Can You Add Gears to Your Single Speed Bike?

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adding gears to single speed bike
Converting Single Speed Bike

A single-speed bike requires you to exert more physical strength and effort to maneuver and accomplish various routes and courses. But have you ever asked yourself whether there’s something you can do to your single-speed bike to make cycling easier? Simple–adding gears. 

Bicycle gears help increase pedaling efficiency. They maximize your mechanical advantage according to the trail you’re cycling on. One of the advantages of having bicycle gears is energy preservation, especially when facing aggressive headwinds and steep hills.

This article will help you understand what gears do when added to your single speed bike, how to do it and more. Read on to understand everything about single-speed bikes and bicycle gears.

Can You Add Gears to Your Single Speed Bike?

You can add gears to your single-speed bike, but only under one condition–your bike frame’s dropouts can accommodate a multiple-speed wheel hub. 

After setting the multiple-speed wheel hub, you can install a derailleur and multi-gear cassette. To ensure you change your single-speed bike to multi-speed successfully, you have to buy a new drivetrain kit.

If your bike’s frame is too narrow, consider internal gear hubs or try “cold setting” the frame. The latter applies if the frame is made out of steel.

Over Locknut Dimension

The most important factor when laying down a plan for conversion of your single-speed bike to multiple-speed gears is the O.L.D or Over Locknut Dimension for which your bike frame is designed.

Over Locknut Dimension (OLD) refers to the distance between the outer sides of the two lock nuts found on the usable part of the rear hub. Below are some standard rear O.L.D dimensions for various bikes:

  • 141mm: Boost hubs
  • 135mm: MTB, road bikes with disc brakes
  • 130mm: Road bikes without disc brakes
  • 120mm: Track bikes + fixes
  • 110mm: BMX

If your bike frame is engineered for O.L.D above 130 mm, you can go ahead and install a multi-gear cassette and derailleur. However, if it’s designed for O.L.D under 130mm, you only have two options:

  • To use an internal gear hub
  • To cold-set the frame.

Adding Gears to Your Single Speed Bike: Derailleur

Converting a single-speed bike to a multi-speed is no easy task. It requires the largest investment in labor, tools, and parts, especially if you want to convert one with a dedicated single-speed frame to multiple gears working with a derailleur.

What’s more, chances of your bike having O.L.D wide enough to accommodate a geared hub are low. Fortunately, it’s technically possible to convert to a gear system using a rear derailleur if the frame spacing is sufficient or where the frame suits a “cold setting.”

What Parts Do You Need?

1. A New Wheel With a Hub Designed for Gears

The design of single-speed hubs is such that they cannot accommodate cassettes. Therefore, you have no choice but to purchase a new hub designed for gears, and consequently, a new wheel.

2. Derailleur & Hanger

You’ll need a new rear derailleur for the conversion. By installing the derailleur, you necessitate the need for a special hanger. The hanger helps in positioning the derailleur to accommodate all rear cogs.

Unfortunately, most dedicated single-speed bike frames feature no built-in derailleur hanger. Neither do they have special bosses where you can install the hanger. Therefore, you have two options. To purchase a derailleur that includes a hanger or come up with a way to add a derailleur hanger to the frame.

If your single-speed bike frame is a fixie (track one), it’ll have rear-facing dropouts. If this is your case, buying chain tugs featuring a derailleur hanger is one of the possible solutions. Originally, the function of chain tugs is to help you adjust the chain tension.

3. Shifters

At least, you’ll need one new shifter. The investment won’t be too much if you’re on flat handlebars. 

However, you can expect the investment to be substantial if you’re running drop bars. This is true, especially if you have the so-called brake shifters. These integrate brake levers and shifters into one, allowing drop bars users to switch gears comfortably without moving excessively.

4. Shifting Cables & Housing

You’ll have to add new shifting cables and housing to your purchase list.

5. New Chain

A single-speed bike uses a significantly thicker chain than a geared bicycle. Its inner width is approximately 3.175 mm. On the other hand, geared models have a width varying between 2.38 mm and 2.18 mm. It depends on the number of gears the bike has.

