Tyre pressure

Discussion in 'Motorhome Chat' started by Malg56, Feb 12, 2010.

  1. Malg56

    Malg56 Read Only Funster

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    I am new to motorhome, first year, and own a Fiat Adria. the tyre size is 215/70 R15 can anyone advise me what tyre pressure to run them at. Handbook advises around 80psi but local tyre company say it should be around 65.:Blush:
     
  2. madbluemad

    madbluemad

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    Hi
    Your local tyre company is correct. 80 PSI is too high.
    Jim
    :Smile:
     
  3. JeanLuc

    JeanLuc Funster

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  4. movan

    movan Funster Life Member

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    Thank you for starting this thread. I was confused too as same happened to me when I took van for its MOT and asked garage to fill tyres for me. Grateful.
     
  5. madbluemad

    madbluemad

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    Just so that you dont get confused with the C C leaflet on Tyres. The tyre should be capable of taking the load that it is bearing at the speed that you are travelling.

    All tyres have a Load Index and Speed Rating. You can tell what yours are by looking at the side wall on your tyre.

    You should set your tyre pressure by looking at the axle weight plate on you mh.

    Determine the load index for the tyre that you have and translate that in to ("This is how much weight my tyre can take"). Then check that against the actual axle weight.

    Believe me, everybody has trouble with tyre sizes, pressures etc at first and it is worrying so dont panick.

    The 80 PSI that HANDBOOK reccomend is the MAXIMUM COLD TYRE PRESSURE. This doesnt mean that its the pressure that you should be using.

    Jim
    :Smile:
     
    Last edited: Feb 12, 2010
  6. Molls-Phot

    Molls-Phot Funster

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    I found the handbook was far too generic and not specific to my van. I then found a label on the passenger door frame - 60 & 65 psi.
     
  7. Braunston

    Braunston Read Only Funster

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    Hi,

    I don't think that is a correct answer, you should always follow your manufacturers stated pressures, if you were unfortunately to be involved in a RTA and they felt the tyres may have been a contributing factor, quoting that someone on a web site or a local tyre seller told you to use different pressures than specified by the Motor-home/ base vehicle manufacturer you could be in serious dodo ?

    If you read the link given in one of the posts, you will see there is a chart at the end of the document that give pressures against axle loads, some of which are quiet clearly in the 5.5 bar(80psi+-) range depending on your vehicles axle weights,

    If you weigh your vehicle and determine the actual axle weights you may well find a lower pressure on this chart, but before you proceed with lowering the pressures given in your handbook you need to determine whether the weight at the time of weighing will ever be exceeded or lowered as, as you will see from the chart this weight fluctuation will change the pressure needed.


    You should also read the whole document and not just jump to the chart as it clearly states in the opening paragraphs you should follow the vehicle manufacturers handbook when it comes to tyre pressures

    Having looked into this recently along with the type of tyres that can be used I would strongly suggest you follow your handbook as god forbid you were ever involved in a RTA where the tyres could be seen as a contributing fact you would always be in my opinion on the right side, as we are no experts in tyres and pressures and if the handbook tells me that's what it should be why do i as a complete novice in this area want to stick my neck out and say I know better than the manufactures, some people may but I certainly don't.

    Just another major item you may want to double check is if the tyres fitted are the same as specified by the manufacturer as camping type tyres can use a higher pressure than most normal van tyres, so it's really worth double checking as a lot of people appear to be fitting non camping type tyres to there motorhomes when it comes time for replacements and if you follow the manufacturers handbook in those situations you could be exceeding the safe operational pressures of the tyres, the link earlier shows you how to check the safe working pressures on the tyres you have fitted.

    I am no expert on tyres, its just my opinion, Hope that helps



     
  8. madbluemad

    madbluemad

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    This is now imo where the confusion starts. If you work out the axle weight to tyre Load Index ensuring that the Speed Rating is covered, there is no better way to ensure that you have the correct tyres and they are at the correct pressure.

