Determining the perfect tyre pressure for your mountain bike is difficult - because there is no set rule. There are so many contributing factors that finding the magic number might take some trial and error.
Here's some information that will help decipher the tyre pressure mystery, and help you to find your own PSI perfection.
Before we go anywhere: jargon busting
The unit measurement for pressure, in this case, is PSI, which stands for Pounds per Square Inch. The tool required is an air pump - usually a solid track pump at home, and a smaller trail pump for when you're out and mobile.
You’ll pump the air in via the valve – and there are two main types of valve: Presta and Schrader - check out this piece to help you work out which style you have.
Having removed the little black hat that is the dust cap, unscrew the valve (if it’s Presta) and attach the pump directly on top, then start pumping.
Each air pump comes with a gauge to allow you to measure how much pressure is in the tyre. Most tyres come with inner tubes which are essentially liners that retain the pumped air, though some riders use tubeless tyres where the inner tube is replaced by a liquid sealant that rolls within the tyre whilst riding. This eliminates a lot of puncture problems where the sealant will immediately repair the puncture without the tyre going flat.
Time to get under pressure
So now we know the terminology, the tools and the components, let's look at working out what pressure is good for you. There are a number of variables to consider when inflating/deflating your tyres:
- Rider Weight: The heavier you are, the higher the pressure your tyres needs to be to cater for the weight of you and your bike. Remember that the two of you combined put pressure on the tyres against the surface – so the heavier you are, the more pressure you apply, whilst lighter riders produce less pressure so should opt for a lower PSI.
- Terrain: You have to consider the terrain you're riding on. Rocky loose terrain will benefit from a lower tyre pressure as it will give the feeling of a smoother ride by the tyre deforming itself over rocks and uneven ground. Better traction between the tyre and ground is derived from the increased surface area of the softer tyre compressing to the terrain. Running softer tyres offers a more comfortable ride also, especially on terrain that's loose and uneven.
- Riding Style: Whether you like to hurl yourself down technical rock sections, or take the more cautious and smoother line options, your tyre pressure will affect your performance. For more aggressive riding styles, you can benefit from a harder tyre to roll over anything that comes in your path. For the thinkers out there, like me, where you like to assess and line check, softer tyres will help with better traction.
- Weather Conditions: Even the weather will affect the performance of your tyres. A muddy trail will allow you to pump up your tyres a little higher so you can use the mud for traction whilst being able to roll a lot of the obstacles that you face. On dusty dry days where the ground is loose, it's better to let some of the air out and use your tyres for getting that additional grip with the ground.
- Put in context: All of these variables can seem quite daunting. To put it into context, I'm 53Kg and my bike weighs 12.7Kg. My wheels are 27.5" and 2.4" in width, and I run both front and back tyres at approximately 24 - 27 PSI. My riding style isn't super aggressive, and I like to pick the smoother lines where possible.
Find your own perfection
As you see, there are many variables to consider when finding the best mountain bike tyre pressure for you, and it may take some time adjusting to find a comfortable ride. Tyre pressure does play a key part in bike performance so it's important to get familiar with it.
A majority of riders will hover around the 30 PSI level in both front and back tyres, but it's not uncommon to run different pressures in each tyre or to adjust the pressure level for changes in trail conditions. The best way to work out what works for you is to experiment – perhaps start with 35PSI, and let a little air out if you feel you’re rolling too hard. As long as you’re carrying a hand pump, you can increase and decrease the pressure as much as you like until you find the sweet spot.
Good luck finding your magic number!
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