Have I destroyed my bottom bracket?

big_southern_jesse

I was out riding to day and my bottom bracket developed a lot of play. In the space of about 2 or 3 miles, it went from a barely noticeable movement to about 2 - 3mm of play on the drive side where the axle exits the bottom bracket. It's an external bottom bracket, and both the outer rings are tight and don't appear to have moved at all.

It's the first external bottom bracket I've had, and will be borrowing tools tomorrow to remove it and inspect it. The problem I have is I am racing on sunday, so need to start looking for a replacement immediately if it's a gonna!

So if the cups are tight, is there any other way for this play to have developed without something breaking?

Oh, I'm about 16 stone and running singlespeed, so although it's only a few months old, it has been subject to some fairly high loading!

supersonic

It may not have been preloaded properly (assuming it can be).

What crank is it? And how old?

big_southern_jesse

It's an FSA V-drive MegaExo... I think that's the answer...

And it was new with the bike back in January...

supersonic

Can't remember the exact way this work, but Park Tools has a good rundown on installation and adjustment of these systems.

big_southern_jesse

Thanks 'Sonic, I'll have the tools to have a proper look tomorrow, and see what comes out when I remove it. If it's failed, any reason why it wouldn't be a warrantee replacement?

peter413

Bad installation (your fault it broke/whoever installed it)

big_southern_jesse

peter413 wrote:

Bad installation (your fault it broke/whoever installed it)

Well it was installed by the company I bought it from, so their fault, but I get your point!

I pulled it apart this morning, and now need to ask some very simple silly questions if you will indulge me... I need it sorted by tomorrow for a final training run before a race this weekend.

What holds the whole thing tight in the bottom bracket?

It seems that the non drive crank eased outward, and that allowed the play from side to side.

Is the cap in the non drive side crank used to keep the bottom bracket tight?

Should there be washers between the crank and the bearing face on the non drive side?

On the drive side, is it just that angled face that bears the load?

Thanks for any help and simple explanations....

supersonic

Did you read Park Tools? All there!

http://www.parktool.com/repair/readhowto.asp?id=95#fsa

The key is here:

"The left cap simply bring the arm over to the bearing. It is used as a bearing adjustment, and it does not secure the right arm.
"

Imagine it works like a headset.

big_southern_jesse

supersonic wrote:

Did you read Park Tools? All there!

http://www.parktool.com/repair/readhowto.asp?id=95#fsa

The key is here:

"The left cap simply bring the arm over to the bearing. It is used as a bearing adjustment, and it does not secure the right arm.
"

Imagine it works like a headset.

Read that, it's the "does not secure the right arm" that I wanted to check... What stops the right arm pulling out? The left crank? Does that mean it's pulled tight with the cap, then secured in that position by the left crank?

supersonic

The pinch bolts on the crank arm secures it. Once secured to the axle (which is welded to the right arm), with the bearings loaded correctly, both arms have nowhere to go. The 8mm bolt takes out the play, the 5mm bolts lock it down.

big_southern_jesse

Ace, thanks Sonic... the Park Tools is probably clear when you know what it means, but a little foggy to the ignorant!

I'll check with FSA about washers or bearings between the faces... There were a few bits and pieces when it came apart that had been broken or stripped....