How to Check Tire’s Air Pressure Taught by Professional Mechanic!

Whether it's the high-powered engine or the powerful brakes, the tires that make contact with the ground allow you to use them to their full potential. On the flip side, if the tires aren't good enough, the latest models full of electronic controls are too scary to drive. It's easy to get distracted by grip and thickness, bias or radial when you're looking at tires, but the more basic and important thing you need to consider is the air pressure, and that's what makes your motorcycle more fun to ride.

Even if you don't have a flat tire, you can still get the air out of the tire.

Tire pressure is measured when the tires are cold (the same temperature as the ambient). Strictly speaking, there should be a difference in the temperature of tires placed under the hot sun in winter when the temperature is 0°C (0°F) and in mid-summer when the temperature is 40°C (40°F), but only if it's before you drive.

In both cars and motorcycles, tires transfer drive and braking power to the road, change direction with steering and banking, and absorb shock from the road while supporting the weight of the vehicle and the rider's weight. Not to mention the history of solid rubber on wooden wheels, which has greatly improved performance with the introduction of tubes filled with air, air pressure is an important part of the tire's performance.

The major difference between a motorcycle tire and a car tire is that the tread surface in contact with the road surface is round in cross-section, and the contact surface moves from the center to the side of the tread surface as the vehicle leans around corners.

As the ground contact area increases or decreases with changes in bank angle, the grip strength also changes, and stability decreases, so tire manufacturers design their tires so that the contact area does not change significantly no matter where the tread contact is made.

In addition to the importance of tread shape and the stiffness of the tire itself, the air pressure is also an important factor in determining the shape of the tire. If the pressure is lower than the specified pressure, the handling becomes heavier due to increased rolling resistance, and the stability of the tire becomes less stable due to the increased deflection of the tire itself, which results in a squishy ride. Conversely, if the pressure is higher, shock absorption from the road surface is reduced and riding comfort deteriorates, and even if a bank angle is achieved, the high internal pressure makes it difficult to deform the tire properly and cornering performance deteriorates.

This means that the air pressure must always be correct, but the tricky thing is that the air inside the tire will gradually decrease over time. If it drops all at once in a short period of time, like a puncture, everyone will notice it, but with a typical decrease of 5-10% per month (as stated on the tire manufacturer's website), some riders may not even notice it when they ride.

Whether it's a tube or tubeless tire, it's easy to assume that the rubber should be impermeable to air and that air valves can't leak air if the bug is healthy. However, in reality, there are very small gaps in the rubber molecules that allow air molecules to pass through. In addition, a very small amount of air leakage also occurs at the threaded area between the air valve and the bug, or in the case of a tubeless tire, at the area where the rim and bead meet. Periodic pressure checks are necessary to detect and replenish that natural loss.

Correct air pressure information is on the body sticker.

The Yamaha YZF-R25 has a label on the chain case that lists the tire size and pressure. When pillion riding, the same tire pressure is required for a single passenger. Some riders have been following their own tire pressure for many years out of habit or preference, but it is important to know the standard ride quality of the stock and specified tire pressure first.

The reason why tire pressure is important for motorcycles is as mentioned above, but when it comes to how much air is recommended, it differs depending on whether it is a moped, middle class or big motorcycle, whether it is an on-road model or an off-road model, and whether the tire structure is bias or radial, so it cannot be said in general that "if the tire size is ●, the air pressure is ■■kPa.

Let's list the tire pressures for different models of tires from one manufacturer.

It looks roughly like this. The 900cc Sport has radial tires and the rest are bias, and the 250cc Trail has tube tires and the rest are tubeless tires. For the models with one passenger on the proviso, the specified air pressure is different when two people are on the motorcycle.

More to the point, the specified pressure is the best pressure for the stock tires installed when new, and if you change tire brands, the best matching pressure may change, to put a fine point on it. Of course, that's about the difference between a 40kg rider and an 80kg rider, and that's about the difference between one and two passengers, so you may need to make adjustments.

In any case, the absolute best guide is the air pressure specified by the manufacturer. The best way to know this is the air pressure label, which is often attached to the swingarm, chain guard, or, if it's a scooter, inside the trunk box.

If you buy a used motorcycle with the label removed, refer to the owner's manual or service manual. Depending on the model and year, some manufacturers post the owner's manual and basic service data on their websites.

In order to measure the air pressure, you also need an air gauge. There are various types of air pressure gauges such as analog and digital ones depending on their price and function. There are gauges that can measure up to about 1200kPa for large vehicles such as trucks and buses, but the scale of low values around 200kPa may be difficult to read because of its fine scale.

By lowering the air pressure, the 10-inch scooter tire is responsible for catching the impact from the road, along with the suspension. If you raise the pressure to nearly 200 kPa, which is about the same as a medium-sized sportbike, you'll notice a noticeable push up from the front.

If you're not trying to raise the bead by replacing the tire, but rather to replenish the missing air, a bicycle air pump or a foot pump will suffice. The air gauge that comes with the pump is also useful, but if you're not sure of its accuracy, get a gauge made by the manufacturer.

On the other hand, some of the gauges that are mainly intended for off-road use have a maximum of 200 kPa, which may not be usable for measuring on-road tires, so be careful when you are planning to purchase an air gauge.

Once you know your motorcycle's air pressure, measure the current pressure, and replenish the air if it's low. If you haven't checked it regularly, it should be down some. It doesn't matter if you use a manual pump, a foot pump, or an air compressor to fill up the air.

If the air gauge is equipped with a release button, it is more efficient to add more air than the specified value, and then push the button to release the air inside the tire while adjusting it to the specified value.

Another important point is that checking and topping up the pressure should be done when the tires are cold. After a ride, the tire temperature is higher and the air pressure in the tire increases as a result of the increased temperature. If the tires are measured and adjusted when hot after riding, the pressure will be somewhat lower than it would be at room temperature. The manufacturer's pressure specification is for room temperature, so the normal check should be done before riding.

Be careful not to let the rubber get too fresh.

There's a lot of information on the sidewall, but instead of convex letters, the branded, concave four digits indicate the year and month of manufacture. This tire is a 3116, so it would be manufactured 31 weeks in 2016. If the year of manufacture of the front and rear tires are completely off, it could be due to a puncture that cannot be repaired (such as damaging the sidewall with a curb) as well as replacement due to wear.

This is a bit of a digression from tire pressure, but the passage of time is a problem for tire performance. As the years go by since manufacture, the nature of the rubber changes, and simply put, the tire becomes harder and less grippy.

The speed of deterioration of rubber varies greatly depending on the environment and storage conditions, but some tire manufacturers recommend that all tires, regardless of the amount of tread grooves remaining on the tread surface, should be checked by the dealer after five years of use and all tires that are ten years old should be replaced.

You can find out when the tire you currently have on your vehicle was manufactured by using the sidewall engraving. The information on the sidewall, which includes the tire manufacturer, brand name, and size, is stamped with a four-digit number.

The first two digits of this number are the week the tire was manufactured and the second two digits are the last two digits of the year of manufacture in the Western calendar display. If this number is "3116", then you know that the tire was manufactured in week 31 of 2016 (early July).

If the tires on a used motorcycle have grooves but lack elasticity, check the year of manufacture and if it turns out that the tires were manufactured before "●●15", that is, before 2015, it would be safer to replace them with new ones, including for safety reasons.

See YAMAHA Moto Index Page
See Accessories for YAMAHA YZF-R25 (R25)