The only contact between our motorcycles and the surfaces they travel on is its tyres. And unlike cars, which have four wheels and are supported on a flat surface, motorcycles only have two and the area of contact with the road is curved so that we can tilt them on turns and other manoeuvres. That’s why safety while riding a motorcycle depends not only on the state of the tyres but on their respective pressures, which for the majority of bikes isn’t the same for the front and rear wheels.
On top of that, the tyres’ area of contact with the surface we’re riding on is quite small, so it’s fundamental that they have the proper pressure. And at the same time, they should be adjusted depending on the type of bike, the usual speed, and the total weight of the bike and rider. We should also consider additional factors like passengers, luggage, and other approved accessories added to our bike. In that regard, we always have to take into account the maximum load of the vehicle, which should appear in its technical data sheet and which should never be surpassed. To calculate this, we should consider the total weight of the rider, passenger, luggage, and any accessory installed on the bike such as tail bags, panniers, security elements, etc.
What happens if the tyre pressure is lower than recommended levels?
If we ride our motorcycle with improper pressure, it could cause us to lose control of the bike and possibly get into an accident, so it’s very important that we don’t let this important aspect slip.
If we drive with a low front tyre, we may notice that the bike understeers, or in other words, that it’s difficult to stick to the inner curve when making turns and the bike tends to hug the outside of lines on the road before it should.
When it’s the back tyre that’s low, the sensation of struggling to manoeuvre the bike on turns will be even more obvious; and it will be hard to tilt the bike and balance it from one side to another on turns.
And, of course, if the pressure it low on both, the bike will generally be difficult to ride and will feel like it’s braking, even when pushing it with the engine off.
And if the tyre pressure is too high?
In the event that we drive with higher-than-ideal tyre pressure, it’s most likely that we won’t have trouble when it comes to handling turns or leaning the bike from one side to the other. What we will notice is that bumps and other irregularities in the asphalt will be felt more intensely, which is to say, we lose driving comfort, directly affecting our own comfort.
On the other hand, we have to keep in mind that riding with incorrect pressure could cause improper wear on the tyres. If the pressure is low, the sides of the tread will wear more than they should; and if the pressure is high, the centre of the tread will wear first. Additionally, low tyre pressure increases petrol consumption since there is greater friction.
How often should we check tyre pressure on our bikes?
To keep our bikes healthy, it’s typical to read in the owner’s manual that tyre pressure should be checked before every use and always adjusted when necessary, but in reality that’s not necessary if we use our bike daily and with great care. If that’s the case, checking tyre pressure every 10 to 15 days should be sufficient. If we only ride on weekends, then yes, it’s recommended that we have a look each time before we hop on. And if the time between one use and another is even greater, that’s even more reason to verify that the pressure is correct every time we plan to take a ride. It’s not unusual that a sitting motorcycle’s tyres deflate faster than one that’s used daily.
How can we measure the pressure of our tyres?
Not everyone who rides has an air compressor at home with a good quality pressure gauge to ensure proper pressure. Many of us need to check our tyre pressure at service stations or at a trusted shop. If we do it at a gas station, many times the machines aren’t so easy to use, so it’s recommended that you over-inflate them, then adjust the pressure manually with your own pressure gauge. These instruments, which cost between €10 and 30, are small in size and weigh little. There are analogue and digital versions; and they’re usually pretty simple to use. They can decrease pressure, but they don’t increase it, so you have to be careful not to release too much air than you should.
It’s true that on some bikes, getting to the valves can be tricky, given the wide-diameter brake disks and the design of the wheels. To make this task simpler, you can install some valve adaptors, which are angled to the outside of the tyre and help us to check the pressure easily and reliably. To avoid spending too much money putting them in, just have them installed the next time you change tyres.
How should motorcycle tyre pressure be measured?
Tyre air pressure should be checked and adjusted when tyres are cold, that is, when they are at ambient temperature. If we have no other choice and need to check the pressure when the tyres are hot, we should always keep in mind that the pressure may be increased by between 0.2 and 0.3 kgf/cm2, which means we should inflate them just over the proper pressure.
