Caravan Tyre Pressure Guide – How to Calculate the Correct Inflation PSI

Hi, I’m Chris, I run Horton Common along with my father Robert.

Before you set off with your caravan its best practice to examine the condition of your caravan tyres and their pressure. I’ve previously written a post on how long do caravan tyres last where I briefly reference tyre pressures. However, it’s an important topic in its own right, so it deserves its own post. I’ll be referencing a series of different websites and tools, so you can double-check how to calculate the correct pressure for your caravan tyres.

Now, please don’t interpret my use of the image below as a sufficient means to determine the correct tyre pressure for your caravan. Its purely to illustrate how visual clues can indicate when caravan tyres need to be checked.

Visual tyre pressure indications
You need to properly calculate the pressure of your tyre, however quite often the shape of the tyre can indicate if it’s not inflated to the correct pressure. Image: Continental Tyres

Caravan Tyre Safety Checks

When guests have turned up to our site with visibly under-inflated tyres I have been asked on several occasions what is the correct pressure for caravan tyres. Standard advice as with most things is to check the caravan manufacturers manual for tyre pressures. However, some guests have purchased second-hand caravans that didn’t come with a manual. But I have also had guests with new caravans where no manual appeared to be present. Some caravans may actually state tyre pressures somewhere on the van (typically the weight plate).

The video below from TyreSafe is a quick summary of the various checks (including tyre pressures) you should carry out before you set off:

This video from TyreSafe covers a range of checks for your caravan wheels and tyres including how to check tyre pressures.

Caravan Tyre Pressure Calculators

If you watched the video above from TyreSafe you will be aware that they have their own caravan tyre pressure calculator. So, if you want to quickly calculate what is the best inflation pressure for your caravans tyres, I would encourage you to jump over to TyreSafe (link opens in a new window).

TyreSafe Caravan Tyre Pressure Calculator
Caravan tyre pressure calculator on the TyreSafe website.

I’ve played about with the calculator and the thing I particularly like is it will inform you if the tyre load rating is actually even safe for your caravan. For instance, I put in a caravan with an MTPLM of 2,000kg, on 2 wheels/1 axle on a 145R13-74 tyre. Now, from the tyre specification (more details on that below) I knew this tyre was not suitable for a 2,000kg MTPLM single axle caravan. I’m also aware a caravan of that MTPLM on a single axle is not available. I just wanted an extreme example to test the tyre pressure calculator. The TyreSafe pressure calculator returned the following result:

TyreSafe caravan tyre pressure calculator false result
The TyreSafe calculator will also inform you if the tyres fitted to you’re caravan are rated for the caravans MTPLM, previously know as the caravans gross weight.

Now, most people will be happy with the link the caravan tyre pressure calculator over at TyreSafe and go on with their day. However, some people (probably you if you’re still reading) are interested in how that calculator works to produce a PSI inflation pressure. So below I’m going to go through an example caravan tyre pressure calculation. First, we need to find out the weight of your caravan.

Caravan Weight (MTPLM)

I’ve previously written a post (here) on how much caravans weigh and why it’s important. That post will tell you where on your caravan to find its MTPLM rating. Briefly, the MTPLM refers to the caravans Maximum Technical Permitted Laden Mass. Essentially its the maximum legal weight of the caravan including your possessions.

Caravan weight plate MTPLM
A typical example of a caravan weight plate – Image: outandaboutlive.co.uk

On the example caravan weight plate above we have the MTPLM of 1415kg. In this particular example, you will also notice it actually states the approved tyre size and pressure. You would, therefore, think all caravan weight plates contain the tyre pressure information. Logically this should be true, but it’s not. Therefore, we are going to use the 1415 kg MTPLM of this caravan to calculate its correct tyre pressure as if it wasn’t stated. We can then compare my calculation results to the manufactures weight plate and also the results from the TyreSafe tyre pressure calculator.

Swift Sprite Major 4SB
For reference, the caravan weight plate above belong to this single axel Swift Sprite Major 4SB – Image: Swift Group

Caravans Tyre Details

Now, we have the caravans MTPLM (1415 kg) before we can go through the tyre pressure calculation we need the details of the tyre. The weight plate above actually also gives us the tyre details of 185 R14C 102. But what does this actually mean and how do you read the tyre details on your own caravan?

