Fixed cup width

[lenfield]

Does anybody know the distance between the flats on a traditional fixed cup?

I've got one that keeps loosening itself. I know you can buy specific spanners but I'd rather by an adjustable one so it can be used on other things.

 

[Paulus]

Normally a fixed cup is 35mm between the flats.
If you were to buy a fixed cup spanner they Normally double up as pedal or headset spanners for both.

 

[C R]

Normally a fixed cup is 35mm between the flats.
If you were to buy a fixed cup spanner they Normally double up as pedal or headset spanners for both.

Headset yes, but isn't it too big for pedals?

 

[C R]

Does anybody know the distance between the flats on a traditional fixed cup?

I've got one that keeps loosening itself. I know you can buy specific spanners but I'd rather by an adjustable one so it can be used on other things.

View attachment 804739

I'm surprised it loosens itself. The design makes them sort of self tightening, and they are notoriously difficult to remove because of how tight they become.

An adjustable spanner doesn't work very well because the flange is thin and the adjustable doesn't get much purchase. Attempting to use an adjustable may result in damaged knuckles and loud swearing, DAMHIKT.

 

[Paulus]

Headset yes, but isn't it too big for pedals?

Some have a dedicated pedal slot built in.
Pedal spanners are usually 15/16mm

 

[fossyant]

I'm surprised it loosens itself. The design makes them sort of self tightening, and they are notoriously difficult to remove because of how tight they become.

An adjustable spanner doesn't work very well because the flange is thin and the adjustable doesn't get much purchase. Attempting to use an adjustable may result in damaged knuckles and loud swearing, DAMHIKT.

I'd also second getting the right tool for the job. Especially if you want to preserve the paint on your vintage bike ! The tools aren't expensive, and you may get a 15mm pedal spanner on the other end - bonus very handy tool. Assuming this is a fixed cup BB.

 

[Paulus]

I'm surprised it loosens itself. The design makes them sort of self tightening, and they are notoriously difficult to remove because of how tight they become.

An adjustable spanner doesn't work very well because the flange is thin and the adjustable doesn't get much purchase. Attempting to use an adjustable may result in damaged knuckles and loud swearing, DAMHIKT.

Old style fixed cups have the opposite thread on the fixed/drive side so undo clockwise. They must be done up very tight to stop them coming undone.

 

[midlife]

They have a left hand thread because precession tightens them up in use. Same with pedals, in theory. Have you an LBS who can use the proper tool, probably cheaper than buying something.

 

[C R]

Old style fixed cups have the opposite thread on the fixed/drive side so undo clockwise. They must be done up very tight to stop them coming undone.

My understanding is that the drive side thread is always a reverse thread because the bearing precession will tend to tighten them. There are old French and Italian standards that use normal threads in the drive side, so undo counterclockwise, those will tend to undo themselves unless done up very, very, very tight.

All this is according to Sheldon, who also recommends against trying to use an adjustable spanner.

 

[Ming the Merciless]

What is wrong with using a hammer and chisel?

 

[C R]

What is wrong with using a hammer and chisel?

Oh, please, can we kill that meme already, pretty please?

 

[fossyant]

https://winstanleysbikes.co.uk/cyclo-pedal-bottom-bracket-fixed-cup-spanner

 

[lenfield]

https://winstanleysbikes.co.uk/cyclo-pedal-bottom-bracket-fixed-cup-spanner

Thanks it says they're 36mm.