Check my math: 1x conversion

[icepick_trotsky]

So, I'm thinking of dipping my toes into some cross races this season. The plan is to convert my commuter.

Right now the commuter is sporting a triple which I'll move to another bike. I plan to use an old Shimano 600 crankset (6207) as a single crank.

The 600 cranks have 52 and 42 rings, so I want to remove the 52 and bump the 42 to the outer position. Question is, what length of spindle do I need? Seems to be some conflicting info out there re: the correct length. Velobase says it normally takes a 116mm, but Sheldon says 113mm. Any idea which is correct? And how much should I subtract to get the chainline correct?

[cp43]

Are you going singlespeed or 1x?

If singlespeed, you do need to be careful about correct chain line.

If 1x (one chainring, and a multi-cog cassette) you don't need to worry about a couple of millimeters of chainline, since the chain will be moving around on the cassette anyway.

[icepick_trotsky]

1x

[grawk]

why not replace the large ring with a bash guard and leave the 42 on the inside?

[icepick_trotsky]

I plan on using a chain keeper.

[ColonelJLloyd]

I plan on using a chain keeper.

Here are my thoughts.

You don't want to drop a chain during a race. Maybe the combo of a 30 year old chain ring and a chain keeper will do fine, but a narrow/wide ring would offer a lot more security. I'd look for a new or lightly used 130 narrow/wide ring.

You'd want a shorter spindle if putting the single ring on the outside. If you don't care that it looks Fredly then I'll bet chainline is good enough with the single ring on the inside with the original spindle.

[icepick_trotsky]

Would the outer ring bashguard be a more effective route?

[jtbadge]

I've got a 130BCD 42T Wolf Tooth Drop Stop if you want it. Shouldn't need a chainkeeper or bashguard.

[icepick_trotsky]

Jtbadge for the win

[oldpotatoe]

1x

Put the CR on the inside and use the proper -113mm, JIS BB. Better chainline.

[Mikej]

Don't forget the 1x variable of dropped chain in your equation...