Brompton Chain Replacement

Using the chain wear indicator, it says the chain is over 0.75 wear, therefore due replacement.  Leeds Bike Mill Amanda told me these Brompton uses narrow chain.  Amanda also reminded me to check the number of links from manual, not from previous replacement.

I have changed chains before, and I never had to worry about any of these, just a standard chain and repeat the last setup. 

Armed with this information, I did some research. Because Brompton is like a fixed gear bike, chain is not expected to move laterally, so narrow chain 3/32" will be better suited for application.  Brompton customer service was not particular helpful in helping me to determine the number of links required, but their website does have a guide, it also confirmed 3/32" chain.  So I counted up the teeth and confirmed it needed 98 links.

When I read up what 0.75 means, 0.75 means 0.75%, and that is enough to cause extra movement between chain and sprocket to cause undue wear!

I double checked on the Brompton, the old chain was definitely sliding sideway, unnecessarily.  I got the chain and the tool ready, lo and behold, the old chain had 100 links!  Maybe the reduced tension caused accelerated deterioration?  

When the chain is off, I can see there is visible wear on the chainring, so let's hope it holds.  I gave the rear sprocket a good clean.  

I cut the new chain to size, put it side by side with the old chain, unperceivable.  So the combination of the roller wear and the chain stretch making 0.75% difference to the original chain.  I took the rollers to check, also unperceivable, even on caliper.

I fitted the new chain and it seems okay.