    The tyre pressures for your mh may well be labelled somewhere on the inside of your mh, mine are and do not comply with the "manufacturers reccomendations".

    Dont forget that there are three companies specifiying stuff here. The base vehicle Manufacturer, the Converter and the Tyre Manufacturer, all will give different information depending upon the bit that they have manufactured.

    Jim
    :Smile:
     
  9. JayDee

    JayDee Funster

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    And, of course, the base vehicle manufacturer thinks it's a white van loaded to the gunwales and being driven by a maniac in a hurry (apologies to white van drivers who don't drive like maniacs :BigGrin:).


    John
     
  10. wayfarer

    wayfarer Read Only Funster

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    Here's my 2 cent worth. I also thought that the 5.5 bar was too high in my camper so I reduced it to about 60psi. But on my second year in France I had two new front tyres fitted, and the mech checked my pressures and said they were too low so he put 5.5bar in the front and 5.2bar in the back. These were the correct pressures for a camper according to him.
     
  11. Braunston

    Braunston Read Only Funster

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    Hi, Jim

    That's why i decided to stick with the tyre types e.g. camping that the manufacture fitted originally and the pressures they specify in the handbook, as that way it only cost a few quid more for the tyres and you are always going to be on the side of right, god forbid you are involved in an accident where tyres could play a part,

    I know its digressing but to change any of those things could be seen as a modification and as such leave us in very difficult situations. probably never happen but you know that blokes law (Sods)

    Thanks
    Braunston

     
  12. chewy

    chewy Read Only Funster

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    I went through this process as well I have ended up running same size tyres (Fiat ducato based A class) at 60 PSI...for me the lower pressure absorbs minor bumps better but any lower and my van 1) doesn't look right and 2) will roll too much... Just from habit I always feel my tyres if I think they may be getting too hot on long runs (3 or 4 hours at 60mph plus ) a digital guage takes a lot of guesswork out of your readings. You will probably get a different answer from everone you meet but I would say for safety be very carefull when going outside of the 60 to 80 parameters.
     
  13. American Dream

    American Dream Read Only Funster

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    The 60-65 psi sounds about right.....

    My Manual specifies 60 and it "feels" right at this.

    My previous one I tried at a higher pressure than those stated and it promptly "threw" the tread...:Doh:

    This was on a tyre with very low mileage and age.:Sad:

    I have a habit of checking the temp of the tyre and doing a quick visual now because of this.

    Always look at the max pressure/load rating on the tyres themselves.
     
    Last edited: Feb 12, 2010
  14. pappajohn

    pappajohn Funster Life Member

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    the tyre manufacturer is always right when it comes to load, speed and pressure.....they made the tyres and they know the limitations.

    for an accurate pressure take your van to a weigh bridge and have both from and rear axles weight.
    take the van in its normal loaded state as if you were about to go on your travels...dont forget water, gas and the wife.

    then contact your tyre manufacurer...not the dealer.

    give them the axle weights and gross weight and they will calculate the pressure for those given weights.

    they must have both axle weights...not just the gross.

    as Jim said, the pressure it says in your handbook is the maximum allowable cold pressure for the tyre and not necessarily the pressure for your van.
    just as the speed rating doesn't mean you have to travel at that speed but to exceed it is dangerous

    as an example....the tyres on my twin axle 3500kg trailer are 195/50/12 and the pressure sticker on the trailer says 90psi.
    if i run at 90psi i wont need tyres....train wheels will do as there will be no flex in the tyre at all and the trailer will shake itself to bits.
    i run at 50psi and thats a harsh ride.

    .
     
  15. sandyketton

    sandyketton Read Only Funster

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    I had the same concerns a couple of years ago and ended up e-mailing the tyre manufacturer with the axle weights and asking their advice. Their figure is quite a bit lower than the base vehicle recommendations.

    On the basis that the tyre maker knows what he is talking about in relation to his product I use his figures. This also gives a softer ride.

