Barracuda - Totally Driven!

I am working on a bottom bracket and was looking for some information. The BB installed was a Shimano BB-LR26 with square taper. Measuring from end to end on the spindle, I get 111.72mm.
Question 1: My choices for replacement are 110mm and 113mm. Should I go for the 113mm?
Question 2: What is the difference in the Shimano 26 series and 54/55 series bottom brackets? Is it quality?

I bow to Neo but I used a un72 110 before I put the Ti RaceFace in which will work with both size bb shells and the spindle length is 110 with RaceFace cranks... the crankset sets the spindle length by the way. If you have a bit of space between frame and granny gear I would use the 110...have not seen a 111.72 which my guess is they would call that a 112. I could swear I read that BB spindle length run even numbered, but I bet Neo will know the facts! As said I like 110 and ran that size on my son's Trek with Bontrager race cranks which work great as well. And yes the first part shows what model it is..the 72 is the XT version.

I checked the travel on my front derailleur and looks like the 110mm will be within adjustment. Thanks..

Your caliper doesn't lie... Vinny is right, it would have been 112 b.b. but that was when there was nothing but square taper so the manufacturers made way more sizes than what is offered today. Spindle width comes down to two things... rubbing and front derailleur throw. You have to consider the gap with the small chain ring on drive side chain stay or non-drive crank arm on chain stay rubbing. Counter consideration is the throw of your front derailleur, more than a 20 tooth difference between your big and small will likely cause the cage to throw your chain. I prefer the wider width as it tends to give relief to the knee but that's just me and my snapped ACL.

Total width is what they mean by Q factor right ??? I mention the space between the granny gear and the frame but forgot about the crank arm, that comes into play with older style crank arms because they were in my terms straight where as the new type flare a bit correct ? Have never had a problem with the derailleur not tucking in enough nor having enough throw before.

Dang.. You guys are killing me..

Reviving this thread, as it looks like I need to replace my BB. Trying to decide between a 68x110 vs. 113. The one wild card is my crankset which is a '95 Shimano compact. I'm wondering if that sets the rings on a slightly different plane vs. the original, and thus it might influence the 110 vs. 113 decision. Anyone have any idea or guidance on how to determine?

110 vs. 113?

Think of it in these terms...

old knees

&

chainring replacement

If your knees are getting old and/or don't always work properly (my right is ruined with a snapped ACL) then go with the 113 as the additional 3mm will remove a minor amount of the work load on the interior of your knee joint.

As far as your chainrings, the added 3mm will increase your options when wanting to change rings, specifically increasing the tooth count on any oon your triple crank.

So, as you can see... I see no benefit in going with the narrower 110 bottom bracket. The only time proper chain line is crucial is when running a single speed set up. If you're running a rear derailleur, you have built in flexibility.

Good luck!

-D-

p.s. One added benefit to going with the 113 is the possibility of recycling the B.B. into another frame down the line.

neo_pop_71 wrote:If your knees are getting old and/or don't always work properly (my right is ruined with a snapped ACL) then go with the 113 as the additional 3mm will remove a minor amount of the work load on the interior of your knee joint.

Thanks for the insight, but too late - I already ordered the 110!

I figured I'd err on the side of closer to the frame, given the challenges I had with a too long spindle. BTW, looks like the one that's in there is at least a 120.

If nothing else, I'm a little educated on this topic now. I had no clue before.

Always a good idea to consult with the ultimate bike guru, Sheldon Brown (R.I.P.), half way down the page under bottom bracket:

http://sheldonbrown.com/gloss_bo-z.html

Good luck!

-D-