Symbol/Dorset tyre pressure

Members might be interested in some advice I have just obtained from Bridgestone on this thorny topic. When I bought the a 61 plate Dorset earlier this year I was recommended to use 60 psi on all tyres but I have got fed up with the harsh ride, particularly at the rear. It runs on Bridgestone Duravis R630 225/70/R15C tyres and has axel weights in Running Order 1497 F and 1387 R, and MTPLM (for the Symbol but near enough for the Dorset) 1750 F and 1900 R. The technical department of Bridgestone said their table gave psi pressures RO 44 F and 42 R, MTPLM 48 F and 54 R. The RO pressures are somewhat higher than the Tyresafe motorhome leaflet http://www.tyresafe.org/images/tyre-safety-guide/motorhome-leaflet.pdf but the MTPLM pressure are the same.

Could I have that again in English please   

Frank

So, tyre pressure for my Symbol should be ...   

Definitions for the Symbol (2.2 litre, 2011 model) according to my handbook : 

Mass in Running Order (MRO) includes the standard converted vehicle (excluding optional extras) with coolants (oil and water) 90% fuel, Spare wheel, crockery, washer fluid, tools, driver (75kg representing the EC standard person), fire extinguisher, giving a total of 2805kg. Bridgestone recommended pressures 44 front, 42 rear for the axle weights as defined by Autosleepers for this state.

MTPLM (maximum technically possible laden mass) is the maximum permitted weight of the vehicle and all of its contents both inside and out. The difference between this and the MRO is the User payload. The axle weights will usually exceed the vehicle MTPLM (but apparently not the MRO), so in the case of the Symbol the MTPLM is 3300kg whereas the sum of the MTPLM axle weights defined by Autosleepers 3650kg (please don't ask me why!). The vehicle value must not be exceeded. When fully loaded the recommended pressures are 48 front, 54 rear.

The user payload includes the Essential Habitation Equipment defined as LPG cylinders 90% full, freshwater 90% full, water heater full, waste water empty, toilet flush tank full, toilet holding tank empty. In the case of the Symbol the User Payload is 495kg and the Essential Habitation Equipment is 118kg leaving 377kg for optional extras, extra people and the rest of the stuff you load up. You could of course run with an empty fresh water tank and more kit.

The Dorset has a slightly heavier MRO at 2884kg, therefore slightly less payload. The MRO axle weights quoted below are for the Dorset but no MTPLM weight is given hence my reference to the Symbol weights, but I regard the impact on tyre pressures to be negligible.

I hope this clears it up for Frank and Nain. 

NB: I am not giving any recommendations, just relaying information from Bridgestone and Autosleepers.

Roger

Thank you