Tyre wall max psi vs cab plate psi

[OneAntOfMany]

We recently bought our first MH and the tyres wall states max PSI 65, whilst the cab recommends for max load 80PSI. The weight in running order is 2850kg, max 3400kg. I have not been to a weighbridge fully laden to get accurate weights, and assuming I am close to the max, I assume no matter what the cab says, the tyres cant go above 65.

I would assume the wrong tyres have been fitted by previous owner, they have plenty of miles left on them and the ride at 60PSI is pretty comfortable although I think quite wobbly (but I dont know if this is the motorhome experience in general)

Is 60PSI fine, or would it be best to bite the bullet and get new tyres.

Any advice most welcome!

 

[Ivory55]

At 80 psi you will get a hard noisy ride. Have never had ours that hard

 

[HandyAndy]

What ply / load rating are the tyres on it.

 

[Lenny HB]

The tyre wall rating is only for the US market.
The 80PSI is what Michelin always state for their camping tyres, only required if running at the max axle weights. I would try the rears at 70 psi & the fronts at 60 PSI as at 3400 kg you are not very heavy.

 

[Mr Chrysalis]

This has been discussed at length. I think this is the thread

https://www.motorhomefun.co.uk/forum/threads/tyre-pressure-quandary.162906/#post-2550821

You’ll also find a link in this thread to an online Motorhome Tyre Pressure calculator ( put in tyre size and axle weight to calculate pressure)

I think you will find all of your answers here. If not pm me and I will find some other stuff for you

As others have said the max pressure in the tyre is for US market only and depending in your van 60psi will feel spongy and wobbly ( please excuse technical terms

By the way welcome to the forum and motorhoming in general

I guess once you know all about tyres, you will start asking about payload . Most of us do!

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[OneAntOfMany]

What ply / load rating are the tyres on it.

Hi HandyAndy, one tyre states 2 Polyester+2steel+1nylon , sidewall 2 polyester.
They seem rated at 975kg to 1030kg on sidewall
109/107 s
215/70R15C

 

[OneAntOfMany]

This has been discussed at length. I think this is the thread

https://www.motorhomefun.co.uk/forum/threads/tyre-pressure-quandary.162906/#post-2550821

You’ll also find a link in this thread to an online Motorhome Tyre Pressure calculator ( put in tyre size and axle weight to calculate pressure)

I think you will find all of your answers here. If not pm me and I will find some other stuff for you

As others have said the max pressure in the tyre is for US market only and depending in your van 60psi will feel spongy and wobbly ( please excuse technical terms

By the way welcome to the forum and motorhoming in general

I guess once you know all about tyres, you will start asking about payload . Most of us do!

Thank you and thanks for the calculator link (https://www.tyresafe.org/check-your-pressures/motorhomes/ ). I have tried searching the threads. I still remain quite worried why a PSI rating would only apply to the US and would not be accurate for all countries.

 

[OneAntOfMany]

On the question of Max PSI on the sidewall, most UK sites and global manufacturers I have visited suggest that max PSI is the max. Nothing I have come across says this can be disregarded.

The only thing I can really find, in some US legislation and consultation was this:-

While General Motors and the
International Tire and Rubber
Association (ITRA) supported retaining
the maximum inflation pressure label
because it provides a ‘‘point of
reference’’ inflation pressure, most
commenters argued that the maximum
inflation pressure should be removed
from the sidewall of tires because
consumers confuse it with the
recommended inflation pressure found
on vehicles and because inflating a tire
to maximum inflation pressure may
cause uneven wear and other failures.
Further, one tire manufacturer
association commenter suggested that
consumers will look at the certification
label or vehicle placard for pressure
information if pressure information is
not contained on the tire. One tire
manufacturer association commenter
asserted that removing the maximum
inflation pressure would improve safety
if the correct inflation pressure is clearly
and conveniently communicated to
consumers and if consumers act on this
information. One vehicle manufacturer
commenter remarked that there should
be a marking requirement for tires that
would direct operators to use the
information contained on the vehicle
tire placard.
i. Dissemination of Tire Safety
Information
• Commenters neither supported nor
opposed a tire inflation warning label.
Most, however, suggested that consumer
awareness of correct tire pressure, size,
and the relationship of load and tire
pressure is appropriately addressed
through consumer education.
• Commenters, as a group, said that
messages about tire inflation, vehicle
loads and handling, and other safety
effects need to be communicated
repeatedly and through the use of
different media such as agency
brochures, manufacturer labels, owner’s
manual entries, and point-of-sale
literature provided by tire
manufacturers. Also, a hierarchical
system of providing safety information
to consumers in varying forms and
details based on the essential nature of
the performance and safety information
should be employed. The placard
should be mounted consistently in the
same place on all vehicles and be both
easily found and readable.

I am trying to delve through UK and EU legislation.

 

[Reallyretired]

I would think 80psi would give a very hard ride. Mine are as recommended by Continental 69psi rear and just 52front. Mercedes rear wheel drive. Obviously depends on tyres and axle weight.

 

[Minxy]

I had a similar query regarding the maximum tyre pressure stated on the tyre which was different (lower) than the recommended pressure given by Fiat ... as above, it was to do with USA requirements.

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[pete4x4]

Hi HandyAndy, one tyre states 2 Polyester+2steel+1nylon , sidewall 2 polyester.
They seem rated at 975kg to 1030kg on sidewall
109/107 s
215/70R15C

Your running C rated tyres which are Van tyres and are perfectly acceptable, The 80psi on the motorhome is for CP rated tyres which have thicker sidewalls.
Do not exceed the max pressure on the sidewall and that pressure is for the max load ie 975kg
I think you said 60 psi on the rear, not sure what your axle load is but C rated tyres can normally go to 65psi.

If you want to know what CP rated mean Michelin and Continental have it on the website, they are motorhome tyres for people who dont use the motorhome very much and its stood for long periods and are run overweight.

 

[OneAntOfMany]

Thank you all. I think the safest thing is not to exceed max psi on tire wall. Whether this is a US requirement or not I think is beside the point. If that is the max PSI, and EU manufacturer sites and tire fitters seem to agree as per their webs, going above may not be safe.

If anything,if I want to go higher on rear, a couple of higher rated tires are needed.

 

[Jim]

The Handbook will be referring to the factory fitted Michelin's. Your tyres will have their own pressure/weight pressure guidelines and you should refer to the maker

 

[Mr Colpot]

We are on 225/75 R16 CP 116 Q with 1820kgs (max 2100kg) on front and 2120kgs (max 2400kg on rear.
52psi for the fronts seem low to me (I am ashamed to say I haven't checked the pressures yet but will do as soon as I am dressed!)
The max PSI mark on the Tyre is 80psi and the checker says "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."

 

[Minxy]

(I am ashamed to say I haven't checked the pressures yet but will do as soon as I am dressed!)

Not dressed yet ... do you know what time it is?












I suppose I better get out of bed soon ... ?

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[tacr2man]

Generally speaking the bigger the tyre (section) the lower the pressure you can run for the same load . , and subsequently the better (smoother) the ride .