Repair guides › Frame & Fork
First check on a store-bought or used bike
The backbone. Everything bolts to it, and its geometry decides how the bike fits, steers and how wide a tire it clears. 6061 aluminum tubes TIG-welded into a front triangle (top, down, seat and head tube) and a rear triangle (seat stays and chainstays). Threaded inserts (nutserts) take racks, fenders and bottle cages. Aluminum does not rust, but it can crack, especially near welds, and it does not bend back.
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Steps
- Fork: the fork curves forward and the front disc brake caliper is on your LEFT as you sit on the bike. Store bikes, and used bikes someone has taken apart, are sometimes put back together with the fork backwards. If yours is, don’t ride it: take it back or to a shop.
- Brakes: the left lever works the front brake and the right lever the rear (US). Squeeze each hard: the lever stops well before the bar, and the wheel won’t turn when you push the bike.
- Quick releases: both levers fully closed, on the left side, firm enough to leave a mark on your palm. Never spin them like a wing nut.
- Headset: hold the front brake and rock the bike forward and back: no clunk. Turn the bar side to side: smooth, no grinding.
- Stem and bar: stand in front with the wheel between your knees and twist the bar: nothing moves, and the stem lines up with the front wheel.
- Pedals and cranks: wiggle each pedal and push each crank arm sideways: no play, no knock.
- Wheels: spin each one: no wobble or rub. Squeeze the spokes in pairs: none are loose. Rock the wheel sideways at the top: no play at the hub.
- Seat: twist the saddle: it doesn’t move, and the seatpost’s minimum-insertion mark is hidden inside the frame.
- Tires: squeeze them: firm. You’ll set the exact pressure in the Pump & patch missions.
- Disc brakes: the rotors run straight and the calipers don’t move when you wiggle them.
- Gears: in a stand or riding slowly, shift through every gear: no skipping, and the chain doesn’t fall off at either end.
- Anything loose or wrong? Don’t ride it yet. Each fix has its own mission later in the story, or a shop can sort it quickly. If the bike is new or was just put back together, check again after 2 weeks or 100 km (60 mi): new cables stretch and bolts settle.
Diagram
Seen from behind the bikeWheel axle and dropouts
Signs it needs doing
- Creaks that follow you even after the BB, pedals and seatpost are greased
- Hairline crack or paint flaking in a line at a weld
- Rear wheel no longer sits centered (bent dropout)
- Dent in the down tube or top tube
Articles about this job
- How much is a used bike worth? What I learned about pricing one
- The best first upgrades for a cheap bike (and what to skip): what I found as a beginner
- Walmart bike vs bike shop bike: what I found you really get for the money