Caravan tyre problem

[paddy1]

Hi all i have a new set off alloys and tyres 175/14 and i want to fit them to my Bailey caravan,the problem is the tyres removed from my bailey are 185/14 the load index is correct 0n the alloy wheel tyres will it make a difference please being 10m smaller thanks mark

 

[ProfJohnL]

I am not a tyre expert, but if the load index does not match the originals, then you may not be legal. The load index should match or exceed the caravan manufacture specification.

 

[gary]

As John says the load they can carry is most important, a 175 is unlikely to carry quite as much as a 185. However; they may be of a different construction so this will also affect their capabilities

You can check exactly what type tyres you have, their load index and their rolling diameter to see if their suitable here;

http://www.tyresafe.org/data/files/caravan 08.pdf

 

[Lutz]

The tyre width, whether it be a 175 or a 185, does not have a bearing on its load carrying capacity. What is important is that the load index which follows details of the tyre size is adequate. The load index is usually a number between about 80 and 105.

 

[gary]

I beg your pardon Lutz but tyre width among it's other dimensions, including wall thickness, is directly related to it's load carrying capacity and at what pressure

Tyres of a certain construction have a maximum air pressure throughout that range, add to that, the volume or air required to support a given load is a constant.

Therefore the pressure required to get the required volume of air into the smaller volume within a tyre will vary depending on the area contained within any given tyre.

So given a 6ply tyre with a maximum designed pressure of 54psi.

175 being smaller internally than 185 will carry somewhat less load than the 185 at the maximum pressure, or below the maximum 54psi, the 175 will carry the same load but at a slightly higher pressure than the 185.

All tyres of the same size are the same dimensions externally, any changes in construction that effect wall thickness will then change the available volume internally.

Therefore, the same two tyre sizes of the lighter 'car' tyre type with their thinner walls, will carry more load for a given pressure than the 6ply, but only of course up to their specific designed maximum pressure.

 

[Lutz]

Of course the pressure in a 175 and 185 will be different, but a reinforced 175 can have a higher load index than an unreinforced 185. What you are saying is only true if all other factors (construction, brand, type, etc.) remain equal.

 

[paddy1]

hi all thanks for you coments checked tyres 1709lbs per tyre and max pressure 65psi my caravan is a discovery 100 2006 which is light weight 1137kg thanks mark