Tyre pressure

Discussion in 'Motorhome Chat' started by Bart, Aug 9, 2016.

  1. Bart

    Bart Funster

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    Ok so now out on the road on our 1st outing in our MH and it's clear our tyre pressure are wrong as the rear waste water pipe made contact with the ground when gping 40mph on a road with slight bumps.
    On the front of the mh are the original Michelin XC camping tyres 215/70 r15 and then on Friday kwik fit put two Michelin agillis 215/70 r15 cp on the rear . I asked him what pressure he put in them and he said 50 psi .
    Well after the rear grounded out I took it to the garage to compare the rear tyre pressures with the front.
    The front was 70psi and the rear 50 psi . I inflated the rear to 65 . So below is my axel weights from the weighbridge this morning . Based on that and the make /size of my tyres can someone please tell me what pressures I should have in the tyres.
     
  2. hilldweller

    hilldweller Funster Life Member

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    Ask Michelin is the usual way.

    But send them the weights.
     
  3. kevan

    kevan Funster Life Member

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    Michelin say 80psi i have 80psi rear 75psi in front they go up when warm by approx 10psi back and front been using like this since new nearly three years ago, these are straight from MITCHELIN
    hope this helps(y)
     
  4. TerryL

    TerryL Funster

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    Okay, your tyre pressures are off and if you take the advice offered above that'll sort it out. For the record I run mine at 56 psi front and 65 psi rear.

    But tyre pressures shouldn't be the reason the waste pipe hits the ground and from what you say there's clearly something else wrong. Best case, the fixings have broken allowing the pipe to droop, easily rectified. Worst case, vehicle suspension is compressed too much, possibly broken springs - how does the van ride, most have a slightly nose down attitude. Sorry to be alarmist.

    Our waste pipe is easily 6 inches above the ground, otherwise I couldn't empty it and your Bessie is the equivalent model to our Swift Bolero.
     
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  5. sdc77

    sdc77 Funster

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    Doesn't it depend on axle weight though? Can't see that the op posted his axle weights yet.
     
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  6. emmitdb

    emmitdb Funster

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    What were your axle weights. I don't see them?
     
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  7. kevan

    kevan Funster Life Member

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    Michelin always give same answer, I presume that they assume we all are over weight at some point so so 80psi;)
     
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  8. kevan

    kevan Funster Life Member

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    sounds like it's not the tyre's but the suspension, would fit air suspension
     
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  9. SUGGY

    SUGGY Funster Life Member

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    We ran 70 psi all round on our Fiat but noticed it went up to around 90 psi when the tyres were hot , we put nitrogen in them and the pressure stayed more constant and the tyre walls were a lot cooler .

    when we had new tyres fitted they only put 45 psi in the tyres ... it rolled and bounced all over the road and only did just over 20 mpg ,
     
  10. emmitdb

    emmitdb Funster

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    I for one, cannot accept that the Michelin "80psi" is correct. How can it be?
    We have a variation in types of vehicle ranging from Van conversions weighing in at less than 3000kgs to A Class Gin Palaces weighing in at over 4.5 tonnes with different profiles in the tyres and different load index's and what do Michelin say, "80psi"

    I would rather go for the "Axle Weight" system where, the heavier the load, the greater the pressure (to a manufacturers maximum of course)

    That's why I run on 54psi front and 65psi rear.
     
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  11. sdc77

    sdc77 Funster

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    Although we don't use Michelin. . Our continentals are:
    Front 1720 45psi
    Rear 2220 62psi

    Doesn't seem to make sense to be 80 all round... but then again the ops problem may well be suspension anyway.. or overloaded
     
  12. kevan

    kevan Funster Life Member

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    Just the messenger(n)
    If that's what the Tyre manufacturer says then its good enough for me. but you seem to be better informed than I or Michelin, the man asked for advice, and it was given.;)
     
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  13. Clarky

    Clarky Funster

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    Michelin always give the rears as 80psi as they are aware that motorhomes are often loaded to the max or over.
    It's known as 'watching your back'.
    However, they will give the correct pressures for the front if you tell them the axle loading.

    Richard.
     
  14. My Dog Likes Fishing

    My Dog Likes Fishing Funster Life Member

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    I have recently installed Tyrepal to monitor the tyre pressures mainly for the toad. As somebody has said i was amazed to see my tyre pressures go up by nearly 10psi after an hours travelling. My manual that came with the van said my tyre pressures should be 72 in the front and 80 in the rear. I lowered the pressure in the front as the ride was really hard. I dropped the pressure down to 65 and the ride was a lot smoother. However the tyre pressures are over inflated when they are hot. Should i put my tyres at the correct pressures when they are hot or cold?
     
