Wider is Better

Posted by Ryan Cate on

Let’s talk about tires. More specifically, let’s talk about wide tires. There is a movement in the bike industry to ride wider tires in every category. FitWell Bicycle Company is fully behind this movement because it makes your bike more comfortable and more stable. Let’s get in depth with the benefits of a wider tire, how a wider rim ups those benefits and the limiting factors wider tires.

First the benefits. The most important benefit relates to the tire’s suspension function. Every time you go up a tire size, you can reduce the required air pressure required to support your weight. Think of it this way, we measure air pressure in pounds per square inch (PSI), right?  When we go up a tire size, the Square Inches increase, so the Pounds get reduced to maintain the same equilibrium. The benefit of this is comfort. When you hit a bump, a lower pressure tire has more capacity to absorb the impact. Why not just run the smaller tire at a lower pressure? You can, and should to a point… You need enough pressure to maintain the tires shape so you can turn and enough pressure to minimize the possibilities of pinch flats (when the tube gets pinched between the obstacle and the rim resulting in a torn tube).  A wider tire prevents pinch flats by putting more distance between the obstacle and the rim, figure C. The other major benefit is increased traction. A bigger tire can simply put more rubber on the ground. The looser and rougher the terrain, the more the benefit. Lastly, wider tires also reduce the tires resistance to rolling so it takes less effort to go.

The benefits of going to a wider tire are pretty great, but we can maximize those gains by using a wider rim. A wide rim maximizes the air volume of any tire as seen in figure A. Remember, more area, lower pressure, more comfort. The light blue area represents the increase in air volume. A wider rim also optimizes the profile of the tire. The tire goes from looking like a lightbulb to more of a U shape. This results in more support of the tire’s sidewall and more tread in contact with the riding surface. This pumps up the straight line stability. The tire deflects less in turns, figure B, so your control is way better in the corners. So how wide of a rim should I look for? The ultimate goal would be to match the rim width to the tire width. A 23mm tire performs optimally with a 23mm wide rim. As you get wider than 30mm tires, rims don’t keep up with tire widths. This is mostly due to weight which we’ll explore more in the next section. A side benefit is that on road bikes, where aerodynamics matters, matching the rim to the tire creates lees drag than a narrower rim.

If wider is better, why doesn't every bike run 6” wide tires at 5psi? Many reasons, but weight is the biggest issue. Rubber is heavy and wide spinning rubber is really heavy. The same is true for aluminum rims. The tires described would be really awesome in regards to comfort and traction, but they would be slow to accelerate and difficult to maneuver. The other issue are the physical restraints imposed by the human body. Wide tires force pedals further apart making the bike harder to pedal. In most cases, going a bit wider has big gains, but going way wider can be a hindrance. Like all things, it’s a balance.

So, what’s the right balance? The things you want to look at are the surfaces you want to ride and what your performance expectations are and the weight of you + your bike + your riding gear. When you think about the surface, think about the average obstacle size, like on the road, you’re likely to see cracks in the road from ½- 1cm deep, on gravel roads, you’ll encounter stones from 1-2 cm in diameter. If your tire is larger than your typical obstacle, then you can largely ignore them so you can ride more confidently. The goal is to be wide enough to be smooth and reliable, but skinny enough to be lightweight and fast. So you’re not flying blind, here are some recommendations for a few scenarios. These recommendations are made without consideration of the bike you may have. Every bike will have a maximum tire capacity that cannot be exceeded.

Road Racing

Typical obstacles: cracks, stones, sticks under 2 cm in diameter

Old School: 19-23mm tire on 19mm rim

New School

Tire Width: 25mm (23-28mm tires are acceptable)

Rim Width: 23mm (19-24mm rims are acceptable)

Notes: This is the baseline our recommendations are made from. Larger riders should size up for improved performance and reliability. Smaller riders can size down to save some weight.

Road Riding, centuries, group rides

Typical obstacles: cracks, stones, sticks under 2 cm in diameter

Old School: 23-25mm tire on 19mm rim

New School

Tire Width: 28mm (25-32mm tires are acceptable)

Rim Width: 24mm (19-24mm rims are acceptable)

Notes: Trading a little weight for more comfort is beneficial for longer rides. Larger riders should size up for improved performance and reliability. Smaller riders can size down to save some weight.

Commuting, Touring

Typical obstacles: cracks, stones, sticks under 2 cm in diameter, potholes

Old School: 25-28mm tire on 21mm rim

New School

Tire Width: 32mm (25-32mm tires are acceptable)

Rim Width: 24mm (23-28mm rims are acceptable)

Notes: You’ll likely carry weight on the bike which will require a larger tire to offset. Larger riders should size up for improved performance and liability. Smaller riders can size down to save some weight.

Gravel Riding

Typical obstacles: Gravel 1- 3 cm in diameter, potholes

Tire Width: 32mm (28-38mm tires are acceptable)

Rim Width: 24mm (23-30mm rims are acceptable)

Notes: The surface is consistently bumpy and can be quite loose. Gravel varies by region, so tire choice will as well. If your roads are looser and softer, go wider, if they are hard and worn in you can go narrower for more speed. Larger riders should size up for improved performance and reliability. Smaller riders can size down to save some weight.

Cyclocross Racing

Typical obstacles: Gravel 1- 3 cm in diameter, sand, roots

Tire Width: 33mm (28-38mm tires are acceptable, Pro racers cannot go wider than 33mm )

Rim Width: 24mm (23-30mm rims are acceptable)

Notes: The surface is consistently bumpy and can be quite loose. Wide tires at low pressure will smooth out the bumpiness. Larger riders should size up for improved performance and reliability. Smaller riders can size down to save some weight.

Cross Country Mountain Biking

Typical obstacles: Rocks and roots 2-6cm diameter, sand, logs and jumps

Tire Width: 52mm (48-58mm tires are acceptable)

Rim Width: 24mm (23-32mm rims are acceptable)

Notes: The surface is consistently bumpy and can be quite loose. Wide tires at low pressure will smooth out the bumpiness. Rims get quite heavy as the approach the tire width and the tradeoff between weight and performance is high so we recommend narrower rims based on value. Larger riders should size up for improved performance and reliability. Smaller riders can size down to save some weight.

To sum up, tire width varies by discipline and by rider hopefully you get an idea of why. We focused on width because tire volume is a huge factor in ride quality. Rims are slowly getting wider to match. At FitWell we support the use of wide rims and tires to provide the best ride characteristics to our products. All of our bikes are designed to let you go as wide as is appropriate for the category and we encourage you to do so. Maybe it’s time to take a look at what you’re riding and go a little wider.


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