Have I commited a sin?

[maingate]

Following this thread with interest as I'm picking up a new to me MH on Friday which has CP tyres and the bottom of the Tyresafe page states:

"CP-type tyre construction enables the use of higher inflation pressures to provide resistance to the difficult conditions of use encountered on motorhomes. Therefore, when CP-type tyres are fitted on the rear axle in a single formation set the inflation pressures to 5.5 bar (80 psi) for all loads"

View attachment 65637

That is referring to a one axle configuration (the way I read it) and is general advice nowadays. For a single rear axle, whatever axle weights you input, on whatever size tyre you choose, you will always get 80 psi in the rear. I don't know why that is but it is. For a twin rear axle it will give accurate figures. A few years ago you could ring the tyre maker, give them the axle weights and they would tell you the correct pressures. Very few still do that.

The 'difficult conditions' you refer to probably mean that motorhome tyres consistently run at or towards the maximum load rating due to their application. CP tyres are alleged to have stronger sidewalls to compensate for this. Because my rear axles are well within the max loading, I just fitted 4 new Michelin Agilis Commercial (ie not Camping) tyres. I still fitted new high pressure tyre valves though.

 

[wildebus]

Are the weights you gave from the handbook, or are they actual weighed weights?

VIN plate for Axles and GVW
Weighbridge based weight for actual normal running weight I quoted.