I am in the process of converting an old road bike of mine into a single speed. I bought new crank arms, rear wheel (with a conversion kit), and a rear derailleur.

Do I need to use a 3/32" chain, or can I use a 1/8" chain that I see being used on all other fixies?

Edit below

  1. the rear derailleur is because I have vertical dropouts on the bike, so this will be used as the chain tensioner

  2. the new rear wheel with conversion kit is because the old wheel broke (this is part of the reason I'm converting it)

  3. The new crank arms I bought have just one chain ring on them (similar to this) enter image description here

  • 1
    Why derailleur for singlespeed build? And also, why new wheel with conversion kit instead of conversion kit for old wheel or new singlespeed wheel. And why crank arms instead of chainring?
    – ojs
    Commented Jul 22, 2020 at 5:58
  • Do you intend to use the RD as a chain tensioner?
    – Carel
    Commented Jul 22, 2020 at 13:56

2 Answers 2


Yes, you can use an 1/8" chain instead of 3/32", is the other way around you can't go.

However, it may have problems going through your deraileur, but we can't say for sure. For normal single speed or fixies that's not a concern.

I would use a normal 8 speed chain anyway, it'll probably be cheaper. Only get an 1/8" chain if you get track chainrings, or you want the colored chains, which I've only seen in 1/8" size.


Since you're only using the rear derailleur to add chain tension, it will only press on the chain's top and bottom... there will be no lateral push as there would be when changing gear.

So it would be fine to lock the rear derailleur into one plane using the limit screws, and to modify the side plates to bulge out where the chain passes through.

You might find that singlespeed chain is more expensive and that your existing chain width is more affordable.

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