What is the best ratio for your fixed gear (or single speed) bike? A single-speed bicycle as the name suggests is a bike with just one gear ratio. So, having the right gear combo from the get-go is very important, and this is why there has always been a lot of debate regarding the right gear ratio for fixed gear bikes.
On the other hand, there is no one-size-fits-all answer to this question: every single-speed bike and every rider is different. And, the terrains where you’ll ride the bike will also affect the answer to this question.
In this guide, we will explore all the ins and outs about the best gear ratio for fixed gear or single speed bike.
Common Gear Ratios for Fixed Gear Bike
Two of the most common fixed gear ratios are 44:16 (2.75) and 46:16 (2.88). Let’s understand these numbers in depth.
As we can see from the above examples, there’s the principal number formatted as aa:bb (44:16) or aa/bb (44/16). Here, the number xx represents the number of teeth on the bike’s front gear (the chainring), which is the gear placed on the side of the front wheel. So, in this example, the chainring has 44 teeth.
On the other hand, the number yy refers to the number of teeth of the back gear (the cog). So, on the above’s example, the back gear has 16 teeth. The front gear and back gear are connected with the crankset system.
So, why are the 44/16 and 46/16 gear ratios the most popular ones? Here is why:
44:16 Gear Ratio
A 44:16 gear ratio, or also referred to as 2.75 ratios promotes easier acceleration but will make for a lower top. So, it’s generally a better ratio for recreational riding, commuting, or any other riding activity that prioritizes comfort rather than top speed. If the terrains around you are mostly flat, then a fixed gear bike with this gear ratio is probably the best choice for you.
46:16 Gear Ratio
The 46:16 ratio, or 2.88, offers higher top speeds than the 44:16 ratio. Although, it will be much harder to accelerate. The 46:16 ratio will allow you to cover more distance with less effort. Typically this gear ratio is better for performance-related rides like races, but it’s still great for leisure riding.
So, in general, the smaller your gear ratio, the easier it is to accelerate, but the lower your top speed, and vice versa.
How To Calculate Gear Ratio
Here, we will discuss the basics of calculating gear ratios and how to use the calculation if you want to change your fixed gear bike’s gear ratio.
In general, there are two basic ways to calculate a bicycle gear ratio: straight ratio and gear inches.
Straight Ratio
The simplest way to calculate the gear ratio that we have also used above. Here, we simply divide the number of teeth of the front gear (the chainring) with the number of teeth of the back gear (the cog). A 2:1 ratio, for example, means that the front gear has twice as many teeth as the cog, for example, 32:16.
In a 2:1 gear ratio, with each pedal (and one revolution of the crank), the rear wheel will rotate 2 times. So, with a 2.75 wheel ratio, the rear wheel will rotate 2.75 times. This is why the bigger the ratio, the higher your bike’s top speed will be but the harder it is to accelerate the bike.
In practice, a lower ratio will translate into easier pedaling but you’ll need to spin the crank more to produce speed. On the other hand, it’s easier to increase your cruising speed with higher ratios but it’s going to be harder going up hills.
However, it is important to note that the gear ratio is not the only thing to affect how easy or hard your bike can build speeds. Wheel size, for example, will significantly affect how easy it is for the wheel to rotate.
When should we use straight ratios:
Straight gear ratio is the basis for all other calculations related to the bicycle, and so is very useful for comparative purposes. This calculation is most useful to figure out gear ratio, and also when explaining the concept of gear ratios (like our discussion above).
Gear Inch
A more advanced and more accurate way to calculate gear ratio is using gear inch calculation, which combines straight ratio calculation with wheel diameter. In this calculation, we are going to measure the overall diameter of the wheel (that is, including the fully-inflated tire).
Gear inch calculation is useful to calculate how far the bike will travel with one revolution of the crankset (one pedal). Ther formula to calculate gear inch is as follows:
Gear inch: (the diameter of the rear wheel x the number of chainring teeth)/ the number of cog teeth.
So, if for example, our straight gear ratio is 44/16 and the rear wheel has a standard overall diameter of 26”, then the calculation would be: (26 x 44)/16= giving us 71.5 gear inches.
The higher the gear inch number, the farther your bike can travel on one revolution of the crank. We can multiply gear inch result by pi (?)= 3.14 to get the actual distance traveled every revolution of the crank. With the same example, the distance traveled is 71.5 x 3.14= 224.5 inches.
When should we use gear inch:
You should use gear inch over straight gear ratio when tire size is an important factor. If, for example, you are only changing the chainring of your bike but nothing else is changed, then you don’t really need to use gear inch.
This calculation is, for example, useful when you have a fixed-gear bike with 26” wheels and you’d want to replicate the same feel and performance in your new bike with different wheel sizes. For example, if your new bike has 29” wheels, then 44/16 would produce a 79.75 gear inch (vs 71.5” with 26” wheels). So, you should change the cog to 18” where you’d get a 70.8 gear inch, much closer to the 71.5 gear inch of the old bike.
There are certainly many other calculations we can use to measure gear ratio and how it can affect the revolution of a crank, but these two remain the most basic and should be sufficient enough for most applications.
FAQs Regarding Gear Ratio
1. How can we change a fixed gear’s gear ratio?
Since in a single speed bike we can’t change our gears, the main way to manipulate gear ratio is to change the cog (the rear gear). Changing the cog will affect the denominator of the straight ratio.Another way is to change the chainring (front gear), although it’s less common than changing the cog.
The number of teeth on the cog acts as the denominator of the gear ratio: xx/16, with 16 being the cog’s teeth. On the other hand, the number of teeth of the chainring acts as the numerator of the gear ratio: 44/yy.
So, the smaller the cog, the bigger the gear ratio will be. On the other hand, the bigger the chainring, the smaller the gear ratio.
2. How will gear ratio affect speed?
The lower the gear ratio is, the easier it feels when you ride the bike. If you want your bike to gain a substantial amount of speed with each pedal, you’d want a lower gear ratio. Also, the fewer total number of
teeth you have on your cog and chainring (higher ratio), the harder you’ll need to pedal. Yet, you’ll cruise more efficiently and your bike will have higher top speeds.
It’s important to note that different chainring and cog combinations can produce the same ratio. For example, both 32/16 and 36/18 has 2:1 ratio. This is where you should also factor in gear inch instead of just a simple gear ratio.
Final Thoughts
In a fixed gear or single speed bike, having the right gear ratio according to your needs and cycling habits is very important since you can’t change your gears while riding.
The most common gear ratios in fixies are 44/16 and 46/16: 44/16 produces higher acceleration but you get lower potential top speeds. On the other hand, 46/16 offers better speeds and performance but it’s going to be much harder to build acceleration.
It’s important to understand, however, that the size of the wheels will also matter. So, when comparing two bikes with different wheel sizes, we should calculate gear inch instead of using straight gear ratio calculation to properly assess their speed and acceleration potential.
There are also other factors like crank length, tire weight, and bar width that will also affect the calculation. However, all of these calculations are based on straight gear ratio, and this is why understanding what’s the best gear ratio for your fixed gear bike in the first place is very important in optimizing its performance.