I’m cobbling together a gravelly cx type bike from bits kicking around the shed. I have a 105 octalink triple chipset with the corresponding bottom bracket. Can I just put a cheap eBay wide narrow ring on the meddle position and all will be well? Will I need a shorter bottom bracket?

Please any wisdom will be most gratefully received.

shorter (or cut down if you have the tools to hand) chainring bolts is all I’d say you need – BB should be fine (assume it belongs to the 105 chainset? If not, be a bit careful as there are TWO octalink spline designs and road ones were a bit “finer”)

Excellent.thank you!

You might have problems with the BB shell. I’m pretty sue 105 is 68mm. It depends on what frame your putting it on. MTB is generally 73mm BB.

Are the chain rings 5 X 130mm? You might have trouble finding suitable chain rings.

I’m pretty sue 105 is 68mm. It depends on what frame your putting it on. MTB is generally 73mm BB.

To clarify that a bit…

The bb shell width shouldn’t be relevant (assuming traditional threaded cartridge bb) to whether the crank will fit. It affects the bb variant you use not the groupset or crank.

Edit: assuming you can get it in 73mm. My Google attempt tells me that might be challenging

Assuming the alternate bb is available…

If the crank came off a 68mm bb bike and is going into a 73mm bb frame you will need a new BB that has a cartridge/sealed unit that suits the wider shell. The crank will still fit. You may need to select a different bb axle length for the right chain line.

This all assumes you can still get road octalink spares in both shell widths. I’d be surprised if you couldn’t but at what quality level you can still get choice is another matter.

I guess the middle BCD is 110 on these? If so then a CX Narrow Wide should be easy enough to track down, but might not be as cheap as an eBay 104 Narrow Wide.

I’m cobbling together a gravelly cx type bike from bits kicking around the shed.

🙂

I hope your “cheap” build doesn’t get as expensive as mine has!

A Shimano 105 octalink triple chainset is designed for a 68mm bb shell (or 70mm if Italian bb) with a 118mm bb, it uses? 130mm BCD outer and middle chainrings and a 74mm BCD inner chainring.

This all assumes you can still get road octalink spares in both shell widths. I’d be surprised if you couldn’t but at what quality level you can still get choice is another matter.

You can’t. They have never been available. Road bikes don’t use 73mm bb shells.