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I have a road bike (2013 Schwinn Tourist) with a sealed bottom bracket (107mm spacing) with a square taper and triple chainwheel (48, 38, 28) assembly that is one of the inexpensive riveted types. I want to upgrade to a crankset that has replaceable chainwheels. Can I use any crankset of my choice? If not, what are my choices?

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    You'll probably end up spending more than the bike is worth for a quality new(ish) crankset and bottom bracket plus the installation cost if you aren't planning on doing it yourself. It might not be worth it. – ebrohman Mar 27 '16 at 16:53
  • What kind of bottom bracket it is? Square taper? You need to match it to the crankset. – ojs Mar 27 '16 at 17:16
  • If you are keeping your bottom bracket, you need to be careful as there are two standards for square tapper spindles. They are not completely cross compatible and can result in a damaged the crank if mixed up. – Rider_X Mar 27 '16 at 18:39
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    In theory, you shouldn't mix ISO and JIS. In practice, you can mix them fairly safely with modern bottom brackets (but you will need to do a few mm spindle length adjustment for chainline). This is a fancy BSO -- I'd suggest just leaving it alone and riding it with necessary upkeep or selling it and buying a better bike which is more worthy of upgrading. It won't be cost effective to do things like this (plus, I doubt you've worn out the chainrings already significantly, so why switch?). – Batman Mar 28 '16 at 0:01
  • Its great that you're showing a mechanical interest in your ride. But this is a cheap chain store brand/model and the parts alone could cost as much as your bike did new. If you find parts cheap off a donor then it becomes more viable. Search around and see if you have a local bike cooperative nearby who may be able to help. – Criggie Mar 28 '16 at 6:02
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There are a number of factors to consider here as others have stated in comments, this upgrade may cost more that you are willing to pay given the cost of the bike originally. I'm going to assume you know that and answer as if you are going to do it regardless.

This bike is an 8 speed rear cassette, which controls the type of crank sets you can use without upgrading more parts. You will need an 8 speed crankset, to make sure your chain is compatible.

The BB is a "standard" 68mm threaded shell, which can be adapted to a variety of options for cranksets.

The SHIMANO M361 Hybrid crankset 48/38/28 tooth in square taper is an inexpensive and reasonably likely direct fit replacement.

It is impossible for me to judge the length of BB spindle required after you change the crankset, however, so you should be prepared for the need to change that also.

Depending on the offset of the chain rings on your original crankset, and the difference in offset on the new one, you may need to get a longer or shorter BB spindle to adjust the chain line with the new crank.

The best way to do this is to measure from your seat tube to the center of the teeth on your middle chainring with your original crankset, and note the measurement.

Install the new crankset, and measure again. Note the difference. If the new measurement is larger, you need a BB with a spindle which is shorter by the difference in your measurements. If measurement is shorter you need a longer BB spindle.

Since this can't be checked ahead of time, you be to be prepared to have the bike non-functional while you get the new BB.

Then you need to readjust the shifting on the front derailleur to match the new crank. This may require a new from derailleur cable and housing, or it may not.

This will cost a fair bit of time and work, and between $100-150 dollars. Whether that is justifiable on this bike is up to you, but it is approximately half the cost of the bike, not including labor.

I hope that is helpful.

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