steveandlisa Posted September 7, 2016 Share Posted September 7, 2016 Hi folks, I did what you guru`s suggested and put my m/home on our local weighbridge today fully laden, only cost a fiver :-D Can somebody please confirm my calculations, just to put my mind at ease thanks. Here are the results Front axle weighed 1.52 UK tonne. Rear axle weighed 1.64 UK tonne. My calculations came out to approx. F 1545kg, R 1666kg Max axle weight limits are F1850, R2000. 215/70/15C 109/107 tyres pressures using the Continental tyre chart should be F 47psi (3.25bar) R 51psi (3.5bar) Please correct me if I`m wrong :-S Kind regards Steve Link to comment Share on other sites More sharing options...
Keithl Posted September 7, 2016 Share Posted September 7, 2016 Hi Steve, Going by the figures you've quoted IMO you look good to go. My only question is your weighbridge units, UK Tons are in pounds, whereas Metric Tonnes are in kilograms, you have mixed up the names :$ Either way the difference is small and it comes back to the same figures. Just remember if you ever increase your weight you will need to get re-weighed and then re-calculate accordingly. Finally I would carry a print out of the Conti booklet and your weighbridge certificate in case you are ever challenged on your tyre pressures. I know it's very unlikely but you never know! Keith. Link to comment Share on other sites More sharing options...
steveandlisa Posted September 7, 2016 Author Share Posted September 7, 2016 Hi Keith, Thanx for the quick response, regards the weighbridge units the guy said these were the new tonne units which ever that meant? :-S Thanks again Steve Link to comment Share on other sites More sharing options...
Keithl Posted September 7, 2016 Share Posted September 7, 2016 steveandlisa - 2016-09-07 5:00 PM Hi Keith, Thanx for the quick response, regards the weighbridge units the guy said these were the new tonne units which ever that meant? :-S Thanks again Steve So they will be in thousands of kilograms. That makes your actual axle weights as 1,520 kg Front and 1,640 kg Rear. At these weights you could calculate the split between quoted weights and reduce slightly further, eg 1,520 kg is approx 1/3 between 1,490 and 1,590 so you could opt for 45 psi. Equally 1,640 kg is approx half way between 1,590 and 1,685 so you get 49 psi. Does that make sense? Keith. Edit to add: If you are any good with Excel try changing the weights and pressures in my chart attached to suit your tyre size.Tyre Pressures v Axle Load.xlsx Link to comment Share on other sites More sharing options...
aandy Posted September 7, 2016 Share Posted September 7, 2016 There seems to be a bit of confusion over the units used. From the figures Steve gives I suspect the weighbridge gives the weight in imperial units and the operator has converted it to metric. 1.52 tons is 1.54 tonnes, and 1.64 tons 1.66 tonnes. That said, 20kg per axle is neither here nor there. Andy Link to comment Share on other sites More sharing options...
Keithl Posted September 7, 2016 Share Posted September 7, 2016 aandy - 2016-09-07 8:35 PM There seems to be a bit of confusion over the units used. From the figures Steve gives I suspect the weighbridge gives the weight in imperial units and the operator has converted it to metric. 1.52 tons is 1.54 tonnes, and 1.64 tons 1.66 tonnes. That said, 20kg per axle is neither here nor there. Andy Andy, I asked exactly the same question and Steve replied... steveandlisa - 2016-09-07 5:00 PM ... regards the weighbridge units the guy said these were the new tonne units... Which surely means multiples of a thousand kilograms? But as you finish, only makes a very small difference to calculated pressure. And is any pressure gauge really that accurate? Keith Link to comment Share on other sites More sharing options...
colin Posted September 7, 2016 Share Posted September 7, 2016 My experience of using Conti recommended pressures would lead me to suggest you run them a bit higher, say 3.5 and 3.75, this may make the suspension a bit more 'stable' and if you happen to load more or in different position you will be covered. Link to comment Share on other sites More sharing options...
steveandlisa Posted September 7, 2016 Author Share Posted September 7, 2016 I`m getting really confused with this tyre pressure issue! I`ve put the m/home on a weighbridge as recommended and given the figures, Keith you agree with my calculations more or less, now I read Colin suggests I run them a bit higher. Please, please can someone agree on a reliable figure :'( Regards Steve Link to comment Share on other sites More sharing options...
