What is the correct tyre pressure?

Discussion in 'Motorhome Chat' started by FlyBob, Aug 7, 2013.

  1. FlyBob

    FlyBob Read Only Funster

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    Hi. I'm fairly new to the motorhoming world and I'm trying to clarify (once and for all) what the tyre pressures should be on my wagon. Our local tyre fitter wasn't sure and I didn't really get a precise answer from the dealer.

    So, I'm not sure how much of this is relevant, but hopefully from the various information below someone more experienced will be able give me a sensible answer.

    Vehicle:
    Hymer 684CL Classic on a Ducato 2800 JTD, Year 2007.

    Tyres:
    Kumho Radial 857
    215/75 SR 16C
    113/111 R LT
    (it states) Max Load Single 1150kg at 69 psi

    From the weighbridge (full fuel but unladen):
    Rear axle 1560
    Whole 3080

    From the manufacturer's weight plaque:
    3850
    5500
    1 1850
    2 2120

    Any help would be greatly appreciated. Thanks.
     
  2. SUGGY

    SUGGY Funster Life Member

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    Tyre pressures

    Hi, i have a ducato maxi based motorhome with similar weights ,
    i recently changed my tyres for continentals camper 225,s as they were £30 each cheaper ,than the 215,s
    I run mine at 80psi all round , it handles well ,and the fuel economy is good , hope that helps you .
    Graham
     
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  3. pappajohn

    pappajohn Funster Life Member

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    according to those weights and using the tyre pressure chart download in the resources section on here the pressures should be 42 all round :Eeek:

    I used to run my 3850kg kontiki at 52front and 60/62 rear
     
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  4. FrankK

    FrankK Read Only Funster

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    There is a plate (foil sticker)on my Ducato based van on the passenger door pillar, same as what you would find on a car.
    5 and 5.5 Bar in my case. This was after a call to Trigano who said it was in the manual.

    "But I don't have manual as it is released as a PDF to save a tree" Gave me the pressures over the phone after a bit of a search.
     
  5. FlyBob

    FlyBob Read Only Funster

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    That's my problem. I have the owner manuals both for the Fiat and the Hymer. They list pressures for a huge range of tyres, none of which seem to match what I have.

    Thanks for the advice that's been posted. It's quite a variation!
     
  6. SUGGY

    SUGGY Funster Life Member

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    When i had the new tyres fitted ,

    They only put 65psi in the tyres and it rolled all over the road and i reckon i lost 5mpg ,:Sad: every time you dipped the clutch the van slowed down there was so much drag .....:Eeek:

    My van also has the pillar tyre presure plate it is 5.5bar for 216 , 75 ,16 .I am on 225,75,16 so i am running a bit more psi for the larger tyre ,

    They have done nearly 10k ml now including Morocco and back and they are wearing evenly,:Smile:

    I think ,It is a bit of trial and error till you get the right handling feel for your mh with your tyre combination ,
    Graham
     
  7. hilldweller

    hilldweller Funster Life Member

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    Don't listen to anyone one here. This is safety critical. Your licence and your insurance depends on the right pressures.

    Either use what the maker says or get it in writing from the tyre manufacturer after you have weighed the axles at normal travelling weight.

    I use what it says on the door. If a tyre caused an accident I can point to the door.
     
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  8. buttons

    buttons Funster

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    If you change your tyres to another make model why are you using the door pressures. Surely this will no longer stand up in a court.:Wink:
     
  9. hilldweller

    hilldweller Funster Life Member

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    Good question but since the spec on the tyre wall is the same I'm going with the argument the pressures will be the same.
     
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  10. icantremember

    icantremember Funster

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    As Brian (hilldweller) says the only safe and sure way to get the correct pressures is to take your m/h fully laden, as you would be going on your travels including passengers and pets, to your local public weighbridge and weigh each axle separately and the complete vehicle. You will get a printed ticket with the weights shown.

    Then contact,preferably in writing, the customer services of your particular tyre manufacturer giving details of the weighbridge ticket together with full details of the vehicle weight plate and the size and type of tyre fitted requesting the pressures.

    They will give you the correct pressures and you will be able to show this to any official interested parties such as VOSA, police or insurance.
     
  11. WillH

    WillH Funster

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    We should have a separate forum for tyre pressures!

    I have been playing around with mine with the assistance of a Tyre Fitter in our local ATS. I now run at 55 front and 60 rear, much more comfort, less noise, consumption much the same and handling unchanged.

