This post compares the advantages and disadvantages of 25mm and 32mm tires in relation to one another.
1. Weight Comparison
The next table compares the weight of 700×25 and 700×32 tires:
|Continental Grand Prix 5000
|Vittoria Corsa G2.0
|Continental Grand Prix 5000
|Continental Sprinter GatorSkin
|Schwalbe Pro One Tube
|Giant Gavia Fondo 1
|Panaracer CG CX
|Schwalbe One TLE
|Bontrager R3 Hard-Case Lite
|Veloflex Corsa EVO Folding Tire
|Vittoria Zaffiro V
|Schwalbe Pro One Evolution
|Challenge Strada Pro TLR
Conclusion: On average, 25mm tires are 39% lighter (about 95 grams). This is expected because wider tires require more material and thus weigh more.
In the best-case scenario, 25mm tires will save you close to 200 grams. If you want to build the lightest bike, then 25mm tires will help. That said, the weight of the tire greatly depends on the model. Some 32mm models in the table are lighter than 25mm units.
2. Air Pressure Comparison
The next table compares the air pressure of 25mm and 32mm tires:
|Continental Grand Prix 5000
|Donnelly Tire Strada LGG
|Grand Sport Race
|Panaracer Pasela ProTite
|max. 95 PSI
|Cont. Grand Prix 4-Season
Conclusion: 32mm tires operate at a 22%-25% lower air pressure. The lower air pressure of 32mm tires results in more comfort as the tire has an easier time changing its shape according to the irregularities on the road.
In different, narrower tires have to operate at a higher air pressure, or else the tire will suffer from flats and the rim will be damaged. The higher air pressure offers less comfort but more speed because a firmer tire rolls faster on paved roads.
That said, one can argue that the 32mm tire offers a high enough air pressure plus comfort that a 25mm model cannot match.
Another important factor, especially in the world of road and gravel cycling, is clearance. Naturally, a wider tire will take up a lot more space than a narrower one. The nominal width difference. in this case, is 7mm. Doesn’t sound like much, but it could be when the frame and fork have little tolerance.
For example, I cannot run full fenders on my road bike with tires over 25mm. Without the fenders, I can fit 32mm tires with very little clearance. Since full fenders are an indispensable commuting accessory for me, I run 25mm tires.
That said, newer road and gravel bikes (especially those with disc brakes) have plenty of clearance and can accommodate fairly wide tires.
4. Rolling Resistance
When the tire tread and the air pressure are the same, wider tires have lower rolling resistance because they deform less under pressure. As a result, their shape remains closer to a perfect circle and the wheels roll faster.
In different, narrower tires experience greater deformation (for the same air pressure) which hurts the shape of the tire and increases rolling resistance.
However, in practice, narrower tires use higher air pressure than wider models. This property prevents the aforementioned deformation. Hence it’s not correct to conclude that wider tires have lower rolling resistance in real-world scenarios.
Wider tires offer greater traction when the following conditions are met:
- The tire’s air pressure is appropriate for the terrain.
- The tire’s tread corresponds to the terrain.
Contrary to popular belief, slick tires (no knobs) offer more traction on paved roads thanks to the larger contact patch. MTB tires with massive knobs offer less traction on asphalt because only the knobs are in contact with the ground.
Meanwhile, knobby tires offer better traction on terrain that the knobs can dig into (mud, gravel…etc.) In similar scenarios, slicks lose traction. Hence why you only see slicks on bikes designed for the road.
If all parameters are identical, a wider tire will offer more traction than a narrower one. If the treads are inappropriate for the terrain, however, the extra width will not compensate.
Wider tires make sharp cornering more stable thanks to the larger contact patch resulting from the extra width and the lower air pressure.
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.
32mm tires are a bit less aero than 28mm models. The difference is small and has no impact on an average cyclist’s performance.
The lighter weight of narrow tires results in lower rotational mass. Or in other words, 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 (25-26mm 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 (depends on the model). The weight savings are inconsequential for recreational riders.
- Support higher air pressure resulting in lower rolling resistance
- Slimmer profile allowing installation on frames and forks with tight clearance
- Faster acceleration
- 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 and the inner tube
- More difficult to install (depending on the model).
- Inferior cornering due to the smaller contact patch
When do 25mm tires shine?
25mm tires are a mix of comfort (in comparison to 23mm tires) and speed. They have been the norm for road bikes for years. If you intend to race, 25mm tires are a standard choice. If you want to use your bike for commuting and touring, however, 25mm tires will be unnecessarily uncomfortable.
The advantages of 32mm tires are:
- Softer and more comfortable ride (better for commuting)
- A larger contact patch results in better cornering
- Lower rolling resistance when operating at air pressure matching that of 25mm tires
- More grip (when the tread is correct for the terrain)
When do 32mm tires shine?
32mm tires offer a softer ride and speed too (when inflated to high air pressure). They allow you to pass through large obstacles and reduce the chance of getting your wheel stuck in a drain (although that’s always an option).
32mm tires are great for recreational riders and even racers. The main problem with them is clearance and the extra weight. The vast majority of older frames barely have clearance for 32mm tires.
If your bike and frame have enough clearance for 32mm tires, and you don’t care about maximum speed at the expense of comfort, then 32mm models are a good choice.