Hi again. I have a question. What is a Bottom Bracket on a Bike ?

6 messages
19/09/2012 at 07:21

Is it the part the crank goes through?

I've seen pictures and I'm guessing what it does.

Is it important for me to understand it's use and how to maintain\when to replace\if it ever needs replacing, or is it something that isn't really needed to be considered.


19/09/2012 at 07:37


Rarely needs replacing. Some are sealed units some require stripping and greasing. Buy a good bike book or take your bike to a local bike mechanic.

19/09/2012 at 12:16

If your bike is fairly new then it could be one of a number of standards (press-fit, threaded, bb30, ...) so its probably easiest to leave to the bike shop mechanic unless you are confident and have bought the correct tools.

Coming from a mountain biking background, where they tend to suffer due to being a moving part at the bottom of the bike, if its worn you'll notice that the cranks don't rotate as smoothly as before.  The best check is to hold the pedal ends of both cranks and push/pull towards the frame - if its good then there should be no movement, but if the bearings are worn then you'll see a little bit of play. 


Symes    pirate
20/09/2012 at 22:22

Relatively cheap and easy fix really, plus, the longer you leave it the less easy it is to do, without the aid of soaking it in coke and heating the frame with a heat gun or similar! 

Edited: 20/09/2012 at 22:23
21/09/2012 at 12:22

It's not something I need to look at as my bike is new.

I was just in the pub when my one of my bosses was chatting about it and I didn't know what it was.

When I asked him what it was he just looked at me funny and told me to google it.

So I thought I'd ask some strangers on a forum as I was bound to get a better reply than from that t*sser.

meface    pirate
21/09/2012 at 22:46

Generally my experience of it is they are expensive. I have a habit of destroying them sooner than anyone would think. And they are best left to the man at the shop.

I would just mention to your boss that you get through BBs after about 3000miles which is sooner than you would expect but it is probably due to over gearing and putting too much power through the crank arm. You've considered titanium ones but aren't sure if the extra cost would give you more wear/£. Then ask him if he thinks the new carbon buttons for Di2 that save 0.002g are worth £100 and voila you are a triathlete!

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