Bicycle Mechanics - Secret to measuring chainline?

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Chi
09-11-04, 10:10 PM
Is there a secret to get the right chainline on the first try? I'm talking about those BBs that have the infinitely adjustable cups on them (Phil Wood, Campy Record, etc).

I just spent about 2 hours trying to get the perfect chainline for my cranks (46.5mm), so I was wondering if there is an easier way to do it next time?

I thought about using a pair of dial calipers to measure the BB vs the shell spacing ... maybe I will bring those home from work next time I take the thing off.

legalize_it
09-12-04, 07:03 AM
park tools has a chainline gauge for about $30. makes adjusting chainline a breeze, whether its a SS/fixed or geared.
Chi
09-12-04, 08:04 AM
I already know what the chainline is, I just need to have an easier way to set it there.

winston
09-12-04, 11:02 AM
This isn't exactly a method of measuring chainline, but it is very simple a way of making sure it's straight... I just look down at the chain from above and make sure it's parallel with the top tube of my bike. If you look down from a bit in front of your handlebars, you can visually line up the whole length of chain with the top tube. I think it's possible to detect if the chain is off by 1mm if you're careful.

It doesn't work as well for bikes that have very sloped top tubes, though.

Here's a view of my bike from the top -- this photo doesn't show the chain and the top tube lined up as closely as they can be, but it should give you some idea of what I mean.