Once you’ve compared the pressures, you should also check to see if the valves are leaking. We can do this just by listening, but it’s more reliable if you wet them a little with water, or if you don’t have any, with some saliva. If we detect a leak, it’s most likely we can stop it by pushing the valve core with a special key. This simple tool takes up very little space and costs around €2 or 3, so you should definitely have one on hand. A similar and even easier solution is a cap that has two small pins for pushing or loosening the valve cores. Regardless, we should tighten the caps well on each valve to avoid dust from getting in and losing air from the centrifugal force that the valve core suffers when the wheel spins at fast speeds.
Today, there are bikes that have valve sensors that constantly control the pressure and transmit information to the instrument panel so they we are always aware of it, even in gear. In the event that our bike doesn’t have this feature, there are wireless systems on the market with two valve caps that have a sensor and a small LCD screen that lets us know the air pressure at all times. It alerts us when they are lower than recommended and also when there is a rapid loss of air. These “plug and play” systems are fast and easy to install.
Should we follow manufacturer recommendations for air pressure? If so, what is the ideal pressure for motorcycle tyres?
The most common manufacturer pressure recommendations are 2.5 kgf/cm2 for the front wheel and 2.9 kgf/cm2 for the back. These are ideal pressures for travelling at high speeds on fast roadways and with the maximum allowed load. However, if we plan to be on the motorcycle alone without constantly travelling at high speeds, we can play with the pressure a bit. If we’re going to stick to curvy roads and our bike is medium displacement or not excessively heavy, then we can lower the pressure up to 2.3 kgf/cm2 for the front and 2.5 kgf/cm2 for rear. That way, we’ll ensure that the contact area of the tyre with the asphalt is greater so the tyres can reach their optimal operation temperature sooner, thus improving their grip when tilting the bike on curves and building traction when speeding up.
When it comes to bigger and heavier bikes like off-road or Grand Touring, we can lower the pressure slightly, but no lower than 2.4 kgf/cm2 for the front and 2.7 kgf/cm2 for the rear. It’s also true that when you ride an off-road bike on sandy or wet terrains, we can lower the pressure just a little more, but we shouldn’t forget to increase it when we get back on the road. For sport scooters, we can lower the pressures to 2.2 and 2.5 kgf/cm2, and if we’re talking about even lower displacement bikes, we can decrease the pressures up to 2.0 and 2.2 kgf/cm2. These are ideal pressures if we’re going to ride alone and with little extra load. If that’s not the case, we should inflate them more and follow manufacturer recommendations.
If we don’t have our hands on the owner’s manual, we can follow recommendations from the tyre manufacturer, which are typically indicated on the side of the tyre, along with the rest of its characteristics.
Are they the same for all motorcycles?
Depending on the characteristics of each bike and the type of tyres it has, tyre pressure can vary. If we’re going to lower the pressure more than recommended, we should do it slowly and keep trying it out to see how our bike responds. This is easier than it sounds. We just need to find out the manufacturer recommendation and keep testing it out from there.
When it comes to endurance and motocross bikes with knobby tyres and tubes, recommended pressure is around 1.0 kgf/cm2 on both tyres; and that can be lowered up to 0.8 kgf/cm2 and even less for very muddy or wet terrains. In the opposite conditions—on dry and rocky surfaces—it’s better to increase tyre pressure to 1.2 kgf/cm2 to avoid possible damage to the wheels. If we’re going to use lower pressure, it’s important that the wheels at least come with a rim lock to avoid the tyre from spinning on the wheel and damaging the tube. For trial bikes, ideal pressures are very low in order to achieve the greatest grip possible and considering they’re not meant for constant high speeds. Their recommended pressure is 0.4 kgf/cm2 for the front wheel and 0.35 kgf/cm2 for the rear.
On the other hand, sports tyres that have been designed to be used on asphalt circuits can have pressures below 2.0 kgf/cm2 given their carcasses are designed to support pressures this low. If we must follow tyre manufacturer recommendations, the rear wheel should be inflated higher than the front, unlike on the road. In this case, we can use pressures of around 1.5 kgf/cm2 for the rear and 1.9 kgf/cm2 for the front.
An interesting fact is that in MotoGP, per regulations, minimum pressure limits are 1.9 kgf/cm2 for the front tyre and 1.7 kgf/cm2 for the rear. These limits are set to avoid teams from lowering pressures more than they should and causing major safety issues for riders. In fact, in the past there have been some high-speed rear tyre blowouts when riding straight, which forced a change in the regulations and random pressure checks at the end of races.