Tyre pressures

[rupert123]

I have no doubt this has been discussed before but would like any opinions on the matter of tyre pressures. On my new Ducato based van Fiats recommendations for motorhome tyres are 5.5 bar front 6 bar rear, Swift have no opinion, they say ask Fiat. My reaction was to contact the tyre manufacturer, Continental, and ask them. They have replied and their answer is 3 bar front, my axle load is 1200 kgs, 4.75 bar rear, axle load 1800 kgs. My maximum loads are rated at 1900 rear, 1600 front. This seems a large variance, has anyone else come across this. Tyres are 215/70/15 cp Vancocampers

[enodreven]

Hi,

 

You are correct this subject has been discussed many many times, and i believe one of the magazine's recently printed some information on the topic.

 

However, from my point of view and i believe the traffic laws, tyre pressures are a subject that may well be brought up in the case of an accident and therefore i personally would want something in writing from a respected source just in case.

 

My recommendation would be to either use the pressures that are usually stamped on the door pillars or perhaps in the hand book, or in the absences of these.

 

I would take the vehicle to a weighbridge loaded with all of the equipment that i think i would normally take with me when touring and get both axles weighed independently as quiet often this differs from the plated information stamped on the vehicle , i would then email this information to your tyre manufacturer and ask them for there recommendations in writing (email reply).

 

I would then follow there recommendations and keep this reply in a safe place alongside of all of the other motorhome documentation so if in the unlikely event of you being involved in an accident you can produce written evidence from a reputable source e.g the tyre manufacturer indicating why the pressures you are running at may be different from those indicated elsewhere in your documentation

 

Hope that helps

 

rupert123 - 2008-09-04 11:42 AM

 

I have no doubt this has been discussed before but would like any opinions on the matter of tyre pressures. On my new Ducato based van Fiats recommendations for motorhome tyres are 5.5 bar front 6 bar rear, Swift have no opinion, they say ask Fiat. My reaction was to contact the tyre manufacturer, Continental, and ask them. They have replied and their answer is 3 bar front, my axle load is 1200 kgs, 4.75 bar rear, axle load 1800 kgs. My maximum loads are rated at 1900 rear, 1600 front. This seems a large variance, has anyone else come across this. Tyres are 215/70/15 cp Vancocampers

[rupert123]

Thanks for reply but perhaps I have not made myself clear. I have had it weighed and have quoted weights in my post, i have contacted tyre people and pressures given are quoted in my post. the manufacturor, in this case Swift do not quote pressures and Fiat only quote on what i would assume is a wide base. What concerns me is the large variance between Fiat and tyre people, my instinct is, like yours, to go with tyre people.

[trooper]

Hi Rupert 123

I think you are correct in what you did, I have done this on 3 M/H.

If in the future you need conformation on the pressures ring the tyre manufacturers again and you would get exactly the same pressures

as they work of a standard chart, I have been told this by tec chap when getting my pressures.

 

cheers

[rupert123]

trooper - 2008-09-04 4:49 PM

 

Hi Rupert 123

I think you are correct in what you did, I have done this on 3 M/H.

If in the future you need conformation on the pressures ring the tyre manufacturers again and you would get exactly the same pressures

as they work of a standard chart, I have been told this by tec chap when getting my pressures.

 

cheers

 

OK Don thanks, think I will go with tyre company.

[Shaun]

I bought an Adria Twin early this year. The tyre pressures quoted by Fiat, in the handbook, looked suspiciously high. I contacted Continental, the tyre manufacturer, and came away much more enlightened. Their camper tyres (with which the van was shod) reflected the fact that motorhomes had far less variance in payload, compared to a typical panel van. The latter could be empty then completely full, from one journey to the next, whereas the motorhome would vary much less. These particular tyres also reflected the fact that the vehicle was likely to do much lower mileages and the average owner wouldn't want to change them every few years, still with decent tread on them.

