As said it depends on the tyre's construction and MPTLM (maximum loaded weight) of the caravan.
Years ago some caravans around 900kgs were fitted with ordinary car tyres.
In my opinion the tyres on your caravan should have a load index of at least 84 or more (maximum weight per tyre of 500kgs). This will give you a reasonable safety factor.
Need to know the actual tyre size, max pressure and load index to give you the correct pressure.
According to my workings out , 965lbs x 2 tyres = 1930lbs max load for the axle , converted to Kgs it comes to 875kgs , so if your loading your caravan to 900kgs your actually going over the tyres rating .
Not sure its done on new caravans, but old ones were allowed "bonus" loading, theory was they would never get near max speed (113mph) so a little extra load is OK.
Given what's said I'm wondering how old these tyres are?
It is true that in the 'old days' 10% bonus load was allowed taking the actual load over the stated maximum load of the tyre by 10%.
Until this year when Swift broke ranks they still used this bonus but only up too the maximum stated on the tyre.
The tyre manufactures themselves have for some time stated that for caravan use, the load should be no more than 10% 'less' than stated on the tyre. this then adding to what was the 'speed bonus' gives a total of 20% BUT in the other direction.
You then want a pair of tyres that can carry a minimum of 1100kg between them, your van then would suit 155x13C 6ply, (1200kg) and at 900kg the pressure will be 42psi
Caravan tyres should be renewed every 5 to 7 years regardless of apparent condition. You can check the age by the reference number at the end of the DOT code. If the last 4 numbers are 0604 it means the tyres were manufactured in week 6 of 2004. If your last 4 numbers cannot be identified as since 0100 they are over 7 years old. If this is the case I'd definitely change them.
Gary is correct that around 1990 manufacturers claimed a bonus on caravan tyres of 10%. That was in the days when 50m.p.h. was the limit for towing.
Nowadays they do mostly abide by the 10% safety factor (but regularly deduct the noseweight from the MPTLM before doing the sums). The 10% safety factor is not a legal requirement but is strongly recommended by the tyre manufacturers association and this is endorsed by the Caravan Club.
If you don't accept this recommendation I advise you not to load your caravan above 875kgs and also ensure that neither wheel is overloaded (max. of 437.5kgs) otherwise you'll be breaking the law as well as risking tyre failure.
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Topic: tyre pressure
