This article compares the advantages and disadvantages of 650b and 700c wheels for commuting.
The Advantages of 650B Wheels
- Nimbleness and Maneuverability
Smaller wheels offer snappier turning and are therefore easier to maneuver. (Hence why stunt bikes such as BMX continue to use 20″ wheels.)
The rim diameter of 650b wheels is 584mm whereas that of 700c wheels is 622mm. The difference of 38mm or 1.5 inches may not seem substantial, but it’s definitely noticeable, especially when doing technical riding.
If your commute involves a lot of maneuvering in the city, then the slightly smaller size of 650b wheels could be beneficial.
- Faster Acceleration
It takes more torque to spin a bigger wheel up to speed. Hence why smaller wheels accelerate faster. This could also be a highly beneficial property when commuting in city traffic.
- Stronger Rims
All things being equal, a smaller wheel is a stronger wheel. A quality 650b wheel built well will need less truing than a 700c one and can take more abuse before spoke failure.
- Softer Ride (potentially)
If the bike is originally designed for 700c wheels but is then converted to 650b successfully, the user will be able to fit larger tires that can operate at lower air pressure. The lower the air pressure of a tire is, the greater the suspension effect. Thus, 650b tires could be beneficial to people looking for comfort.
The downside is that 650b conversions are rarely “smooth”. For example, if you have rim brakes, they won’t be able to reach the brake track of the new wheel. If you’re going from a smaller wheel to 650b, the brake shoes will be too low. If you’re going to 650b wheels from 700c, the brake shoes will sit above the rim.
Note: Another advantage of switching to 650b tires from 700c is the extra clearance which allows the installation of full fenders (an accessory that’s highly beneficial for city commuting).
- Lower Weight
650b wheels are smaller and therefore have the potential to be slightly lighter since less material is used for their production.
That said, the difference is negligible and has no impact on commuting.
The Disadvantages of 650b Wheels
- Lose Acceleration Faster
Larger wheels may be more difficult to accelerate, but once you get them up to speed, they keep on rolling thanks to the extra mass and circumference.
That being said, it will be illogical to conclude that 650b wheels are slower. (This point will be developed further down the post.)
- Fewer Tire and Rim Models
700c wheels are the road standard whereas 29″ MTB wheels are dominating the MTB market.
It’s also worth explaining that 700c wheels and 29″ MTB wheels are technically the same size. (The rims of 700c and 29″ wheels are of equal diameter, but the tires are thus the overall wheel circumferences are different.)
Ultimately, 700c wheels offer a greater variety of tire and rim models for the user to choose from.
Meanwhile, 650b wheels (27.5″ inches in the world of MTB) are a lot less common albeit still popular and not nearly as outdated as 26″ wheels.
- Lower Roll-over-ability
Another advantage of larger tires is that they have an easier time rolling over obstacles. Hence why 29″ MTB wheels just eat road irregularities. 650b (27.5″) wheels are fairly close, but they’re still smaller and have a lower roll-over-ability.
When it comes to commuting, however, this property isn’t crucial unless you have to cover off-road sections, but even then 27″5 wheels will be plenty capable.
The Advantages of 700c Wheels
- Speed Maintenance
Once accelerated, larger wheels just keep rolling thanks to the extra mass and circumference. This property makes it easier to maintain a higher average speed.
Thus, if your commute has long stretches of flat roads or descents, 700c wheels make it easier to maintain a higher average speed.
- More Options
As already mentioned, 700c wheels provide more rim and tire options thanks to their greater popularity.
The Disadvantages of 700c Wheels
- Smaller Tires/Less Clearance
A 700c wheel takes up more space and will therefore limit the tire size that the user can install. There will also be less clearance for fenders.
- Reduced Maneuverability
The extra size of 700c wheels could make the bike feel less nimble. (Of course, the final result depends on the frame’s geometry too.) Unless you have to get through some very tight spots, this shouldn’t be a great issue when commuting.
If ultimate maneuverability is desired, then 26″ or even smaller wheels could be used since the difference between 700c and 650b isn’t very large.
Tire Size Matters Too
The width of the tire has a direct effect on the wheel’s circumference. In some cases, a 650b wheel may end up having a greater circumference than a wheel with very narrow tires.
For that reason, the comparison is a lot more accurate when each rim size is equipped with tires of identical width.
Larger Tires Are Not Faster
There’s a myth according to which larger wheels are faster than smaller ones. That’s not true because the top speed of a bike is ultimately determined by its gearing rather than the size of its wheels.
The drivetrain of a bicycle constitutes of chainrings (front) and rear cogs (back).
Each chainring + cog combination, gives the rider a certain maximum speed.
The greater the gear ratio, the faster the rider can potentially be.
The term gear ratio refers to the relation between the chainring and the rear cog.
For instance, if the rider is pedaling in a big chainring with 44 teeth combined with an 11 teeth rear cog, the gear ratio is 44:11 = 4:1
This means that in that particular gear, each full revolution of the cranks causes the back wheel to spin 4 times (thus you have a 4:1 ratio).
The larger the gear ratio is, the faster the bike can be because each spin of the cranks equals more revolutions of the rear wheel per minute and thus a greater traveled distance.
The formula for speed is: Speed = Distance/Time.
Therefore, a bike that covers more distance in the same amount of time than another one is moving faster.
The next scenarios illustrate how higher gearing creates the potential for more speed.
The only dissimilarity in both situations are the gear ratios. The rest of the variables (time, crank RPM, wheel circumference…etc.) remain a constant to illustrate the difference.
Case A: Gear ratio – 44:11=4:1
Case B: Gear ratio – 50:11= 4.5:1
Time of travel = 1 minute
Rotations of the cranks (rpm) per 1 minute = 80
Wheel circumference = 220cm
In 44/11, the rear wheel spins 4 times per 1 crank revolution.
Since the rider is pedaling at 80rpm, the rear wheel makes 4×80=320 turns per 1 minute/60seconds.
If the wheel circumference is 220cm, the bike will move 220cm x 320 = 70400cm = 704m = 0.704km
The speed of the bike will be:
704m/60s = 11.74m/s = 42.24km/h = 26.24mph
In 50/11, the rear wheel spins 4.5 times per 1 crank revolution.
At 80 rpm, the rear wheel makes 4.5×80=360 turns.
If the wheel circumference is 220cm, the bike moves 220cm x 360 = 79200cm = 792m = 0.792km
The speed of the bike is:
792m/60s =13.2m/s = 47.52km/h = 29.5mph
Conclusion: In the higher gear, the bike is about 5km/h faster at 80rpm.
Therefore, if all other parameters are equal or close to it, the bike with the higher gearing will offer more top speed.
For that reason, one shouldn’t conclude that 700c wheels are faster than 650b. A bike that has 650b wheels combined with higher gearing will have the potential for more speed than a 700c bike with lower gearing.
Potential for larger tires
|Greater variety of rims and tires
Easier to keep rolling
|Limited Product Choice
Reduced tire clearance
Truth be told, the difference between 650b and 700c wheels isn’t substantial when it comes to commuting and more often than not the choice will depend on the rider’s personal preference.
For example, if you want to run full fenders + wider tires, and the 700c wheels of your bike do not offer enough clearance, a conversion to 650b wheels could be of great help. But if your frame and fork have enough clearance even with 700c wheels, switching to 650b wheels makes little sense.