Trailer and Caravan Tyre Pressure Calculator

from Western Towing –

Having the correct tyres and tyre pressures on your caravan or trailer is one of the most important safety aspects of towing. We all know that the tyres should be in good condition, just like the towing vehicle, but getting the tyre pressures right is not so easy.

Below we’ve put together a calculator to aid ascertaining the ideal tyre pressures for your caravan or trailer.

First of all, some understanding of the tyre marking is required, if you are not familiar with them, here’s a summary of the meaning of a tyres markings.

Trailer and Caravan Tyre wall markings
  1. This is the tread Width in millimeters, in this case, 145mm wide.
  2. This is the Aspect Ratio of the tyre wall over the width of the tread. In this example, the tyre wall height is 80% of the width of the tread
  3. The next letter is the Construction, in this case, “R” stands for Radial
  4. The following number is the rim diameter (in inches), in the above example the tyre has a is 13 inch diameter.
  5. The last number is the load rating of the tyre, this is required for the calculation, it can range from 60 to 130 which equates to a maximum load per tyre of between 250 Kgs to 1900 Kgs. Your tyres should be rated for at least 90% of the MTPLM (Maximum Technically Permissible Laden Mass) of your caravan or trailer.
  6. The last letter is the speed rating for the tyre.

The other bit of information we need to find from the tyre is the Maximum Tyre Inflation Pressure. This is usually located on the side wall below the tyre data in smaller text. It will say something like ‘Max Load 387kg At 42psi Cold’ it might have the pressure given in Bar. Bar can be converted to psi by using the converter below.

Bar to pci converter


Finally, you will need to know the MTPLM of your caravan or trailer them the correct tyre pressures can be calculated.

The information gathered can now be entered into the calculator below and the answer will be given in PSI and BAR.

The Ideal Caravan & Trailer Tyre Pressure Calculator

* If you intend to continually use a trailer below its stated Maximum Gross Weight then you could enter the Actual Gross Weight instead but you must remember to increase the tyre pressures to the correct pressure when the trailer is loaded to its maximum.

** It’s worth bearing in mind that as a rule of thumb, the inflation pressure of a hot tyre is usually about 4 psi higher than when cold. This is based on the fact that for every 10℉ temp change the tyre pressure changes by 1 psi (or for every 1℃ temp change the tyre pressure changes by approximately 0.19 psi).

The above information and calculator is meant for guidance only. If you have any questions or are unsure what your tyre pressures should be please contact us for guidance. If you have any doubts about the suitability or the condition of your trailer or caravan’s tyres please consult a caravan or trailer tyre specialist. Remember any tyre defects that you can be prosecuted for on your towing vehicle, also apply to your caravan or trailer tyres when towing it on public roads.

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