    I have now printed a copy of their e-mail with the pressure recommendations and this is kept in the motorhome in case of queries by the authorities.

    HTH

    Sorry. This has crossed with Pappajohns.
     
  16. madbluemad

    madbluemad

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    Hi Braunston

    One of the problems is nothing stays the same. When I bought my mh all of the tyres were at 70 psi.

    These were not the tyres that were fitted by the vehicle manufacturer/Converter.

    I contacted the converter who advised me what make and type of tyre was fitted when it left the factory but not what the pressure was.

    The tyres that were fitted to my mh were manufactured for the Australian and North American Markets.

    The Specification markings on the side wall of these tyres is different to the Specification Markings for the UK.

    I then find that I need a new tyre because one is damaged. I look at the tyre markings on the existing tyres and find that I cant get one in the UK because the Specification Markings are not the same.

    I ask the C&CC what the equivelant UK markings are and they dont know. They ask the British Society of Tyre Manufacturers and they dont know.

    So I work it out from the Michelin Web Guide.

    I then buy a Michelin Camping Tyre which blows out on the Motorway within a week of me buying it. No response from Michelin.

    I then buy another two tyres (Because when the Michelin Trye went it took another one with it).

    In amongst all this I work out the axle weights and Load Indexes for the tyre that I need. I then stumble across a sticker on the mh side wall, over my overcab bed (where else would it be).

    The only things that made sense were the markings on my mh wall and the calculations that I made on the axle weights.

    Rant Over :Eeek:

    Jim
    :Laughing:
     
  17. geoff1947

    geoff1947 Read Only Funster

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    This is a mindfield (minefield even) and pappajohn put some good info on here some weeks ago. My van has 52 front/60 rear when I bought it EMPTY but when I had it topped up and weighed the pressures were far too low. I don't know the answer & neither did the local tyre fitters so god help us all. sorry but I don't know the answer --just thought I'd contribute as its raining her in Spain.
     
  18. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    Just to add a little more confusion-my tyres on a Fiat based van are the same as the OP-the plate inside the drivers doors states 79.5 psi.This I duly did at Tescos last Sat, on Tues of this week my tyres were checked by a tyre fitter using a calibrated gauge which he said was accurate-all four tyres gave a reading of 70psi :BigGrin: We decided on 65psi in the end-it might be interesting to now check that Tescos.
    So,I guess that whatever pressure you decide to use,you need to have an accurate way of checking that and not relying on 'forecourt' gauge which might.or might not,be accurate.

    Mike
     
  19. pappajohn

    pappajohn Funster Life Member

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    i beleive all garage forcourt gauges have to calibrated on a regular basis but not regular enough obviously.

    maybe Geo can confirm or refuke this. ?
     
  20. lebesset

    lebesset Read Only Funster

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    camping tyres are a con ; if you look at the load and speed indices they are no different to the tyres sold for vans ; if they would carry more weight they would have a higher load index ; the confusion has come from the tyre manufacturers trying to cover themselves because so many motorhomes are overloaded ; if you are told the pressures which are correct for the vehicle at it's maximum approved weight many tyres will be overloaded

    so it is quite simple

    weigh your axles when fully laden , driver and passengers included
    refer to the official ETRTO charts and get the correct pressures for that weight
    please remember that there is a dual load index , eg 109/107 and you can find the maximum loads you can carry on that tyre ; the reason for the dual index is that twinned tyres DO NOT carry double the load of single tyres , so if you have twins check that the twinned load in the load index chart is sufficent for your vehicle

    if you are overloaded , at the very least make sure that your tyres are not ...it might be ME that you hit

    for an illustration I will quote my current vehicle , came fitted with michelin tyres [ never again , but that is another thing ]
    contacted michelin ...motorhome ? 5.5 bar on both ends was the response
    weighed the loaded motorhome ....in by 40 Kg overall [ phew ]
    applied ETRTO pressures
    4.5 bar front , 5.0 bar rear
    this operates the tyres at the pressure /weight combination for which they are designed , therefore safely
     
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