Sometimes, one of the most importance parts of a bike's maintenance is passed over - checking tyre pressure. But it shouldn't be: this is one of the things that can make it or break it in a race. If it's off, it will also make you work harder to maintain control. This should be part of your pre-ride ritual. Read on for the details on how to make this as painless as possible.
What purpose do the tyres have?
For one thing, they're an integral part of the suspension. If you were riding on solid rubber tyres, believe me, it would be haemorrhoid time. Also, just think about how important traction is to your performance. This is the job of your tyres.
Why do you check the tyre pressure before the ride? Because air expands when it warms up. The tyre's pressure rating is specified for cool air. Also, keep in mind that your bike is not like your car. The mission and environment are different and so is the air pressure. For optimal performance, your front tyre should hold about one PSI less than the back.
Do you need to check your pressure more than once during an event?
Absolutely. As stated above, the actual pressure is dependant on the temperature of the air. Check it before each rest period or when the day gets progressively hotter or cooler. At some events, the racing will extend into the night under the big lights. The temperature can drop considerably once the sun goes down.
Types of terrain
The type of terrain you're riding on can affect the air pressure you need to maintain for effective riding. Remember, fine tuning to specific conditions is one of the keys to success. Following are some recommendations:
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Sand or mud - 10 PSI in the rear tyre and 12 in the front. These conditions get a better bite with a lower pressure, flatter geometry on the rear but the higher pressure in the front accents tracking.
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Hard pack surfaces - This is a bit more equalized, only 11 PSI in the rear and 11.5 in the front. This is average supercross conditions.
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Intermediate surfaces - This is the average type of condition we referenced above. A good way to go is 13 PSI in the rear tyre, 12 in the front.
These guidelines are for a known MX track. That's where you know before hand what to expect. If you go riding on trails you might encounter any number of different conditions. In this case you should go for more pressure for optimized performance. I'd suggest 14 PSI rear and 13 PSI front. This is a bit higher than for racing conditions but remember that the speed will be greatly reduced and the chance of that dreaded flat tyre is much higher. So, take care of your tyres and they'll take care of you.