Bottom Bracket width

[fastpedaller]

And there I was thinking I was pretty clued up on the subject, and along comes a curve-ball........
Today I took my old bottom bracket (loose cup/spindle/balls type) out of my track frame, and over the next hour tried 2 cartridge Shimano ones, both with the same problem, so I wonder if anyone else has experienced this? Basically put the cartridge in, also the 'free cup' went to tighten down, to find the ensemble was too wide for the bottom bracket (I thought at first it may have been a thread issue) On examination on the bench, pushing the 'free cup' onto the cartridge, the width of one was 70mm, the other 69mm. My bottom bracket of course is a 68mm. Both cartridges are marked 68mm. I had not thought to do a check prior to fitment (I will another time), but on my other 2 bikes the FSA cartridge bottom brackets I fitted both clamped down fine. It would seem prudent to me that these cartridges would have a tollerance on the free cup such that when clamped they could be a little closer than 68mm, without any detriment, similarly if the shell is a little wider (say 68.5) there wouldn't be a problem - but for me the thread sticking out/shoulder not on bracket face is an issue.

[NATURAL ANKLING]

Hi,
I would say that the clamping cup is not correct for that BB
I might be wrong but I had an idea that the cups plastic / metal and even the same material type can be different

[Brucey]

which model shimano BB is this?

If it is one with a plastic LH cup, note that the 'shoulder' on the plastic cup isn't necessarily meant to butt up to the BB shell; the 'shoulder' is there simply to help stop the cup from splitting during installation (I think...). IIRC the equivalent part (when made in metal) usually has no external shoulder.

In any case a few threads poking out is kind of normal, I think.

cheers

[Valbrona]

- but for me the thread sticking out/shoulder not on bracket face is an issue.

That's exactly how Shimano cartridge bottom brackets are meant to be, and Stronglight to name another.

Why don't you take them back to the shop and say they are faulty? That would be fun to see.

[rjb]

If a couple of threads sticking out is an issue you could cover them with a lock ring to disguise them.

[fastpedaller]

Ah that's it then - I've only used the metal cup ones before. I can see that clamping tight on the cartridge is preferable to clamping on the shoulder.
As they say "every day is a school day".
I'll just file the plastic shoulder off so it looks better

[cycleruk]

I keep the metal cups from previous cartridge BBs and use them in place of the plastic ones.

[Brucey]

....I'll just file the plastic shoulder off so it looks better

fine, but don't expect to get it out again without wrecking it, even if it is well lubed, there is no corrosion etc.

Perhaps it is a moot point, after all they are usually in for long enough that they do break anyway when they come out...

cheers

[fastpedaller]

....I'll just file the plastic shoulder off so it looks better

fine, but don't expect to get it out again without wrecking it, even if it is well lubed, there is no corrosion etc.

Perhaps it is a moot point, after all they are usually in for long enough that they do break anyway when they come out...

cheers

My (failed?) attempt at humour........

[Valbrona]

It seems bonkers to have an important element of an important component of a bike made out of plastic. To prevent corrosion?

[531colin]

It seems bonkers to have an important element of an important component of a bike made out of plastic. To prevent corrosion?

Yeah, much more fashionable to have the actual bearings made out of cheese......

[fastpedaller]

It seems bonkers to have an important element of an important component of a bike made out of plastic. To prevent corrosion?

Could be quite handy if a bb proved very difficult to remove though? A bit of heat, a lot of drilling etc would be easier with plastic.

[drossall]

It's still not easy with plastic. I've tried it.

I strongly recommend one of these things to stop the fitting tool slipping around. Those plastic cups are really easy to damage.

[Valbrona]

I strongly recommend one of these things to stop the fitting tool slipping around. Those plastic cups are really easy to damage.

If you want to pay £10 for a bolt and a washer.

[Keezx]

It seems bonkers to have an important element of an important component of a bike made out of plastic.

No. it isn't.
Clever design because it's lighter, does not corrode and makes no noises.