Broken Bottom Bracket

[JasonErvin]

After 6,000 or so touring miles, the bottom bracket on my Trek 920 broke. Does anyone know what is compatible for a replacement? If I were to choose to replace the entire drive train, what would be compatible? Finally, if I were to replace the drive train, should I go with a 1x for gravel?

[ray b]

Depends a little on what's broken. If the part of the frame called the bottom bracket is broken you have problems that will require someone who can repair frames.

If only the bearings are gone, which can happen about 6000 mi, then you might want to save a lot of money and just replace them - part of routine maintenance.

If the axle has fractured, then you have an excuse to change things up, I gave up ftont derailleurs a couple of decades ago, as I ride either fixed gear or 14 speed Rohloff in back. For touring, I still like the idea of a strong chain or belt, and always winced a little when pounding up a hill on a rented or borrowed bike with more than 8 gears in back.

The term gravel bike is very fashionable, but the 920 was really built to handle any surface with the right wheels and gear ratios. You can call it a gravel bike if you want without changing a thing, and no one will argue.

[JasonErvin]

Thanks for the reply. After taking off the from crank set, I found that the bottom bracket (the bike body is fine) is intact, but worn, which is why the crank came off. Ideally, I'd like a single up front somewhere between the 42 and the 28. I'm willing to give up the high gears, but I'd like to keep things manageable climbing mountains. I'm just wondering how involved changing to a 1x will be. I'll likely take it to a shop, as I don't really have all the right tools nor bike stand at home.

[ray b]

Your local shop will have fun with this and you will likely get a great, free consultation, but if you have the time, I recommend taking a peek at any of the 1X conversion videos available on YouTube.

[DaveB]

Changing to 1X while still keeping a low low gear and a reasonably high top gear is going to require more than just a new crank and bottom bracket.  Plan on a new very wide range cassette (like 11x42 or bigger), a rear derailleur with a sufficient range to work with a large big cog and a lot of "wrap capacity" and possibly new shifters and chain if you don't already have a 10-speed or greater cassette.

[BikeliciousBabe]

Why is that not going to happen again if the bottom bracket shell was the cause the first time?

[DanE]

I don't know if any of you have been to your local bike shop lately, but converting a bike to a 1x right now is probably going to be a real challenge. My shop guy told me just this week that he can get zero Shimano individual components right now and SRAM is not much better. Your shop might be better depending on how well connected they are to their supplier. The easiest way to probably get a 1x is most likely going to be to buy a brand new bicycle. The OP has a very nice Trek 920 currently. The easiest solution is to fix that bike as it probably just needs new bearings. Finding one BB bearing set is going to be easier than finding a bunch of components to change to a 1x. My shop also has a six week backup on repairs. That is for getting such things as new cables and a chain put on. Do you think a shop is going to be excited to chase down a bunch of components they probably can't get to switch out. They could do a dozen tune ups that people are standing in line for in the same amount of time to do this. Perhaps if you are well connected to your shop they would be willing to do this. Once again, they would probably be willing to sell you a new bicycle. I think this season is going to be about riding what you got and keeping it going for now and wait for another time for your bike projects.

[staehpj1]

I don't know if any of you have been to your local bike shop lately, but converting a bike to a 1x right now is probably going to be a real challenge. My shop guy told me just this week that he can get zero Shimano individual components right now and SRAM is not much better.

Local sourcing may indeed be impossible for most of us.  Ordering online looks a lot more possible though.  Colorado Cyclist seems to have quite a bit of the SRAM 1X stuff on hand.  Between them, Jenson, Tree Fort and others, it looks like you could find what you need for a conversion despite the supply chain issues.  Shimano stuff looks more scarce, but may not be impossible with a bit of searching.  If someone really wants to do a conversion it is probably possible.