 

Anyway, I was asked for the maximum weight the vehicle could carry, then the maximum loads for the front and rear axles. The tyre pressures then quoted to me were noticeably lower than those stated in the Fiat handbook. Furthermore, it was mentioned that if the van ever travelled regularly unladen, in the sense that it wasn't packed to the gills with passengers and their belongings, then the pressures could be reduced. However, this was more for comfort, rather than safety.

 

For me, the most interesting thing was that before ringing Continental, I'd been driving the van a few weeks and really liked its comfort and road-holding. I was sure someone would tell me the tyre pressures I was currently using were wrong and by changing them, I'd end up being safer, but that I'd find handling and/or comfort would suffer. It came as a pleasant surprise to find that the tyre pressures which Continental gave me, were the same as those which the tyre were inflated to at the time. Deep joy.

 

Shaun

[Robinhood]

You might find it revealing to download the pdf item on motorhome tyres from http://www.tyresafe.org/tyre-safety/

 

There is a good amount of information on this, including a pressure chart vs axle loadings for various tyre sizes that matches the information given to me by Michelin for my last three vans (for supplied axle loadings).

 

Every quote I've had, and the information in this pdf, recommends pressures significantly lower than the base vehicle handbook has (and my experience has been in all cases that the driving characteristics and ride comfort have been better on these lower pressures).

[rupert123]

Thanks for all replies, this seems the same as my current experience, pressures given by Continental are much lower for the front and a little for the rear than Fiats. Would guess this is because in addition to rear kitchen I carry a small scooter so rear axle load is quite high, although a 140kgs below maximun. Am going to lower them tomorrow and try things out.

[Brambles]

Fiat quote the absolute max tyre pressure.

 

However most people seem to miss the other label which is fitted. Fiat I believe normally place it in the hinge area, it shows correction factors (pressures) for 3 different weights.

[Derek Uzzell]

Fiat has a history of recommending ultra-high tyre pressures for light commercial vehicle chassis fitted with 'camping-car' tyres, irrespective of the vehicle's particular technical specification. This originally seems to have been prompted by a recommendation from Michelin (who, for many years, was the sole manufacturer targeting the motorcaravan market) that its XC Camping tyre should be inflated to 80psi (5.5bar) when fitted to the rear axle of motorhomes used on mainland Europe and operating at maximum load. It now appears that Fiat is adopting the same philosophy for more recently introduced tyres like Continental's VancoCamper.

 

When VancoCamper first came on the scene I wondered whether a 6.0 bar (87psi) inflation pressure would be recommended if Fiat chose to factory-fit this tyre. (In fact I'm pretty sure I mentioned this on the forum). "6.0 bars" does indeed come up in the VancoCamper section of Continental's website, but this pressure recommendation may not relate to all tyre sizes, merely to the 215/75R16C variant. This is the link to the relevant webpage:

 

http://www.conti-online.com/generator/www/uk/en/continental/automobile/themes/vans/mobile/vanco_camper/details/dimensions_en.html

 

and this is what's said about inflation pressures:

 

"As the CP standard acc. to ETRTO is only valid for 8 PR tyres, the 10 PR size 215/75R16C marked only as a "C" tire requires a front inflation with 5.25 bars and a recommended and permitted rear inflation with 6.0 bars. Despite its C marking this tyre provides safety reserves like a CP tyre."

 

(It would be worth knowing if the side-wall markings on Rupert's 215/70R15C VancoCamper tyres indicate a 6.0 bar maximum pressure recommendation.)

 

Initially, I was going to suggest that Continental's recommendations were a mite low for the front axle and fairly high for the rear axle of Rupert's motorhome, based on his weighbridge-measured data. However, it looks like a 1200kg axle-load is well below the base of this size tyre's load-bearing design-'window' (around 1450kg), so 3.0 bar should be plenty. And it will undoubtedly be a good idea to have plenty of pressure in the motorhome's rear tyres to counter the scooter's leverage effect. No details are provided of Rupert's motorhome's make/model, but, if its wheelbase is shortish and/or there's a goodish length of rear overhang, the low-front/high-rear axle-loadings + scooter may have an adverse effect on available grip at the front wheels when accelerating on slippery surfaces (particularly on hills), and there may be a tendency for the front wheels to 'tramline' on roads that aren't smooth.