Keithl Posted September 7, 2016 Share Posted September 7, 2016 Steve, As has been said in reply to your earlier posts on tyre pressures there is only really one person who is qualified to provide you with accurate tyre pressures and that is the manufacturer of YOUR tyres. Your next step will have to be contacting that particular manufacturer and ask them the question after giving them your weighbridge figures. Anything else is purely guesswork from us 'Internet amateurs'. Keith. Link to comment Share on other sites More sharing options...
steveandlisa Posted September 7, 2016 Author Share Posted September 7, 2016 Hello Keith, Amateurs I think not, I respect and take notice from your wisdom one and all ;-) Salutations Steve Link to comment Share on other sites More sharing options...
colin Posted September 7, 2016 Share Posted September 7, 2016 steveandlisa - 2016-09-07 9:39 PM I`m getting really confused with this tyre pressure issue! I`ve put the m/home on a weighbridge as recommended and given the figures, Keith you agree with my calculations more or less, now I read Colin suggests I run them a bit higher. Please, please can someone agree on a reliable figure :'( Regards Steve I'm sorry if I've muddied the issue, but the pressures you have quoted are if the axles are only ever loaded to that weight as a maximum, if you are convinced that you will never exceed those figures that's fine, but a bit extra will not harm the tyres and will allow you to put extra load in if you want to without having to put extra pressure in. also I find the conti figures give too soft a ride for my liking, but don't take my word for it, I would suggest you run at the pressures conti suggest, then run at .25bar higher and see what you think, you will not harm the tyres. in case you think this sounds strange advice I would point you to the recommended pressures on a car, mine have two, the lower figure is for four people in the car, I rarely carry anyone else in my car, yet the manufacturer gives a figure that caters for over 200kg of load more as a minimum. Link to comment Share on other sites More sharing options...
Agaric Posted September 9, 2016 Share Posted September 9, 2016 Those pressures seem wrong to me looking at a Continental tyre chart. Rear pressures with the the same weight as the front are always quite a bit higher. My chart comes out at 3.25F and 4.25R, there are two lines on the chart one for front and one for the rear. On my chart there is also figures for different rims 5J which have a lower load, 6J and 7J and CP Link to comment Share on other sites More sharing options...
colin Posted September 9, 2016 Share Posted September 9, 2016 Agaric - 2016-09-09 11:14 AM Those pressures seem wrong to me looking at a Continental tyre chart. Rear pressures with the the same weight as the front are always quite a bit higher. My chart comes out at 3.25F and 4.25R, there are two lines on the chart one for front and one for the rear. On my chart there is also figures for different rims 5J which have a lower load, 6J and 7J and CP Viewing the chart on a small screen as i'm doing at present is a PITA, but I think you are looking at the CP tyres. BTW just to muddy the waters just a bit more, the vehicle manufacturers recommendation for that type of tyre on that chassis are 4.1/4.5bar obviously based on the max axle loads. I have been throu a similar quandary to OP, the vehicle manufacturers recommended pressures on my maxi van are 'bone jarring' (based on 2.4t) the conti figure for my axle loads I found too soft for my liking so I now run on a figure inbetween. Link to comment Share on other sites More sharing options...
Agaric Posted September 9, 2016 Share Posted September 9, 2016 colin - 2016-09-09 11:57 AM Agaric - 2016-09-09 11:14 AM Those pressures seem wrong to me looking at a Continental tyre chart. Rear pressures with the the same weight as the front are always quite a bit higher. My chart comes out at 3.25F and 4.25R, there are two lines on the chart one for front and one for the rear. On my chart there is also figures for different rims 5J which have a lower load, 6J and 7J and CP Viewing the chart on a small screen as i'm doing at present is a PITA, but I think you are looking at the CP tyres. BTW just to muddy the waters just a bit more, the vehicle manufacturers recommendation for that type of tyre on that chassis are 4.1/4.5bar obviously based on the max axle loads. I have been throu a similar quandary to OP, the vehicle manufacturers recommended pressures on my maxi van are 'bone jarring' (based on 2.4t) the conti figure for my axle loads I found too soft for my liking so I now run on a figure inbetween. My figures are from page 73 of the 2013/14 tech sheet, I have just downloaded the current one and the figures are different, so I stand corrected. On original sheet the CP figures and the 6J/7J figures are the same, go figure. Link to comment Share on other sites More sharing options...
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