Tyre pressures yet again

[William_374566083]

Just had van serviced and two new tyres fitted. spec on new tyres are the same as originals fitted except for max pressure stated on new tyres is now 51psi instead of 44psi stated on old ones. Manufacture recommended 39psi for originals, fitter calculated 42psi for replacements but using formula to calculate as given in previous threads, works out to 49psi....which is correct.

 

[gary]

To give anything like an answer, it would be more useful to state the exact tyre size and load index number of the tyre fitted and in this case the make could also be useful, Matador?

As for the 'calculation' it's not accurate and always gives a higher than required pressure.

 

[William_374566083]

Thanks Gary.....tyres made by Kleiber, size 165/70R13/79T. Max weight of van is 850kg....hope this helps....thanks.

 

[gary]

Well regardless of the maximum pressure written on the tyre, the maximum load for those tyres,per pair, is 874kg at 36psi with a strong recommendation that 790kg at 32psi is taken as the maximum for caravan use.

I'd then say their not up to the job.

The fact it's what was fitted originally is probably down to the outmoded attitude of applying a 'speed bonus load' of 10% above the tyres maximum load if the speed was restricted to less than the tyres maximum.

Current thinking is to ignore the speed bonus and take 10% OFF the tyres maximum load, as per the tyre industries advice in the old and current Tyresafe charts.

Link to older Tyresafe pressure chart below; (it does enlarge on screen, or print it?)

http://www.arcsystems.biz/Pictures/tp.jpg

 

[George_374396015]

HI. The pressure stated on the tyre is for U.S. regulations for initial inflation. Go by your caravan handbook and use the presures there which may be higher than that embossed on the sidewall. to inflate to the 44 psi when your own caravan manufactured states something else is both asking for trouble and probably invalidates insurances etc. Go by the book.

geo

 

[William_374566083]

Hi everybody....thanks for all your advice.....will probably stick to manufactures recommended psi.....thanks again.