This post compares the advantages and disadvantages of 50/34 and 48/32 cranksets.
The Advantages of 50/34
- Higher Top Speed
To understand the effect of chainring size on speed, one has to become familiar with the term gear ratio.
The gear ratio indicates the number of rotations that the rear cog and respectively the rear wheel make per 1 complete spin of the cranks/chainring.
The higher the gear ratio, the higher the top speed. One can increase the gear ratio by getting a larger chainring and/or a smaller cog.
If the gear is 50T (chainring) / 11T (rear cog), the gear ratio is 50:11 = 4.54. In that situation, one revolution of the cranks results in 4.54 revolutions of the rear wheel.
The speed of a bicycle is dependent on two other factors as well – cadence (rotation of the cranks/chainring per minute) and wheel circumference.
Higher cadence and larger wheels will result in greater speed when the gearing of two bikes is identical because the rear wheel will make more revolutions per 1 minute and travel a greater distance. More distance in the same time frame equals extra speed.
The next table shows the top speed that 50/34 and 48/32 cranksets generate when pedaling at 90RPM and using standard 700×25 road tires.
| Chainring | Cog | RPM | Gear Ratio | Speed mph | Speed kph |
|---|---|---|---|---|---|
| 50 | 11 | 90 | 4.54 | 32.23 | 51.87 |
| 34 | 11 | 90 | 3.09 | 21.89 | 35.23 |
| 48 | 11 | 90 | 4.36 | 30.89 | 49.70 |
| 32 | 11 | 90 | 2.9 | 20.61 | 33.17 |
Conclusions:
- A 50T chainring provides a 4.4% higher top speed than a 48T chainring.
- A 34T chainring provides a 6% higher top speed than a 32T chainring.
The higher top speed that comes with a 50/34 crankset makes the crankset better for racers and amateur riders who want to get stronger and improve their times.
It’s also a good choice for commuters in decent shape who don’t have to overcome extremely long hills on their way to work.
- A Good Stepping Stone To Larger Gearing
A compact 50/34 crankset is a good choice for beginners who plan on getting even bigger chainrings (e.g., 53/39) in the future.
The Disadvantages of 50/34
- Potentially Unnecessarily High Gears
The main argument against 50/34 would be the high gearing offered by the 50T chainring. Truth be told, many recreational riders can’t take advantage of a high gear such as 50/11. For that reason, many consider it beneficial to get a smaller chainring that comes with lower but more practical and usable gearing.
- Large Gaps Between The Chainrings
Both 50/34 and 48/32 are cranksets with a massive (16T) drop between the chainrings. As a result, it’s often necessary to make a few upshifts or downshifts upon switching chainrings to get into the proper gear.
The Advantages of 48/32
- Low Gears
The main incentive to get a 48/32 crankset is to acquire low gears making it easier to maintain high cadence and climb hills.
Cadence is a term that indicates the number of chainring rotations per minute. A higher cadence such as 90 RPM results in more efficient power output over a long period of time and translates to higher average speeds. Hence the saying “spinning is winning”.
Also, the 32T chainring provides a very low gear ratio. For instance, if you’re using a cassette with а 28T large cog, the gear ratio (32:28) is 1.14. If the chainring has 34 teeth, the gear ratio climbs to 1.2. A lower gear ratio requires fewer rotations of the rear wheel per 1 spin of the cranks and makes climbing easier.
Another benefit of smaller chainrings is that can you get a cassette with a smaller large cog without massively sacrificing your low gearing. The advantage of those cassettes are the smaller jumps between the cogs. The smaller transitions make it easier to maintain a smooth cadence.
- User-friendly
A hardcore rider can pedal just fine with a 53/39 crankset, but untrained individuals will find similar cranksets too challenging, at least in the beginning.
A sub-compact crankset such as 48/32 is a good starting point for new riders or those who simply want to commute calmly on their road bike.
Another benefit of the low gearing is the lower stress on the knee joints.
- Gravel-friendly
Gravel bikes use lower gearing due to the additional friction. If you plan on converting your road bike into a gravel or semi-gravel machine, a low gearing will therefore be beneficial.
The Downsides of 48/32
- Limiting Growth
Serious riders will outgrow 48/32 after a while. At this point, it will be necessary to switch to 50/34 or larger chainrings. In some cases, it will be wiser to skip 48/32 altogether and go for 50/34 instead of introducing an extra step.
- Spinning out
The lower gearing of 48/32 may cause you to “spin out” on descents. Spinning out happens when the bike is already going at a speed that the pedals cannot generate. In that case, it’s pointless to pedal because the motion doesn’t contribute to forward movement.
Summary: What You Need To Know
- The difference between 50/34 and 48/32 is not substantial in most cases.
- The main advantage of 50/34 is the higher top speed making the bike more capable during racing and long descents. For recreational purposes, however, the higher top speed is of questionable value.
- 50/34 is a good choice for riders oriented towards racing and achieving decent average speeds. It could be slightly demanding for untrained individuals.
- 48/32 is a decent option for gravel riders and commuters. It offers decent top speed and the ability to conquer hills without requiring outstanding stamina.
