As the only part of the bike in contact with the ground, your MTB tyres have a major effect on your riding. They directly influence numerous factors such as grip, safety and even overcoming obstacles.
We will decode the different markings on the side of a tyre and the factors that determine what tyre pressure to choose.
THE MARKINGS ON THE SIDE OF A TYRE
Among the numbers you will find on an MTB tyre are:
1. The dimensions
There are two types of tyre dimension:
– Standard dimensions
– Historic size markings.
Standard dimensions meet European Tyre and Rim Technical Organisation (ETRTO) rules. This organisation aims to standardise manufacturers’ tyre diameters. They are given in millimetres:
Example: 50-559. The first number indicates the width and the second indicates the inner diameter.
In the case of historical sizes, values are given in inches.
Example: 26×1.95 (again, width than inner diameter)
2. The model
On the side of your tyre, you will also find the brand (Hutchinson, Michelin, Continental, Vittoria, etc.) as well as the model of the tyre, as every manufacturer makes several ranges for different uses.
3. The pressure
The maximum and/or recommended pressures may also be indicated on the side of the tyre.
Example: Competition rec. Pressure (Competition recommended pressure) 29 PSI/2 Bar and Max. Pressure (Maximum pressure) 80 PSI 5.5 Bar
4. Mounting direction
In addition, there may be an arrow indicating the direction in which to fit the tyre to the wheel. The arrow should be pointing in the direction that the wheel moves when fixed to the bike.
5. Manufacturer’s own references
You may also find the batch number and serial number on certain models, which could be useful in the case of an anomaly or fault. For example HU005_003 and 09061011.
FACTORS THAT DETERMINE THE CHOICE AND PRESSURE OF A TYRE
1. The type of tread
There are three types of tread:
– FLEX BEAD TYRES
These tyres are lighter, more efficient and easier to mount, but they are also more fragile and at greater risk of coming off the rim. They are therefore not recommended for downhill mountain bike.
– STIFF BEAD TYRES
The weight of the tread will penalise you in competition, but it assures you that the tyre is properly fitted to the rim, even in extreme conditions.
– TUBELESS TYRES
With this tube-free technology, you will suffer no more (or almost no) punctures and lost tyres.
The pressure is weaker (around half a bar) than on a flex bead or stiff bead tyre
2. The wheel size
Since the arrival of the 29 inch MTB, the choice of wheel size has been the hottest topic around. This size has an impact on your use. There will be another article on wheel size later.
3. The weight
Your weight is one of the criteria that determines the tyre choice and above all the pressure it should be inflated to.
The heavier the person, the higher the pressure needed will be.
Rather than boring you now with the figures, check out this comprehensive table on the Michelin website. There you will find all of the info you need about your weight and usage (road cycling, MTB, city cycling, hybrid bike).
4. The weather conditions / Firmness of the ground
Different factors can affect the pressure of your tyre.
The weather is one factor to take into account, especially as it influences ground conditions. In fact, if the ground is muddy you should inflate your tyre less than if the ground is dry.
The type of terrain also comes into play when calculating the optimal tyre pressure. Obviously, you would not use the same pressure for rocky ground as for muddy fields.
You can find information about tyre pressure according to the type of bike (suspended or rigid), your weight and the ground firmness in this table. Source: VTTeam St Polois.
You now have all the tricks of the trade for choosing not only your tyre but also the optimal pressure to use to ensure your comfort and safety. So what are you waiting for? Get on your bike and enjoy your next ride.