What’s this bit?

[Kbrook]

I’ve just finished putting a new 105 cassette , rear derailleur and chainset on the bike, all went well until I found this.

Im pretty sure it’s come with the bits ive put on today rather than slipping out of my toolbox, my only thought is maybe part of the packaging for the cassette, any ideas anyone? It’s too wide for a hub spacer

 

[fossyant]

Not missing a spacer on the rear mech where it bolts onto the frame - my Old Ultegra has one - it's just a cover rather than anything else - can't see size though.

Also double check it's not a headset spacer that's fallen out of the tool box !

 

[AndyRM]

Headset spacer was my thought too. Looks about the right size for one.

 

[Kbrook]

Yes thanks all and well done headset spacer it is!

 

[fossyant]

Seriously, it's a super dohicky spacer that goes on the freehub first. Failure to fit, makes the bike implode.

 

[C R]

Seriously, it's a super dohicky spacer that goes on the freehub first. Failure to fit, makes the bike implode.

Worse, makes the bike implode and explode at the same time.

 

[Ming the Merciless]

Worse, makes the bike implode and explode at the same time.

It which case it doesn’t anti matter

 

[RoadRider400]

It is the left phalange.

 

[Cycleops]

It is the left phalange.

Must be off Corbyn's bike then

 

[FrankCrank]

Long as it's not the nut behind the handlebar - that's the important bit.

 

[freiston]

Headset spacer was my thought too. Looks about the right size for one.

My first thought was headset spacer too - the diameter/thickness/height look in the right proportion to each other but from those photos, I couldn't work out the size at all - to me, it could have just as easily been a 20mm ID short bushing.