tyre pressure

Discussion in 'Motorhome Chat' started by sinbad1, Mar 23, 2009.

  1. sinbad1

    sinbad1 Deleted User

    Trying to find the tyre pressures for an autotrail tracker EKS, looking at previuos posts
    am still non the wiser.
    I am aware that the pressures may vary depending on axle weights;but the sticker on my van shows

    View attachment 2306

    79.5psi:Eeek: seems quite high what do you think?

    Pressures in the Fiat handbook are somewhat confusing

    vin plate axle weights

    View attachment 2308

    just looking for a guidence pressure

    Regards
     
  2. sandyketton

    sandyketton Read Only Funster

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    Hi,

    My Fiat shows 79.5 too, however I wrote to Michelin with axle weights and tyre type and they came back to me with 55 front 65 rear based on that info.
    They look OK and the ride seems softer too.

    I would suggest that you contact your tyre manufacturer for guidance, with your weighed axle weights, and keep a copy of their reply in the motorhome for reference purposes.

    Sandy
     
  3. JayDee

    JayDee Funster

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    You can check using the following link. You just need the actual weight on each axle and the tyre type (the letter 'C' means commercial usually - not 'Camping'; that's a different suffix.

    http://www.tyresafe.org/data/files/motorhome 08.pdf

    Hope this is of use.

    John
     
  4. sinbad1

    sinbad1 Deleted User

    Think that this maybe the option can't be 79.5 is correct unlless thats a max:RollEyes:

    Thanks for the link still a bit confusing ;but if i'm reading it correct the pressures look to be around the 60psi

    215/70R15 CP not sure what the p stands for?
     
  5. Jaws

    Jaws Funster Life Member

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    Looked at that info site ( bloody handy ! Thank you !! :Smile: )
    Went and took pen and paper outside..
    Crawled around on hands and knees writing all the tyre details down and getting crap all over me !!

    Opened the door to look at the weight plate and lo ! Bloody tyre pressures clearly showing on the sticker inside the door jam ! DOH !!!!!

    But now I have a new problem.. I cannot find the weight plates !
     
  6. sinbad1

    sinbad1 Deleted User

    My vin plate is on the crossmember just under the bonnet
     
  7. sinbad1

    sinbad1 Deleted User

    Having googled around i am no closer to finding some kind of guide to pressures.

    One school of thought is that the stickers represent maximum load pressure and should be used at all times, others say that these pressures are unrealistic.

    Others say that the tyre companies (knowing your axle weights) are usually much lower and that they know more about tyres than the manufacturers.

    I am more inclined to believe the tyre manufacturer than Fiat /Autotrail( who will just refer you back to Fiat)

    Over inflated or under inflated cause problems, just would like to be somewhere in the middle.

    I have sent an email to Michelin with front and rear axle weights see what comes back

    regards
     
  8. JeanLuc

    JeanLuc Funster

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    Sinbad1 Quote "215/70R15 CP not sure what the p stands for?"

    The P in CP indicates that you have CamperVan tyres that have strengthened sidewalls to withstand the strains of long stationary periods.

    According to the Fiat inflation diagram, the pressure of 79.5 psi refers to maximum loading. However, according to your VIN plate, the MAM of your van is 3,000 kg and the max loading for the rear axle is 1,650 kg.

    So, from the tyre facts table, the appropriate pressure for the rear tyres would be around 60-62 psi when fully loaded. (It is the fifth one down in the final table on the last page of the guide.)

    Hope this is useful, but I'm sure you will get a professional view from Michelin.

    Philip
     
  9. sinbad1

    sinbad1 Deleted User

    Thanks another look at the guide does indicate 60/62 ;however, quick response from Michelin re: tyre pressures kinda puts things more in perspective and hopefully helps other members.


    Dear Mr xxxxx

    Thank you for your recent e-mail.

    We suggest that individual axle weights from weigh scale readings are used, in order to calculate pressure recommendations for each quoted load condition. These would be preferred, due to readings being taken in the actual vehicle 'running' condition - that is to say, with all water/fuel/baggage & passengers etc. onboard - and may result in better comfort if the vehicle is running way below maximum capacity.

    The results of roadside surveys indicate that some motor homes have been found to be over laden, especially the rear axle, with potential for subsequent tyre related problems.

    The overall tyre industry, therefore, tries to build-in a safety factor by fitting strong tyres, inflated to high pressure, in order to remove the potential for consequences of overloading &/or under-inflating the tyres.

    The drawback of this safety factor, at the corresponding high pressure, may be an extremely hard ride. The contents of the motor home may rattle, but the tyres will cope nicely.

    One 'overall' weight is of no use in calculating tyre inflation pressure levels, since the vehicle may appear to be within the maximum permitted, but in reality may have the rear axle severely over laden & the front axle very lightly laden.

    As a guideline from the axle weights that you have supplied on tyre size 215/70 R15 C (if the XC Camping tyre) the pressures for those weights should be as follows:-

    Front axle load of 1600kg the pressure should be – 55 psi (pounds per square inch)
    Rear axle load of 1650kg the pressure should be – 50 psi (pounds per square inch)

    The Front axle pressure in this case may be higher than the Rear even though the axle load is lower. Therefore the slight increase in pressure which has been added to the front axle is due to the braking forces and shift in weight that’s being exerted onto it.

    We have allocated your message the reference number indicated above. If you need to contact us again regarding your message, we would be grateful if you could include the reference number.

    Once again thank you for your interest in Michelin.

    Yours sincerely
    Michelin Tyre Public Limited Company

    Regards

     
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