Caravan Tyre Load Rating

Tyre load rating
The load rating of your caravan tyres is the number just before the speed rating letter – Image: Protyre.co.uk

For the caravan tyre details in our example, 102 is the load rating. We now need to turn this load rating figure into an actual weight figure, which can be done with a tyre load index table:

Caravan tyre load index table
TyreSafe also provide a load index table for caravan tyres – Image: TyreSafe.org

So in our example, we have a caravan tyre with a load rating of 102, which using the table above means the tyres have a capacity of 850kg. Remember, that’s per tyre on a single axle caravan, so that’s 1,700kg in total. The caravans MTLM weight is 1,415kg, so obviously 1,700kg more than covers it. The reason for this is that industry best practice, including advice from TyreSafe, is that you shouldn’t exceed 90% of the tyre’s capacity. So the 90% figure of 1,700kg is 1,530kg, much closer to the caravans MTLM of 1,415kg. So per tyre, the 90% tyre load figure is 765kg.

Caravan Tyre Maximum PSI

On the side of your caravan tyres sidewall, it will state (often in very small text) the maximum inflation PSI. For the tyres in our example (185 R14C 102) they have a maximum inflation pressure of 65 PSI. So just to summaries our example caravan tyre details before we look at the calculation, they are as follows:

  • Specification – 185 R14C 102
  • Tyre Load Rating – 102
  • Load Capacity – 850 kg (per tyre)
  • Load Capacity (90%) – 765 kg (per tyre)
  • Tyre Maximum Inflation – 65 PSI

Caravan Tyre Pressure Calculation

Previously, both Simon from CaravanChronicals and Dan at Meet the Trudgians have gone through the method of calculating caravan tyre pressures. So if you want to double-check my maths below, by all means, do so. The calculation is as follows:

Caravan tyre pressure calculation
This is the formula to calculate to caravan tyre pressures – Image: the-trudgians.com

Before we run the calculation lets summarise the figures we are using for our example caravan:

  • Max PSI = 65
  • Load Rating 90% (per tyre) = 765 kg
  • MTPLM = 1,415 kg
  • No of Tyres = 2

Therefore, the calculation proceeds as follows:

(65/765) x (1415/2) = 60 PSI

TyreSafe Calculator

So, I also entered the example caravans details into the TyreSafe calculator. I wanted to compare the manufacturers tyre pressure recommendation with TyreSafe and my own calculation.

TyreSafe caravan tyre pressure calculator
I put the example caravan details into the TyreSafe calculator.
TyreSafe caravan tyre pressure calculator example results
The TyreSafe calculator returned a result of 59 PSI (matching the manufacturer’s recommendation).

Caravan Tyre Pressure Results

So let’s summarise the results we have for our example caravan, from the manufacturer’s weight plate, the TyreSafe Calculator and the calculation above:

  • Caravan MTPLM Plate = 59 PSI
  • TyreSafe Calculator = 59 PSI
  • Our Example Calculation = 60 PSI

Obviously, our example calculation is slightly higher by 1 PSI. This will be caused by certain figures being rounded down or up.

NOTE: Now, as a general rule, the cold pressure of a tyre will increase by 4 PSI under warm conditions. The tyre pressures above are the recommended cold tyre inflation pressures, so please bear that in mind. As the maximum inflation PSI pressure of the tyre in our example is 65 PSI you do need to check the caravan tyres are not over-inflated in the summer months.

Caravan Tyre Pressures and Motor Movers

First and foremost it’s important to check and inflate your caravan tyres to the correct pressure for safety reasons. However, if you have a caravan motor mover fitted, caravan tyre pressures are important. Under-inflated caravan tyres may have issues receiving sufficient traction from the motor mover drive cylinder. Some caravan motor movers use spring tension engagement which is set to engage with the caravan tyre at the recommended pressure.

Caravan motor mover tyre pressure
The Powrtouch classic is the most common motor I see fitted to guests caravans which uses spring tension engagement.

Conclusions on Caravan Tyre Pressures

Caravan tyre safety with regards to pressures is often something many caravanners are not clear on. I often don’t think the information provided by caravan dealers on tyre pressures is not sufficient or accurate. If it was I wouldn’t have guests asking me for advice on what their tyre pressures should be. At your annual caravan service, the service centre should be checking your tyre pressures. However, its important you also understand what is the correct pressure for your caravan tyres.

Hopefully, the information above on how to calculate caravan tyre pressures was useful to you. And I also hope at some point to consider a visit to us here at Horton Common to use our fully serviced pitches. 🙂

Chris - Site Manager

Hi, I’m Chris, I along with my father Robert we operate and maintain Horton Common.

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