11-29 3:51 PM

EJB - 2009-11-29 2:23 PM Base vehicle pressures are often plated as 80PSI. However this is the highest safe pressure that allows for all situations and legally lets FIAT etc off the hook. My MH pressures are 55 and 50PSI recommended by the tyre manufacturer after a weighbridge check and a 2 minute phone call. Even a telephone call with the plated maximum axle loads to the tyre company will give a more sensible answer.

Sadly I'm not sure that's true any more - I did all of this and got pressures for weighbridge weights from Michelin of 55/50 psi. Van runs much better at this than at 80 psi. But I think I've subsequently read on another forum that VOSA have leant on (OK, "advised"!) tyre manufacturers and they are upping the recommended pressures to usually 80 psi. Can anyone else recall this?

Go here: http://tinyurl.com/ygj67lm and download the one about motorhome tyres (all except Syd, he's not allowed that one as he has a caravan.  :-)  However, just above it is the caravan one.  OK Syd?  ;-)). 

Tyresafe is allied to the British Tyre Manufacturer's Association, which is the trade association for all the main tyre manufacturers who sell in UK, including Michelin and Continental.

Can't imagine why VOSA might do as suggested above, but I guess an e-mail to them might get an explanation.

In the leaflet, you will find pressure charts for loads by tyre size and ply and speed ratings.  Not exhaustive, but a good starting point before telephoning the manufacturer's technical dept if your tyres aren't covered.

However, I would recommend against just proceeding on the strength of a telecon, and get your informant's e-mail address.  E-mail him with the weighbridge results (making sure the van is at max load) and the tyre make, type, and size, fitted to your van, and ask him to e-mail back their recommendations for pressures.  That way you have the evidence if challenged.  If your tyres are as in the leaflet, then just carry the leaflet.

Any pressures quoted on a vehicle plate should co-incide with those given in the base vehicle's handbook, which should be the same as in the converter's handbook - if quoted.  If they don't, check that the chassis details are correct, since chassis delivered for conversion to motorhomes usually incorporate a number of special facilities, and are often on different tyres to the standard production variants.

It is true that the quoted pressures are higher than strictly necessary, because they are designed to cope with the maximum permissible load for each individual axle, and a motorhome loaded to that extent would be exceeding its MAM!  However, in the absence of information on the actual laden axle loads (which manufacturers obviously cannot have), they are the only safe pressures to recommend.

[teflon2]

Hi carol if you look on the sidewall of the tyre it will show a maximum pressure and as a motorhome is always near the maxmum vehicle wheight I personaly use this as my benchmark. Probably now I will be told how wrong that is but you takes your choice and goes with it, the one thing you can be sure of is if the Vehicle check guys stop you it can be pointed out to them that the makers indicate that pressure. Lifes cofusing isn't it? all the best. John (^)

[747]

If you have an accident and it is found that your tyre pressures are not correct then your Insurance company are entitled not to pay out on the claim.

 

On my first van, the dealer had them at 80 psi, Elddis (on their website) said 43 psi, Michelin said 55 psi when I gave them the axle weights.

 

That is enough of a discrepancy to void a claim I believe.

[Solwaybuggier]

 

Brian

 

I had a dig around on "another forum" - I don't think I found the posting I meant (which was around 6 months back) but did find a very recent one which says:

 

"Much talked about subject on the forum I too have spoken to Michelin as I have Michelin tyres. Mine are marked 80PSI on the sidewall but that is the max permitted pressure and as stated above for some reason does not apply to Europe. However they will, and have in my case given me the pressures they recommend when thay are given axle weights and tyre information including load index. They will tell you on the phone or by e mail. This of course is assuming you have Michelin tyres but you may have another make.

And as an aside if your tyres happen to be 215/75 R16 Michelin XC or Agilis they will now say that the rear axle should be 80 PSI. Yes the maximum. This follows discussion with VOSA who feel that motorhomes will be at their max weight on the rear and pressures should reflect this. Prior to this discussion they advised me by e mail that 70 PSI would be correct. (For the same given axle weight)

If the OP has another make perhaps other manufacturers will give tyre pressure advice.

Regrds, Dave "

 

This seems to suggest that VOSA are in effect "upping" the recommended pressure, at least on rear axles. Unless of course the poster is misinterpreting what Michelin have said?

