Looking forward to getting on the road and making the most out of your caravan! Tyre pressure is an important factor on these trips as it can affect your safety, fuel economy, tyre wear and tyre damage. The tyres on the Caravan itself are often overlooked and not checked regularly.
Now if you have a new caravan on the compliance plate it should
have the cold tyre pressure so this is a good starting point. But a lot of people
have older caravans and the tyres have been changed and also things have been
added to the van that will increase the weight.
First thing to do is to look at your tyres on your caravan and the code of the wall of the tyre.
It will look something like this: 205 / 65 R 15 94 H
205 = Tread Width of the tyre in mm so 205mm wide.
65 = Tyre wall height so it is 65% of the width of the tread.
R = Tyre construction so in this case it is Radial
15 = Rim diameter so 15”
94 = The load rating see table below
H = Speed rating of the tyre
Now what we mainly want to look at is the Load Rating of the tyre. The load rating table can be from 60kgs to 1900kgs load per tyre.
From the table above you can see that 94 = 670kgs maximum load for this tyre. We never want to go over 90% of this weight. So, for a single axel van you will have 670kgs x 2 Tyres so it would be 1340kgs but you do not want to go above 90% of this so the true maximum load for these two tyres is 1251kgs.
The next thing we need is the maximum pressure of the tyres this should be marked on the tyre somewhere. “Maximum Pressure 60PSI”
We will also need the ATM (Aggregate Trailer Mass) of your
caravan this should be on the caravan. This is the total weight of the caravan
including cargo (payload). However extra things may have been added over time
or who knows what has happened in the life of the caravan so best bet is to
load it up and if you are close to a weigh bridge go and weigh the caravan to
give you an accurate reading.
Now for the maths part! 1200Kgs ATM on single axel caravan.
Maximum Pressure / Maximum load weight from table = A1
A1 x (ATM / per Tyre so single axel it will be half ATM or
quarter for twin axel) = Tyre Pressure
So from the numbers above we will do the example for a single axel caravan.
60 / 670 = 0.08955
.08955 x (1200 (ATM) / 2 (Single Axel, Would be 4 for tandem) ) = 53.7PSI
So the correct tyre pressure should be 54PSI.
Now that pressure is when the tyre is warm so the cold pressure should be around 4PSI less. This is a rough rule of thumb. If you inflate your tyres to 50PSI when they are cold you should be sitting around 54PSI after 30mins or so of highway driving. Also remember as you travel around Australia the temperature will change a lot so you will need to take this into account.
Now this is for general road/highway driving and if you are driving off the main roads we will cover that in another post.
We recommend a Tyre Pressure monitoring system to keep an eye on your pressures and will warn you if anything goes wrong. The best thing is the pick up the temperatures as well so will pick up a bearing or other issues.
See our range of TPMS Systems here.