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

You can convert a single-speed bike to fixed gear only when the rear hub has a dedicated fixed-cog thread and separate reverse-thread lockring thread, and the frame provides an approved way to set chain tension. The chainline, cog, lockring, chain, axle retention, and brakes must also match. A freewheel hub cannot become safe fixed gear through adhesive or extra tightening.

This seven-step guide is research-based. It does not replace the hub, frame, brake, or drivetrain maker’s instructions. If you cannot identify a component or obtain its service procedure, have a qualified bicycle mechanic inspect the bike before buying conversion parts.

Check compatibility before removing anything

Check compatibility before removing anything

Part	Required evidence	Stop condition
Hub	Fixed-cog thread plus smaller reverse-thread lockring thread	Freewheel-only thread, cassette body, damaged or unknown threads
Frame	Horizontal/rear-facing dropout, sliding dropout, or approved eccentric	Vertical dropout with no approved tension method
Cog and lockring	Exact hub-thread match and maker-approved engagement	Cassette lockring, bottom-bracket lockring, or partial engagement
Chainline	Chainring and cog align within component instructions	Visible angle or improvised spacing at cog/lockring
Chain	Width and pitch compatible with chainring and cog	Binding, damaged links, incompatible width
Wheel retention	Hub and frame-approved axle hardware and engagement	Axle movement, damaged dropout, inadequate thread engagement
Brakes	Functional brakes compliant with instructions and applicable law	Pedal resistance treated as the only dependable brake

Do not proceed because a wheel is advertised as “flip-flop.” Confirm which interfaces are actually machined on each side and which cog, freewheel, and lockring standards the maker permits.

Fixed gear changes how the bicycle behaves

A single-speed freewheel allows coasting while the cranks stop. A fixed drivetrain makes crank rotation follow rear-wheel rotation whenever the bicycle moves. That changes starting, descending, cornering, pedal-strike exposure, cadence control, and stopping technique.

Keep working friction brakes. The CPSC bicycle requirements describe braking-system requirements and tests for consumer bicycles (CPSC bicycle FAQ). Product compliance and road-use law are separate questions, so also check the current rules where you ride.

1. Identify the frame, hub, and threads

Find the hub maker, model, and current service information. A fixed side typically has a larger conventional thread for the cog and a smaller reverse-thread section for the lockring. Do not judge thread direction or standard from appearance alone.

Inspect both thread sets under good light. Reject flattened, crossed, corroded, or incompletely formed threads. If a used cog has loosened repeatedly, inspect the hub rather than installing a stronger adhesive.

The frame needs controlled fore-and-aft axle movement or an approved eccentric system. Vertical dropouts normally do not provide enough adjustment. A half link or lucky tooth combination does not guarantee stable tension as parts wear or the wheel moves.

2. Choose the exact cog, lockring, chain, and ratio

Use the cog and reverse-thread lockring specified for the hub. A cassette lockring or bottom-bracket lockring may look similar but is not an acceptable substitute. Confirm material, thread standard, width, and minimum engagement from the component documents.

Match chain width to both chainring and cog. Inspect tooth profiles and replace hooked, chipped, or badly worn parts. Choose a moderate ratio suited to the rider and terrain. Ratio selection cannot correct unsafe chainline, weak brakes, or an incompatible hub.

Our single-speed conversion kit guide covers coasting cassette-freehub conversions. Those spacer-and-cog kits do not create a fixed-cog thread or reverse-thread retention interface.

3. Remove the freewheel or reverse a prepared wheel

Park Tool’s freewheel removal and installation guide shows how threaded freewheels differ from cassette systems and why the correct remover matters. Secure the remover as instructed and support the wheel without loading spokes or brake rotors incorrectly.

If a flip-flop wheel already has a properly installed fixed cog and lockring on the other side, wheel reversal may be the intended method. Confirm chainline, brake alignment, axle hardware, and rotation direction after reversing it. Do not assume the two sides share identical spacing.

4. Install the fixed cog and reverse-thread lockring

Clean the threads and inspect them again. Apply only the lubricant or compound specified by the hub or cog maker. Start every threaded part by hand.

