There are two options. Maximum length and minimum length.
Minimum length: Put the chain on the two largest cogs and pull the chain and derailleur as tight as possible, find the shortest length where you have an inner to outer link connection, add one more inner and outer link and set the length.
Maximum length: Put the chain on the two smallest cogs and pull the chain to an inner outer connection until it doesn’t contact the derailleur cage.
You’ll usually have 1-3 links diffence between these techniques. The maximum length can increase wear life by 1-3% (not statistically significant) by spreading wear over more links. The shorter length will make shifting feel more snappy due to increased derailleur spring tension.
Either way, make sure you adjust the B tension on the rear derailleur once the chain is fitted. B tension is set by having the chain in the rear large cog and front small chain ring and ensuring the top derailleur pulley and rear large cog have one link (inner or outer link) clear between them.
Good luck.
For anyone reading this with a dual suspension bike, the chain length should be set with the rear suspension fully compressed. You’ll usually need to use the minimum length technique.
3 Comments
The easiest will be to duplicate the length of the old chain – assuming that the old chain is the right length.
If you want to start from scratch, follow the instructions in section 4 here: [Chain Length Sizing | Park Tool](https://www.parktool.com/en-us/blog/repair-help/chain-length-sizing)
Put the chain on the largest chainring and the largest cog without threading the chain through the rear derailleur.
See where the chain meets at the front chainring, and then follow this diagram:
https://preview.redd.it/bbiqtypvplqd1.png?width=1150&format=png&auto=webp&s=7b636157c2e8fb1dbe377be727a6230efb539ea4
There are two options. Maximum length and minimum length.
Minimum length: Put the chain on the two largest cogs and pull the chain and derailleur as tight as possible, find the shortest length where you have an inner to outer link connection, add one more inner and outer link and set the length.
Maximum length: Put the chain on the two smallest cogs and pull the chain to an inner outer connection until it doesn’t contact the derailleur cage.
You’ll usually have 1-3 links diffence between these techniques. The maximum length can increase wear life by 1-3% (not statistically significant) by spreading wear over more links. The shorter length will make shifting feel more snappy due to increased derailleur spring tension.
Either way, make sure you adjust the B tension on the rear derailleur once the chain is fitted. B tension is set by having the chain in the rear large cog and front small chain ring and ensuring the top derailleur pulley and rear large cog have one link (inner or outer link) clear between them.
Good luck.
For anyone reading this with a dual suspension bike, the chain length should be set with the rear suspension fully compressed. You’ll usually need to use the minimum length technique.