Is switching to integrated BB possible?

tjancijr said:

Scenario: I have a 2003 Specialized Sequoia road bike. I bought it from the original owner who has appeared to have treated it pretty well. I ride pretty much daily for commute purposes, and take it out on 30-40 mile rides on the weekends. I've been doing more and more climbing as of late. A couple weekends ago, mid-climb, I discovered that my front derailleur wasn't allowing me to downshift to the inner chainring. I pulled myself as hard as could up the hill and I think I did some damage to the bottom-bracket in the process. If the BB is stock, and I have no reason to believe it isn't, it's a Shimano UN25. After reading up on this BB, it doesn't appear to be very difficult to jack one of these things up if you're putting any sort of torque on it.

What I want to do: I would like to replace the BB, though the UN25 specs are 68 x 118, square-taper, and my options for upgrading to a BB that is compatible with my Crankset are not only extremely limited, but unattractive given the type of riding I want to do - I'll just end up trashing another UN25 or 54. Going with a different BB will require me to switch out my crankset, which I'm more than happy to do. Ideally, I'd like to move to an Ultegra triple setup, or at least a late-model 105 triple.

So here's my question: will a more modern integrated BB fit my bike? There are older Ultegra setups that don't require the integrated BB, though the used setups I'm finding on eBay have more miles on them than I'd like.

Any help would be appreciated.

I'm going to presume that you actually mean the cranks which use an EXTERNAL BOTTOM BRACKET (e.g., Shimano Hollowtech II, FSA MegaExo, or Campagnolo UltraTorque) rather than meaning an "integrated BB" such as a BB30 which requires the frame to be constructed in a way that the bearings can be pressed into the frame's BB shell ...

If you indeed meant External BB, then the answer is 'YES' ... you can update your crank & BB, but there is no assurance that the BB's bearings will last as long.

FYI. The threading on your frame's BB shell is "English"; so, you will want to buy a BB with English threading -- the driveside has a LEFT HANDED thread & the non-driveside is a normal RIGHT HAND thread.

How does your BB spindle feel when you turn the crank by hand?

Thanks for the response, and yes, I mean an external BB. Thanks for the correction.

I haven't actually tried spinning the cranks by hand without putting weight on them. Now, when I'm riding the bike, whether it's on the flats or climbing, I feel/hear a sort of "knock" on the crank that I'm putting pressure on. The harder I pedal, the louder/more evident the "knock" is. It didn't start doing this until I started doing rides where I was climbing a lot. The weekend climb where I had no "grannie gear" is when it started happening.

I'll spin the cranks tonight by hand and get back to you. Thanks again!

Tom

tjancijr said:

Thanks for the response, and yes, I mean an external BB. Thanks for the correction.

I haven't actually tried spinning the cranks by hand without putting weight on them. Now, when I'm riding the bike, whether it's on the flats or climbing, I feel/hear a sort of "knock" on the crank that I'm putting pressure on. The harder I pedal, the louder/more evident the "knock" is. It didn't start doing this until I started doing rides where I was climbing a lot. The weekend climb where I had no "grannie gear" is when it started happening.

I'll spin the cranks tonight by hand and get back to you.

If the "knock" is occurring at the same place in the pedal stroke, then one of the crank arms may have loosened ...

That is, the bolt that holds the crank on the BB may have loosened & therefore the crank arm may have worked its way loose from the BB spindle.

That is not a good thing since the tapers inside the crank arm can become damaged. This is a much worse situation if it happens to the driveside than to the non-driveside ...

If the non-driveside crank arm has loosened, it may not be the end of the world since you may be able to tighten the bolt & secure the crank arm sufficiently ... it's just not ideal ...

If the LEFT SIDE crank arm still wobbles after you tighten the crank bolt, you can possibly shim the taper ...

If it is the DRIVE SIDE that wobbles (i.e., the chainrings move in a wavey motion rather than being in a plane that is parallel to the bike's central plane), then you will need a new crank.

Good idea. I'll check on that tonight as well. I feel it in both cranks though - maybe they've both come loose? Will check all of this stuff out and check back tonight.

Thanks for all the replies, keep 'em coming!

Tom

Sounds like a loose crank arm, as suggested above. For what it is worth, Thor Hushovd wouldn't be able to trash a well-installed BB-UN25 in a sprint; these old-fashioned solid-axle cartridge BBs are very strong, just a little heavy. I have a UN-53 (I think) on my commuter that has been there for more than 10 years, and it is still going strong after a very large number of kilometres. External BB systems are a plain and simple marketing gimmick, but have, unfortunately, become the standard.