Tuesday, January 10, 2006

Lining up Langster

I just bought a Specialized Langster and I notice the chainline is off by about 3 cm. I need to move the chainring inward to get it right—but I can't move it to the inside of the spider, or it will be off in the other direction. My question is, can I adjust the crank spindle at all? It's a sealed cartridge with square-tapered spindle.

—LANGuiShing left of cenTER


Dear Lefty,

Off by three centimeters!? Ye gods, it's a miracle you can pedal that single-speed more than six feet without throwing the chain. I'll assume for now that you meant three millimeters.

To answer your question, you can't adjust the spindle inward or outward by conventional means. With a Shimano or Shimano-style cartridge bottom bracket, you can only remove it completely, hurl it far away with a cathartic scream (feel better now?), then buy a new one in the spindle length you need. However, the Langster comes with a 103 mm spindle, and you'll be hard-pressed to find one shorter than that. Maybe you could change the bottom bracket and the cranks together—to some track-classic set such as Sugino 75—but I've heard of Langster owners having crankarm/chainstay clearance problems when they try that.

So what to do? You might be able to safely use an old-school trick. Back before cassette freehubs, when all freewheels screwed on, you could get a spacer to place underneath the freewheel to move it out a millimeter or two. Freewheels and bottom bracket shells have the same diameter (as long as both are English thread), so you could use the same spacer(s) between the bottom-bracket shell and the lip of the right-side cup, to move the spindle outward. Then you could move the chainring inside the spider, and voila—you do it all over again with one more or one less spacer. But eventually you get the perfect chainline.

Now all you have to do is call around and find a shop that still has such spacers (and maybe also Prince Albert in a can). If young whippersnappers tell you there is no such thing, don't give up. This is a case in which—unlike the old hippie/boomer slogan—you can't trust anyone under 30.

Now just in case you did mean three centimeters, I'll bet you bought the bike used, not new. (You didn't say which.) If so, I'll bet someone blew up the original bottom bracket and bought a replacement carelessly—so instead of the original 103 mm, you have a 122 mm intended for an early 90s mountain bike. You'll just need to find a 103 mm, and I hear tell that FSA makes a good one. You might also check the rear hub and right crankarm against what's spec'd for Langsters on the Specialized web site, to see if those parts have been replaced.

3 comments:

Ben Munson said...

CityBikes Coop has the spacers. I had to use one for my single speed freewheel to keep it from rubbing the hub just the other week. And the youngster that helped me knew where to find them.

Mark said...

This is a can of worms. The owner did not specify whether it is fixed or freewheel, so there are lots of possibilities. If it is fixed the first thing is that the cog may be facing the wrong way, producing the 3mm inward chainline descrepancy. The shoulder on a fixed cog should face inward.

I have also noticed that some flip-flop hubs do not have symmetrical chainlines, that is, if you put a fixed cog on one side and a freewheel on the other, the axle needs to be re-spaced to get the chainline dialed in, so both sides are the same when you flip the hub. Then the wheel needs to get re-dished to center the rim.

There is a remote possibility that if it is freewheel that the freewheel is installed on the fixed side, but I think that would put the chainline out in the opposite direction.

Anonymous said...

Thanks Mark, but keep in mind this was 2006, and Langsters came equipped with freewheel only--no fixed cog--until the 2007 model year.

But you're right--the owner could have added one and not told me.

--WOBG