This post compares the advantages and disadvantages of 11-25 and 11-34 cassettes.
The Advantages of 11-34 Cassettes
1. Lower Gearing
The main advantage of 11-34 cassettes is the presence of a lower gear making climbing easier.
The difference between the lowest gear of 11-25 and 11-34 cassettes is substantial (9 teeth) and results in dissimilar gear ratios.
The gear ratio depends on the size of the chainring and the rear cog and indicates how many times the rear cog and consequently the rear wheel rotates per 1 rotation of the cranks.
The gear ratio can be easily calculated when one knows the number of teeth on the rear cog and the chainring.
For example, a 25t rear cog and a 32t chainring result in a 25:32 or 1:1.28 gear ratio. This means that the rear cog rotates 1.28 times per 1 spin of the chainring.
Meanwhile, a 34t rear cog and a 32t chainring result in a 34:32 or 1:0.95 gear ratio. Or in other words, the rear wheel makes short of one spin per 1 rotation of the cranks. The difference between the two gear ratios is 35%.
The cog offering a lower gear ratio makes pedaling easier because each revolution of the cranks equals a shorter distance.
The shorter the distance that the bike travels per 1 pedal stroke, the easier it is to move forward.
This can be achieved via three modifications:
- Smaller chainring
- Larger rear cog
- Smaller chainring + larger rear cog
- Better Compatibility With 1x Drivetrains
Since 11-34 cassettes come with lower gearing, they are not as limiting when the rider is relying on a single chainring (1x drivetrain).
- Lower Gearing Without Changing The Chainring
By switching from an 11-25 to an 11-34 cassette one will instantly acquire lower gearing without having to swap chainrings.
Meanwhile, if you want the low gear that an 11-34 cassette offers while running an 11-25 cassette, the only option will be to switch to a smaller chainring. The change could give you an even lower gear, but it will come at the expense of the bike’s top speed.
- More Suitable For Touring Cycling
Touring cyclists have to cover great distances and carry a lot of stuff. Thus, a lower gear is always welcomed.
The Downsides of 11-34 Cassettes
- Large jumps between each individual gear
11-34 cassettes come with larger jumps between the gears. That property makes it harder to maintain a high cadence and pedal with maximal smoothness.
The tables below compare the gradations of 11-25 and 11-34 cassettes:
9-speed
| Cassette | Shimano | SRAM |
| 11-25 | 11-12-13-15-17-19-21-23-25 | – |
| 11-34 | 11-13-15-17-20-23-26-30-34 | 11-13-15-17-20-23-26-30-34 |
Jumps in %
| Range | Speeds | Jumps In % | Average | |
| Shimano | 11-25 | 9 | 9%-8%-15%-13%-11.7%-10.5%-9.5%-8.7% | 10.67% |
| Shimano | 11-34 | 9 | 18%-15%-13%-17%-15%-13%-15%-13% | 14.87% |
| SRAM | 11-34 | 9 | 18%-15%-13%-17%-15%-13%-15%-13% | 14.87% |
Conclusion: The average jump of 11-34 cassettes is about 4% larger than that of 11-25 cassettes.
10-speed
| Cassette | Shimano | SRAM |
| 11-25 | 11-12-13-14-15-17-19-21-23-25 | 11-12-13-14-15-17-19-21-23-25 |
| 11-34 | 11-13-15-17-19-21-23-26-30-34 | – |
Jumps in %
| Range | Speeds | Jumps In % | Average | |
| Shimano | 11-25 | 10 | 9%-8%-7.7%-7%-13%-11.7%-10.5%-9.5%-8.7% | 9.45% |
| SRAM | 11-25 | 10 | 9%-8%-7.7%-7%-13%-11.7%-10.5%-9.5%-8.7% | 9.45% |
| Shimano | 11-34 | 10 | 18%-15%-13%-11.7%-10.5%-9.5%-13%-15.3%-13.3% | 13.25% |
Conclusion: The average jump of 11-34 cassettes is about 4% larger than that of 11-25 cassettes.
11-speed
| Cassette | Shimano | SRAM |
| 11-25 | 11-12-13-14-15-16-17-19-21-23-25 | 11-12-13-14-15-16-17-19-21-23-25 |
| 11-34 | 11-13-15-17-19-21-23-25-27-30-34 | – |
Jumps in %
| Range | Speeds | Jumps In % | Average | |
| Shimano | 11-25 | 11 | 9%-8.3%-7.7%-7%-6.6%-6%-11.7%-10.5%-9.5%-8.7% | 8.5% |
| SRAM | 11-25 | 11 | 9%-8.3%-7.7%-7%-6.6%-6%-11.7%-10.5%-9.5%-8.7% | 8.5% |
| Shimano | 11-34 | 11 | 18%-15%-13%-11.7%-10.5%-9.5%-8.7%-8%-11.11%-13% | 11.85% |
Conclusion: The average jump of 11-34 cassettes is about 3% larger than that of 11-25 cassettes.
The data makes it clear that the jumps on 11-34 cassettes are not nearly as large as one might expect.
Moreover, the biggest jumps include the three largest cogs which aren’t used as much as the mid-ones. Thus, the cadence of the rider will not suffer dramatically.
- Incompatibility With Short Cage Derailleurs
A 34T cog is notably larger and therefore requires a derailleur with a longer cage. Another way to increase the capacity of the derailleur would be to get a derailleur hanger extender.
- New Chain
The large cog will require a longer chain. If you’re switching from an 11-25 cassette a new chain will be needed.
The Advantages of 11-25 Cassettes
- Smaller Jumps
11-25 cassettes come with smaller jumps between the gears. The smaller gaps make shifting transitions smoother. Conversely, larger jumps can keep the rider in the wrong gear for a longer period of time and hurt comfort and efficiency.
- No Unused Gears
While it’s great to have a very low gear such as 34, if it’s rarely used, one is getting only the negatives of 11-34 cassettes and none of the benefits.
For some people, 11-25 cassettes offer “just enough” low end to the point where an extra gear is considered needless/redundant.
The Disadvantages of 11-25 Cassettes
- High gearing
The high gearing of 11-25 cassettes might work just fine for people in good shape and when riding on flat terrain, but cyclists who aren’t in top shape and/or suffer from joint pain could need lower gearing to make the sport safer and more enjoyable.
- Less suitable for 1x Drivetrains
If you want to have a 1x drivetrain, 11-25 cassettes are not the best option because they will greatly limit the lower range.
What to choose?
If you’re a competitive cyclist in good shape or want to become one, then an 11-25 is a good choice, especially when combined with compact cranks. 11-25 cassettes will allow you to maintain a high cadence and maximal smoothness between gear shifts.
If you are a recreational cyclist who doesn’t obsess over riding cadence, then an 11-34 is a logical choice because it’s better to have a very low gear and not need it than need it and not have it.
