Bicycle Repair & Fabrication

8 min read

Bicycle Repair & Fabrication

The bicycle is the most energy-efficient vehicle ever invented. A person on a bicycle covers ground 3-4 times faster than walking while using half the energy per kilometer. In a post-collapse world, every working bicycle is a strategic asset. Repair skills keep them rolling.

Common Repairs

Flat Tire Repair

Flats are the most common bicycle failure. With basic supplies, any flat is fixable.

Patching a tube:

  1. Remove the wheel from the bike
  2. Deflate completely. Push one side of the tire bead off the rim using tire levers (or screwdrivers, spoons — any flat prying tool)
  3. Pull the inner tube out through the gap
  4. Inflate the tube and listen/feel for the leak. If you can’t find it, submerge in water and watch for bubbles.
  5. Mark the hole. Deflate.
  6. Rough up the area around the hole with sandpaper or a rough stone (about 3 cm diameter area)
  7. Apply rubber cement (vulcanizing glue) and let it dry until tacky — about 2-3 minutes
  8. Press the patch firmly over the hole. Hold pressure for 30 seconds.
  9. Reinstall tube and tire. Inflate.

Improvised patches when kit is gone:

  • Cut patches from other damaged inner tubes. Use contact cement, super glue, or even rubber cement made from dissolved latex.
  • In a pinch: wrap the punctured area with electrical tape (multiple layers) as a temporary fix.
  • Stuff the tire with grass, rags, or strips of rubber for a solid but rough ride. This destroys the tube but gets you home.

Chain Repair

A broken chain stops you immediately.

Removing a broken link:

  1. Find the damaged link — usually a bent or cracked outer plate
  2. Use a chain tool (or a nail and hammer on a hard surface) to push the connecting pin partially out
  3. Remove the damaged link(s). You need an even number of links for the chain to rejoin.
  4. Push the pin back through to reconnect. Don’t push it all the way through the far plate — leave it flush.
  5. Flex the stiff joint by hand until it moves freely

The chain will be shorter, which means you may need to use a higher gear combination or shorten the rear derailleur range. A chain shortened by more than 4-6 links probably needs a replacement section spliced in.

Lubrication: Keep the chain lubricated. Any light oil works: motor oil, vegetable oil (temporary — it gums up), 3-in-1 oil, even rendered animal fat in an emergency. Apply to each link, wipe off excess.

Brake Adjustment

Rim brakes (most common):

  1. Check pad alignment: pads should hit the rim flat, not touch the tire
  2. Adjust cable tension: loosen the anchor bolt, pull cable tighter, retighten
  3. If pads are worn smooth, rough them up with sandpaper for better grip
  4. Pads worn to metal backing must be replaced — they will destroy the rim

Coaster brakes (backpedal brakes):

  • Internal mechanism, rarely fails
  • If the brake drags, the hub needs repacking with fresh grease
  • If the brake doesn’t engage, the internal brake shoes are worn — requires hub disassembly

Bearing Maintenance

Bicycles have bearings in three places: wheel hubs, bottom bracket (where the pedal cranks attach), and headset (steering). All use the same principle: steel balls rolling in a cup-and-cone race, packed in grease.

Wheel Hub Bearings

Service interval: Every 3-6 months of regular riding, or whenever the wheel feels rough or loose.

  1. Remove the wheel
  2. Remove the axle nuts and pull the axle out one side
  3. Catch the loose ball bearings — usually 9 or 10 per side. Put them in a cup so you don’t lose any.
  4. Clean bearings, cones (threaded cone-shaped pieces on the axle), and bearing cups (inside the hub) with a rag and solvent (gasoline, kerosene, or alcohol)
  5. Inspect: any bearing with a flat spot, crack, or pit must be replaced. Check the cups and cones for pitting.
  6. Repack with grease. Fill the cups about 2/3 full.
  7. Drop bearings into the grease. They should sit in the cup without falling out.
  8. Slide the axle back in and thread the cone down until it just touches the bearings with zero play but no binding. This adjustment is critical — too loose causes clunking, too tight causes grinding.
  9. Lock the cone in position with the locknut.

Bottom Bracket

Same principle as hub bearings but harder to access. The bottom bracket sits inside the frame’s bottom tube.

