Visiting Caravan Tire Demands and Loading Weights

The unfortunate truth is caravan tires are not often at the top of our priorities when we are loading up for a holiday. Even if pressures are checked, do you really know what they should be? Your car tyres are easy in this respect as there is usually a sticker somewhere on the car telling you what the correct pressures are, or you can refer to the manual.

Your caravan is not that easy because the weight can vary so much depending upon how much it is carrying. Two people popping off for a long weekend away are likely to be carrying far less than a family of four taking the same caravan for two weeks in France. The tyre pressures will need to be different in both cases, but how do you find out what they should be?

Tyre Sidewall Codes

Here is a typical tyre size code:

P205/65 R16 80 V

The '80' is the Load Index for the tyre. This will typically range from 60 to 130 and represent a maximum load of between 250 and 1900kg for that tyre.

Obviously the first thing to be sure of is that the tires are capable of carrying the total weight of your caravan.

There should also be markings on the tyre giving the maximum pressure it can be inflated to.

Calculating Total Weight of Your Caravan

It can come as quite a shock the first time you work out the true weight of the thing you are happily towing around behind you because it will probably be much higher than you realise.

The VIN plate will contain various details relating to weight. The one you need for this exercise will probably be marked as the MTPLM which stands for Maximum Technically Permissable Laden Mass, or more simply, the total weight of the caravan and all of the stuff you packed into it before you set off.

There are two ways to find out what this is. The most accurate and quickest way is to load up and take the thing to a weigh bridge. The other way is to get a set of those scales we use to weigh our luggage before getting on a plane these days and weigh every single item you carry aboard the caravan. Add the total figure to the basic unladen weight of the caravan which should also be recorded on the VIN plate.

However you work it out the figure should be no more than the MTPLM. It's worth noting here that the manufacturer of your towing vehicle will usually state that the figure you have just worked out should be no more than 85% of the kerb weight of the towing vehicle.

There are a couple of things that can catch you out if you are getting close to that MTPLM. If you weigh each item rather than use a weigh bridge, do not forget that anything you have attached to or built into the caravan, like an awning attached permanently to side or perhaps a television and associated satellite equipment must also be added to the factory-fresh weight recorded on the VIN plate.

Secondly, if the cupboards are full of crockery or the fridge is full of food these also need to be accounted for. It's amazing how things like this add up, so it's probably better to take the van to a weigh bridge to get an accurate check.

Once you know what the weight really is, divide it by the number of wheels on the caravan and confirm from the above table that this is within the allowable weight for the tyres.

Finding the Correct Tyre Pressure

Once you have sorted out the total weight of your caravan, have confirmed that it is within the safe limit of the tyres and have found the maximum permitted pressure from the markings on the tyre, usually near the wheel rim, we can work out the correct tyre pressure.

Take the figure for the max. pressure and divide it by the max. weight from the above table, then multiply by the actual load on each tyre. This will give the correct pressure.

For example, if the tire is marked with, say, 64psi for the max. pressure and the max. weight is 950kg, with the actual weight on each tyre worked out from the table above at 450kg, use your calculator to do the following:

64 divided by 950, then multiplied by 450

and you should end up with 30 as the recommended tyre pressure. Substitute your own values to get your correct tyre pressure.

Confidence Check

A good way to check this is to inflate the cold tyres to the pressure you have just worked out and take the caravan for a drive. You need to cover about 50 miles, preferably on a motorway, to ensure they reach their working temperature. Pull off the motorway and park up as soon as you can. Check the pressures while the tyres are hot.

The hot pressure should be around 4psi more than they were when cold.

If there is more than 4psi difference the cold pressure was too low.

If there is less than 4psi difference then the cold pressure was too high.

Make the necessary changes and try again.

This may seem a bit long-winded, but it's much better than a blow out!

To discover many more hints, tips and guides to help you make your holiday safe and stress-free visit Mike's web site at An illustrated version of this and many other useful and informative articles appear on the web site, including a comprehensive table of tire load indexes and their corresponding weights.

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