Chainline Query

Okay stick with me…

I’m in the process of restoring a track bike. The Shimano 600 cranks that I got with it travel really close to the chainstay, and I read on Sheldon that JIS cranks on an ISO bottom bracket (which I have) will set the chainline inboard about 4.5mm.

So I measured the front and rear chainlines and they are: Front 41mm, rear 47mm. I don’t think a 6mm variance is within acceptable limits.

So I figured if I got some ISO cranks, the front would come out to 45.5mm which isn’t too bad.

Then I had a closer look at the rear spacing, the Maillard hubs I’m planning to use have three 2mm spacers on the non-drive side. As such there is 20mm on the non-drive side and 23mm on the drive side measured from the hub flange to the dropout.

If I take a spacer and swap it to the other side the chainline comes in a bit to 45mm, but the spacings become 18mm/25mm respectively - which tells me my hub isn’t centred between the dropouts.

So my question is; with some ISO cranks setting a 45.5mm chainline up front, am I better to swap the spacer at the rear to get a 45mm chainline a the rear, or leave the hub as central as I can get it and be happy with a 47mm chainline at the rear?

Thank you for your patience on this matter.

I’d say try it with the hub as-is, to begin with. You wouldn’t want the hub too much off centre. Is the wheel dished symmetrically?

If the chain turns out to be noisy, or not landing properly on the teeth, I’d swap the spacers, or find new spacers, to fine tune it.

Why do the French have to make things so difficult?

They are distracted by French women.

c’est magnifique!

Vive le frogs

What is the width of the bottom bracket spindle you are using Lyndon? Any reason why you wouldn’t consider changing the BB out? Probably cheaper than changing cranks as well I would have thought.

68mm BB shell and it came with a 109mm spindle. I guess I was thinking new cranks for a few reasons - I wasn’t overly taken with the 600s (two piece construction), and it seems there wasn’t many options for a JIS square tapered spindle (keeping in mind I am trying to keep everything period correct, eg; 1982.)

Ideally I would like the square tapers to match (ISO/ISO or JIS/JIS) which gets me about 1.5mm from a straight chainline, so that’s either by finding a JIS spindle/BB or putting ISO cranks on the 109 spindle. There just seems to be a lot more options with ISO square tapers.

As far as price - it seems cranks of that era come up for sale a lot more than the old cup and cone bottom brackets, which means the BB’s manage to pull the high prices. Plus a scratched up crank is still usable, where a BB usually needs to be NOS or hardly used.