 

I agree totally that written confirmation from tyre manufacturer is wise - I keep hard copy of email and weighbridge tickets with me in the van.

[rupert123]

Bet you wish you had not asked this question Carol but it has been asked several times before and you will always get the same confusing set of answers. The problem is no one knows what weight you are going to load your van up to so neither the base vehicle maker or the M/H builder can give an answer. The pressures marked on the van plate are the base vehicle ones, you will also get a set of these in the base vehicle handbook. I have heard the VOSA one but have never seen any evidence of this. This is the reason haulage companies have a weighbridge, first to make sure they are not overweight second to make sure tyre pressures are ok. Without doubt you should take your van to a weighbridge get both axles weighed together with the total weight, you should do this anyway to make sure you are not overloaded. Email the tyre company with the information and as has been suggested keep the weighbridge ticket together with the tyre companies reply with your vehicle documents.

[Derek Uzzell]

The driving force behind Michelin's current stance regarding using maximum pressures for rear-axle 'camping car' tyres seems to be ETRTO rather than VOSA. See:

 

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=15438&posts=25

 

The simple answer to Carol's question is that she should follow the tyre pressure recommendations shown in her new motorhome's handbook. These recommendations may not be optimum when it comes to on-road performance or ride comfort, but the pressures will be safe and they won't be controversial as far as the police, DofT inspectors or insurance providers are concerned.

 

There will be (rare) instances where pressure recommendations are wrong, but it's likely that few motorcaravanners will recognise such errors unless they are actively looking for them. As I've said before, my Hobby carries a Ford dataplate advising that the vehicle's rear tyres should be inflated to 80psi for maximum load conditions, despite the tyres being marked with a maximum pressure of 70psi. This was clearly cock-eyed and, eventually, Ford acknowledged the error.

 

It's quite possible that the tyre pressures advised by Carol's dealer would be more suitable for her Mohican motorhome than those given in the vehicle's handbook and still be 'safe'. But there's no way of guessing if that's so without knowing what the handbook/dealer figures are. Even if the dealer's suggested pressures are 'better' than the handbook ones, it's the handbook advice that counts.

 

I fully agree that weighing a motorhome is wise, but it's also sensible for the owner of a new motorhome to stick to the handbook recommended tyre pressures until the vehicle has been weighed.

[Solwaybuggier]

Derek Uzzell - 2009-11-30 8:42 AM

 

The driving force behind Michelin's current stance regarding using maximum pressures for rear-axle 'camping car' tyres seems to be ETRTO rather than VOSA. See:

 

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=15438&posts=25

 

 

Derek

 

Thanks - that thread is far more detailed than the one I was looking for on MHF.

 

Ian

[747]

I cannot see VOSA asking the manufacturers to up the recommended tyre pressure. This will cause no end of problems.

 

Earlier in this thread I mentioned that my van came from the dealership with 80 psi in the tyre on a MWB Boxer coachbuilt. It was a death trap at those pressures as I had to corner very slowly after a couple of heartstopping incidents.

 

Apart from anything else, the ride was far too hard and everything rattled about (including my teeth).

[spartan3956]

I have a Mohican and have experimented with tyre pressures

I ran the tyres at 60 psi as per the handbook supplied.

I found that the steering was very light and wandered at 60mph and above.

Taking them down to 55psi i found that the vehicle was much better any lower and it has an affect on the mpg.

I tow a motorcycle trailer most of the time and have had no adverse handling.

[Derek Uzzell]

spartan3956 - 2009-11-30 8:58 PM

 

I have a Mohican and have experimented with tyre pressures...

 

Please could you confirm that your Mohican has the same specification as Carol's?

 

Auto-Trail has used the model-name "Mohican" continuously for many years, for quite different designs of motorhome based on both Fiat or Mercedes chassis and using various tyre sizes and types.

 

I don't know what Carol's (Auto-Trail?) handbook advises regarding tyre pressures, but I would have expected the recommendation to be above 60psi for the rear axle given the size/weight/specification of a current Mohican. (I'm not suggesting that 60psi is wrong - in fact, it may well be 'about right' for a current Mohican - it's just that large Fiat-based motorcaravans fitted with camping-car tyres have tended historically to have motorhome-handbook tyre-pressure recommendations significantly higher than that.)