Thread the cog onto its designated thread until it seats as specified. Install the correct lockring onto the smaller reverse-thread section in the opposite direction. Use the specified tools and tightening procedure. The opposing thread direction helps retain the cog when reverse pedal force is applied, but it cannot compensate for mismatched, damaged, or partly engaged threads.

Never substitute thread-locking compound for the mechanical lockring. A natural workshop rule applies here: retention comes from the designed interfaces, not wishful tightening.

5. Establish a straight chainline

The chainring and rear cog should run in the same plane. Check from above or behind using the component maker’s measurement method. A visibly angled chain can make noise, wear unevenly, climb teeth, or derail.

Correct chainline only through approved chainring position, bottom-bracket length, hub spacing, or maker-specified spacers. Do not stack washers behind a fixed cog or reduce lockring engagement. After any adjustment, recheck crank clearance, chainring fasteners, cog seating, lockring engagement, and wheel centering.

6. Size the chain and set tension at the tight point

Fit a compatible chain without twisted or stiff links. Move the rear wheel evenly in the dropouts and keep it centered. Rotate the crank through a full revolution because chainrings and cogs are not always perfectly concentric.

Set tension according to the component instructions at the tightest point. The chain needs enough movement to articulate freely but not enough slack to derail. “Guitar-string tight” can overload bearings and make the drivetrain bind. Excess slack can allow the chain to leave the teeth.

Confirm these conditions before tightening the axle:

• the axle is seated consistently in both dropouts;
• the wheel is centered and the tire clears the frame;
• chain tension remains acceptable through a complete crank rotation;
• the chainline remains straight;
• axle nuts or bolts have required thread engagement;
• tensioners or retention devices are installed only where approved.

Tighten axle hardware to the hub or frame maker’s specified procedure, then recheck tension and alignment. Hardware can pull the wheel out of position during tightening.

7. Retain, inspect, and test the brakes

Service the brakes before riding. Confirm pad or rotor condition, cable or hose routing, lever travel, caliper security, and wheel installation. Do not treat resisting the pedals as the only predictable stopping system. A chain, cog, lockring, crank, pedal, or rider-control problem can remove that resistance without warning.

First test on a repair stand, keeping hands and clothing away from the moving drivetrain. Apply forward and reverse load by hand while watching the cog, lockring, chain, axle, and wheel. Stop for movement, noise, binding, or a loosening fastener.

Then use a flat, traffic-free area. Practice starts, brake-controlled stops, low-speed turns, cadence control, and cornering clearance. Avoid descents and traffic until the rider can manage continuous pedal motion without relying on skidding.

Run an early-service inspection

Check the conversion before every early ride and after any hard stop, impact, wheel removal, or drivetrain service. Inspect:

• cog and lockring security;
• axle position, hardware, and dropout condition;
• chain tension at the tightest point;
• chainline and chain condition;
• chainring, crank, and pedal security;
• tire pressure and condition;
• both brakes and their fasteners.

Stop riding for a clicking or moving lockring, loosening cog, derailing chain, shifting axle, bent tooth, crank play, pedal damage, wheel movement, or changed brake feel. Diagnose the cause rather than repeatedly tightening a failing interface.

Our fixed-gear versus single-speed guide explains the riding differences. The single-speed chain-tension guide covers tight-point checks, and the stuck-pedal guide explains thread directions if crank access requires pedal removal.

Frequently asked questions

Can a normal single-speed freewheel hub use a fixed cog?

No. A fixed setup needs the hub’s dedicated fixed-cog thread and separate reverse-thread lockring interface. Adhesive and a conventional freewheel thread do not reproduce that retention system.

Can vertical dropouts work for fixed gear?

Only with a frame-maker-approved tension system such as a compatible eccentric arrangement. A random gear combination or half link is not a durable substitute for controlled axle adjustment.

Do fixed-gear bikes need brakes?

Keep functional brakes and verify the applicable product and road-use requirements. Pedal resistance depends on an intact drivetrain and is not a substitute for a predictable friction brake.

Bottom line

A safe single-speed-to-fixed conversion is a retention, chainline, tension, axle, and brake project. Use a true fixed hub, exact cog and reverse-thread lockring, approved tension adjustment, straight chainline, secure wheel, and working brakes. Stop when any interface cannot be identified or documented.