 

Brambles' "3 weights" comment is interesting. It's certainly commonplace for car manufacturers to stick labels on their vehicles giving tyre-pressure recommendations that vary according to load. My VW Golf Estate has a label that recommends different pressures according to how many passengers are being carried and the amount of their luggage, and the figures are given in two sets according to whether the car has 'ordinary' profile tyres or the optional lower-profile ones. These recommendations are repeated in the Golf's handbook.

 

But neither of my Transit-based motorhomes carry a 'multiple choice' label (though my present Hobby has a Ford-originated label on its cab door-pillar giving 'singleton' tyre-pressure recommendations that are plainly wrong!) and the Ford handbooks, for each Ford Transit model, provide only one pressure recommendation for respectively the front or rear tyres (usually relating to a pressure suitable for each axle's maximum permitted loading limit). There's no advice suggesting that these pressures may be altered to take account of load variations.

 

I can't say I've studied Fiat Ducato cabs very closely, but I'm sure this is the first time I've heard that they have a multi-weight tyre-pressure label similar to that on my Golf. I haven't seen a recent Ducato handbook either, but I happen to have a chunk of the Fiat workshop manual for the 2002 Ducato and this gave tyre pressure recommendations based on wheel/tyre size, whether or not the vehicle was a 'camping-car', and whether or not 'snow tyres' were fitted. However, no correction formulae were provided to assist with adjusting those pressure recommendations to cope with load variations.

[breakaleg]

Ihad my Lancashire weighed front and rear and emailed the details and tyre sizes to michelin, Ihad to reduce the pressures around 20 pound front ans rear.

However, when Itook my van into auto-sleeper for a service, they increased the pressures by around 10pound front and rear, saying that many vans had been advised to reduce the pressures far too lowin their oppinion as vibration was damaging fixtures and fittings, nothing more specific than that, so you can't win can you?

Pete

[djchapple]

If you wanted serious advice on, lets say meat, you could got to a butchers which had been existence for a large number of years or you could go to a small local shop that sold everything as well as meat. Who do you think could offer you the best advice - surely the butchers!!!

 

Its the same with tyres. You could go to, say, Continental who have been making tyres for yonks or you could go to a motorhome converter who simply sell vans fitted with tyres sourced by someone who happens to work in the company whose motive is to get reasonable tyres at the cheapest price..

 

Without doubt the tyre manufacturer is the one with the best knowledge.

 

Please bear in mind that you ideally need different tyre pressure for the unloaded, partially loaded and fully loaded conditions.

[rupert123]

Some good points here, thanks for that lot Derek, interesting reading. To answer a few points made. I have looked all over and find no tyre pressure stickers on the van. Fiat do give recommended pressures for M/H in their handbook but they seem non specific to the loads just tyre size. My van is short wheelbase, around 19 feet but have found no problems with grip on high pressures. The front axle load did reduce 60kgs with scooter on the back but no problems. However i have today reduced the front tyres by 20 lbs and the steering is a little more positive. My tyres are the cp and I think the max pressure indicated is 5.5 bar but will have to go and check that to be sure. I feel as David does and am going with tyre people. Reading these posts and going back to this subjects past threads it would seem the question of motorhome tyre pressures is not a very exact science so it makes sense to take notice of the real experts and perhaps vary things by a few pounds if you feel the need. Once again thanks for taking the trouble to post replies and it has certainly helped me to make my mind up.

[everhopeful]

My pressures quoted by Peugeot were miles higher than the pressures quoted by Explorer. The van was delivered with pressures right between the two!

 

Rang Explorer and they said the Peugeot figure was only for the bare vehicle and that I should use their figure.

