Ducato tyre pressures

[IVAN]

Don't ask me why but since I've owned the van I've always had the tyre pressures round about 45psi !!!! Like I said, don't ask. I eventually looked at the pressures today in the handbook and it says 5 bar back and front !!! I know after 8 years I should really know, but that's a lot of air. That equates to about 74psi. I have had no unusual tyre wear. I just replaced the front tyres last year and the speedo reading is nearly 52k so that is good(they had been on since new). Does anybody else think the pressures quoted in the handbook seem high

[Cliffy]

Tyre pressures are determined by a few variables. The safest method to find out what the pressures should be for your van is to contact the tyre manufacturer, tell them the actual weight on each axle when fully loaded, verified on a weigh bridge. They should give you their recommended pressures.

 

I keep mine at 5.5 bar in the rear (1650 kgs) and 5 bar in the front (1330 kgs), very near to the maximum for the tyre as shown on the tyre wall. They still look a little under inflated to me so 45psi would look very under inflated.

 

I am sure there are a number of people on this forum that could advise you better if you give the make and model of your van, the make and size of tyre and the axle weights.

 

 

 

 

[Derek Uzzell]

IVAN

 

I believe you own a 2002 McLouis LAGAN 410 motorhome, and it's probable this will have been originally fitted with Michelin "XC Camping" tyres in 215/70 R15C size.

 

Such tyres were factory-fitted to Ducato-based motorhomes that had Fiat's "Camping-Car Package" that included heavier-duty suspension and tyres, and Fiat's advice (based, presumably, on Michelin's recommendations) was (for the 215/70 R15C size) invariably a one-size-fits-all recommendation of 5.0bar (72.5psi) for front and rear axles. This recommendation was usually transferred directly into the handbooks provided by motorhome manufacturers.

 

You've been a forum member since 2008, so I'd be surprised if you hadn't noticed the discussions/arguments about motorhome tyres that regularly come up.

 

As Cliffy says, if you want advice on whether your 45psi pressures are 'correct', you'll need to provide the details he's mentioned.

 

If you'd like a finger-in-the-wind reply, I think 45psi (front and rear) is likely to be on the low side for the rear axle, but 72.5psi all round would almost certainly produce a harsh ride.

 

I note that you replaced your motorhome's front tyres in 2012, but (as I understand it) the remaining tyres are the originals. Assuming that your motorhome is 2002-vintage, that would mean you've got some 10-year-old tyres on it. Tyre manufacturers would usually consider this age a maximum and would recommend replacement at (or before) 10 years irrespective of tyre condition.

 

(Let's not go into the new front tyres/old rear tyres thing...!!!)

 

 

[IVAN]

Thank you. you're quite right it is a Mclouis 2002 Lagan 410. With 45psi in, it didn't look underinflated even when full laden. This is one reason why I never thought anything could have been amiss. It has always sat well and never looked anything other. The original tyres are now on the rear and show no sign of any type of wear....Regards Ivan

[gocro]

I went to the trouble of getting our van weighed twice, the first time they had just combined the axle weights, so I went back again before our last trip. Using the data forms from the website I used 45psi front 50psi rear ,they did look rather under inflated.I checked that they weren't gettig too hot after 150 miles and they were just warm to the touch as I expected. I thought that I may have suffered from worse MPG but the trip computer remained steadily at 30.7mpg. As I couldn't see or feel any difference I reverted to my previous pressures of 60/65, which is still less than the recommended pressures on the door label. Having an Alko chassis the van rode the similarly at both pressures, although this is very subjective.

[snowie]

Hello Ivan;

If you've bought a couple of new tyres, and you have "in service" axle loads, maybe from a visit to a weighbridge, then you could email the tyre manufacturer,.

I recently fitted a couple of new tyres to the front axle; emailed the manufacturer, and I got a very helpful reply.

The recommended tyre pressures have made our ride appreciably better.

It's a tyre and motorhome specific enquiry; so don't expect an answer on this forum,

good luck, and hope you get a comfy and safe solution,

regards

alan b

[Derek Uzzell]

IVAN - 2013-07-25 1:06 PM

 

Thank you. you're quite right it is a Mclouis 2002 Lagan 410. With 45psi in, it didn't look underinflated even when full laden. This is one reason why I never thought anything could have been amiss. It has always sat well and never looked anything other. The original tyres are now on the rear and show no sign of any type of wear....Regards Ivan

 

Assessing whether a motorhome's tyres are under- or over-inflated by visual or 'hands-on' means is poor practice.

 

There's no doubt that, if a tyre is seriously under-inflated for the load that's being placed on it, it will heat up to the point that gocro's touch-test technique should reveal that something is amiss. It's a useful indicator, but crude.

 

Checking how 'squashed' a tyre looks is also a useful indicator of serious under-inflation but, once again, it's a crude method of trying to decide whether the pressures you are choosing to use are correct. Similarly with tyre wear - serious under-inflation will cause serious tyre-wear, but mild under- (or over-) inflation won't.

 

As I said earlier, received wisdom is that 10 years should be considered the life-span of a tyre, irrespective of its condition or even whether it's actually been used (eg. where a spare-wheel has never been deployed). Whether you follow this advice is up to you.

 

Received wisdom is also that, when a pair of new tyres is fitted, those tyres should be fitted to the rear axle. The logic is that new tyres will provide greater grip than old/worn ones and that oversteer (where the rear of the vehicle breaks away) is less easy for a driver to control than understeer (where adhesion is lost at the front wheels). With a 52K mileage, your original tyres MUST have lost some tread depth even though their wear pattern may not be unusual.

 

If your motorhome now has a mixture of 'white van' and 'camping-car' tyres, the 5.0bar pressures quoted in your handbook almost certainly wouldn't be appropriate for the 'white van' tyres.

 

Snowie suggests that "It's a tyre and motorhome specific enquiry; so don't expect an answer on this forum". What can be said is that, without exact details of the makes, 'models' and size(s) of the tyres currently fitted to your McLouis's front and rear axles, and details of the vehicle's maximum permitted overall weight and maximum permitted axle-loadings (as shown on the motorhome's data-plate), there's little point guessing at what pressures might be appropriate.

 

It might even be the case that, if you weighed your motorhome in fully-laden state and obtained its axle-loadings in that state, the 45psi pressures you are using turn out to be a perfect match. But the only way to know that would be to weigh the motorhome.

[Muswell]

Leaving aside all issues of comfort and wear I would have thought that if you were to have an accident the police and the insurance company would have a view if your tyre pressures were outside a reasonable margin around that recommended by the vehicle and tyre manufacturers.

[IVAN]

Thanks for all the replies, it is food for thought. The tyres are all camping car tyres and are all exactly the same....I would never fit normal van tyres. I think I will email the manufacturers as I have the axle weights.

Once again thanks everybody

[Derek Uzzell]

If your 'camping-car' tyres are made by Michelin and you e-mail Michelin for inflation-pressure advice, I predict they will recommend 80psi (5.5bar) for the rear tyres. If the tyres are made by another company, you should have more success with your inquiry.

 

If by "axle weights" you mean the maximum permitted axle-loadings as specified on your motorhome's data-plate, it should be straightforward enough to obtain representative inflation-pressure-to-load figures as these are available on-line. But those pressures won't necessarily be the optimum if you are interested in ride comfort and/or safety. The only way to obtain such pressures would be to weigh the vehicle fully laden and identify its 'real world' axle-loadings.