 

I'm also a mite surprised that dropping your motorhome's pressures from 60psi to 55psi made such a noticeable improvement to the steering. Did you actually reduce the pressures below 55psi and found that mpg dropped, or are you just assuming that it would if you went any lower.

[jadatis]

On the Dutch camperforum the question was also often asked.

But now not anymore, because I got hold of the formula the tire-and car-manufacturers also use to determine the tire pressures.

Learned myself Excell to make spreadsheets for it.

Also put in my own input about the Load-percentage.

Translated a few to Englisch to bring it over the world.

Hope I can place a link on my first post here.

http://cid-a526e0eee092e6dc.skydrive.live.com/self.aspx/.Public/pressurecalculationwithtemp.xls

This one you can use for motorhomes, I would leave the Load-percentages at front 95% and rear 85% for overloading and pressure-loss in time.

From this link you can navigate my complete public map from hotmail, for more usefull spreadsheets. For the one with the caravan here I have a not yet translated spreadsheet.

Also for the car I made a spreadsheet for re-calculating when other then original tyres, but can also be used to check the original tyres and see if you can go lower in sertain conditions.

http://cid-a526e0eee092e6dc.skydrive.live.com/browse.aspx/.Public/Recalculating%20tyre-pressure

in this map always take the newest spreadsheet and there are examples.

 

I read the motorhome pdf at the link someone posted her from tiny url.

Calculated the advice pressures and axle-weights there and this confirmed that they use the same formula.

For CP tyres I discovered something new

they use 475 kPa as reference pressure, for dual load and reduce the maximumload for that with 7.5 %. most C-tyres give two loadindexes say 195/75 R 16 Q 106/104.

for the dryving wheels they use 550kPa as reference pressure in the formula. this sound me a little strange but I am overthinking it.

When I know why they do it I will post it, but it has the same effect as the putting the Load-percentage lower . I would calculate with the 550kPa for all situations for CP tyres.

 

 

 

[CarolMaria]

Thanks to everyone who replied to my question. We are now totally confused!! Hadn't reaslised buying a motorhome was going to present this type of problem. Didn't have these problems in 27 years of caravanning!

We've weighed the empty van at 3460kgs.

Autotrail's handbook says use the figures in the Fiat handbook.

The dealer said subtract 10 from the figure on the wall of the tyre.

All very confusing.Wouldn't like to think the insurance company would challenge any claim in the event of an accident-could be VERY expensive!

Carol

 

[Derek Uzzell]

Carol

 

I haven't got a current Auto-Trail brochure, but I have a 2007 one and I don't think the Fiat-based Mohican model has altered significantly since then.

 

My brochure gives the Mohican's 'unladen mass' as 3350kg. This is for a standard Mohican with 2.3litre motor and no extras. According to the brochure the 3350kg figure includes weight allowances for a driver (75kg) and for a 90% full fuel-tank, but no allowances for fresh water, passengers, luggage or (seemingly) gas bottles. If a Mohican had a different engine (ie. the 3.0 litre motor) or heavy accessories (eg. an awning or tow bar), then the basic 3350kg 'unladen mass' figure would need to be increased accordingly.

 

You say that you've weighed your Mohican "empty" at 3460kg, so let's work with that figure.

 

My brochure says that the Mohican is built on an Al-Ko chassis with a maximum permitted weight of 4250kg and with maximum permitted axle-loadings of 2100kg (front axle) and 2400kg (rear axle). Subtracting your 3460kg from 4250kg gives 790kg, which is effectively your motorhome's 'payload'.

 

The tyres fitted to your Mohican are of 225/75 R16 size and will (almost certainly) be 'camping car' type. To the best of my knowledge only two tyre manufacturers (Michelin and Continental) currently produce this type of tyre in that size and, in both instances, the tyre has a Load Index of 116, indicating that the tyre is designed to carry a maximum load of 1250kg. Two of these tyres can, together, carry 2500kg, which exceeds your Mohican's 2400kg rear-axle limit by 100kg and its 2100kg front-axle limit by 400kg - essentially, your motorhome's tyres are more than capable of carrying any weight that you can legally place on them when operating your motorhome.

