Purpose-built single speed bikes have a horizontal dropout; that’s the groove where the rear wheel axle fits. These dropouts allow for easy chain tensioning. Most hardtail mountain bikes have vertical dropouts so another means of getting the correct chain tension is required.
Converting a Hardtail to Single Speed
The most important factor for a single speed mountain bike is matching the gear chosen to suit the normal riding terrain. Most single speeders use a 32 tooth front chainring matched to a 16 tooth rear cog. This is fine for relatively flat riding but for hilly off-road terrain consider an 18 or even 20 tooth rear cog.
Single Speed Bike Conversion Tools
- Single speed converter kit.
- Chain-tensioning device.
- Some chain half links.
- 5mm chainring bolts.
Building a Single Speed Bike
- Chain. Split and remove from the bike.
- Gear mechanisms. Remove all gear shifters, gear cables and front and rear derailleurs.
- Front Chain Rings. Undo and remove the small and large chainrings. Keep the middle chainring. The bolts that hold the middle and outer chainring onto the crank will be too long to hold the single chainring and should be replaced with shorter BMX style 5mm bolts.
- Rear Wheel. Remove the rear gear cassette and replace it with a single speed converter kit. The kit contains a single cog that can be positioned correctly on the freewheel hub by the use of a series of spacers so as to achieve the correct chainline.
- Chainline. This is the line between the front chainring and the rear cog. On a single speed this should be a perfectly straight line.
- Achieving good chainline. By the use of the spacers supplied with the single speed converter kit it is possible to move the rear cog inwards or outwards on the rear freehub so as to achieve the perfect, or near perfect chainline. Tip! Buy a converter kit with as many spacers as possible. This gives more options for positioning the rear cog on the freewheel.
- Chain replacement. Once the rear wheel is back on the bike, wrap the chain around the front chain ring and rear cog. The chain must be as short as possible without causing the drivechain to bind.
- Chainwrap. The rear chain needs to wrap around the rear cog as close to 180 degrees as possible. That’s all the way around the back of the cog – a U-turn. It is very important to get the chain length as short as possible before fitting the tensioning device.
- Chain tension. This is the most important aspect of single speeding. If the chain is too loose it could slip causing the rider a certain amount of discomfort. Correct chain tension on a vertical dropout bike is achieved by first getting the chain as short as possible and then taking up any slack by use of a chain-tensioning device. These can be spring loaded or fixed.
Tips on Setting Up a Single Speed
Most chain tension devices now mount to the rear gear hanger although some still mount to the chainstay. They achieve chain tension by either pushing up or down on the fitted chain taking out any slack in the system. For absolute adjustment it is possible to buy “chain half links”. This is simply a chain link, which is shorter than a standard link but does exactly the same job. Get the chain length right and a chain-tensioning device may be unnecessary.
Ride a Single Speed Bike
Having done all this, the bike is ready to ride. If the first ride does not feel quite right, a little tinkering with chainline adjustment or chain tension may be required. Enjoy.
