tyre pressure

[Billggski]

Welcome to the forum and the murky world of tyre pressures.

You will get varying opinions, as the thread indicates.

You did the right thing by checking with manufacturer, but experience shows that comfort and carrying capacity don't always match. If it's better with higher pressures, use them, as it's also safer.

You don't mention tyre size and axle weights, this would help others to give their views.

[Derek Uzzell]

Nikko

 

It’s always useful to know the exact model and the age of the motorhome involved when attempting to answer a ‘technical’ question.

 

For an Auto-Trail motorhome based on a Fiat Ducato Maxi chassis the specification of the tyres originally fitted will be either 215/75 R16 (pre-2007 Ducato) or 225/75 R16 (2007-onwards) and it can be expected that the tyres will be ‘camping-car’ type. As you’ve chosen to seek advice from Continental, this suggests that the tyres on your motorhome are Continental “VancoCamper”.

 

I’m wary that Continental will have told you that the inflation pressures SHOULD be 3.5bar/4.0bar for your tyres based on the weighbridge-measured axle weights, but Continental could well have advised that those inflation pressures would be appropriate for the axle weights you provided. Basically, it should be safe for you to operate the motorhome using 3.5bar/4.0bar pressures and with the axle weights as measured. However – as you’ve discovered – safe but softish tyre pressures may translate to roly-poly handling.

 

As Bill says, as you’ve found by experiment that reducing the pressures significantly below the figures stated in the motorhome’s handbook(s) has seriously harmed the vehicle’s handling, reverting to the original higher pressures makes sense.

 

(It’s perhaps worth adding that, although the 3.5bar/4.0bar Continental-provided pressure-figures may be safe minima to use for the measured axle weights, you could experiment with intermediate pressures (eg. 4.5bar/5.0bar) if the 5.5bar/5.5bar pressures produce a really uncomfortable ride.)

 

[flyboyprowler]

Having fitted tyre pressure monitors, it is interesting to see the change in the pressures with a change in weather. We have just driven through France having set the pressures in UK at around 6 degrees C, and driven through France to Spain, where the resting pressure has risen by .02 bar, and the running pressures up by .03 bar. Set at 4.7 bar cold, the running pressure after only a few miles at 4 tonne, was 5.5 bar, with 13 degrees ambient.

So, not a good idea to get the pressures checked after a run, as I believe they should be checked cold, and will also change, maybe not significantly, with a change in temperature.

Coincidently, the local Spanish police today were testing mobile pressure pad weigh bridges, probably with the intention of catching overweight motorhomes, once the season starts again! And we all know that no motorhome ever exceeds its gross weight, does it!!!

 

[Derek Uzzell]

In this 2013 thread

 

http://www.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Tyre-pressures/31351/

 

I said

 

"If I remember correctly, 20°C is considered 'cold' by tyre manufacturers when providing inflation-pressure recommendations. A motorhome's tyres inflated to 60psi in the UK on a 0°C winter's day, are likely to read well over 70psi if the vehicle were then driven to Morocco and the pressures re-read there. It's not something to agonise over - just make sure tyres are not under-inflated and, if you must err, err high.”