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This post compares the advantages and disadvantages of 25mm and 28mm bike tires.

Weight Comparison

The table below compares the weight of 700×25 and 700×28 tires:

The wider the tire, the more material it requires. Hence why wider tires are expected to weigh more.

But since the nominal difference between 25mm and 28mm is only 3mm, the average weight of 25mm and 28mm tires is similar.

When all parameters are equal (matching models), 28mm tires weigh about 30-60 grams more. When used in a pair, the extra weight goes to 60-120 grams.

60-120 grams make no performance difference, especially in the world of recreational cycling.

Air Pressure Comparison

The next table compares the air pressure of 25mm and 28mm tires.

Narrow tires operate at a higher pressure because it’s needed to protect the rim whereas wider tires can offer sufficient protection even when the air pressure is lower.

As expected, 25mm tires can support slightly higher air pressure whereas the 28mm models do better on the low end. The top difference is negligible. Good luck feeling a difference between 120 and 116 PSI.

However, the lower discrepancy is greater – about 15 PSI/1 bar. The lower PSI allows the tire to change shape around road irregularities.

If you choose a 28mm tire supporting lower PSI, you will have the option to soften the ride while still being able to inflate the tire to very high air pressure when speed rather than comfort is the goal.

Clearance

Clearance is also an important factor when talking about road bikes. For example, my old road bike has clearance for 28mm tires, but I can’t use them with full fenders due to the lack of space. Hence why I rely on 25mm tires.

Keep in mind that tire sizes are not incredibly accurate. A 25mm tire might measure more than 25mm. Thus, the difference between a 25mm and a 28mm tire could be greater than 3mm. Ultimately, it depends on the models.

Rolling Resistance on the Road

When the air pressure is the same, wider tires have a lower rolling resistance than their narrower brothers.

Why?  

Because wider tires deform less under pressure. Consequently, they remain rounder (closer to a perfect circle) and roll more easily.

In different, narrower tires deform over a greater length and showcase a more pronounced deformation (less perfect circle). This hurts rolling resistance.

However, this is the case only when both tires are representatives of the same model and have identical air pressure.

Most of the time, narrower tires are inflated to greater values. The extra pressure prevents the tire from deforming and decreases its rolling resistance on the road.  

When comparing 25mm and 28mm models, the same principle stays true – 25mm tires can operate at a higher air pressure keeping their rolling resistance low.

That said, if you use the same air pressure for both widths, the 28mm tire should actually roll better provided that all other parameters are equal. 

Note: The difference in rolling resistance between 25mm and 28mm tires is too little for an average cyclist to notice on their daily commute to the office. 

Traction

A wider tire offers more traction when:

a. It’s inflated to the proper air pressure for the terrain.

b. Its tread corresponds to the terrain. For example, slick tires offer better grip on paved roads because the contact patch is larger. Knobby tires offer poor grip on asphalt because only the top layer of the knobs comes in contact with the ground.

However, on off-road terrain, the knobbies can dig into the ground and provide more traction than slicks.

Ultimately, 28mm tires will offer more grip and stability than 25mm when all other parameters are equal.

Cornering

Wider tires make sharp cornering feel more stable thanks to the larger contact patch resulting from the extra width and the lower air pressure.

Climbing

Wider tires have a larger overall circumference than thinner tires. The additional height and the low air pressure (squishiness) have a slightly negative effect on the bike’s climbing performance.  

Aerodynamics

In theory, 28mm tires are a bit less aero than 25mm models. The discrepancy is small and has no impact on an average cyclist’s performance. 

Acceleration 

The lighter weight of narrow tires results in lower rotational mass.

In simpler terms, this means that slimmer tires are easier to get spinning because there’s less material to move. The end result is better acceleration.

This is also one of the reasons why professional cyclists stick to fairly slim tires (25mm is the current standard.) 

That said, the difference is non-perceivable when a bicycle is used for recreational purposes.

Summary: What You Need To Know

The advantages of 25mm tires are:

• Potentially lighter (it depends on the model). The weight savings per wheel can reach about 60 grams.

• Support slightly higher air pressure resulting in lower rolling resistance.

• Slimmer profile allowing usage on frames and forks with tight clearance.

• Slightly faster acceleration (depends on the model’s weight).

• Better climbing abilities

The disadvantages of 25mm tires are:

• Harsher ride due to the smaller contact patch and the higher air pressure needed to protect the rim

• More difficult to install (depends on the model).

• Inferior cornering due to the smaller contact patch

The advantages of 28mm tires are:

• Can operate at a slightly lower air pressure and thus offer a softer ride

• A larger contact patch resulting in better cornering and more comfort

• Lower rolling resistance when operating at air pressure matching that of 25mm tires

• More grip

The disadvantages of 28mm tires are:

• Less clearance (can fit on fewer frames and could make the installation of full fenders impossible)

• Slightly heavier (depends on the model)

• Support slightly less air pressure (the difference is minimal)

• Could feel a bit sluggish (depends on the model and the air pressure)

Winner?

One could make a strong argument that 28mm tires are superior overall because they can offer the speed of 25mm but also more comfort. If the frame and fork can adequately support a 28mm tire, it would be logical to choose them over 25mm.

That said, 25mm tires are a classic and have proven to be a good compromise between speed and comfort.