Franco Posted September 13, 2012 Share Posted September 13, 2012 Hi folks, just referring to my previous thread, and update. I bought 5 new Michelin 215/75 R16(113) Agilis Camping Tyres recently. I got good info/advice from Forum re weighing camping/axels. Pending getting the camper weighed I put 70 psi in front and rear. I found this gave a very comfortable ride indeed. Eventually I got around to weighed the van- I was in fact 100 Kgs overweight. Van is a Compass Castaway, ALKO plates show Front Axel:- 1850 kgs, Rear;- 2120kgs Max 3850 Kgs By taking out surplus items, and redistributing load I can stay under the 3850 kgs limit. I queried Michelin re pressures for van at the above loading (maximum) per axel, and I was advised that the rear pressure should be 80psi, and the front should be 59 psi. I also queried the pressures if I was not fully loaded, front Axel load 1760 kgs and rear axel load 2050kgs (max 3810 kgs). I was advised that the pressures would be respectively, 55 psi (front) and 80 psi (rear). So in keeping with earlier threads it seems that the max 80 psi for rear tyres, seems to be the policy. I am not sure yet what kind of a ride I will get at the stated pressures, as I have not yet got on the road in recent days. Any views on the pressures? Frank Link to comment Share on other sites More sharing options...
Robinhood Posted September 13, 2012 Share Posted September 13, 2012 ....over the last few years, Michelin have become increasingly more conservative in their quotes for tyre pressures, particularly for the (more often overloaded) rear axle. It should be acknowledged that they are in the best position to quote for their tyres, particularly if you wish to rely on the pressures used for any legal or para-legal circumstances, so use of any other pressures would be at your own risk. (FWIW, I still have on record a quote from Michelin of 60/64 psi for a 3850kg Ducato at the max axle loads of 1850/2120 - but on the previous, though similarly sized and rated as your tyres, XC Camping. Given that the original pressures were 79.5 all round, I chose to run slightly above the 60/64 psi - BUT, I had weighed the van, and knew it wasn't overweight on either axle). This does not constitute a recommendation from me. Link to comment Share on other sites More sharing options...
lennyhb Posted September 13, 2012 Share Posted September 13, 2012 Michelin appear to run their camping tyres at higher pressure than other makes 80 psi sounds about right for the rear. Pressures given for my Hymer in the manual are 5.5 bar (80psi) for Michelin 4.5 bar (65psi) for all other makes. Link to comment Share on other sites More sharing options...
DuxDeluxe Posted September 13, 2012 Share Posted September 13, 2012 I think that they will always say 80psi for the rear. They did with me when I weighed my van a few months ago and said something like they could not be sure of the actual axle load. I pro rated according to axle load same as a few others have done. 56/64 - rides so much better than the 80/80 it came with. Link to comment Share on other sites More sharing options...
Franco Posted September 14, 2012 Author Share Posted September 14, 2012 OK folks, tks for your advice. I suppose I felt that the recommended 55 psi in front and 80 psi in rear was a dramatic difference. I will try the advised pressures and see how smooth that is. How critical is a difference of say 10 psi or is that a non-answerablw question? I feel in the interest of safety I need to follow the official Michelin advise, and indeed I dont doubt the accuracy, only wondering about the possibility of a hard ride. In truth I have no yet driven with the higher pressures so maybe that is the next part of the answer. Tks again for replies. Frank :-) Link to comment Share on other sites More sharing options...
DuxDeluxe Posted September 14, 2012 Share Posted September 14, 2012 I think that continental's advice is a little different to Michelin in terms of rear tyre pressure, which is why I took the lower route. Appreciate what you say, though. Link to comment Share on other sites More sharing options...
Guest Peter James Posted September 14, 2012 Share Posted September 14, 2012 There was a survey done a few years ago where most motorhomes were found to be overloaded on the rear axle. Since then, whatever axle loads you give Michelin, as soon as you tell them its a motorhome they recommend the maximum 80psi on the rear axle - yes really - ask anyone who has contacted them including me. I gave Michelin my weights 1540kg front axle, 1470kg rear axle and they quoted 50psi on the front and 80psi on the rear. I still have their email. (I keep them at 50psi all round) Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 15, 2012 Share Posted September 15, 2012 I'm not clear whether you noted the actual laden axle weights when you weighed your van. You quote axle weights when not fully laden, but not those when fully laden, but the pressure for the front sounds about right for either eventuality. You have not said what the axle loads were when the van weighed 3,950kg, it is just feasible (but unlikely!) that neither axle was overloaded - see below. If you find 80psi gives a harsh ride, Google "Tyresafe" and look for a download on motorhome tyres entitled "Motorhome Tyres and Your Safety". You will find this quotes pressures for axle loads for, among others, 215/75R16 113 "Camping" tyres. I think you will find this document recommends a lower pressure at the rear, but it is imperative you know the actual, fully laden, rear axle load, before you embark on any changes. Bear in mind that that axle loads are dynamic, and will vary as you use the van - for example if you travel with full a rear mounted waste tank, or with a rear locker full of booze, the load on the rear axle will rise quite sharply, possibly at the same time reducing that on the front axle. These changes must be allowed for. So, once you are satisfied you truly know the maximum rear axle load condition, armed with the Tyresafe recommendation, contact Michelin again and ask them if they consider the Tyresafe pressure inappropriate. Tyresafe is part of the British Tyre Manufacturer's Association, of which Michelin are members, so what is in the Tyresafe document should have Michelin's full approval. However, do bear in mind also that your van, although plated at 3,850kg, has a relatively fine margin on both axles when fully laden, the combined maximum load for which is only 3,970kg, so overload on one, or other axle, will be easy to achieve in normal use. It think this is why Michelin are erring on the side of caution. If in any doubt, it would be wisest simply to accept their advice, because running tyres under-inflated for their load is positively dangerous and can lead to a blowout, whereas having the tyres a little over-inflated only loosens your fillings and wears the centre band a bit more, but it won't kill you! :-) Link to comment Share on other sites More sharing options...
