DIRT GARAGE: UNDER (TYRE) PRESSURE
The only part of your bike that should be touching the ground (most of the time) are your tyres. They are the glue that hold you and your ride to the dirt, gravel, sand, grass or whatever it is you are ripping on, so it is a really good idea to have them performing as best you can for the specific type of riding you are doing.
There is a lot variation when you talk to people about proper tyre pressures. What is the best for wet conditions, what hard pack pressures should be and what works best for Jim, Dave and Susan. A lot of people will just throw their hands up and slide 12psi in the front and rear and leave it at that. If that works for you then awesome! And to be honest, it’s not a horrible setting either and sits in between our general rule settings.
But there is no ‘right’ answer all across the board because many different factors need to be taken into account. For example...what kind of compound is your tyre? Is it a hard terrain or soft terrain rubber. How skilled are you and how fast do you ride? What kind of bike do you have and what is the terrain type you are riding on? All these different variations and more could determine what your tyre pressures should be for any given situation. Without getting to complicated and having an exact psi for every combination, we will instead give you good recommendations and a psi range that is a starting point that you can work off and adjust to your liking.
Remember this important point though - once you let the air out on the trail, there is a good chance you won’t be able to add any back in until you get back to the pits. So it’s important to think ahead before you shed (air).
10psi - 13psi
As a general rule and if you can’t factor anything else in, keeping between 10-13psi should keep you in good stead on the trail. It has kept us in pretty good form for the last 30 years so it will do you proud. 10-11psi for soft and slippery conditions and 12-13psi for the harder tracks, especially ones with rocks etc.
But now let’s get a bit more specific and talk about tyres and what pressures do to the tyre and how it performs.
Low Pressure
A lower psi (8-11psi) in a tyre will allow the tyre to mould over objects and flatten out on the ground, allowing more of a contact patch to connect with the ground and effectively give better traction. Especially in situations where it is muddy, slippery and soft. Sand is also a good example where lower pressures will give you better grip and drive. But lower pressures make you prone to more flat tyres and valve rotation as the pressure is not there to hold the tyre from slipping on the rim.
High Pressure
Higher psi (11-15psi) tyres will hold their shape better and not mould around objects you are riding over and are better for harder terrain where you are not always searching for grip. They are also better at keeping flat tyres away and are better at dealing with valve stem rotation. The drawback is that the bike can feel like it deflects off things easier and you have less of a ‘feel’ for the terrain.
But let’s also be honest here - pretty much no one will actually notice a 2 psi change so don’t get too hung up about not being able to recognise different pressures. Guarantee you can notice a flat tyre so always keep a feeling out for that one. But what about ability and how does that affect psi choice? Well, I’m glad you asked!
Beginner Riders
You can run lower pressures. Think 8-10psi if you’re just starting out. However, if you weigh in at 100kg and just starting out you should put more air in - obviously. But beginners are not usually hitting logs, riding over rocks and putting real stress on the tyres. So the chances of getting flats are relatively slim. Not impossible - just slim.
Intermediate Riders
So you have passed the beginner stages of riding and you are out there on trail rides and trying more things you see other people do on a dirt bike. Up those pressures to around 10-12psi team to combat with the amount of stress you are putting through those tyres. Higher speeds means you hit things harder. One great way to deal with pinch flats is with higher pressures. A pinch flat is where the tyre folds or rolls over and pinches the tube inside. Not cool and it makes it hard to get back without your tyre coming off the rim.
Expert Riders
Expert riders should have their shit together already but if you have only just reached this self appointed stage here is some info for you. The good thing about being an expert rider is that you can ride to the conditions. If it's wet, an expert can use good throttle control and not worry too much about tyre pressures. If it’s rocky and looks puncture perfect then an expert rider should be able to ‘ride light’ and help prevent that. But as a general rule, run the higher pressures to help stop pinch flats with the higher speeds and harder terrain.
Adventure Bikes
For Adventure Bikes - it’s a whole new world out there. The bikes are much bigger and the terrain is usually easier - depending on how gnarly you think you are. So we hit up Adventure Riding expert and KTM ambassador Chris Birch to get his tips on tyre pressures for the ‘Big Birds’ of the off-road world. And here is what he had to say.
“Tyre pressures are tricky in adventure riding. It’s about getting that perfect balance between traction and protection. Adventure bikes are prone to pinch flats and rim damage when running lower pressures, but you need to be able to drop the tyre pressure when the going gets tough. So it’s a good idea to carry a pump with you for when you make it back onto the road. An ideal pressure can range anywhere from 12 psi to 35 psi, depending on the tyre compound and your riding ability. Starting at around the mid 20s is a good compromise, and you can go up or down from there depending on what you are needing - traction or protection.
“I usually get the riders who come on my schools to think more about how it feels, as apposed to what the actual pressure is reading on the gauge and that seems to work well.”
Conclusion
It also helps to try and run the correct tyres for the correct terrain. Ripping a mud tyre through the rocky South Island will not give you very good results and likely ruin the tyre pretty quick. Conversely, riding with a hard pack type tyre during a mid-winter mudder wont have you smiling for very long. So just something else to think about. Now here is a quick checklist to take a screenshot of - for the average rider.
10-11psi for softer conditions and lower riding ability
12-13psi for harder conditions and higher riding ability
Lower Pressure:
are more prone to flat tyres
give you more ‘feel’ to the ground
allow the tyre to mound around logs, rocks, etc for better traction
Higher Pressures:
are better at stopping flats
give you less ‘feel’ to the ground
deflect off logs,rocks, etc which can make the bike twitchy at speed
Don’t be afraid to play with your pressures if you have the ability to. And by that, we mean to make sure you can pump them back up again if it goes all wrong. Have fun out there and learn more about your bike at the same time.
If you have any more questions on Tyre Pressures please feel free to contact chris@thedirt.co.nz and I will get back to you as soon as I can. Happy riding!