How To Convert a Single-Speed Bike to a Fixed Gear

You can convert some single-speed bikes to fixed gear only if the rear hub has a proper fixed-cog thread and a separate reverse-thread lockring thread. You also need adjustable rear-wheel position, a straight chainline, correct chain tension, secure axle hardware, and legally required working brakes.

Do not thread a fixed cog onto an ordinary freewheel hub or rely on thread-locking compound instead of a fixed-gear lockring. Back-pedaling force can unscrew an improperly retained cog.

Fixed gear is not the same as single speed

A single-speed freewheel lets the rear wheel turn while the cranks remain still. A fixed drivetrain ties crank rotation to rear-wheel rotation whenever the bike moves.

That changes starting, cornering, descending, stopping, and pedal-strike risk. Keep functional brakes even if local law permits a different minimum. Legality varies, so check official rules where you ride.

1. Verify the frame and rear hub

A suitable frame usually has horizontal or rear-facing dropouts, sliding dropouts, or an approved eccentric system so chain tension can be adjusted.

The hub needs:

• A fixed-cog thread
• A smaller reverse-thread lockring section
• An axle system approved for the dropout
• Enough spacing for a straight chainline

A flip-flop hub may have a freewheel thread on one side and fixed-cog plus lockring threads on the other. Identify the actual hub rather than assuming from appearance.

If the bike has vertical dropouts, do not use a half link or random gear combination as the only tension strategy. Use a manufacturer-approved eccentric or other fixed-gear solution.

2. Choose a compatible cog, lockring, and ratio

Match the cog and lockring threads to the hub. A cassette lockring is not a fixed-gear lockring.

Choose a moderate starting gear based on terrain and rider ability. Extremely high gearing can make starting and climbing difficult; extremely low gearing can produce very high cadence on descents.

Our single-speed conversion kit guide explains freewheel-oriented kits, but those parts do not automatically create a fixed-compatible system.

3. Remove the existing freewheel or wheel side

Use the correct remover for the existing freewheel, cassette, or cog. Park Tool’s freewheel removal guide explains how to distinguish a threaded freewheel from cassette sprockets.

On a flip-flop wheel, the simpler approach may be removing and reversing the wheel if the fixed side is already equipped. Follow the hub and frame instructions.

4. Install the fixed cog and lockring

Clean and inspect the hub threads. Apply the compound specified by the hub maker.

Thread the fixed cog clockwise by hand until seated. Install the proper reverse-thread lockring counterclockwise by hand, then tighten both with the approved tools and torque or securing procedure.

The opposing threads help prevent the cog from unthreading during back-pressure. Damaged, mismatched, or partly engaged threads are a stop condition.

5. Establish a straight chainline

Viewed from above or behind, the chainring and rear cog should align. A poor chainline creates noise, wear, derailment risk, and uneven tooth loading.

Adjust with hub, bottom-bracket, chainring, or approved spacer options from the component makers. Do not stack improvised washers under a fixed cog or lockring.

6. Size the chain and set tension

Use a chain compatible with the chainring and cog widths. Place the wheel in the dropouts and adjust it evenly.

Fixed-gear chains need a small amount of vertical movement at the tightest point in the chainring rotation. They should not be guitar-string tight or loose enough to derail. Chainrings are rarely perfectly concentric, so turn the cranks and find the tightest section before final adjustment.

Confirm:

• The axle sits evenly in both dropouts
• The wheel is centered
• The tire clears the frame
• The chain does not bind
• The axle nuts or bolts reach specified engagement and torque

7. Retain and test the brakes

Keep the front brake and any required rear brake in working order. Back-pressure on the pedals is not a substitute for a predictable friction brake, especially during a chain, cog, or pedal problem.

The CPSC’s bicycle requirements guidance includes federal braking and structural requirements for consumer bicycles. Road-use rules can add state and local requirements.

Test the conversion on a stand, then in a flat, traffic-free area. Practice starting, stopping with the brakes, cornering without pedal strike, and controlling cadence before entering traffic or descending.

Final inspection

Before every early ride, check:

• Fixed cog and lockring security
• Axle security and wheel alignment
• Chain tension at its tightest point
• Chainring and crank fasteners
• Pedals and toe-retention equipment
• Tire condition and pressure
• Front and rear brake function

Stop immediately for a loosening cog, clicking lockring, derailing chain, moving axle, brake change, or crank play.

Our guide to removing crank bearings explains why crank or bottom-bracket looseness must be diagnosed separately.

If pedal removal is needed for crank access, follow the thread directions and stop conditions in our stuck-pedal guide.

Frequently asked questions

Can any single-speed bike become fixed gear?

No. The rear hub needs fixed-cog and reverse-thread lockring interfaces, and the frame needs a safe way to set chain tension and secure the axle.

Can I use a normal freewheel lockring?

No. Use the lockring specified for the fixed hub. Cassette lockrings and bottom-bracket lockrings are different parts.

Do I need brakes on a fixed-gear bike?

Keep working brakes and verify the legal requirements where you ride. Pedal resistance is not a reliable replacement for a mechanical brake.

Bottom line

A safe conversion is a hub, chainline, tension, retention, and braking project, not simply a cog swap. Use a true fixed hub with a reverse-thread lockring, align the drivetrain, secure the wheel, and keep functional brakes.