Chain 1/2 link too short (or long

[rider69]

I'm new here so hello to all.
I'm converting a bike from a 7 speed derailleur system to an 8 speed Shimano Nexus internal hub. I'm using the original 44T front chainring and the stock 20T Shimano rear. The issue I'm having is that the chain (new SRAM PC-1) comes up either 1/2 link too short or 1/2 link too long. Would changing to a larger (or smaller) front chainring (sprocket) make any changes in the way the chain lays out? I did this same conversion on and identical (same brand and model and both were new) bike a few month ago and everything laid out perfectly, so I'm assuming it's a manufacturing variance causing the issue.

 

[rider69]

OK, I think I found the answer. Shimano makes a chain tensioner specifically for conversions with vertical drop-outs. I'll give it a try and post my results.

 

[Deleted member 1258]

Another thing you could look into is a male/female half link. Is the chain 3/32 or 1/8th?

 

[Deleted member 1258]

I use one of these on my fixed.

https://www.velosolo.co.uk/kmcm2f.html

 

[Big John]

I had a similar problem with a single speed bike I built. The chain was half a link out, no matter how I placed the wheel in the dropout. I bought a chain tensioner in the end and it solved the problem. I toyed with the idea of a half link chain but read a few reviews about those sort of chains and opted for the tensioner route.

 

[MichaelW2]

A 1/2 link has it's uses but if your bike has vertical dropouts and no other built in chain tensioner eg eccentric bottom bracket, then you probably need a spring style chain tensioner.
If you just use a half link, the chain will get lose with wear.

Spring tensioners are not ideal for hub gears. They attract dirt like derailleurs and degrade the low maintenance characteristics.


BMX kids sometimes use whole chains made of half links but you can just get the 1.5 links to fit to a normal chain.

 

[Ajax Bay]

Would changing to a larger (or smaller) front chainring (sprocket) make any changes in the way the chain lays out?

You've found the solution yourself (post #2). But to answer the question in the OP, an increase or decrease by 2 teeth in the size of the chainring would make a difference to the required chain length of very close to 1/2". Two extra or fewer teeth means one extra/fewer tooth engaged by the chainring ('front' half) and thus one half inch longer/shorter chain.

 

[rider69]

After looking at the Shimano tensioner, It occurred to me that I had one already. It's the derailleur from the bike being converted. I installed it this morning and it appears it will work like a charm. I've adjusted the limit screws to lock it in place. Saved $30 in the process. Thanks for all the replies and input. Ride safe!

 

[GuyBoden]

These 1/8" £5 screw in Izumi half links work too:
https://www.hubjub.co.uk/izumi-chain-link-91-p.asp