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Schwinn 1990 World Sport Lower Bracket

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Schwinn 1990 World Sport Lower Bracket

Old 04-29-12, 09:29 AM
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Schwinn 1990 World Sport Lower Bracket

Last year, I finally took the World Sport to the bike shop I bought it from for a full tune-up. While there, I also had them replace the original tires, inner tubes, and rear derailleur along with several other cosmetic changes (new handlebar tape, removing the original bottle dynamo and wired lights, etc..) The bike has been running fine, once I adjusted the gear shifters, so it wouldn't keep popping back into a higher gear.

After getting it back and riding it more, I noticed a "popping" every time the left peddle passes over the top. A friend and fairly experienced rider suggested that I replace the lower bracket. I've done some searching around, but not having much luck finding the part I would need. I see different sizes and lengths of them.

The "Made in Taiwan" sticker is still on the bike if that helps identify the manufacturer and narrow down the parts list.

I've tried going directly to Schwinn, but didn't have much luck there.

I would greatly appreciate any assistance in finding the correct lower bracket.
Thanks!
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Old 04-29-12, 10:10 AM
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Assuming you have cotterless aluminum cranks (based only on the vintage of the bike, since you provided no details). you'd need a square taper bottom bracket for a 68mm, 1.370x24tpi (or British standard) shell. This is the most common type of bottom bracket, and you will find many choices, but probably a low cost cartridge type is best for you. The last variable is the spindle length, which you can measure by taking the cranks off with a crank puller.

Note that changing a bottom bracket can require a number of fairly pricey tools, a situation made worse because the new one may require different tools than the one you're removing. So this is something to consider and it could easity be less costly to let the shop do this job.

Also, before spending a penny on a bottom bracket, make sure that's the real problem. From your description, my first guess would have been a loose/work crank arm. If you've been riding for any length with a loose crank, the crank itself will be damaged, and won't be any tighter on anew bottom bracket than it is now. Regardless of what the real problem turns out to be, making the effort to have a good diagnosis will prevent you from wasting time and money on something that won't solve the problem.
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