pepe63xnotuse Posted March 2, 2011 Share Posted March 2, 2011 Mornin' all.... Tyre pressures have been touched upon in another thread but I didn't want to totally derail that ... So can someone please clarify something for me,as I want to get my tyre pressures "correct" but I also want to still cover my backside,legally. ;-) So..if having determined your "correct" tyres pressures(by weighing vehicle/axles and contacting tyre manfacturer,get pressures in writing etc),you then deviate from the EXACT weight that you supplied them,even by only a few kg,would that then mean,in the case of an accident,that you would be liable? In having chosen to "ignore/disregard" the figures provided by the base vehicle manufacturer and the converter,would we then theoretically,need to be running exactly the right pressues,for exactly the right weight,at all times?? :-S (..and all backed up in writing from the tyre manufacturer?!?) A few psi either way I could understand but from what I'm reading, it seems that the figures can vary quite considerably,depending on their source. :-S What do we reckon? Chris Link to comment Share on other sites More sharing options...
Melvin Posted March 2, 2011 Share Posted March 2, 2011 I tried the 79 psi front and rear, it understeer, in the wet is was just unsafe, I have been using 58 psi front and 70 psi rear. If you go on the Autotrail Owners Club site you can download their tyre pressure chart. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 2, 2011 Share Posted March 2, 2011 pepe63 - 2011-03-02 9:15 AM Mornin' all.... Tyre pressures have been touched upon in another thread but I didn't want to totally derail that ... So can someone please clarify something for me,as I want to get my tyre pressures "correct" but I also want to still cover my backside,legally. ;-) So..if having determined your "correct" tyres pressures(by weighing vehicle/axles and contacting tyre manfacturer,get pressures in writing etc),you then deviate from the EXACT weight that you supplied them,even by only a few kg,would that then mean,in the case of an accident,that you would be liable? In having chosen to "ignore/disregard" the figures provided by the base vehicle manufacturer and the converter,would we then theoretically,need to be running exactly the right pressues,for exactly the right weight,at all times?? :-S (..and all backed up in writing from the tyre manufacturer?!?) A few psi either way I could understand but from what I'm reading, it seems that the figures can vary quite considerably,depending on their source. :-S What do we reckon? Chris If you feel it necessary to agonise over this sort of thing, you should stick to the pressures advised in your motorhome's handbook. Link to comment Share on other sites More sharing options...
Robinhood Posted March 2, 2011 Share Posted March 2, 2011 Do you diligently adjust the tyre pressures on your car if you vary the load? On mine, the recommendations for full and light load have significantly different pressures. I run at a tad above the light load pressures, and don't adjust them unless I'm doing long-distance, heavy running. I don't see it as being much different for a MH. I normally travel loaded, and the variance from that loaded state is not great at any time. Hence, I get it weighed, and run at the tyre-manufacturer quoted pressures for those weights. If I ever empty it out (for repairs/service etc.) I'm uninclined to reduce the pressures, as the distance covered and speed of travel will both be relatively low. Link to comment Share on other sites More sharing options...
pepe63xnotuse Posted March 2, 2011 Author Share Posted March 2, 2011 Oh! :-S ..well,I wasn't agonising Derek,far from it,I was just asking,what I thought,was a perfectly sensible question. 8-) (..and not that unreasonable,in view of the fact that this site is usually awash with pedantic banter from "stalwarts" and "experts",bickering over the specifics of axle weights,payloads,gas cylinder filling points etc (lol) ) Robin'..agreed we don't "diligently" alter our car pressures...but there again,when it comes to the car,we're not being advised by "experts" on forums,that the only way to get the correct pressures,is to get it weighed and to then contact the tyre manufactures..we just go by what's in the handbook.. :-S Like yourself,I tend to leave it at the "loaded pressures",so I'll leave well alone then.. ;-) Cheers Chris Link to comment Share on other sites More sharing options...
Guest 1footinthegrave Posted March 2, 2011 Share Posted March 2, 2011 I would love to find an accurate pressure gauge in the first place, does one even exist, my tyres always look flatter on the bottom. Link to comment Share on other sites More sharing options...
