[Moto] Motorcycle tire pressures: can they be lowered or raised?

[#Wittels-]

The pressures of the wheels are a key factor in the behavior of the motorcycles: what effect does lowering them have to raise them with respect to the improved?

The importance of tire pressures in the behavior (and safety) of a motorcycle is something that we never tire of insisting on. The most understandable example is that a car can continue to drive with a flat tire (or all!) but on a motorcycle it is impossible... We know that we must follow the manufacturer's recommendation when checking the pressures, but is there room for adjustment? or does it improve by slightly raising or lowering the “stock” pressures? Let's see it, and let me point out that we are talking about the normal use of the motorcycle on streets and highways.

 

Agility or grip
The pressure originally recommended by the manufacturers (of motorcycles and tires) allows the tire carcass to deform in a certain way. Thus, the "footprint" (the part of the tire that hits the ground) is a well-studied surface of a few square centimeters. If the wheel remains with less pressure, the tire deforms more in contact with the ground and this has various effects, some positive and others negative.

Positive effects of having a slightly lower pressure: with more rubber in contact with the ground, we have more grip (the footprint will be a few millimeters larger, it's like mounting a wider tire). As the tire deforms more, it will absorb irregularities better (we will be a little more comfortable). And as it deforms more, the rubber will heat up sooner since the tires heat up due to the continuous deformation they suffer when turning by pressing on the asphalt.

Disadvantages of somewhat low pressure? Increased tire flexing can cause lack of stability, so carelessly leaving tires low on pressure is dangerous. In addition to heating up faster, as the deformation will be greater in each lap, the rubber will work at higher temperatures. It will last less and if the pressure is too low it could overheat and burst. Yes, blowouts are always caused by LITTLE pressure, not too much. Another disadvantage is that as the "footprint" (part in contact with the ground) is greater, it will take more force on our part to turn and move the bike: it will be less agile. In particular, be careful with this: with the bike tilted, when braking (front) the bike will rise and open the path with more force. Finally the wear will be more irregular.

 

As you can see, all the disadvantages of having low pressure (even just a little) can cause a lack of safety: that's why if you don't have a pressure gauge (and better if it's with a compressor), when in doubt at gas stations always leave the wheels "high" ”. What happens when the tires are too swollen? Well, the opposite of going down: the bike becomes a little more uncomfortable (“hard” tires), a little more nervous (smaller footprint and less deformation) but more agile. Keep this in mind when the front tire wears out (lose profile) and you notice your bike is "harder" in curves, but also keep in mind that it will grip much less as it has less rubber and is more swollen...

in practice
Although the weights change quite a bit (especially taking into account the pilot and passenger) the truth is that the manufacturers have reached a "standard" that complies well with most commitments, including legal safety standards. Thus, for most motorcycles, an inflation pressure of 2.5 bars at the front and 2.9 at the rear is recommended. These pressures, on the high side, make it possible to meet the maximum weight (and speed) standard for many tires and motorcycles.

But depending on the motorcycle model, our weight (and the eventual passenger and luggage) and above all the use, these pressures may not be the ideal ones, with which those tires work better. These pressures, the recommended ones, should be taken as the reference if we use the motorcycle at full load and high speed on the highway: it is “the maximum”. At the other extreme, if we were to ride on the circuit in a few batches, it would be convenient to lower the pressures of those same tires considerably: the organization will tell you about it, but you can leave as little as 2.2 in front and 2.0 in the rear.

 

I insist: this is ONLY on the circuit, where very sporty driving and the tire will work will be much more forced and hot. The pressure will go up in practice, in fact, around 0.4 at the front and 0.6 at the rear. Beware of going below 2.0 because racing or track tires (slick or not) have stiffer casings designed for even lower pressures and very high outlet temperatures (at least 80 degrees) using heaters. And on the road what can you do? Thinking of maximizing sporty driving, you can try lowering them slightly, even progressively (1 or 2 tenths each time), up to (generalizing a bit) 3 tenths in front and 5 behind. Every bike, rider and tire can be different. For that, as I mentioned before, it is essential to have your own, reliable pressure gauge, and better if it is one of those that now have a “pocket” battery-powered compressor included.

 

Link: https://www.moto1pro.com/reportajes-motos/presiones-de-las-ruedas-en-moto-se-pueden-bajar-o-subir