  15. sdc77

    sdc77 Funster

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    Cold
     
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  16. emmitdb

    emmitdb Funster

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    My novice mate has just bought a 'van with Conti's all round.

    He reported to me when he was away that the 'van was skitting all over the place. The dealer said 80psi:eek::eek::eek::eek: and on asking at ATS, they said 70 psi.:eek::eek::eek::eek:

    When I saw him I pointed out to him that on the tyre itself it stated max inflation 69psi.
    Using this site I was able to tell him what the tyre manufacturer stated, BASED ON AXLE WEIGHTS!!!
     
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  17. emmitdb

    emmitdb Funster

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    But Michelin themselves say that their Max pressure is 80psi (unless I'm wrong).
    How does that stand with the difference in load index, type of vehicle, weight of vehicle.

    Look in the appropriate place of any modern car and it will give different tyre pressures dependent on the load to be carried. What is so different about a Motorhome in the same circs.
     
    Last edited: Aug 9, 2016
  18. Speve

    Speve Funster

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    I run our Exsis 2400 rear 2100 front at 5 bar and 4.5 bar that seems to give a comfortable ride using Micheline Agilis Camper we found the 80psi is a very hard ride.
    Of course it depends a lot on loading
     
  19. mikebeaches

    mikebeaches Funster

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    I sent the following note to Michelin last month:

    "I have a new camper which is a Fiat Ducato panel van conversion. It is fitted with Michelin 215/70 R15 CP 109Q tyres. The maximun gross vehicle weight is 3,500kg.

    I have checked the individual axle loads at a local weighbridge, with the vehicle fully loaded with all passengers, fuel, water, gas, food and personal belongings etc

    The front axle weighs: 1,660kg; and the rear axle: 1,620kg.

    Please could you advise the minimum tyre pressure (cold) front and back that the vehicle can be operated at?

    The ride, as supplied, is harsh and unpleasant.

    My previous van was fitted with Continental camping tyres, which could run at much lower pressures and gave a comfortable ride.

    Thank you for your assistance.

    Regards
    -------------------------------------
    And the reply (which I can't quote in full because there was a note at the bottom saying it should not be copied or disclosed to anyone), included stuff about how wonderful the tyres are and

    ... suggested tyre pressure for the rear of a motorhome running on the Agilis Camping is 80psi.

    ... front pressures however can be adjusted according to accurately weighed axle loads for a more comfortable ride and optimum performance. ... recommended pressure is 55psi.
    ----------------------------------------
    So as many have observed, Michelin always advise 80 psi on the rear axle regardless, which is way to high as far as I'm concerned.

    Why do they do it, one can only surmise it is as a result of guidelines from 'The European Tyre and Rim Technical Organisation' ETRTO!

    The link below is to a document they published in 2014, and on page 46 there is reference to camping tyres for motorhomes.

    "Tyres usually fitted to motor-caravans are of a "light commercial (“'C”' or “CP”)" type. CP type-tyres (commercial vehicle tyres for service on motor-caravans) have only been marketed in the last few years. This followed a study which demonstrated, that overloading is generally the main cause of tyre failure, due to the fact that this type of vehicle often carries an excessive or badly distributed load, which, may be higher than that permitted by the load index (LI) of the tyre; usually on tyres fitted to the rear axle."

    http://www.pneusnews.it/wp-content/...RECOMMENDATIONS-EDITION-25-SEPTEMBRE-2014.pdf

    Details about ETRTO were passed to me by Derek, on the Out and About Live forum, and to whom I'm indebted for the information.

    Clearly, Continental take a different view and recommend pressures that are consistent with the tyre type and, importantly, the axle loading. Is the construction of Continental Vanco camping tyres and Michelin Agilis camping tyres so different?

    For me the big questions are: what is the legal position running Michelins on less than 80psi on the rear, and what are the insurance implications?

    Apologies for the length of this post. Oh, and yes I use Tyrepal for monitoring pressures and temperatures.
     
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  20. Billggski

    Billggski Funster

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    This topic keeps recurring.
    The only way to be sure is to weigh each axle and then check one of the many charts on the Internet.
    My 215 70 15 cp 109 rated camper van tyres have a maximum load of 1030k each at 80psi (5.5 bar)
    When my rear axle was approaching 2000k I changed to 225 section tyres to give me a safety margin. Still at 80psi, for safety, not comfort.
    Normal white van tyres with a similar rating will carry the load, but are not designed for camper van conditions.
    At 80 psi you need high pressure, metal valves.
    Most tyre fitters have no idea of these requirements.
     
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