Colin Leake Posted March 2, 2011 Share Posted March 2, 2011 1footinthegrave - 2011-03-02 2:24 PM I would love to find an accurate pressure gauge in the first place, does one even exist, my tyres always look flatter on the bottom. That's easy. Take the pressure at the top then drive forward so that the valve is at the bottom and take the pressure there. Add the two together and divide by two and you will have an accurate pressure (which should be the same as the first reading you took)! Only too glad to be of help! Link to comment Share on other sites More sharing options...
nuevoboy Posted March 2, 2011 Share Posted March 2, 2011 Colin Leake - 2011-03-02 3:36 PM 1footinthegrave - 2011-03-02 2:24 PM I would love to find an accurate pressure gauge in the first place, does one even exist, my tyres always look flatter on the bottom. That's easy. Take the pressure at the top then drive forward so that the valve is at the bottom and take the pressure there. Add the two together and divide by two and you will have an accurate pressure (which should be the same as the first reading you took)! Only too glad to be of help! (lol) Link to comment Share on other sites More sharing options...
rolandrat Posted March 2, 2011 Share Posted March 2, 2011 pepe63, you are right to show concern about your tyre pressures because as you probably know there is a maximum pressure rating on your tyres that indicates 69psi so increasing them to 79psi is out of the question. Not only that your motorhome will feel like it is driving on solid tyres and that is not what your suspension is designed for. My motorhome which is a 3ltr Tracker EKS runs at 55psi all round and the tyres are barely warm at any time, the ride is very smooth and the roadholding is as it should be, perfect. It's all about what suits you, as long as you are driving it it a lawfull manner it's nothing to do with any one else. There is nothing wrong with sound,friendly and helpfull advice, this forum is what it is all about. You will always come accross people who are perfectionists but in the real world it is far from the norm. Link to comment Share on other sites More sharing options...
Guest 1footinthegrave Posted March 2, 2011 Share Posted March 2, 2011 All joking apart I always assumed running with less pressure than is recommended would lead to increased fuel consumption, I just use the commercial van pressure indicated in the handbook, unless you have special camping tyres which seem to need a great deal more pressure than normal van tyres. Link to comment Share on other sites More sharing options...
pepe63xnotuse Posted March 2, 2011 Author Share Posted March 2, 2011 Yes,the pressures shown in the "Camper versions" section of our Renault handbook,are 65psi Front and 80psi rear..against 55psi and 63psi for the "normal" van tyres. (These figures are rounded up slightly,as they were given in bar..) Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 2, 2011 Share Posted March 2, 2011 Chris My point was that, if you feel a need to fine-tune your motorhome's tyre pressures to the degree that you were suggesting in your original posting so that you could be sure of remaining 'legal', then you'd be better staying with the handbook advised pressures as it would be very difficult to argue against that strategy in court. In fact you've overlooked an additional significant factor - ambient temperature. Tyre manufacturers quote tyre pressures at 20°C. If you inflated an average motorhome tyre on a frosty morning to a quoted pressure of, say, 60psi, this would be at least 65psi at 20°C. There's no 100% certain guarantee that the data you've been provided by the tyre manufacturer are correct (people make mistakes), nor that the weighbridge you've used was 100% accurate when you weighed your vehicle (machines go wrong). At the end of the day, if you are prepared to ignore your handbook's advised pressures (and I certainly am because I know my handbook's wrong) and accept alternative advice, then you also need to be accept there may be consequences for making that decision. Link to comment Share on other sites More sharing options...
everhopeful Posted March 2, 2011 Share Posted March 2, 2011 My base vehicle handbook had one set of pressures, the converter had another and the sticker on the door jamb yet another. The van was delivered new with another combination, and every time my van goes to the base vehicle dealership they adjust the pressures to yet another figure. I phoned the converter who was adamant that their figures are correct and that the other figures related to the bare chassis only. With all the confusion and ambiguity how on earth would a court decide guilt on my part regardless of what I'd set the pressures to? I actually settled on the converter supplied figures as these give the best ride. I tried higher pressures somewhere between all the others and found the handling to be worse and the fuel consumption no different. Link to comment Share on other sites More sharing options...
