Michelin Tyre Pressures

I just wonder if Dora (of Michelin) Is aware that "motor home" weight can vary from 2500 kg to 4850 kg maybe more ?

i cannot see that an around figure of 80psi would suit all ?

Rgds

You can use the TyreSafe Motorhome Tyre Inflation Pressure Advice -   https://www.tyresafe.org/check-your-pressures/motorhomes/  - to find what pressures they advise for your vehicles tyres..

I'm never sure why Motorhomes are run at the tyres maximum, usually 80psi, which gives a harsh ride and on many roads could dislodge your false teeth and certainly rattles the chassis with the hard tyres and no 'give'.

You need to know the front and rear axle weights (around £5 to use a local weighbridge) and the size and type of tyres you have before adjusting your tyre pressures.

Any guesswork will mean your tyres probably won't last as long and may wear unevenly.

With the tyres I have fitted - Continental (225/70 R 15C 112/110) - on my Pilote on a Ducato base and with front axle 1560kg and rear axle 1940kg, confirmed fully laden by a weighbridge, the recommended pressures are 47psi front and 61psi rear.

Michelin have always recommended the maximum pressure in their tyres, and many of you will continue to take their advice, but those who have actually weighed their vehicles and reduced pressures will know what a big difference to ride and comfort is achieved.

We also have a Carthago and the same tyres.  I have found that the best way of establishing the right pressures is to put the van into fighting trim and get it weighed.  You need to have 90% or above fuel, all the passengers you would normally carry, yourself, and the water tank filled to the maximum level you would normally travel with.  We travel with full water (170 Ltrs).  Make sure you have all the clothing and equipment on board that you would normally carry.  At your local weighbridge get two or three checks, the full weight, and front and rear axle, or just two and do a calculation.  Phone or email Michelin product support with the info and ask for recommended tyre pressures.  They are very helpful. 

Alternatively, also in full fighting trim, use the relatively low pressures you have quoted and drive for about 20 miles, park and place your hand against each tyre.  At ambient OAT they should be just comfortably warm, not cold and definitely not hot.  Heat is the biggest killer of tyres.  If hot add about 10 psi and repeat the test in about 10 miles.  Others may disagree but this is a well proven means of ensuring you are not running the tyres too soft.  

This " pigheaded Dutch selfdeclared tyrepressure-specialist "  came to this topic, and the list given is strangely composed, cant figure out what they done the 225/75R16 Michelin CP only gives 116 loadindex is 1250kg maxload a tire, but 2550kg axleweight given at 5,25 bar is 50 kg more then 2x 1250kg. 

But I made my own calculator, so only use these lists to determine the maxload and reference-pressure ( pressure behind AT, but Continental  gives often also max inflation pressure on sidewall, is also cold pressure) 

Then I add first 10% to the determined axleload( spreadsheet does that , so dont do it double), and then calc it with safer formula then the original of ETRTO.

Then outcome will be higher then  those read from the lists. 

Will try to give link to motothome-map on my public map on onedrive that belongs to my hotmail.com adres with username jadatis( combine yourselfes if you want to mail me, spamm robots cant this way) 

Did not work on my mobile, so mail me , or give data here.

To be continued later.

CY, you may have Michelin to my Continentals but our loadings are roughly the same yet our pressures are vastly different...

see below a note from tech support at Continental. they had previously given me pressures for my loadings but recently there has been much chat about Michelin stating 80 psi for all rear 'campers' even when they can vary tremendously from a lightly loaded PVC to a rear biased, garage loaded coachbuilt...

i put this recent info to Alex Wilson of Continental who reiterated my pressures and also suggested (as many thought) that this 'change of heart' was to cover off the heavily loaded commercial vans that never get weight yet whose weight can fluctuate wildly from fully loaded, early morning, to empty, return to depot.

MH weights arent like this...they are pretty consistent and just need to be know once and then suitable pressures applied.

here is the email conversation....

continental Vanco CP tyre pressure

FAO Alex Wilson...

Hi Alex, a couple of years ago you sent me the following info regarding my tyre pressures, which i am very happy with as they give me a good ride, good grip.
However, there has been much discussion on motorhome forums lately regarding ERTRO and their involvement with tyre companies such as Michelin and yourselves, where advice for rear CP pressures seems to have changed from 'axle loading' based to a blanket figure of 80 psi.
but different MH can vary....one person i know drives a PVC and has a very light rear axle of only 1360kg yet was apparently told that ALL CP shod rear axles should be at 80 psi. this seems incredibly hard compared to the 54 psi i run at for my (considerably heavier) 1820kg.
Has this rear tyre advice changed at Continental?...i cant see how two vastly different vans with (say) rear axle weights of 1360kg as above, upto 2000kg (the max for a std 3.5t chassis) can both be 'safe/correct' with the same blanket 80 psi recommendation.

thanks again for your help.
rgds

YOUR PREVIOUS MAIL IS BELOW.

Rear axle 1820kg (max 2000)
Front axle 1600kg (max 1850)
Gross 3420 kg (max 3500)

Good afternoon,

Thank you for sending all the relevant information it is most appreciated.

It is extremely likely that the relevant information supplied with the chassis is documented for use as a commercial vehicle, therefore proposed before the conversion to a motor home. For this reason, Continental tyres would always recommend having the motor home weighed on a weigh bridge at your heaviest travelling weight, including liquids to achieve specific axle weights. In some cases the coach builder will also put their recommended pressures on the vehicle plate. However, the majority put this to the maximum inflation pressure of the tyre to cover all loads being applied and not specific loads which often, are not near the plated weight you actually travel at.

The volume and pressure of the inflation medium is what carries the load and if it is not sufficient then the tyre can suffer damage, hence why it is extremely important for the correct loads to be obtained, in order to inflate the tyre correctly.

Experience shows that due to the weight distribution of vehicles in the leisure industry such as motor homes the likelihood of overloading or uneven weight distribution tends to put a greater load on the rear axle rather than on the front axles, where the weight tends to remain more consistent. It is true that when braking occurs the weight transference is to the front, but this only tends to be for short periods, whereas overloading on the rear axle can be present over long periods, when the tyres are rotating at high speed.
This is the main reason that with CP Camper type tyres the inflation pressures at the rear is deliberately set higher. Although this also has a bearing on the contact area when negotiating grassy parking areas and also to the sidewall deflection, which influences the body roll.

Based on the following:

ContiVanco Camper 225/75 R16 (CP*) 116 R tyres.

Front Axle: 1600 Kg - 3.0 bar/ 43.5 psi (max weight for pressure given = 1730 kg)

Rear Axle: 1820 Kg - 3.75 bar/ 54.3 psi (max weight for pressure given = 1840 kg)

(*CP- Camper) (Single fitment (S) = two wheels per axle, Twinned fitment (T) = four (or more) wheels per axle)

I have included the chart for these specific tyres to help with pressure vs. load if you need to change the weight

I hope this helps and any further enquiries (no matter how small) please do not hesitate to ask, we are always happy to help!

Best Regards

Alex Wilson
Product Support Engineer

i dont have pressure sensors....having read such issues on another forum where they cant be adjusted easily/cheaply, if i wanted some id go for an after market set somewhere, thatbare truly user adjustable.

ive found the Contnentals great, we had them on the previous larger Carthago and i used their recommended pressures then, too.

80 psi rear must be teeth rattlingly hard.....

BTW.....re the earlier mention of the 'max inflation pressure on sidewall', this was Continentals reply...

"The 69 psi written on the side of the tyre is for the Northern American market only and the inflation pressure of the tyre can exceed this value within its safety operating range."