Tyre Pressures (Again)

Discussion in 'Motorhome Chat' started by Peter Ashcroft, May 26, 2016.

  1. Peter Ashcroft

    Peter Ashcroft Funster Life Member

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    I have a new to us AutoSleeper Windrush 2012 van conversion on a Boxer base, and I am having problems with trying to get the right pressure for the van




    After searching this and other forums, the advice on old threads seemed to be weigh vehicle and contact tyre maker.

    I have done this (trying to do the right thing) but had no joy and find myself extremely confused and frustrated with the whole thing.

    Michelin seemed clueless about it and before I even gave them the weights of axle they said put 80psi in all round, when I explained about the weights they said put 50 front and 80 rear, I asked why the big difference when both axles weighed almost the same, and couldn't get an answer ! the person at michelin both on the phone and on the web chat just didn't fill me with confidence especially when I was given the pressures before he even asked what weight I was running, the feedback from him seemed to be the weight didn't matter and the conclusion was kind of 80PSI in the back no matter what, and put what ever is comfortable in the front...



    So I reverted to the tyre safe leaflet here http://www.tyresafe.org/wp-content/uploads/2015/12/motorhome-leaflet.pdf , and even called them, but still I can't get an answer.... so here is my problem!



    My tyres are Michelin Agilis Camping tyres, 225-70-15 CP with a 112 load rating. My axle weight is Front 1560KG and Rear 1520KG



    The second chart on the leaflet has the pressures for CP tyres, but the lowest weight it starts at is 1952KG front and 1736 Rear which is well above my weight. (for this weight incidentally it states 58 PSI all round, which is well off what Michelin are telling me)



    The chart above is for normal commercial tyres, not CP tyres, however on this chart my size and axle weights are listed as they go right down to 1400, for my axle weight in this chart I should be using 40 PSI all round, half of what Michelin are telling me.



    I am completely lost, I have no confidence in either of these recommendations now,



    If anyone could offer an opinion or advice I would be grateful?

    At the moment I am going off the lowest axle weight on the CP tyres chart which is 58 PSI all round, and I must admit the VAN does feel good, however the tyres do look soft when you look at them compared to the old ones. the door card is telling me 59 front and 65 rear which contradicts all of the above.

    I might be making too much of an issue of this, but I just want to ensure our vehicle is as safe and as comfortable as I can make it, and I guess I am getting myself all wound up because I have taken the advice so often offered about doing it right and getting the weights etc, and now I have hit a brick wall with it!
     
  2. scottie

    scottie Funster

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    I have same tyres on a 3500kg white van man conversion. Black circles say 79 for the rear 65 for the front. tyre company say 65 rear 60 front. So until I go on a weighbridge, likely to be 72 rear 67 front.
     
  3. Peter Ashcroft

    Peter Ashcroft Funster Life Member

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    From my experience so far, getting the van weighed hasn't helped :(
     
  4. NickNic

    NickNic Funster Life Member

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    Michelin were brilliant when I did it and from what I've read have been with others too.

    Don't phone or use the web chat.

    Use this email address: michelin-contact@uk.michelin.com
     
  5. Nirvanauk

    Nirvanauk Funster

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    Similar set up and as there is so much debate around it I just put 70 in the back and 60 in the front. It works fine. I have tyre pressure monitors which are well worth the money.
     
  6. Techno

    Techno Funster Life Member

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    Ring them twice
    Give a different weight for the front each time . One of the weights being what your rear weighs
     
  7. Peter Ashcroft

    Peter Ashcroft Funster Life Member

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    My axles pretty much weigh the same. So are you saying just put what they tell me in the front in the back also ? I will email them though. I have had no luck on the phone. It seems to be a guy called George who answers who is the same guy on the web chat
     
  8. Hettie's Crew

    Hettie's Crew Funster

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    This is probably the best guide. My rear tyres certainly looked underinflated at the 'recommended' pressure.
     

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  9. Techno

    Techno Funster Life Member

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    It's Michelin policy to quote 80 psi rear regardless
    They believe that all Motorhomes are overweight anyway at the back
     
  10. premiere99

    premiere99 Funster

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    I have Toyo HO9's fitted, excellent tyres, especially for Peterborough show this year! and 12 hour response to tyre pressure requests.
    When I was at 3500kg I asked them via email.

    "I am going to fit 4 x 225/70 R15C 112/110R Toyo HO9 tyres to my Autotrail Cheyenne 635 coachbuilt motorhome. Can you give an indication of tyre pressure for front axle weight of 1680kg and rear axle of 1960kg."

    Reply,

    "Based on the information you have provided the pressures I would recommend are
    Front: 55psi, Rear: 60psi"


    After fitting Towbar for the two E-Bikes, VB Air suspension and an "upgrade" to 3850kg by SVTech I enquired again.

    "I have 4 x 225/70 R15C 112/110R Toyo HO9 tyres fitted to my Fiat Ducato x250 based Autotrail Cheyenne 635 coachbuilt motorhome.
    It has had the suspension uprated with VB-Airsuspension 4C air suspension (front and rear).
    Details if required at http://www.vbairsuspension.com/upload/files/00001900.pdf
    Can you give an indication of tyre pressure for front axle weight of 1620kg and rear axle of 2200kg."

    Reply

    "Based on the information you have provided the pressures I would recommend are
    Front: 50psi, Rear: 65psi
    I assume that the axle weights given are in a fully laden state, as the rear axle weight is very close to the 2240kg maximum load carrying capacity of the 225/70R15 112/110 tyres.

    Best regards
    Alan Meaker
    Technical and Motorsport Director Toyo Tyre UK"


    I cannot see how Michelin can say 80PSI all round and then change that to 50PSI in the front, seems a bit finger in the air to me, glad I have Toyo's and great grip on grass!





     
  11. Peter Ashcroft

    Peter Ashcroft Funster Life Member

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    Screen Shot 2016-05-27 at 11.43.33.png Just been sent this My Michelin , still doesn't not help as my axle weight isn't on there and is well below the weights listed
     
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  12. Techno

    Techno Funster Life Member

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    Pressure is proportional to weight it's only maths
     
  13. Peter Ashcroft

    Peter Ashcroft Funster Life Member

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    Yes I know it is. Which is why I am trying to find out what pressure I use for the weights I have !
     
  14. Techno

    Techno Funster Life Member

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    use the chart to calculate the proportion of psi to kg
     
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  15. Techno

    Techno Funster Life Member

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    Go up or down 1psi per 17kg
    image.jpeg
     
  16. Techno

    Techno Funster Life Member

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    Looks like they don't like to quote below 50 psi but as your rear is lighter than the front I don't see the issue with applying 50 psi all round
     
  17. Wedgy

    Wedgy Funster

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    • Like Like x 1
  18. Techno

    Techno Funster Life Member

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    Glad you're paying attention (y)
    29kg per 1 psi
     
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  19. TerryL

    TerryL Funster

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    Just interested, as it's unusual to see the front heavier than the rear on modern vans, what are your "plated" weights, i.e. what does the plate affixed to your van read (be 4 sets of numbers)? Should be in the cab area somewhere, maybe in a footwell. Does the MAUW (third set) agree with your V5?
     
  20. Peter Ashcroft

    Peter Ashcroft Funster Life Member

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    Techno, thanks so much for taking the time to work that out, My head is battered though, could you make it even simpler for me and just tell me what PSI I need based on your calculations and my weights??

    Front - 1560KG
    Rear - 1520KG
    Total - 3080KG

    Tyres 225-70-15
     
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