Guest Tracker Posted March 2, 2011 Share Posted March 2, 2011 Take the sticker of the door jamb, hide the base vehicle handbook deep in a locker and if stopped by the constabulary or at a roadside checkpoint show them only the converters handbook with their stated correct tyre pressures? The reason there is no door sticker, if asked, don't know - never seen one - didn't know there was meant to be one - perhaps because the stated pressures do not apply to this Motorhome conversion? A printed email from the tyre manufacturers should be as good especially if it has a contact phone number and name so anyone who feels that they just have to know, or is vindictive enough, can check? Link to comment Share on other sites More sharing options...
Dave Newell Posted March 2, 2011 Share Posted March 2, 2011 Although the official advice is to weigh each axle my preferred method is to monitor the tread depth across the three main grooves of the tread (some tyres have five main grooves) and adjust to get an even wear depth. Having spent several years taking average depth readings across the grooves of many hundreds of motorhomes my conclusion is that virtually none of those I've checked are running at the most appropriate pressures. Having said that, in a bum covering exercise I would always advise weighnig each axle and consulting the tyre manufacturers. D. Link to comment Share on other sites More sharing options...
George Collings Posted March 2, 2011 Share Posted March 2, 2011 Quoting Pepe 63 So..if having determined your "correct" tyres pressures(by weighing vehicle/axles and contacting tyre manfacturer,get pressures in writing etc),you then deviate from the EXACT weight that you supplied them,even by only a few kg,would that then mean,in the case of an accident,that you would be liable? If that were the case there would be very long queues of trucks at service station air lines as HGV drivers continiously changed pressures to suit varying loads. Daves tread wear check is a good if somewhat delayed indicator of tyre loading. Too soft for load wears the edges as the centre of the tread is not pushed down hard enough and too hard does the reverse and wears the middle. The old truck drivers check of feeling individual tyre temperature is also a good indicator. Ideally if they should be reasonably even but in practice rarely are due to factors such as road camber or uneven distribution of weights loading the one side or axle more heavily. On a long run its recomended drivers take a break every two hours or so and particularly on fast roads I get out take a stroll and feel the tyres. I have yet to detect a slow puncture but when it comes to tyres pressures ignorance is not bliss. Link to comment Share on other sites More sharing options...
Melvin Posted March 3, 2011 Share Posted March 3, 2011 I have just recieved dat for my tyre pressure from Continental Tyres, My van runs 225/65 x 16 VanCamper 116 R Front Axle weight 1665 kg 50 psi Rear Axle weight 2300 kg 72 psi Link to comment Share on other sites More sharing options...
tonyishuk Posted March 3, 2011 Share Posted March 3, 2011 I take the view that the only people who can advise what loads and pressures are needed are the people who design, manufacture and sell the tyres. Any "guidence" pressures stuck on a sticky label on the cab door may not even apply to the tyres on a new vehicle, let alone a second hand one. I have seen new vehicles delivered (not motorhomes) with three of type A and one of type B tyres, fresh from the storage compund !! It would seem that cars do at least try to indicate varying loads and pressures on their cab door stickers, again only in general terms and not Brand specific. Not being in the tyre trade at the design end, I do not know how much leeway there is in relation to tyre pressures and loads, and at what pressure a tyre might become over or under loaded. Rgds Link to comment Share on other sites More sharing options...
Brian Kirby Posted March 3, 2011 Share Posted March 3, 2011 pepe63 - 2011-03-02 9:15 .............So..if having determined your "correct" tyres pressures(by weighing vehicle/axles and contacting tyre manufacturer,get pressures in writing etc),you then deviate from the EXACT weight that you supplied them,even by only a few kg,would that then mean,in the case of an accident,that you would be liable? ............... Chris Lets try a different tack. You should weigh the axles at your heaviest loading. Take the manufacturer's recommendation for that. Be aware that removing weight from behind the rear axle transfers more weight to the front axle. So, aim a little high when notifying weights. The upshot should be that you will never run the van under inflated, which is dangerous, but will most of the time be a little over inflated, but far less so than if you simply use the converter's recommended pressures. That way, there should be no question as to the legality of the pressures, so long as you can demonstrate you have arrived at the lower pressures in a proper fashion. Link to comment Share on other sites More sharing options...
