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I am planning to do a massive replacement on my city bike: chain, gears (both front and rear) and also bottom bracket, as I noticed the pedals tend to oscillate to the sides when I load them.

While I can attempt changing chain and gears on my own, I prefer to let a workshop do the bottom braket. This mean that I will probably have some time inbetween the two replace actions.

Since I have read here that it is not a good idea to replace only chain or gear, I wonder if a wore bottom bracket does have a bad influence on newly mounted gears and chaing?

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  • Consider a bottom bracket cartridge instead of cup and cone and bearings. There's no adjustments to make. However you will need tools - a crank puller and a bottom bracket socket to tighten the cartridge..
    – Criggie
    May 22 '17 at 20:12
  • If you're replacing the bottom bracket, you've got the cranks off, which you need to do if you're swapping chainrings in many cases anyway. So, I don't see why you wouldn't do both of those at the same time (or get the shop to do both; the hard part of the labor is done in the course of replacing the bottom bracket). Also, chainrings are pretty hardy, and running a worn chain for a little bit isn't the end of the world.
    – Batman
    May 22 '17 at 20:53
  • Depending on the pedal type, you may be able to adjust the axles if they are of the cone and ball type.
    – Carel
    May 24 '17 at 8:48
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There are good reasons to avoid using a very worn chain for to long as it can wear the cassette requiring both to be replaced.

I doubt that a small amount of play in the bottom bracket would move the chain enough to cause unusual wear to the chain, rings or sprockets. There may be more chance of a problem on a single speed or fixed gear bike where the chain has less give.

There's a small risk of poor shifting with a wobbly bottom bracket, so perhaps take care and avoid any gears which rub.

Otherwise, as long as the shop replaces like for like, you shouldn't have a problem. Likewise, worn gears should not adversely affect your bottom bracket.

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