How to Measure Your Motorcycle Bolts
Use this guide to identify the correct bolt size, thread diameter, pitch and length for your motorcycle fasteners. If you are replacing existing hardware or matching a missing fixing, these measurements will help you choose the right Racebolt product with confidence.
What you need to measure
When checking a motorcycle bolt, focus on the four key dimensions that determine whether a fastener will fit correctly.
Thread Diameter
Measure across the outside of the threaded section to identify the bolt diameter.
Bolt Length
Measure from under the head to the end of the fastener, unless it is a countersunk bolt.
Thread Pitch
Check the distance from one thread crest to the next to confirm the pitch.
Thread Length
Measure the part of the bolt shank that is actually threaded.
Thread diameter guide
Most motorcycle fasteners are metric, so you will usually be dealing with sizes such as M5, M6, M8 or M10. The “M” number refers to the outside diameter of the thread in millimetres.
To measure the diameter, use calipers across the widest part of the thread. If you do not have calipers, a precise ruler in millimetres can still help you estimate the size.
Thread pitch guide
Thread pitch is the distance between one thread and the next. On metric bolts this is measured in millimetres, and getting it right is just as important as choosing the correct diameter.
Standard Pitch
The default thread spacing commonly used on many production fasteners.
Fine Pitch
A tighter thread spacing often used where more precise clamping or fitment is required.
How to measure bolt length
For most bolt types, measure from the underside of the head to the tip. Countersunk bolts are the exception, as they are measured from the top of the head because the head sits flush in the surface.
- Hex, cap and button bolts: measure from underneath the head.
- Countersunk bolts: measure the full length including the head.
- Always compare the replacement bolt against the original where possible.
Need help choosing the right fastener?
If you are unsure about thread size, pitch or fitment, our team can help point you in the right direction. Bring the original fixing dimensions where possible and we can help you match the correct replacement.
