Reference
Bolt & Fastener Quick ID
When you can't remember what tool fits a particular bolt, find it here. Sizes shown are the most common across modern bikes; older bikes and oddball...
When you can’t remember what tool fits a particular bolt, find it here. Sizes shown are the most common across modern bikes; older bikes and oddball brands sometimes vary.
By location #
| Location | Tool | Size |
|---|---|---|
| Stem faceplate (4 bolts) | Hex | 4 mm |
| Stem clamp on steerer (2 bolts) | Hex | 4 or 5 mm |
| Top cap | Hex | 5 mm |
| Saddle clamp | Hex | 4, 5, or 6 mm |
| Seatpost clamp on frame | Hex | 4, 5, 6 mm — or QR lever |
| Bottle cage | Hex | 3 or 4 mm |
| Disc rotor (6-bolt) | Torx | T25 |
| Disc rotor (Centerlock) | Cassette lockring tool | (no size — splined) |
| Brake caliper to frame/fork | Hex | 5 mm |
| Brake caliper pad pin | Hex (Shimano) / Allen / Torx | 2.5 mm Shimano; varies |
| Hydraulic bleed port (Shimano) | Hex | 7 mm flat (bleed port nipple) — actually a wrench, not hex |
| Hydraulic bleed port (SRAM lever) | Torx | T10 |
| Hydraulic bleed port (SRAM caliper) | Hex | 4 mm |
| Brake/shifter lever clamp on bar | Hex | 4 or 5 mm |
| Front derailleur clamp | Hex | 4 or 5 mm |
| Front derailleur cable pinch | Hex | 5 mm |
| Rear derailleur to hanger | Hex | 5 mm |
| Rear derailleur cable pinch | Hex | 4 or 5 mm |
| Rear derailleur limit screws (H/L) | Phillips or Hex | #2 Phillips or 2.5/3 mm hex |
| Rear derailleur B-tension screw | Phillips or Hex | #2 Phillips or 2.5/3 mm hex |
| Crank arm bolt (SRAM DUB / self-extracting two-piece) | Hex | 8 mm |
| Crank arm pinch bolts (Hollowtech II non-drive) | Hex | 5 mm |
| Crank arm bolt (square taper) | Socket | 14 mm or 8 mm hex |
| Crank arm preload cap (Hollowtech II) | Plastic preload tool or coin | Shimano TL-FC16/TL-FC18 |
| Pedal | Pedal wrench OR hex | 15 mm flats OR 8 mm hex |
| Cleat (SPD, Look Keo, Time) | Hex | 4 mm typical; some 3 mm |
| Cleat (some Shimano road) | Torx | T20 or T25 |
| Cassette lockring | Splined cassette tool | Park FR-5.2 (HG) or specific (XD, Microspline) |
| Through-axle | Hex | 5 or 6 mm |
| Chainring bolts | Hex or Torx | 4–5 mm hex, or T25–T30 Torx |
| Chain quick link | Master link pliers (or strong hands) | n/a |
| Bar end plug (bolt-in) | Hex | 4 mm |
| Headset top cap | Hex | 5 mm |
| Computer/GPS mount | Hex | 3 mm |
| Bottle opener bracket / accessory mounts | Hex | 3 or 4 mm |
| Fender stays | Hex | 4 or 5 mm |
| Kickstand mount | Hex | 4 or 6 mm |
Bolt sizes most commonly needed #
If you only carry a few sizes on a multitool, these cover most bikes:
- Hex: 3, 4, 5, 6, 8 mm
- Torx: T25
- Phillips: #2
A complete home set adds: 2, 2.5 hex; T10, T15, T20, T30 Torx; #1 Phillips; small flathead.