Franco Posted September 15, 2012 Author Share Posted September 15, 2012 Hi folks, and thanks Brian. I weighted the Van and the figures per Axel were Front Axel weight = 1660 kgs, (Alko Plate= 1850) so in theory I could load a further 190 Kgs in front Rear axel weight = 2240 kgs, (AlKo plate=2120) so it was overloaded by 120 Kgs. Total Van Weigh was 3920 kgs- (AlKo= 3850) so van was overloaded by 70kgs. I had fully loadeed the van for the exercise, so I could afford totake several items out to reduce the maximum weigh. My wife was not on board so I need to factor her petite frame in, allowing say 80kgs for her-on front axel. Hence I dedided that with some care, I would invariable have a front axel weight of approx 1760 kgs, and a rear axel load of 2050 kgs. I fully accept figures will fluctuate, particularly on rear axel as you add say, beer, shopping, and wayer tank fluctuations etc.- perhaps I should just assume that the rear axel will always be close to the maximum of 2120 kgs. Anyway I intend trying the Micheklin pressures and see how it goes. Tks for your imput. The advice from the forums is invaluable and enhances our safety awareness. Regards Frank Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 16, 2012 Share Posted September 16, 2012 Probably the wisest course, Frank. Personally, I think you will occasionally flirt with rear axle overload, and unfortunately, some of the assumptions you are making are not necessarily "safe". For example, your wife's weight will in fact be shared between front and rear axles, not carried on the front axle alone - probably about 60/30 front/rear, but maybe as little as 25/75, depending on wheelbase. If you measure how far behind the front axle centre the front seat is, and take that as a ratio of the wheelbase, you'll get the correct proportion. Water, of course, gets transferred around as it is used and, if the waste tank is behind the rear axle (as most seem to be), although pumping water from the (probably mid-mounted) fresh water tank to a rear mounted waste tank has no effect on actual laden weight, the result on rear axle load can be quite surprising - mainly because a mid mounted tank shares its weight between front and rear axles (every litre weighs 1kg), but also because once in the rear waste tank, the load on the rear axle will be greater than the weight transferred. (To balance the equation, the load on the front axle reduces proportionately.) A spreadsheet, plus a few measurements, helps to fine-tune the estimates but, short of that, or continually re-weighing the van in different load conditions, the safest course is to err strongly on the safe side. That way, at least your tyres will have enough puff in them to keep them happy, so long as you avoid overload at either end. :-) Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 16, 2012 Share Posted September 16, 2012 Peter James - 2012-09-14 2:39 PM There was a survey done a few years ago where most motorhomes were found to be overloaded on the rear axle. Since then, whatever axle loads you give Michelin, as soon as you tell them its a motorhome they recommend the maximum 80psi on the rear axle - yes really - ask anyone who has contacted them including me. I gave Michelin my weights 1540kg front axle, 1470kg rear axle and they quoted 50psi on the front and 80psi on the rear. I still have their email. (I keep them at 50psi all round) Back in 2009 Mike Chapman explored with Michelin why it had become that company's policy to only quote an inflation pressure of 80psi for Michelin 'camping-car' tyres when these were fitted to a vehicle's rear axle. This is the relevant forum thread: http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=15438&posts=25 It seems that Michelin is in a cleft stick over this, believing that ETRTO (European Tyre and Rim Technical Organisation) demand that they must advise the rear-axle 80psi figure. It also doesn't seem to matter whether - when asking for advice - the word "motorhome" is used. If tyre-pressure advice is sought for Michelin camping-car tyres, Michelin will assume those tyres are fitted to a motorhome and will trot out the 80psi recommendation. Plainly, if one wanted to obtain from Michelin a non-80psi pressure-to-axle-weight figure for a Michelin camping-car tyre, it's not difficult to do - you just tell them that the axle-weight you are interested in relates to the vehicle's front axle. The downside of this ploy, of course, is that you'd have to seek advice from Michelin twice to obtain pressure-to-axle-weight figures for both axles. Link to comment Share on other sites More sharing options...
