BMX tires are fat (wide) for the following reasons:
- Suspension effect
- Lower chances of getting a flat tire
- Rim protection
- Extra Grip
Wider Tires = Softer Ride
Wider tires have a suspension effect thanks to the greater contact patch and the ability to operate at lower air pressure. The lower the air pressure, the softer the ride.
However, if the pressure is critically low, the chances of getting a pinch flat tire (a puncture caused by the rim upon meeting a hard obstacle such as a curb) increase.
Wider tires do not need as much air to protect the inner tube from a pinch flat and can therefore run at lower PSI.
It’s also worth mentioning that tubeless systems can operate at even lower air pressure thanks to the absence of an inner tube that could get pinched by the rim.
Fewer Flat Tires
Wide tires result in fewer punctures for the following reasons:
- The lower air pressure makes the tire more compliant and capable of deforming around some of the debris on the road that can cause a flat tire.
- Wide tires have a larger contact patch (the portion of the tire in contact with the ground). As a result, the tire applies less force per square inch against the objects that might cause a flat.
Thin tires, on the other hand, have to operate at high air pressure to avoid pinch flats and have a smaller contact patch. Consequently, the force with which the tire pushes the debris on the road is greater.
This can be easily illustrated if you pump your tires to the maximum and ride on a road with lots of small stones. You will see that the tire is pushing/launching small stones here and there. In some cases, the tire may throw a small stone almost as fast as a bullet.
I’ve experienced this with my road bike. If I pump the tires to 8 bars, they start throwing small stones to the point where I become worried when passing near pedestrians.
If you lower the air pressure, you will see that this phenomenon diminishes greatly precisely because the applied force per square inch is smaller.
Stronger and More Protected Rims
The air in the tire protects the rim from impact. Hence why it’s possible to ride on stairs and perform huge drops without damaging the rim. If the air pressure is dangerously low, however, the rim can be damaged due to the increased stress.
The wide tires of BMX bikes come with wide rims too. The wider the rim, the higher its potential strength. When you couple it with a beefy tire pumped to an adequate setting, you get a very strong wheel.
Of course, the quality of the products matters too. If the rim is of subpar quality, the unit won’t be tough despite its width.
For the same reason, MTBs and bicycles designed for long distances on diverse terrain come with wider tires. Thin tires with slim rims simply fail to provide the needed strength for continuously riding over bumps and medium size obstacles.
For example, the rear rim of my road bike routinely gets out of true when I decide to push my luck on less-than-ideal road sections.
It’s also worth mentioning that BMX bikes use slick tires. By installing a wide slick tire on a BMX, one maximizes traction.
Contrary to popular belief, slicks provide more grip on paved roads (the usual BMX terrain) than models with off-road tread.
Why? Because slick tires have a larger contact patch with the ground when used on paved roads.
Knobby tires provide more grip only on surfaces in which they can dig (e.g., gravel). When used on asphalt, knobby tires underperform because only the top part of the knobs touches the ground. The small point of contact results in less traction.
How wide are BMX tires?
Most BMX tires range from 2″ to 2.5″.
What is the maximum PSI of a BMX tire?
It depends on the model, but usually, the PSI is pretty high e.g. 100. The greater air pressure makes the ride less comfortable but protects the rim from deformations.
Why do some riders have a wider tire at the front and a narrower one at the back?
If you have tires of dissimilar widths, it makes more sense to install the wider one at the front because:
- The front tire is the first to meet an obstacle (provided that you aren’t performing a trick). The wider the front tire is, the easier it is to overcome irregularities.
- The front wheel is crucial for stability. Thus, it makes more sense to install the larger tire at the front since it has a bigger contact patch.
- Additional suspension effect
- It’s easier to perform fakie tricks with a larger tire at the front.
- Wider tires are heavier, and since it’s easier to lift the front wheel than the rear, it makes more sense to add the extra weight to the front end.
- Faster acceleration (a smaller wheel is easier to get up to high RPM than a larger one).
What are the downsides of using super wide tires?
Wider tires are heavier (more material) and in some cases could feel sluggish (like a tractor). For that reason, most riders keep the width around 2.1″-2.3″.