My wife has an eccentric bottom bracket.

[GuyBoden]

I just checked my Wife's bike and it has an eccentric bottom bracket.

I've ordered a new Hollowtech BB, but I might have to adjust her eccentric bottom bracket.

I never worked on an eccentric bottom bracket before.

Any help?

 

[Paulus]

I have never used one, but this might help.
https://www.firstcomponents.com/eccentric-bottom-bracket/

 

[rrarider]

This is a component, I'd never heard of before. I do remember eccentric chain wheels (Biopace ??) being available once; the advantage of these was that they would apply more torque to the spindle in the middle of the stroke, when the foot was half way down. Presumably you will have to mount the crank in the correct orientation with such a bottom bracket?

 

[Ming the Merciless]

Has she spoken to a doctor?🥴

 

[Moodyman]

The EBB is an aluminium shell designed to manage chain tension on hub gears and singlespeeds.

The bottom bracket will screw into the EBB as it would into derailleur framed bike. Once you've mounted the bottom bracket, you need to adjust the chain tension. This is done by loosing the bolts that secure the EBB into the frame. Usually, the bolts are found at the bottom of the BB shell on the bike.

The attached pic from the web shows this better than words alone.

 

[GuyBoden]

Has she spoken to a doctor?🥴

Her eccentric bottom bracket is not causing her any pain at the moment, but her HollowTech BB needs replacing and her chain is loose.

 

[byegad]

I just checked my Wife's bike and it has an eccentric bottom bracket!

Are you boasting or complaining?

 

[rockyroller]

lol, mine's got a screw loose, for sure

 

[DRM]

Well, you live and learn, I thought such things were the reason Hambini swears a lot

 

[MichaelW2]

Seriously, you need to figure out the adjustment system. Is it a wedge from the side or clamp or set screw from the BB shell.
You usually need some access to the face to make the rotation adjustment.
If the gear system is derailleur then no adjustment is required. For hub gears and singlespeed you do need to make adjustments from time to time.

 

[Moodyman]

Well, you live and learn, I thought such things were the reason Hambini swears a lot

His gripes are with the press fit style bottom brackets that certain manufacturers use.

Eccentric BBs are brilliant.

 

[Moodyman]

Guy,

Chain adjustment is the same process as tightening/ loosening of the bottom bracket into the EBB.

So, install your bottom bracket nice and tight BUT don't install the left crankarm.

Then, loosen the two bolts underneath the bike as pictured.

Now, if you loosen the bottom bracket, instead of loosening it, the EBB will turn forwards. This will increase the chain tension.

Once you have your chain tension at the required level, tighten the two bolts and install the left crankarm.

 

[GuyBoden]

Guy,

Chain adjustment is the same process as tightening/ loosening of the bottom bracket into the EBB.

So, install your bottom bracket nice and tight BUT don't install the left crankarm.

Then, loosen the two bolts underneath the bike as pictured.

Now, if you loosen the bottom bottom bracket, instead of loosening it, the EBB will turn forwards. This will increase the chain tension.

Once you have your chain tension at the required level, tighten the two bolts and install the left crankarm.

Excellent info, many thanks, I'll give it a go when I get the replacement HollowTech BB.

 

[Ajax Bay]

[Hambini's] gripes are with the press fit style bottom brackets that certain manufacturers use.

This is fake news. His 'gripe' seems mainly with the quality of the BB shells of (mostly) carbon frames.
He specifically argues (see link) that PF is a better way of interfacing than threading, but the latter is more forgiving of manufacturing either relying on wide tolerances or failing to achieve self-specified tolerances (diameter, orientation).
https://www.hambini.com/pressfit-vs-threaded-bottom-brackets/
Apologies for off topic aspect of this post.