Bicycle Mechanics - Possible to upgrade bottom bracket from square taper?

I'm looking to put longer and stronger crankarms on my commuter bike.

It has a full dura-ace 9spd group on it with the exception of the crank/BB. Currently I have a shimano un54 square taper sealed bottom bracket in it iirc (it's a sealed cartridge shimano I know for sure, but it's been a couple years, it originally had the old style cup/cone floating bearing BB). And a sugino mighty crankset.

Recently I've been getting a rhythmic clicking when I apply power with my right leg, and if I ever put down a lot of power to pedal up hills I can see the chainrings flex around and lots of funny noises happen. In addition the cranks are 172mm and I'm 6'5" and would like to try longer crankarms.


So the short version is: What would be a good upgrade, can I put an octolink BB in with a matching crankset, or even BB30? I like the idea of the stiffest possible BB setup, I would also like a compact double set of chainrings, like 36/52. My current 42/52 isn't very useful with my 9spd cassette which I think only goes up to 23t.

You can't use BB30 unless you have a BB30 specific frame already, which it sounds like you do not. Assuming you have a standard English threaded BB shell, you can put in any external BB you want that uses English threads.... plenty to choose from.

+1

You can use any BB/crank system compatible with a BSC (ISO) 1.370" threaded bottom bracket shell. You can go ISIS, Octalink, better quality sq. taper, or any of the threaded external bearing systems.

Anything except sq. taper means new cranks, but I suspect that your clicking is from a damaged crank arm. If that's the case you need new cranks (or at least one) anyway

so I can upgrade to an external bearing BB like one of these without issue?

272623

so I can upgrade to an external bearing BB like one of these without issue?

272623

Yes, or get them together like this:

http://www.ebay.com/itm/SHIMANO-TIAGRA-FC-4550-4550-175mm-50-34t-w-BB-Road-Bike-Crankset-Crank-NEW-/380470115918?pt=Cycling_Parts_Accessories&hash=item5895c93e4e

Yes, that's an option. As Canam said, you'll probably save some dough if you but it as a set with cranks. There are plenty of choices, so take your time and find one you like at the price you want to pay.

thanks guys, that helps a lot. Now to find a good match for the rest of my 7700 group that isn't too ugly.

However, do you really need new cranks & BB ? Maybe the cups or bolts are a tiny bit loose. Also, noises have MANY causes, and sound often can come from somewhere other than where you think it's coming from. .... seat, pedal, stem/bars, wheels (slightly loose qr, spokes ) ....

it's definitely in the cranks, I can feel it with my feet when it clicks, same spot each revolution, and if I apply pressure and pedal back/forth in that spot it does it in both directions if I push hard enough.

it started after I fell at a red light a few weeks ago, I'm not very good at balancing while clipped in :)

so I can upgrade to an external bearing BB like one of these without issue?

In my experience, going from square taper cartridge to external BB is a *downgrade*.
They don't have a fraction of the longevity of the square taper cartridge.

it's definitely in the cranks, I can feel it with my feet when it clicks, same spot each revolution, and if I apply pressure and pedal back/forth in that spot it does it in both directions if I push hard enough.

it started after I fell at a red light a few weeks ago, I'm not very good at balancing while clipped in :)This 1-rpm click is usually a just loose crankarm bolt or pedal. Typically disassembling the crank, cleaning and inspecting the interfaces and re-assembling with a torque-wrench will fix it. Unless something's actually broken in your existing set-up, there's no guarantee that simply replacing parts will make the problem go away.

so I can upgrade to an external bearing BB like one of these without issue?
IDK about 'without issues' but if you buy the whole thing at once bb & cranks
they will be compatable with themselves.

get the external BB tool to work with your torque wrench, 1/2" better than 3/8 drive
due to torque scale range of (beam) wrench.

this 1-rpm click is usually a just loose crankarm bolt or pedal.
this!

In my experience, going from square taper cartridge to external BB is a *downgrade*.
They don't have a fraction of the longevity of the square taper cartridge.

