Chainring Bolt Buyers Guide
Author: Ray Date Posted:5 March 2017
Chainring Bolts come in many different lengths and are often referred to as single, double or triple which a rough guide only.
It is important to get the correct length of bolt and this is best determined by measuring one of your old bolts or measuring the total thickness of the crank arm spider and the chainring or rings that are to be mounted to it.
The length of the bolt should be less than the total thickness or it will tighten before clamping onto the chainring/s
Chainring bolts are generally measured either between the two raised heads or just the inner shoulder of the female threaded part (nut).
One aspect that is often overlooked is that many chainrings have recessed bolt holes, the depth of the recess should also be taken into consideration.
Single bolts are generally between 3.5 – 5.0mm Long.
Double bolts are generally between 5.0 – 6.5mm long.
Triple bolts are generally 7.0mm or longer.
Triple bolts are normally only used to hold the two outer chainrings as the inner will be smaller and screwed directly to the crank.
Doubles and Triples are often referred to as the same and may be listed as double/triple chainring bolts.
Longer bolts are also used for mounting chain guards; these are used with a spacer to allow for chain clearance.
Not all crank manufacturers use the same set up.
EG: Shimano road cranks use the female nut on the inside and Sram road cranks use the female nut on the outside. The chainrings are recessed slightly differently and depending on the bolt flanges, they can be reversed.