It is a question we get asked here all the time at CarAdvice. If you are going off road, why do you need to lower your tyre pressures?
Q: I’m starting to get into off-roading and I’ve been told to lower my tyre pressure for better traction, but I’m not sure at what stage to do this and what do I lower them to?
A: To get the best answer we spoke with Simon Christie, a seasoned off-road expert from 4WD-TV.
“There are three main reasons why we lower tyre pressures”, says Simon.
“First, it improves the comfort of the vehicle when you are traveling across rough terrain. Whether you are driving on corrugations or rocky, steep hills, lowering the tyre pressure actually enhances how the suspension works and greatly improves the comfort of the occupants of the vehicle.”
“It also improves the traction of the vehicle, as lower pressure greatly increases the footprint of the tyre which means there's more rubber on the ground, resulting in more traction.”
“Last but not least, the softer impact and greater traction help protect the terrain under the car.”
So now we know why, let’s talk about the mechanics of lowering your tyre pressure. What should we set them to?
“It really depends on the terrain”, notes Simon. “If you are just hitting some gravel roads and are travelling long distances at speed, anywhere from 25 to 28 PSI will be perfect.”
“When we get down to some slower crawling, we can lower the pressure a little bit more. Some mud, some rocks, and general 4WD terrain, 20 to 25PSI is the rule of thumb.”
“For sand, you can lower the tyres even further anywhere from 15 up to 20 will give you far more traction. Sand can be quite a variable because you've got wet, hard packed sand brought through dry, powdery sand like you've gone across the Simpson Desert.”
Lowering your pressure will not damage the tyres, providing you remember to re-inflate them before you start travelling on paved surfaces or at any speed again.
Some tyres are better equipped to handle off-road terrain than others, so your overall grip and traction levels will depend greatly on the tyre setup of your vehicle.
To lower your tyres, you can use a standard tyre deflator that is available at any auto-parts store. Pumps to re-inflate the tyres can be bought at most 4WD specialist stores.
Simon notes, “inflators can be quite inexpensive all the way up to quite a few hundred dollars for a high quality one. It's all about the time it takes to re-inflate your tyres. A cheap one might take a bit of time but the more expensive ones, more reliable and will pump it up very quickly.”
So when do we re-inflate?
“As soon as you're on the dirt, let those tyres down. As soon as you're off the dirt, pump them back up.”
Thank you Jack for your question, and thanks to Simon for helping with his expert knowledge.
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