This section shows how to measure your original axle. If your original axle is missing, you’ll need to contact the frame or fork manufacturer and ask them for the four key dimensions. In order to order a replacement axle, you’ll need to know the following: axle diameter, axle length, thread pitch, and thread length.
Look for markings
Before trying to measure your axle, look for markings on it. Many times, the dimensions are laser etched on the axle. Your frame or fork manufacturer should also be able to give you the dimensions.
Find a metric ruler
Thru axles use millimeter measurements. Find a metric ruler or a set of calipers.
Measure axle diameter
Your axle will be either 12, 15, or 20mm in diameter. 15 and 20mm are typically only on enduro and DH forks. Use your ruler or calipers to confirm your axle diameter.
Measure the axle length
Measure the axle length. Do not include the head or washer, just the shaft. A replacement axle should be within 1-2mm shorter or longer than your original axle. If your axle is between sizes, it's better to choose the longer thread.
Measure the thread pitch
The coarseness of threads is called pitch and to find the pitch, you need to count the number of threads over a 10mm section. 10 threads is P1.0. Approximately 7 threads is P1.5mm, and just under 6 is P1.75. If you have any trouble counting, consult your frame manufacturer.
Measure the thread length
Measure the total length of the threads on your axle. A replacement axle should have the same thread length or longer. You should now have all the dimensions needed to order a replacement axle. To measure the threads properly, begin measuring from the start of the threads, or where the shaft ends, whichever gives a longer measurement.
Is it a Syntace Axle?
If your axle has a tapered washer, then it is a Syntace axle. It usually has a fine P1.0 thread pitch.