The more gears you intend to have, the narrower the chain should be. That’s because the spacing between the rear cogs is smaller.

Notably, it’s hard for a single-speed chain to operate well with a derailleur- it’s too wide and thick.

6. New Chainrings

Single-speed chainrings can only work with single-speed chains. They are thicker than multi-speed chainrings, hence cannot fit a bike with multiple gears.

Therefore, you must replace your chainring regardless of whether you plan to add a front derailleur to your bike or not.

7. Bolt-on Cable Stoppers

A single-speed frame has no cable routing for gears. You can circumvent this challenge in two main ways:

  • Run a cable from the shifter to the derailleur, then zip-tie it to your bike frame. Though this is the simpler and cheaper option, most people don’t consider it, citing aesthetic reasons- it’s not pleasing.
  • Buy cable stoppers that you can mount to the frame’s top tube through bolts.

The Tools Your Require

If you’re okay with doing the conversion yourself, there are specific tools you must have that you probably miss. Ensure you have these tools to get the job done:

  • Variety of Allen keys
  • Screwdrivers
  • Wrenches
  • Dropout Alignment tool
  • Cable and housing cutters

It’s recommendable to use specialized cutters (cable and housing cutters) to make a clean cut. Avoid regular cable cutting pliers.

Adding Gears to Your Single Speed Bike: Internal Gear Hub

Most single-speed bikes feature an O.L.D of about 120mm. So, this limits the number of internal gear hubs that can accommodate such a frame. Below is a list of 120mm O.L.D internal gear hubs and the speeds that each offers:

Model                  Speeds

Sturmey-Archer S2 Kick-Shift (920g) 2

Sram Automatix 2 Speeds 2

Sturmey-Archer S3X Fixed Gear 3

Shimano SG-3C41 Nexus Gear Hub 3

Sturmey-Archer S30 X-RD3 3

Sturmey-Archer S80 XRF8 8

Generally, most internal gear hubs (120mm) are limited to 2-3 speeds. This is because it’s difficult for such a small package to pack more than this.

It’s worth mentioning that converting a single-speed frame to multi-speed with the help of internal gear can also be expensive considering the high cost of the hub. You need these components:

  • Internal gear hub
  • Shifter
  • New wheel or to re-lace the old wheel
  • Shifting cable & housing

Cold Setting a Steel Frame

If your bike frame is made of steel, another option would be to cold-set it. This ensures that the frame can accept wider internal gear hubs. Cold setting involves spreading the dropouts apart until the frame can accommodate a wheel featuring a hub designed for gears.

You can accomplish this through two methods- The Sheldon Brown Method or using threaded rods and nuts to spread the dropouts.

Remember, you can only go for a cold setting if the frame is steel. Besides, it must be in good condition. Otherwise, cold setting, in any other case, means the frame could lose its integrity. Such a frame is quite dangerous to ride.

Don’t worry about steel losing its structural integrity. Notably, steel’s ultimate tensile strength is higher than its yield strength. So, bending won’t have any significant effect on its structural integrity.

While this approach can be very tempting because it’s pretty simple, be wary of some of its notable drawbacks. These include:

  • Drop out misalignment resulting in uneven stress on the axle and the hub if you don’t do it well.
  • Constant chain stays tension-If you avoid the cold setting process, expect constant stress on the chainstays. 
  • Inconvenience- You’ll have to open the frame every time you change the wheel if you don’t set it cold.

Final Words

Adding gears to your single-speed bike gives you the advantage of increased efficiency and maneuverability. However, as we’ve already discussed, you need to have advanced knowledge of bicycle parts and how they work together. With this knowledge, all you need is to invest in equipment to change your fixed-speed unit into a multi-gear ride yourself.

The good news is that some manufacturers already have single-to multi-speed conversion speed available for their models, especially if they use the same frame to make both variants of their bike model. 

But even if the frame is engineered for one gear originally, don’t worry. Although the investment can cost a lot, you can still succeed at the conversion. Just weigh out the option of spending on the parts and continuing with a certain frame because it suits you well, or investing in a new multi-speed bike. It’s up to you. 

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