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setting up a good chainline(6 posts)

setting up a good chainlineishmael
Dec 8, 2002 5:30 PM
how's it done? I'm getting miche hubs and cranks but an centuar bottom bracket..the bb has a 111 spindle and the cranks recommend 107, so what do I do? is the bb adjustable? Will it depend on the frame also? its standard track. In my case do I just use washers between the hub and freewheel, bringing it out a bit? What's the simplest method for determining the chainline and adjusting it?
re: setting up a good chainlinemadstork
Dec 9, 2002 6:17 AM
ishmael, I've got the same bb on a couple of bikes. I'm no expert on it, but to me it is not an adjustable type of bb. It has cups with flanges that tighten against the outside edge of the frame's bb shell. If any adjustment is possible with the Centaur bb, it would have to be done with bb spacers, imho. Check with your lbs or see www.thethirdhand.com for those. And if I'm not mistaken, the bb spacers also can be used between the hub and freewheel if you go that route.

Try this. Mount the Centaur bb and the Miche cranks. Measure the distance from the frame centerline (at the downtube) to the chainring centerline. Next, put the rear wheel (or hub if wheel is unbuilt) with the rear cog/freewheel installed in the frame and measure from the frame centerline (should be the center point between the axle locknuts' outside edge) to the centerline of the cog.
This gives you 2 measurements to compare and lets you decide if you want to adjust bb or chainring in front or cog or rear axle in back. (Not sure about the Miche hub, but you may be able to adjust chainline by moving axle spacers around. But that will also involve adjusting the dish of the wheel if it is already built.)

And as always, check Sheldon Brown's site for chainline info. He has some specs on Shimano chainlines, iirc, that may give you some ballpark numbers for your measurements.

Hope this helps you. Sounds like a sweet set up. Let me know later how you like the Miche crank. I'm using a Centaur crank by running the chainring on the inner position. I've seen pictures of the Miche crank and it looks good. I'm always thinking about upgrades!
how does chainline affect the bikeishmael
Dec 9, 2002 6:40 AM
I was told by a fancy shop that even a millimeter off is a risk of throwing the chain....that seems like an exageration to me...is it noisier? does it wear faster?
how does chainline affect the bikemadstork
Dec 9, 2002 8:41 AM
I'm too much of a novice at fixed gears to judge the lbs statement, so I'll leave that to others. I had heard similar statements, so I decided to play if safe. I was lucky in that I could move axle spacers around and get it right (to my satisfaction anyway).

A properly adjusted STI/Ergo drivetrain will be much quieter than one out of adjustment, so I follow the same reasoning for fixed/single speed. If it's noisy, it's probably wearing faster.
Chainline is important!LC
Dec 9, 2002 10:13 AM
The missing skin from my elbow and knee tell me that chainline is definitly important! It was made even worse by a RSX crankset that was not really round. I changed to Stronglight cranks/rings and adjusted the chainline better and have not had a problem since. Are better Shimano cranksets/chainrings (Ultegra/Dura Ace) more round? Is it actually the chainrings that are not truely round?
chainlinefixedgearhead
Dec 9, 2002 4:08 PM
The forces at play in a fixed gear chainline are such that they are magnified in their impact on the components far more than a deraileur which allows for slop within the system. The only resistance in a derailleur system is the strength of the spring in the derailleur. On the other hand in a fixed situation there is only maybe 1/2 inch of give and then everything is taut. You can see that if everything is not in alignment then wear or, in extreme misalignment situations, jumping off the cog/chainwheel could happen. It is best to have it as straight and true between the cog/chainwheel as can be gotten. You will have less wear and problems(noise, chain drop) that way.

fixedgearhead