When looking for a commuter bike there are a number of different types of gearing systems that you can use for commuting. Bike gearing can be as simple as a single speed all the way to 28 speed with deraliuers. For bike commuting you want something simple, and sturdy and reliable.
Remember you are providing the power to the wheels through your pedaling and there is an optimum pedaling range to give the best effort to speed ratio.
First the different types:
- Single speed. This is like the first bike we had when we first learned to ride a bike. No gears, and no worries. The braking system can either be through braking with the pedals or using the handle brakes if you have them. This is by far the simplest, and the downside is if you have a lot of hills, the gearing ratio will not be optimal and your efforts go up significantly.
- There is a subset to a single speed, and it is called a Fixy. The bike does not have any pedal braking and you must continuously pedal. I do not recommend this bike for commuting, because in commuting you must stop at lights, slow down for traffic, and look out for pedestrians. For this reason this type of bike, in my opinion, is much too dangerous for commuting.
- External Derailleur System. Here you can see all the gearing when looking at the bike. Normally you have 2-3 gears in the front and 5-9 gears in the back. This gives you a total of up to 27 gear combinations. The external derailleur system’s advantage overall all others is its better efficiency and less weight for a gear system. External Derailleurs work well for commuting.
- Internal Hub gearing system. This bike gearing has all the gears hidden inside the wheel hub. The gearing uses a planetary gearing system. The advantages of this system are the gears and oil for the gears is protected from the elements. The maintenance with this system is significantly less than all others. The hub system works well for commuting.
The efficiency of converting the human power input into forward momentum is determined by a number of factors – roll or road resistance, air resistance and the best gearing ratio chosen.
- Roll resistance – this is determined by type of road finish, the tire width, tire rubber type and tire pressure. All things being equal, in order to reduce roll resistance chose thin tires and keep tires properly inflated.
- Air resistance – increases greatly as speed increases and is the most significant factor at speeds above 10 miles (16 km) per hour. The drag force increases in proportion to the square of the speed. Therefore at higher speeds this becomes the dominate resistance.
- Optimal gearing ratio – You, the power source, work best when the revolutions per minute are around 100 rpm. If you go much over this, then you lose efficiency as you start to bounce in your seat and your legs are pumping too quickly.
All things being said you can expect the following in efficiencies:
As a good rule of thumb you can expect about a 2% advantage using a external derailleur system over a hub gearing system. This is not huge, but is a slight advantage.
Therefore, when choosing a commuter bike, either an external derailleur or a hub gearing system are good choices. If you prefer speed than an external derailleur is your best bet (2% better) and if you want total simplicity than a gear hub is your best choice (gearing is protected from elements).