I didnt know this existed. Am i measuring right? I thought it was a 73mm BB. This bike ive been building out for a month now. Put on the crankset and took it for a spin around the block. I noticed the chainline was way off. I measured it to around 50mm. I think for standard double road chainline you want 43.5 ideally. I then measured and realized how weird my bb shell is. I have a 113mm JIS spindle and you can see how that the cranks sit on the spindle. And recommendations on how to fix chain-line issue? Shorter spindle? Cranks im 90% sure are meant for JIS so i dont think thats the issue. Any help is greatly appreciated
by soyass
3 Comments
You have a Merlin with their old press-fit square taper system, which is an evolutionary dead end found on a few frames from this era (Gary Fisher, most notably). I don’t remember if this is Grease Guard, or it’s own funky system.
Frankly I only ever dealt with a few of them and don’t remember what worked and what didn’t, but if you google “merlin press fit square taper” or some such, you’ll see plenty of discussion about what your options are here.
Just to double check my understanding here: You never actually changed out the BB on this frame, right? But you swapped the crankset?
>Cranks im 90% sure are meant for JIS so i dont think thats the issue.
The cranks need to be for JIS *and for the width of the BB spindle that they are installed on*. The width of the shell itself is irrelevant. Since you’ve got this ancient/orphaned bottom bracket shell/bearing design, swapping out the spindle may not be an option, so you should be looking for cranks that are designed for the 113mm spindle that you already have.
Gotta ask: how are you measuring chainline? A measured 50mm chainline, when you think it should be 43.5mm, and with a 113mm BB installed… implies that the crankset was designed for a 100mm BB spindle to hit that 43.5mm chainline – and that doesn’t pass the smell test.
Also, ~43mm was the standard on a road double with a 130mm rear hub. If this bike has a 135mm rear hub, you should be targetting more like 45mm.
Phil Wood makes replacement spindles, and I’m 99% sure they’d have the right size bearings if you need them. Which crankset is this? You’ll want to refer to the crank manufacturer’s recommendation for the correct length.