I never had any complaints with my Campy square tapers over the years.

In my experience, going from square taper cartridge to external BB is a *downgrade*.
They don't have a fraction of the longevity of the square taper cartridge.


This can be true... but is not necessarily. The early failure of external bbs is often because the bearings relay on the outer faces of the BB shell for alignment. So if the faces of your shell are not 100% parallel within a very tight margin, the bearings will be misaligned and will fail prematurely. Most decent bike shops have a BB facing tool that shaves a bit off the shell using the threads as a reference to ensure the faces are parallel. My buddy got a budget frame from Nashbar a couple of years ago and the bearings of his Raceface BB were so tight he though the BB was defective. But after having the BB shell faced the crank spun smoothly. Had he ignored the extra bearing drag and just ridden it as-is, I'll bet the bearings would have failed within a month of regular riding.

In my opinion, external BBs are superior to most square taper BBs, except for this reliance on frame condition. Although I think they are superior at sort of an academic level - they are better on paper but make little difference in the real world. Both are far superior to the splined BB with internal bearings designs, as the bearings in these need to be much smaller to fit inside a standard BB shell with the oversized axle.

I think the OP should try out a set of 180s or 185s in whatever crank he can get with whatever BB he needs. I know Sram makes a few cranks in longer lengths, but I think Shimano only makes the Dura Ace ($$$$$+++) longert than 175.

This 1-rpm click is usually a just loose crankarm bolt or pedal..

or a loose chainring bolt. I always tighten these up first since it's really easy.

My noise and flex was a missing chainring bolt :eek:. I like my square tapers. My external bbs don't last long on the mt bike.

The cranks you have arent flimsy at all, are you sure you dont have problems with lose crankset bolts or something ???

Yes, will be easier for you just get a shimano something cranset together with the cups. A detail... im not an expert in shimano but you have to find out if the crankset you have will match fine the group you have because with shimano, specially dura ace there are some issues mixing brands and models... With campagnolo I would say just buy whatever you want because it will work fine, with shimano is not that like a super straight forward swap...

The cranks you have arent flimsy at all, are you sure you dont have problems with lose crankset bolts or something ???

Yes, will be easier for you just get a shimano something cranset together with the cups. A detail... im not an expert in shimano but you have to find out if the crankset you have will match fine the group you have because with shimano, specially dura ace there are some issues mixing brands and models... With campagnolo I would say just buy whatever you want because it will work fine, with shimano is not that like a super straight forward swap...

everything is tight, 50ft/lbs on the crank arm bolts, and as tight as I could get the chainring bolts and pedal bolts by hand, everything assembled with anti-seize.

I haven't taken it all apart and put back together since it started clicking, I may try that tonight.

However strong the sugino cranks may be for others, they visibly walk around if I pedal hard. I'm a big guy, 6'5" and 210lbs. This doesn't happen with my 2 other bikes (shimano 600 and deore xt cranksets).

I'm not too worried about parts compatibility as I've used my current setup for several months before I bailed and this clicking started. Every gear change is crisp and works perfect, and I'm definitely not using a dura-ace BB or crankset right now.

everything is tight, 50ft/lbs on the crank arm bolts, and as tight as I could get the chainring bolts and pedal bolts by hand, everything assembled with anti-seize.
Did you try replacing the pedals and riding that way? I'm curious about the noise, not the "flex".

External bearing bb are great. Easy to work on and spin well and long. I really disagree about square tapers as better. Set correctly I think the external bb are the best in fact my worry is all the press fit new stuff and creaks........issues ect.

Did you try replacing the pedals and riding that way? I'm curious about the noise, not the "flex".

no, I haven't. I can try that tonight though and see what happens, can't hurt.

Also, if you have anti-seize on the bottom bracket spindle taper, wipe it and the taper hole int he crankarm clean. I have had much better luck with dry tapers than lubed. Lube the crank bolt threads, though.