Franco Posted September 17, 2012 Author Share Posted September 17, 2012 Ok, Derek and Brian. Thanks for detailed info. I will give the camper a run with the advised Michelin pressures- 59m psi up front, 80 psi rear and see how it goes. I just find it strange to put 21 psi less in my front tyres than the rear tyres. Sigh! 70 psi all round seems so comfortable.. Regards Frank :'( Link to comment Share on other sites More sharing options...
onecal Posted September 17, 2012 Share Posted September 17, 2012 Hi,And should be more than adequate ,,,,,but then I am afraid most do overload,,,better to be a little over pressurised than under pressurised in tyre pressures that may become overloaded.Regards,Brendan Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 18, 2012 Share Posted September 18, 2012 Franco - 2012-09-17 7:21 PM Ok, Derek and Brian. Thanks for detailed info. I will give the camper a run with the advised Michelin pressures- 59m psi up front, 80 psi rear and see how it goes. I just find it strange to put 21 psi less in my front tyres than the rear tyres. Sigh! 70 psi all round seems so comfortable.. Regards Frank :'( Frank If you've been accustomed to use 70psi front and rear and found the ride "very comfortable indeed", I doubt if going to 80psi for your rear tyres will make a huge difference comfort-wise. Nor, in my opinion, as long as you don't exceed the 2120kg rear-axle load you mentioned earlier, will it make any difference safety-wise. Reducing front-tyre pressures from your previous 70psi to Michelin's 59psi should produce a more comfortable ride, but possibly at the expense of turn-in sharpness when cornering with, perhaps, a hint more roll at the front. If you notice any change, and don't like it, then revert to 70psi. I don't know what other motorcaravanning nationalities do, but I suspect that obsessing over motorhome tyre-related issues may be unique to the UK. French motorcaravanners actively want 'camping-car' tyres on their motorhomes and I've read a number of French magazine letters from buyers of new motorhomes complaining bitterly when they discover their vehicles have 'white van' tyres instead. The idea of deliberately choosing 'white van' tyres over 'camping-car' tyres as an economy measure (even when this would be perfectly safe to do) never seems to arise in France - camping-car tyres are replaced with camping-car tyres. I've read nothing in French motorhome magazines that leads me to believe that French motorcaravanners do other than to accept the tyre-pressure recommendations provided by the manufacturers of their vehicles. If the manufacturer advises high inflation pressures, presumably that's what the French motorcaravanner uses and, if that results in a hard ride, tough luck. I've never read any advice (in French magazines or on French forums) on the lines of "If you think your tyre pressures are unsuitable, weigh your motorhome and contact the tyre manufacturer". I don't know if Brendan has data to support his statement "most do overload" - I certainly have not. I don't overload my motorhome and I'd bet that none of the forum members who have taken the trouble to weigh their motorhomes do either. It has been claimed in the past that roadside checks have revealed that motorhome overloading is far from rare, but that does not automatically equate to "most". Link to comment Share on other sites More sharing options...
Robinhood Posted September 18, 2012 Share Posted September 18, 2012 Derek Uzzell - 2012-09-18 9:25 AM I've read nothing in French motorhome magazines that leads me to believe that French motorcaravanners do other than to accept the tyre-pressure recommendations provided by the manufacturers of their vehicles. ......if, however, you search on "Reisemobil Reifendruck" you will find that German Forums exhibit a marked similarity to the debate going on here. ;-) Link to comment Share on other sites More sharing options...
Franco Posted September 18, 2012 Author Share Posted September 18, 2012 Thanks Derek and Robinhood. I think I have a much clearer picture now. Regards to all who gave advise/replies Franco Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 19, 2012 Share Posted September 19, 2012 Robinhood - 2012-09-18 9:40 AM Derek Uzzell - 2012-09-18 9:25 AM I've read nothing in French motorhome magazines that leads me to believe that French motorcaravanners do other than to accept the tyre-pressure recommendations provided by the manufacturers of their vehicles. ......if, however, you search on "Reisemobil Reifendruck" you will find that German Forums exhibit a marked similarity to the debate going on here. ;-) Is the German debate equally well-informed? Link to comment Share on other sites More sharing options...
onecal Posted September 19, 2012 Share Posted September 19, 2012 Hi,In reply to MOST ,,,,,Most Motorhome owners do not even know they are over the limit,now Derek again Most, is not all may I add. Manufactures of motorhomes leave a very thin line as to payload and this may be one of the main causes of overloading and the necessity to have to use excessive tyre pressures to prevent overheating and blowouts,Regards,Brendan Link to comment Share on other sites More sharing options...
Robinhood Posted September 19, 2012 Share Posted September 19, 2012 As I said, there is a marked similarity -in fact ome of the posts would be (except for the language) easily interchangeable. Wording my reply carefully, I would say that the debate is equally "infomed". ;-) Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.