 

I'm amazed that swift can not even quote a figure because surely a converter is creating a new vehicle and they are the ones that should know its characteristics best. :-D

[Derek Uzzell]

Why a motorhome 'converter' will normally just repeat the tyre-pressure data recommended by the manufacturer of the vehicle on which the motorhome is based is pretty much the same as why the base-vehicle manufacturer specifies the inflation-pressures appropriate to the base-vehicle's maximum permitted axle-loadings - neither has a clue what the eventual buyer of the base-vehicle (or converted motorhome) will do with his/her purchase load-wise.

 

I've driven a grossly-overloaded builder's lorry (an exciting experience as I hadn't been aware how much weight was on board until the thing began to sway unnervingly from side to side down a steep hill) and I'm absolutely certain many motorhomes are driven well overloaded. Recommending high tyre-pressures may be tough on motorhome owners who don't overload, but at least it provides some protection against blow-outs for those who do.

[Myfanwy]

I haven’t read all these threads, but I’m just about to reduce rear tyre pressures in our Hobby Van/Transit Mk7 down from 5.5bar to about 4.5bar. I have suffered rear tyre failures on this van and our previous Ducato - in both cases, the outer tread lost its ovality for about 1/3 of the circumference; the Transit just one tyre and the Ducato both tyres. Looks like they were over-inflated in hindsight.

Current tyres are Kleber - Hobson’s choice when we suffered the last failure in deepest France.

Fronts have always worked well on 3.5bar - seems to me that 5+bar on fronts would give a really harsh ride.

If anyone out there thinks that 4.5bar is too low for rears, I’d appreciate some comment.

Keep on Camping!

[colin]

Myfanwy - 2019-04-03 5:12 PM

 

If anyone out there thinks that 4.5bar is too low for rears, I’d appreciate some comment.

Keep on Camping!

 

Without knowing what tyres you have fitted and what load they are subject to when fully loaded nobody will have the foggiest idea as to what pressures would suit.

[Keithl]

Myfanwy,

 

First comment, why revive a thread that is over TEN years old to basically ask a new question?

 

Second, I agree with Colin! If you could post the EXACT make, size and load rating of your current tyres AND, most importantly, the axle weights when fully loaded for touring we may be able to help with your tyre pressures.

 

Keith.

 

PS If you do not have weighbridge figures for your MH then what is the Max Rear Axle loading figure on your Hobby VIN plate?

[Derek Uzzell]

It would also be useful to know which model of Hobby “Van” Peter owns - a “500" model built on a medium-wheelbase Transit platform-cab chassis or an “Exclusive” model built on a long-wheelbase chassis.

 

The original tyre specification for all Transit-based “Van” models will have been 215/75 R16 and probably “C” (commercial vehicle) type, not “CP” (camping-car) type. Kleber does not market CP-marked tyres, so Peter’s current tyres can (fairly) safely be assumed to have a 215/75 R16C specification. As Keith has said, the tyres’ load rating would be worth knowing (eg. 215/75 R16C 113 or 215/75 R16C 116).

 

From 2005 to 2014 I owned a Hobby T600 FC motorhome based on a Ford Transit long-wheelbase platform-cab chassis with 215/75 R16C 113 Continental Vanco-8 tyres.

 

When I acquired the vehicle I decided that I couldn't trust Ford's or Hobby's tyre-pressure recommendations

 

Ford cab-door plate - 44psi (Front axle) and 80psi (Rear axle)

Hobby handbook - 61psi (F) and 70psi ®

Ford handbook - 47psi (F) and 67psi ®

 

After weighing the motorhome to obtain ‘touring’ axle-loadings I chose to use 47ps/3.25bar (Front) and 55psi/3.8bar (Rear) that, in fact, were a bit higher than what Continental had advised me would be ‘safe’ for the weighed axle-loadings.

 

I have difficulty deciding what Peter’s description "the outer tread lost its ovality for about 1/3 of the circumference” would actually look like, but if a tyre is designed to cope with an inflation pressure of 80psi/5.5bar, then running it at that pressure should not result in it becoming damaged (though the centre area of the tyre’s tread might well wear if the pressure is unnecessarily high for the load being placed on the tyre).