  • Requires a special wrench (or large adjustable wrench) to remove the lockring and bearing cup
  • Contains larger ball bearings (usually 11 per side, 1/4 inch)
  • Clean, inspect, repack with grease, and reassemble
  • If the bottom bracket cups or spindle are pitted, the crankset will always feel rough no matter how you adjust it

Headset Bearings

The headset allows the fork to turn for steering. If your steering feels notchy or gritty:

  1. Support the bike and loosen the headset locknut (top nut on the steering tube)
  2. Unscrew the adjusting cup
  3. The fork drops out — catch the bearings
  4. Clean and inspect everything. Headset bearings are often caged (held in a retainer ring).
  5. Repack, reassemble, adjust: the fork should spin freely with zero play

Tire & Wheel Care

Extending Tire Lifespan

Tires are the hardest part to replace. Maximize their life:

  • Proper inflation. Under-inflated tires wear faster and are more prone to flats. Check pressure weekly.
  • Avoid glass and debris. This sounds obvious, but actively steering around debris saves tires.
  • Tire liners: A strip of tough material (cut from a plastic bottle, an old tire sidewall, or commercial liner) between tire and tube adds puncture resistance.
  • Rotate tires: The rear wears faster than the front (it carries more weight). Swap front and rear every few months.

Wheel Truing

A wobbly wheel rubs the brakes and stresses spokes. Truing means adjusting spoke tension:

  1. Spin the wheel slowly and watch where the rim moves left or right relative to the brake pads
  2. At the wobble, find the spoke(s) pulling the rim to the wrong side
  3. Tighten the spoke(s) on the opposite side by 1/4 turn, or loosen the spoke(s) on the wobble side by 1/4 turn
  4. Spin and check again. Small adjustments.
  5. A proper spoke wrench grips the nipple perfectly. Pliers work but risk rounding the nipple.

Improvised Parts & Fabrication

Tire Alternatives

When pneumatic tires are gone:

  • Garden hose tire: Split a garden hose lengthwise and wrap it around the rim, securing with wire or zip ties. Rough ride but functional.
  • Rope wrap: Tightly wind rope around the rim in a continuous spiral. Coat with pine pitch or tar for durability.
  • Solid rubber: Cut strips from vehicle tires (abundant in salvage) and bolt or wire to the rim. Heavy but nearly indestructible.
  • Wooden rim: In extreme cases, a thick wooden rim with a leather or rubber strip contact surface. This is essentially reinventing the carriage wheel.

Cable & Brake Substitutes

  • Brake cables: Fence wire (smooth, not barbed) threaded through the original housing works as a brake cable. Stiff but functional.
  • Shift cables: Same approach with thinner wire. Friction shifting (no indexed clicks) is more forgiving of improvised cables.
  • Cable housing: Small-diameter steel or copper tubing, or tightly wound wire, substitutes for cable housing.

Frame Repair

A cracked frame doesn’t have to be terminal:

  • Sleeve splint: Slide a larger tube over the crack and braze or clamp it in place. The splint handles the load, not the cracked tube.
  • Wrap with wire and epoxy: Wind wire tightly around the crack, then coat with epoxy, fiberglass, or even pine pitch mixed with fabric for a composite patch.
  • Welding: If welding capability exists, a proper weld repair is the best fix. Use a TIG or brazing torch — MIG welding on thin bicycle tubes often burns through.

Bicycle as Infrastructure

Cargo Carrying

A bicycle isn’t just personal transport — it’s a micro freight vehicle:

  • Rear rack: Salvage or build from steel rod. Supports 15-25 kg in panniers or strapped on top.
  • Trailer: A simple two-wheel trailer towed behind the bicycle carries 50-100 kg. Build from salvaged wheels, angle iron, and plywood. A bicycle trailer is one of the most efficient human-powered cargo systems ever devised.
  • Front basket: A wire or woven basket on the handlebars carries 5-10 kg. More weight makes steering heavy.
  • Frame bags: Bags mounted inside the frame triangle carry tools, food, and small items without affecting handling.

The Bicycle Generator

Beyond transport, a bicycle is a human-powered engine. See Bicycle Generator for converting pedal power into electricity for lighting, radio charging, and small tool operation. A person pedaling comfortably produces 75-100 watts — enough to power LED lighting for an entire household.

Salvage Priority

Bicycles should be a high salvage priority. Every working bicycle found should be:

  1. Assessed for condition
  2. Given basic maintenance (tires, chain, brakes)
  3. Assigned to regular use or stored as parts inventory
  4. Stripped for parts only if the frame is damaged beyond repair

A community with 10 working bicycles has more practical mobility than one with a single car and limited fuel.