    Rgds
    Bill
     
  12. magicsurfbus

    magicsurfbus Funster

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    As far as I can see on my Fiat Ducato 2.3JTD LWB van the book and the plate says 5.5 bar (80 psi) all round, which is the tyre manufacturer's maximum. I was pumping them to lower than that, but now they're at full pressure it runs a lot more smoothly and there's less road noise too. No braking issues that I've noticed either. MHs are heavy vehicles in relation to their axle weight even before you put all your clobber, fuel, and water in them, so surely the tyres need to be well-inflated.
     
  13. FlyBob

    FlyBob Read Only Funster

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    It looks as though my issue is a common one!

    So, a bit more clarification please. I've found a good document on the web with a clear chart giving pressures based on the Load Index and tyre size.

    http://www.motorcaravanning.com/tyresafe_mh_tyres_08.pdf

    My question is (and I'm sorry if I seem dumb); it gives different pressures for different Axle Loads weights. Am I right in assuming that this the load per axle i.e. at the weighbridge my rear axle weighed 1560 and the overall weight of 3080, so is the front axle 1520? Hence, referring to the chart I should use the figure that is the next above 1560, so in my case this would be 44psi ? (it's the concept I need, I can re-weigh the fully wagon and adjust accordingly).

    Incidenatlly, I have no tyre presser plaque on the door pillar. That would have been nice and easy! :)

    Thanks for all your help.
     
  14. pappajohn

    pappajohn Funster Life Member

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    so we agree then. :Laughing:

    That is the same chart as in the downloads section here on fun.

    I maintain those are the correct pressures for the given axle weights.
    Obviously when the van is loaded to holiday weight the pressure needs increasing according to the new axle weights.

    To me, 80psi on a 3500/3850kg van is too high.

    My RV ,at 7500kg runs at 80psi all round on 245/75/19.5 tyres
    Front axle is around 3000kg and the rear is around 4500kg on a twin wheel axle.....which accounts for just 80psi in the rears.

    That's double your front axle weight and 3 times the rear axle weight..
     
    Last edited: Aug 8, 2013
  15. Detnor

    Detnor Funster

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    I've always thought that 80psi is too high on the rear axle, for my 3.5t van, but that is what is quoted in the handbook, and having had the vehicle weighed at a trading standards weighbridge, Michelin have quoted 80psi. on the rear So Hymer, the converter and Michelin, the tyre supplier, both agree - not a lot of room to argue.
     
  16. pappajohn

    pappajohn Funster Life Member

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    I did read somewhere the tyre manufacturers are now quoting 80psi across the board to cover their own arses.

    80 psi is the absolute maximum pressure the tyre can safely take and is not weight related
     
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  17. Chockswahay

    Chockswahay Funster

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    I've just had a look at my tyres (VancoCamper 215/70 R15 CP 109)

    The max pressure is stated on the tyre as 4.75 bar/69 PSI

    Fiat suggest inflation pressure of 5.0 bar/73 PSI on the front and 5.5 bar/80 PSI on the rear

    I too am confused.............which setting should I use :Eek!::Eeek:
     
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  18. Ed Excel

    Ed Excel Funster

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    I undestood the max pressure figure printed on tyres was for the US market. As my father used to say 'It's got laundry on't side of that bus but they don't take it in!
     
  19. JeanLuc

    JeanLuc Funster

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    The manual will give pressures for the tyres that are normally fitted by the manufacturer (in the case of Hymer this is mostly Fiat or Mercedes). The pressures enable you to run at the maximum loading allowed for the van (i.e. what you see on the Hymer weight plate). The brand of tyre is less of an issue than the specification. So long as the Khumo tyres are the same spec. as recommended by Hymer, the pressures stated in the manual should be relevant.
    You can get an accurate pressure spec. by weighing the van (fully loaded) and contacting the tyre manufacturer with the axle loadings. In your case, the weights you have obtained are largely irrelevant as the van was not loaded, so of little use in determining tyre pressures. I would go by the Hymer/Fiat recommendation for your tyre spec. You are correct in saying that the whole weight minus the rear axle weight gives the front axle loading (so long as the van is weighed on the level - i.e. the weigh-bridge does not have a steep ramp on and off).
    Final thought - if you run at more than 4.5 bar / 65 psi, the tyres should be fitted with high pressure, metal stemmed valves. The standard rubber valves are only rated by Schrader to 65 psi.
     
    Last edited: Aug 19, 2013
  20. Popeye

    Popeye Funster

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    Last edited: Aug 19, 2013
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