This post compares the advantages and disadvantages of running a 50/34 crankset in conjunction with an 11-34 cassette.
The Advantages of 50/34 + 11-34
- More Than Enough Top Speed
The highest gear of this combo is 50/11 and provides a 4.54 gear ratio.
The gear ratio indicates the number of rear cog and rear wheel rotations per 1 full spin of the cranks and chainring(s).
In 50/11, the rear wheel rotates 4.54 times per 1 revolution of the cranks.
The speed of a bicycle is determined by three factors:
- The gear ratio
- The cadence of the rider a.k.a. RPM (the rotations of the cranks that the rider performs in 1 minute)
- The wheel circumference (when all other parameters are equal, larger wheels produce more speed)
If the gear ratio is 4.54, the cadence is 90 RPM, and the wheel circumference is 2111mm (700×25 wheels), one can easily calculate the traveled distance in 1 minute or 60 seconds.
A 4.54 gear ratio indicates 4.54 rotations of the rear wheel. By multiplying the number of rotations by the RPM and then by the wheel circumference we find the traveled distance.
In this case, we have 4.54x90x2111=862,554mm=862.5m=0.86km=0.53miles.
The formula for speed is Speed = Distance/Time.
When we input the values, we get:
Bike Speed = 862.5m / 60s = 14.375 m/s = 51.75 km/h = 32.156 mi/h
The table below contains the top speed that a 50/11 combination generates at different RPMs when using standard 700×25 tires.
|RPM||Wheel Size||Speed kph||Speed mph|
Conclusion: 50×11 is a very high gear that provides plenty of top speed for most riders. Spinning out will occur only during big descents.
Spinning out happens when the bike is moving at a speed exceeding the level that can be reached via pedaling. In that situation, pedaling feels effortless, but it’s also pointless as it doesn’t contribute to forward movement.
- Insane Low Gear
The lowest gear is 34/34 and has a 1:1 gear ratio. One spin of the cranks results in one spin of the rear wheel. The lower the gear ratio, the easier climbing becomes because the rear wheel doesn’t have to rotate multiple times.
34/34 is not nearly as low as what we could find on an MTB with a 3x drivetrain (e.g., 22/36), but it’s low enough for a road machine. Road bikes have lower rolling resistance and are meant to conquer paved roads. Thus, they don’t require the low gearing of an MTB.
For trained cyclists, the gearing may even be too low and non-needed. If you’re a strong cyclist and/or you don’t conquer hilly terrain regularly, you can benefit from a smaller cassette.
34/34 is also a good gear for commuters as it reduces the effort needed to climb. This is beneficial when you want to minimize energy expenditure on your way to work.
The Downsides of Running 50/11 + 11/34
- The Gearing Could Be Needlessly High
Even though it’s awesome to have a high gear, sometimes it’s simply not necessary. Many casual cyclists won’t be able to take advantage of 50/11, at least not in “high cadence mode”. Thus, it could be beneficial to look into a set of sub-compact cranks, for example.
- Large Jumps Between the Rear Cogs
Large first gears result in larger transitions between the cogs. In other words, the size difference between each cog is greater. This is problematic because it becomes more difficult to maintain a smooth cadence since each shift throws you onto a notably different gear ratio.
The table below contains the gradations of 11-speed 11-25, 11-28, 11-30, 11-32 and 11-34 cassettes.
The jumps between the gears on an 11-34 cassette are two teeth minimum. The largest jump is between the 10th and 11th gear (30T to 34T).
In different, an 11-25 cassette offers one tooth transitions for the first 7 gears. Consequently, it’s much easier to maintain a high cadence.
High cadence is associated with better energy expenditure, lower joint stress, and greater average speed.
Of course, the difference isn’t massive, and most casual cyclists wouldn’t care. However, those who want to have smaller jumps between the gears allowing them to maintain the smoothest possible cadence will benefit from getting a cassette with a smaller large cog.
The trade-off is that you will lose the bail-out gearing that comes with the 34T cog.
Summary: What You Need To Know
- A compact 50/34 crankset is a fine choice for cyclists who plan on riding seriously.
- Combining a 50/34 crankset with an 11-34 cassette is also a very decent option because you have the best of both worlds – very high gears and very low gears.
- For some people, a 34T cog may be needlessly large, especially if the terrain is mostly flat. If that’s the case, one can replace the cassette with 11-25/32 and benefit from the smaller jumps between the gears.