Celeste Mike

Hi all,
If I want to move my chainline inward 3mm and my bottom bracket spindle is 114mm, am I correct in thinking that a 111mm spindle will achieve this goal? Is that how spindle length works or does the non-drive side factor into it as well?
(I realize there is more than one way to adjust my chainline, but I'm shopping for a new bottom bracket and want to get the correct spindle length for my application.)
Thanks in advance!

_ForceD_

Both sides factor into the spindle length…depending on how far out from the BB your want the cranks. Remember you have to consider that going narrower will cause the crank be closer to the chain stays. You don’t want it to hit them. Perhaps this Sheldon Brown page will be of assistance to you. Good luck.

https://www.sheldonbrown.com/bbsize.html


Dan

Andrew R Stewart 

Maybe. Depends on how the current axle is dimensioned and how the replacement is. If the old axle is symmetrical and the replacement is also than the new axle will need to be 8mm shorter. But not all BB axles are symmetrical, often with loose ball tapered square axles the drive side has more stand off from the bearing surface on the drive side than the LH side has.

This is where some measurements are worth many words of explanation. Even with good measurements and a good understanding as to where a replacement axle is different one can find that the numbers don't produce the best fit. This is why having a few axles to try can be a time saver.

Of course this answer is full of assumptions due to missing description and data. Andy

Celeste Mike

Thanks!

I want to use a road double as a 1x, moving the big ring inward with no small ring. (I don't want to simply move the big ring to the small ring position on the spider for aesthetic reasons.)

Andrew R Stewart 

Make sure that the crank spider tabs don't contact the stay. Depending on various aspects/shapes the OEM inner ring's teeth might not be to closest part to the stay. Andy

Celeste Mike

Thanks! So I have a frame, and I have a crankset, but the frame needs a bottom bracket. I pulled the old one out, it was shot. It was a vintage cup and cone type (asymmetrical spindle), and I want to install a new sealed cartridge type. BB shell is 70mm, Italian threaded. Crank is ISO square taper. This is the crank: https://velobase.com/ViewComponent.a...cc544&Enum=115

Andrew R Stewart 

If you have the OEM axle still you cam measure the RH end and how long it is from the bearing track. Also how far the axle end is from the center spot between the two bearing tracks. Subtract the 4mm from the drive side end. What is this "new end location" from the bearing tracks' center? Double this and you have what a replacement symmetrical axle length might be. Make sure the LH crank end will clear the stay. Andy

ofajen

How many cogs in back? How big of a deal would it be to simply leave the big ring where it is? Modern chains handle chainline angles pretty well so maybe it would be ok?

Otto

_ForceD_

The other factor…that I think others alluded to above but didn’t actually mention…is that if you’re going 1x, and moving the large ring to the inside…there’s a chance that that ring could hit the chain stay. Sometimes that can happen even if you’re not changing to a narrower spindle. So, you should put the large ring on the current spindle to make sure how much clearance you’ll have.

Dan

Celeste Mike

7 speed on the back. I know from riding 2x7 that the small/small combo works but not the big/big, and I intend to essentially do away with the small ring and keep the big one. I want to nudge it in so it will work across all 7 cogs.

Celeste Mike

Yeah, good point. That's another reason I can't simply move the large ring to the inside. It would definitely hit the stay. I know that if I could move the whole crank inward just a few mm though it would clear.

ThermionicScott 

There don't seem to be a lot of choices in ISO bottom brackets anymore, so I'd just buy a 111mm unit and see how it goes. If it doesn't work, you ought to be able to find a buyer in C&V or the fixed-gear forum.