Repair guides › Frame & Fork
Frame crack and damage inspection
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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Tools
- Degreaser: Simple Green All-Purpose Cleaner ($)
- Shop rags + nitrile gloves: shop towels and nitrile gloves ($)
Compare Good, Better and Best for each tool
Steps
- Wash the frame. Dirt hides cracks, so do this on a clean bike.
- Use a flashlight held low so light rakes across the paint. Check every weld: head tube, seat tube to top tube, chainstay to BB shell, dropouts.
- Look for a thin line, a ripple in the paint, or a dark or grey streak (aluminum oxide or dirt seeping out of a crack) at the welds.
- Sight down the bike from behind: the rear wheel should sit in the middle of the stays. If it leans, check the dropout alignment.
- Press on any dent with your thumb. If the tube flexes or the dent is sharp-edged, take it to a shop before riding.
- Check every nutsert and bottle-cage bolt is snug (2–3 Nm). Loose inserts spin and can rattle out.
Torque
| Fastener | Torque |
|---|---|
| Bottle cage / mount bolts | 2–3 Nm |
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