 

The recommendation for Fiat Ducato-based motorhomes fitted with CP-marked tyres is to use 5.0bar (15” wheels) or 5.5bar (16” wheels) for the front tyres and 5.5bar for the rear tyres (15” and 16” wheels). Although this may result in a very harsh ride if the motorhome’s axle-loadings are low, the tyres themselves should cope with the high pressures. Obviously, if the tyres fitted are C-marked not CP-marked and not designed to be operated at (say) 5.5bar, using that pressure MIGHT result in tyre damage.

 

It would be useful to know how Peter has arrived at using 3.5bar for his Van’s front tyres and 5.5bar for the rears - whether this is a personal choice or based on advice (eg. a data-plate) on the motorhome itself or in the motorhome’s documentation. Even if the tyres on a Hobby Van were CP-marked i doubt that using a 5.5bar pressure for the rear tyres would be needed and I’d definitely not use that pressure if the tyres are C-marked (eg. the Kleber tyres).

 

A number of forum-members have owned Transit-based Hobby “Van” motorhomes, so may be able to say what tyre pressures they choose to employ. I know that Brian Kirby owned a Van 500 model and, to address lack of front-wheel grip, swapped the original front tyres to ‘4 seasons’ type (and added air-bellows to the back-axle to gain rear ground clearance). I’m pretty sure Brian used a lowish front-tyre pressure (3.0bar?) but I can’t recall what the rear-tyre pressure was that he chose.

[Brock]

As said, on the information provided, it's difficult to give advice. There are a couple of points I make which may help.

 

First is to be aware that if you have an accident caused by incorrect tyre pressure [very low risk], your insurance may be invalid and you may incur penalties [potentially very high consequences]. Whatever tyre pressure you decide is suitable, have some form of paper trail that supports those figures.

 

Have a look at this site for independent information:

 

https://www.tyresafe.org/tyre-safety/motorhome-tyre-safety/

 

[Brian Kirby]

Derek Uzzell - 2019-04-04 9:07 AM................................I know that Brian Kirby owned a Van 500 model and, to address lack of front-wheel grip, swapped the original front tyres to ‘4 seasons’ type (and added air-bellows to the back-axle to gain rear ground clearance). I’m pretty sure Brian used a lowish front-tyre pressure (3.0bar?) but I can’t recall what the rear-tyre pressure was that he chose.

Indeed he did! :-D

 

A 2007 Transit FWD on the platform-cab base. Front axle 1,750kg max, rear axle 2,250kg max.

Actual axle loads in full touring trim: 1.250kg front, 2,000kg rear. Original tyres were Continental Vanco. As Derek says, these were standard "white van" tyres, and not "Camping" tyres, and were later swapped (N.B. front only - not in accordance with recommended practice!) for Continental Vanco FourSeasons of the same size etc. because the original Vancos caused traction problems on the driven axle.

 

The main problem driving the van was that it had a longish rear overhang relative to the wheelbase, and that it had a large "garage" below the transverse rear bed, which meant that when laden as above the weight distribution was 60% rear/40% front, which left the front somewhat light while the rear biased load meant the rear wallowed somewhat on roundabouts etc, and also induced a fair amount of roll on bends.

 

My choice of tyre pressures was 2.9 bar front and 4.4 bar rear, based on Continental's Databook pressures for those axle loads. However, I do not recommend these tyre pressures for Transit based Hobby Van 500s as they related specifically to the load condition of our van, based on weighbridge records, and should not be assumed appropriate to any other similar "Van". I carried with me the weighbridge ticket showing the front and rear axle loads, plus a print off of the relevant page from the Databook with the nearest axle load/ tyre pressure for those tyres highlighted - just in case!

 

The Armstrong Airride rear air springs were an excellent addition, and cured both the roundabout wallowing and the roll on bends without adding harshness to the suspension. They also improved directional stability and reduced sensitivity to crosswinds/slipstreams somewhat.

 

To be clear, they were not added to, and did not, enhance the permissible rear axle load above Ford's standard limits.