A quick-fix to solving track bike chain alignment
Valerie recently received an email about adjusting the chain line on the adapters. Every frame, crankset, hub, chain, cog, chainring and fixed gear adapter is manufactured with a tolerance allowance. These mechanical tolerance allowances are windows of operation where parts are not overstressed due to being too loose, too tight or out of alignment.
In this instance, someone asked for a fix for an adapter with the chain tracking slightly out of true towards the trainer. The problem could have been caused by any of the components being out of spec as listed above. But it is also likely that a compounding effect of multiple parts of the chain drive system verges on the end of the tolerance limit adding up to a slightly misaligned chain. There is a chance that they may be running a crankset with a slightly different chain line measurement.
Over the course of a few minutes thinking of a quick fix - and anyone else who may be experiencing a similar issue with chain alignment on their trainer - I came up with a handy trick…
Between each cog on a standard multi-speed bike cassette are plastic spacers. These spacers are removable and so happen to slide perfectly over the 1.37” fixed gear cog thread on the adaptors. Once this is slid on, the cog can then be screwed on - spacing it out by 1-2mm to adjust the chain alignment.
Cassettes come with various speeds. 12-speed cassettes run narrower chains, therefore narrower spacers. 8-speed cassettes run wider chains and wider spacers between the cogs. A spacer from an 8-speed chain would probably be too wide for the fine adjustment required in our application, but it illustrates that there is some adjustability there if you feel the need to experiment.