Bicycle disc caliper mount (post / IS) screw size
M6 · 18 to 30 mm long
Our records put Bicycle disc caliper mount (post / IS) on M6 screws in lengths from 18 to 30 mm.
The record covers fastens the caliper body to the frame or adapter.
This entry is marked confirmed and comes from parktool.com.
For reference, M6 is 6 mm across the threads at 1 mm pitch. The imperial size people confuse it with: 1/4in-20 (6.35 mm) — the tripod/camera thread; visibly larger than M6.
Bicycle disc caliper mount (post / IS) screw specifications
One row per fitment record. Head, drive are shown only where the source states them; pitch is the ISO coarse pitch for the thread.
| Thread | Length | Pitch | Head | Drive | Where it goes | Status |
|---|---|---|---|---|---|---|
| M6 | 18–30 mm | 1 mm | not stated | not stated | fastens the caliper body to the frame or adapter | Confirmed |
Fitment records and sources
fastens the caliper body to the frame or adapter
pitch 1 mm · tap 5 mm · clearance 6.6 mm · PH3 / Torx T30
How to check the screw before you buy
- Where the manufacturer publishes a torque value, use a torque driver rather than feel.
- Diameter: across the threads an M6 screw measures about 6 mm with calipers (usually a hair under). If yours measures noticeably more or less, it is a different thread.
- Pitch: 1 mm from one thread crest to the next (10 crests per centimetre). A thread pitch gauge or the pitch-gauge tool settles it in seconds.
- Length: measure from under the head to the tip for pan, button, wafer and cap heads; countersunk (flat) heads are measured overall.
- The records span 18–30 mm, which means different positions take different lengths — match each hole to its own screw.
- Driver: the source does not name the drive. Standard M6 heads take PH3 for Phillips and T30 for Torx, and a 5 mm hex key for socket heads; a bit that fits loosely will cam out and strip the head.
- Tightening: no device-specific torque is published in these records. The site's general figure for M6 is about 7-10 N·m into metal threads and 2.5-4.0 N·m into plastic bosses; snug it up and stop.
Common mix-ups with M6
- UR cobot flange bolts are commonly sold/quoted as 'M6 bolts' but the required length depends on the tool thickness; UR's own guidance is bolt class M6-8.8 to ISO4762 without a fixed length, so length must be selected per adapter/tool stack-up, not assumed as a fixed mm value.
- Mic stand threads (5/8-27) and tripod threads (1/4-20, 3/8-16) are imperial, not metric — only accessory clips like Gravity's M6 adapter are genuinely M6.
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Devices whose records share a thread with Bicycle disc caliper mount (post / IS), closest length match first.
- Suzuki V-Strom also M6 × 20 mm
- Kayak accessory rail T-bolt kit also M6 × 25 mm
- Shimano XTR FC-M815 and SLX FC-M7000 cranksets also M6 × 19 mm
- Motorcycle side panels and tail cowl also M6 × 18–20 mm
- Pride Go-Go scooter tiller lock knob also M6 × 18–25 mm
- Gas grill cart and legs also M6 × 20–30 mm
- Shimano BR-M6100 disc brake caliper also M6 × 18 mm
- Shimano Deore BR-M6100 disc brake caliper also M6 × 18 mm
Questions about Bicycle disc caliper mount (post / IS) screws
- What size screw does Bicycle disc caliper mount (post / IS) use?
- M6 × 18–30 mm for fastens the caliper body to the frame or adapter.
- How long are the screws in Bicycle disc caliper mount (post / IS)?
- The records range from 18 to 30 mm depending on the position, so match each screw to its own hole.
- What is the thread pitch of an M6 screw?
- 1 mm (coarse), which is the standard pitch for M6 machine screws; a 0.75 mm fine pitch exists but is uncommon. The tap drill is 5 mm and the normal clearance hole is 6.6 mm.
- What screwdriver do I need for Bicycle disc caliper mount (post / IS)?
- The sources do not name the drive. For M6, Phillips heads normally take PH3 and Torx heads T30; socket heads take a 5 mm hex key.
- Can I use an imperial screw instead of M6?
- No. Imperial look-alike: 1/4in-20 (6.35 mm) — the tripod/camera thread; visibly larger than M6. Use a true M6 screw so it does not cross-thread or strip the hole.