Melvin Posted March 4, 2011 Share Posted March 4, 2011 Melvin - 2011-03-03 10:03 AM I have just recieved dat for my tyre pressure from Continental Tyres, My van runs 225/65 x 16 VanCamper 116 R Front Axle weight 1665 kg 50 psi Rear Axle weight 2300 kg 72 psi I gave Continental the wrong size it should have been 225/75 x 16, not 225/65 x 16. Hopefully this will help anyone running a Autotrail Cheynne 660 post 2007 or similar. Thank you for the clarification. In this instance, please find the pressures you require, below. Front: 3.0bar - 44psi Rear: 5.0bar - 72psi Regards Craig Sterry Product Support Engineer There is no mention of tyre pressures in Autotrails supplied handbook vehicle specification, The supplied Fiat handbook 5.5 bar or 79 psi. The difference between Continental Tyres recommendations and Autotrail/Fiat is 35 psi, that is a reduction of over 44%. Link to comment Share on other sites More sharing options...
Brian Kirby Posted March 4, 2011 Share Posted March 4, 2011 Melvin - 2011-03-04 10:49 AM Melvin - 2011-03-03 10:03 AM I have just received dat for my tyre pressure from Continental Tyres, My van runs 225/65 x 16 VanCamper 116 R Front Axle weight 1665 kg 50 psi Rear Axle weight 2300 kg 72 psi I gave Continental the wrong size it should have been 225/75 x 16, not 225/65 x 16. Hopefully this will help anyone running a Autotrail Cheyenne 660 post 2007 or similar. Thank you for the clarification. In this instance, please find the pressures you require, below. Front: 3.0bar - 44psi Rear: 5.0bar - 72psi Regards Craig Sterry Product Support Engineer There is no mention of tyre pressures in Autotrails supplied handbook vehicle specification, The supplied Fiat handbook 5.5 bar or 79 psi. The difference between Continental Tyres recommendations and Autotrail/Fiat is 35 psi, that is a reduction of over 44%. There is, however, a slight danger in all this. The tyre you are quoting is very specific, and the loadings are peculiar to your van. I note, for instance that your van is flirting with its designated MAM of 4,000kg (3,965kg actual), and the individual axle loadings will reflect what you carry, and where you carry it. It should not be taken as a "blueprint" for anyone else with a Cheyenne 660, or anyone with other Autotrail vans, or even, necessarily, for vans of other makes with similar axle loadings. Everyone who wishes to depart from the standard recommended tyre pressures should do as you have done, take the fully laden van to a weighbridge, get the individual axle weights as John (flicka) describes above, and then contact the tyre manufacturer, preferably in writing, for their advice. You than have the evidence of the load, and the recommendation for appropriate pressure from the authoritative source.Being a pedant, I would add that (so far as I can tell) the full designation of your tyres is Vanco Camper, 225/75 R16 CP 8PR 116R, where 8PR is the ply rating, 116 is the load index, and is R the speed index. All three are important, as is the CP designation (camping), since Continental make tyres at 225/75 R16 C in both 8PR and 10PR, with load indices between 110 and 121 and with speed indices N and R.Also, remember that the weighbridge gives only a snapshot of the load on the day. As we travel, we consume part of the weight, and we add back things as we replenish them, sometimes adding more, in different places, than when we weighed. This can have quite an affect on the individual axle loads, as well as on actual laden weight, so it is prudent to think in terms of higher actual axle loads than those given by a weighbridge. 5% more on either of your axles would take the rear over load (but, I think, with adequate tyre pressure, possibly up to 2540kg), and the front up to a load that I think would warrant an extra 0.25 bar pressure. However, what Conti have given you is the appropriate pressures for just the load as you advised it to them - not for any higher load. You are right at the limit at the rear, I personally think much closer than is desirable, for the above reason. Hope this helps. Link to comment Share on other sites More sharing options...
pepe63xnotuse Posted March 4, 2011 Author Share Posted March 4, 2011 Well having contacted Michelin today with our actual loaded axle weights (with full water/fuel tanks,kit loaded and OH onboard etc),they've come back with : 53psi Front & 80psi Rear. Although the rear is the same,that front figure is 12psi lower,than stated in the Renault "camper versions" handbook...now that is some sort of difference for a vehicle still on OE tyres... Link to comment Share on other sites More sharing options...
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