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New to Fixed - Question about dropping the chain(8 posts)

New to Fixed - Question about dropping the chainJer77
May 20, 2003 11:59 AM
Just got a single speed with a coaster brake for commuting. It seems that whenever I push hard on the pedals I drop the chain (after stop light, going up a hill, any hard accelerations). I don't consider myself a good wrench so I am seeking advice on what might be causing this.
Chain tension..............Dave Hickey
May 20, 2003 12:18 PM
It sounds like your chain is too loose. If you want to try it yourself, loosen the rear axle bolts, pull the wheel back and tighten the bolts.
Mine does it occasionally ...Humma Hah
May 20, 2003 12:41 PM
I assume you have a one-piece crank with a chainwheel (as opposed to a chainring that attaches with multiple bolts to a spider on the right crankarm). There's a tendency for those to work off-centered. Mine tends to be tightest when the right pedal is a little forward of top dead center, i.e. at about the 1 o'clock position when viewed from the right side of the bike. 180 degrees from that, at about 7 o'clock, the chain is at its loosest.

The bottom of the chain will have the most slack under hard acceleration, and any side-to-side sway on an overly-slack chain will make the chain climb off the rear cog.

Replace the chain before it develops excessive loosness, and keep it adjusted so that there's minimal slack at the tightest crank position, and that may be enough. If not, you'll need to resort to the trick below.

When my cruiser develops this problem, I set the crank to the position where it goes tightest, mark an arrow straight back on the chainwheel (toward the rear axel), and then pull the whole works off the bike. I'll insert thin metal shims between the crank and chainwheel hole so that the chainwheel is held in the direction of the arrow. I may have to do this repeatedly to get the position just right, but once done the fix generally lasts quite a while.

This process is a lot of bother. I put up with it because I'm trying to keep my antique as original as possible, but its a clear indicator of why one-piece cranks are no longer used on high-end bikes. There are kits that allow you to install a modern roadbike spindle in a cruiser's BB shell (properly called the "hangar"), so that you can use a decent set of cranks and a modern chainring that will stay centered better.

If your bike has under 1000 miles on it, the problem is unlikely to be wear. If more than that, you might check for wear. Cheap freewheels wear out fast, and aluminum chainwheels don't last forever either. Changing to a new chain on worn cogs can cause the chain to want to climb off the cogs.
May 20, 2003 1:14 PM
I do have a one piece crank with a chainwheel. Hopefully pulling the rear tire/axle tighter will solve the problem. I would suspect the bike has fewer than 1000 miles on it, but the quality of parts used on these particular bikes are pretty low-end. This particular bike is a specially manufactured bicycle used in the Little 500 bike race at Indiana University, so getting parts and finding mechanical advice is tough as few people have experience with this.
The Little 500 ... they still running that?Humma Hah
May 20, 2003 2:14 PM
... pretty cool! Care to post a picture of the bike?

We had a debate here a couple of years back as to the nature of the brakes, if any, on those bikes. Some figured they were fixies, a few claimed they were coasterbrakes. Now we know!
The Little 500 ... they still running that?Jer77
May 21, 2003 7:35 AM
Sure are - April 26 was the 53rd running. I will post a picture after I get my buddies digital camera.
This will hold you overJer77
May 21, 2003 10:19 AM
Check out Cycling News photography of the Little 500. There are some decent shots of the bikes and how exchanges work.
Neat!Humma Hah
May 21, 2003 3:09 PM
I adore the concept of a coasterbrake roadbike, of course.

And I got a kick out of Team Major Taylor. Taylor was the first black superstar athlete, the fastest man alive at one point, and a pioneer who laid the way for folks like Jackie Robinson. Glad to see that team salute the man.