Having no handbook or much documentation for our first van (20 y/o and just trying it out for the winter as we use the tent in summer) we are stuck to find what pressure the tyres on the van should be inflated to?!
Adria Optima 2 Birth : 650kg unladen and max 850 kg laden with Michelin 155 R13 (78T) tyres.
Run them at 38psi. You can't go much more that that anyway on that size tyre. At max weight those tyres are right on the limit, ie 850kg combined load index. so don't overload caravan.
I filled it in in my caravan-trailer tyrepressure-calculator and it gives 40psi/2.8 bar.
In this calculator I use my own formula wich comes to higher pressures then that of the tire-makers, and I add 10% to the 850kg for reserve .
Because the load it calculates for is 10% higher then the maximum load of the tires, a lower speed is adviced of 80km/50m/h.
If you want to use my spreadsheet click this link
Looking at the link supplied by Michael above, I read it that these tyres should only be inflated to 32psi maximum. Personally I feel these tyres are too close to their limit for the OP's van.
------------- The Chinster.
Some people are just all show. I don’t mind that if the show is worth watching but ….
The pressures they give in the list Michael gives link to, is what they call the reference-pressure, wich is not the maximum pressure of the tyre.
using refencepressure from that list for your tyre in my spreadsheet it even gives 34psi/2,4bar as advice. with all the reserves stil for little over- and mis-loading.
Saw some mistakes in the list, 2,4 bar is converted to 36 psi wich is 2,48 so mostly rounded to 2,5 bar.
Reference-pressure ( Further Pr) is the pressure the tyre-makers use to calculate the maximum load capacity up to the maximum speed of the tyre or if lower 160km /99m/h.
Difference between Pr and Pmax is used for higher speed and camber angle above 2 degrees( alighnment), for normal car tires and Extraload/XL/reinforced.
From C-load/6ply and up this Pr is given on the sidewall somewhat like this "maximum load xxxx kg AT yyy kPa " or LBS and PSI used.
This means that for those tires you are allowed to go higher then Pr. and this is used for more load at higher pressure, there are lists for that.
For Standard load and XL only the maximum pressure is given but Pr is standard 250kPa/2,5bar/36psi in Europe for standardload/normal car tyre. Smaller tires though use down to 2,1 bar and rule also is for 80% hight/width 2,4 bar/35 psi.
Though it is not supported by the tyre-maker, higher pressure gives extra load to carry, and in the past this was used for 10% extra load with 10% extra pressure for caravans. Gave much tyre damage because caravans are often overloaded at least at one wheel.
That is why I advice to use tyres with 10% to 25% reserve load to the Maximum permissable weigt of the caravan.
But if you use these extra's carefully, and take enaugh reserve in load, you can put higher pressure then Pr even for C-load (Pr50to55psi) and up and still is supported by the tyre-makers for lower speed.
In my spreadsheet I use 2,5 bar/36psi for all normal tires to make it easy, but if you use the pressures from the list for your tire the adviced pressure even gets lower.
Mind that American tires use different Pr and the system is not that flexible as in Europe. Pr normal car tyre/P-tire/standard load always 35psi, wich will give higher maximum load to a small tyre for wich in Europe 32psi is used. So if you find these strange differences between the same sises , when searching the market, it is probably because they gave American and European tyres/tires.
If one wants to be pedantic one could say that 78T means the max load rating is at 118mph & as the caravan will doing only half that then there is enough margin. Provided just normal gear is carried in the op's caravan the max weight 850kg will not be reached so the tyres are ok & they are manufacturer spec for this caravan.
I just use my judgement on this, in the absence of any informaton. My caravan is around 700kg all up, I have same size tyres as op & as max pressure allowed as indicated on tyre sidewall is 44psi, I then arrive at 38psi as a sensible compromise which works fine on my caravan & will also be fine on the op's caravan.
The correct pressure for 850kg is 32psi, it's also the max load/pressure for this type and size tyre.
If thinking of changing, I'd suggest the 155R13 82x or 155/80R13 83x reinforced tyres, these both require 34psi at 850kg and well within their working limits
PS, Tentz, as your max pressure is 44psi, I'm wondering if you have the above reinforced tyres?
In this case, 38psi is good for 922kg and only 30psi required for 760kg! assumming tyres max stated load is 950kg or 974kg
Having no handbook or much documentation for our first van (20 y/o and just trying it out for the winter as we use the tent in summer) we are stuck to find what pressure the tyres on the van should be inflated to?!
Adria Optima 2 Birth : 650kg unladen and max 850 kg laden with Michelin 155 R13 (78T) tyres.
Any help would be most appreciated,thankyou.
Further info:Tyres state max load 1015 and max pressure of 56 psi
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Topic: Tyre Pressure.