 

The heavier the load you place on a tyre, the higher the tyre-pressure will need to be to support the load safely. As your dealer has pointed out, tyres are marked with their maximum design-loading and their maximum inflation pressure. It's normal for commercial vehicle handbooks to recommend tyre pressures that are appropriate for the vehicle's maximum permitted axle-loadings, as it's impossible for the vehicle manufacturer to know how a buyer will load the vehicle. This means that the recommended tyre pressures will be higher than ideal when the vehicle is lightly loaded.

 

It's well recognised that many motorcaravanners operate their motorhomes with axle-loadings close to their maximum permitted limits, and that's one of the reasons why 'tough' camping-car tyres have been developed to cope with the continuous heavy loadings. In the case of 'camping car' tyres, the maximum design inflation-pressure is high - at least 80psi - and this has led to similarly high pressure recommendations.

 

I don't know what Fiat's handbook currently advises, but historically there were different recommendations according to whether the vehicle had 'ordinary' or 'camping-car' tyres. In the latter case, for heavy vehicles like yours, Fiat's advice was to use 80psi for front and rear tyres and this recommendation was often repeated in motorhome manufacturers' own manuals. (It would be useful to know what tyre-pressure advice is given in the Fiat handbook provided with your motorhome.) Inevitably, when the motorhome was operated relatively lightly loaded, 80psi all-round produced an uncomfortably hard ride.

 

Although you've established your Mohican's empty weight (which is useful for assessing its payload capability), I'm sure you'll accept that your motorhome will weigh considerably more when you are touring in it.

 

As has been advised earlier in this thread, to ascertain suitable tyre pressures for your motorhome you'll first need to load up your Mohican until it is in 'touring trim'. That is, with a full fuel tank, full fresh water tank, full gas bottles, driver and passenger(s) on board, luggage, baggage, pets, etc. After that, you'll need re-weigh your motorhome to establish its AXLE LOADINGS (front and rear) when the motorhome is FULLY-LOADED, as it's the axle-loadings that will decide the best tyre pressures that can safely be used. Then you can seek inflation pressure advice from the tyre manufacturer by providing exact details of your Mohican's tyres and the axle-loadings you've obtained.

 

Until you've obtained advice from the tyre manufacturer, you would be wisest to follow the recommendations in the Fiat handbook.

[jadatis]

If the weights that Dereck Uzzel wrote are the right ones and also the specifications of the tire, I would advice the next.

 

Front calculated for 2100kg because the front axle is never overloaded.

then a pressure of 64 psi is more then enaugh. If you want to be on the save side use 69 psi so you have some reserve. If you pump them harder, you have less grip and experiënce discomfort by bouncing.

 

Behind I would use the full pressure of 80psi to cover overloading.

The experiënce here in Holland is that the rear-axle is mostly overloaded.

 

So you see that the advices can vary , even If you calculate it.

If you would weigh the car-axles seperately fully loaded you probably see that what I write after this is as in practice.

 

Even when the Gross vehicle weiht of here 4200kg is not exeded the rear can be overloaded and the front underloaded.

That is because the most luggage is stamped behind the rear-axle.

If you want to overload the front, you have to place a motor on your front bumper to get enaugh weigt on the front. :D :$

With my camper I had , also a ducato everything behind the house-door wich was right behind the cabine,would place more weight on the rear then the front, because it was in the midle of the front and rear axle.

 

I calculated the pressures with the spreadsheet I mentioned.

See if I can chance it a little, but for the calculating of the pressure you can, though it only shows LBS and PSI, fill in in KG or LBS and in Bar or PSI , the answers wil be in the same weight-type and pressure-type you fill in , but use only one weight and pressure type in that first part. Dont mix LBS and KG , Psi and Bar.

[Brian Kirby]

I don't doubt the accuracy of Peter's advice above, but it has one important shortcoming.  In the absence of printed evidence from a weighbridge, and some form of written recommendation from the tyre manufacturer (or their trade association) you will have no evidence to prove why you are using pressures that differ from the manufacturer's recommended pressures.  If involved in an accident, and subjected to subsequent police checking of the tyre pressures, you could be considered to be running the van tyres underinflated.  That would not go down well with your insurer, as it would indicate you were not properly maintaining the vehicle.  Be careful!