AbsoluteZ3RO

According to the mechanic at the bike shop, and some trusted friends who know more than I do, I need a new Bottom Bracket. Essentially, the problem is that the crank is "moving" in ways that it's not supposed to.

My bike is mostly made up of Ultegra level equipment. What BB should I replace this one with and why?

Here's what my bottom bracket looks like. What type of BB should I be looking for? Is this a "pres fit" BB?

SkyDog75

Does that say "ISIS DRIVE" by the bolt hole? If so, you'll need an ISIS bottom bracket. Probably 108mm for a road double. Nashbar sells a house-branded one for $27.99. Niagara Cycle also has a bunch of options HERE.

ISIS doesn't exactly have a stellar reputation for durability, though. If there was ever a time to look for a new crankset that uses a different bottom bracket standard, this might be it.

AbsoluteZ3RO

I just checked and it does say ISIS Drive on the crank.... That sucks. Are there no good BBs doing ISIS Drive?

topflightpro

Your mechanic didn't tell you what kind of BB you needed?

bikemig 

I wouldn't lose any sleep over this. Just replace the BB unless you want to change out the crank for some reason (perhaps you've been thinking about a compact of some type).

AbsoluteZ3RO

I didn't ask. I believe his assumption was that I'd bring the bike in, and he'd sell me a bottom bracket and fix it all in one shot.

Bacciagalupe

OK, and you are not doing that because...?

AbsoluteZ3RO

Well, say I get on bikeforums.net and find out that X BB is the best for my needs and it can be ordered from Y at a great price and using tools around the house, I can replace it myself. I like to do my own work, so I'm checking here first.

merlinextraligh

There's nothing wrong with ISIS. ISIS is a standard, and parts properly made to the ISIS standard are fine. There are some cranks that used the ISIS standard that are crap, but that doesn't mean there's something wrong with ISIS.

OP get an FSA BB spec'd for your crank and you'll be fine. I wouldn't buy a new crankset just to get away from ISIS.

FWIW, I have an ISIS FSA SLK crank and it worked fine.

SkyDog75

I didn't mean to imply that he had to switch to something other than ISIS, or even that he should switch. But if he was to consider switching, possibly due to ISIS' less-than-stellar reputation for durability, now would be a convenient time since he'll be swapping the bottom bracket anyway.

Not that a failed bottom bracket is a catastrophic thing. I mean, they usually give plenty of warning before they die completely. They generally won't leave you stranded and you'll have time to find a replacement if you notice your bearings starting to rumble. And on the bright side, ISIS bottom brackets can be found cheap, so even if you go through a few of 'em, it's still cheaper than replacing your crankset.

200miler

Skydog, you still don't get the point. If you really understood what merlinextralight posted, you would stop making off-handed comments and innuendos about ISIS standards based parts.

"due to ISIS' less-than-stellar reputation for durability" is absolute fallacy! The only factor that contributes to YOUR continued concerns about durability of ISIS-based parts is the MANUFACTURER'S PROCESSES. If one makes a part to ISIS standards out of crap material, to hit a cheap price point, it will probably have some durability issues.

OP, if you want to try your hand at DIY repairs, I'd suggest you ask the LBS wrench who diagnosed your problem, what replacement he would use, buy it from him, and give the repair a try. You will probably have to obtain a BB tool suitable for the situation but that'll be part of your new DIY tool kit. Buying the BB from your LBS may cost you a bit more, but doing so will be more favorable to you when you start having questions/problems in the future. If you're up-front with the shop, they're more likely to help you learn and expand your repair skills. Besides, they stand to make more sales to you, parts and possibly tools, as you continue your DIY efforts.

The ground won't open up and swallow you if you buy locally instead of off the interwebs!
YMMV
-dg

RollCNY

You won't change it yourself without the right tools. You need a crank removal tool, which is essentially a bolt within a double threaded nut, and you will need a BB installation tool, which is a socket with many little spline teeth.

https://www.amazon.com/Park-Tool-Comp...k+removal+tool

https://www.amazon.com/Park-Tool-Shim...t+removal+tool

I find having a short metric bolt to screw through the end of the tool into the BB helps keep the removal tool from stripping the spline teeth.

Oh, and you turn the wrench toward the front of the bike to remove the BB, regardless of which side you are on.

Nerull

The issue with ISIS is the reduced bearing size, as this is part of the ISIS standard there is nothing a manufacturer can do about it.

Drew Eckhardt 

ISIS spindles are bigger in diameter than square taper although the bottom bracket shell is the same leaving less room between them and forcing smaller bearings which don't last as long. External bearing bottom brackets have a larger spindle but avoid the problem by using bearings too big to fit within the bottom bracket shell.

SKF makes a nice bottom bracket which works around the problem by not wasting space on cartridge bearings. The spindle runs on the inside of the bearings as with a conventional cup-and-cone setup and the races are machined into the shell so the balls can be bigger. Roller bearings on the drive side have more surface area in contact with the race + spindle than balls and should therefore last even longer.


https://www.compasscycle.com/bb_SKFBXC_isis.html

OTOH, it's $150 which buys 2-5 lesser ISIS bottom brackets.

That said my ISIS bottom bracket was still running fine after 6 or 7 years including time in Seattle and could well have beat the 8 years I got out of my last square taper cartridge bottom bracket. That's long enough and I wouldn't have splurged on the SKF, especially since my American Classic split-ring unit was rebuildable.

SkyDog75

I do understand what he posted and I "get the point" that you and he are trying to make. I'm allowed to disagree. There's enough anecdotal evidence with enough plausible explanation to convince me that ISIS bottom brackets aren't as durable as a number of other designs. If you choose to believe otherwise, you're entitled to that opinion. I won't write you off as "not getting the point" because you simply don't agree with me. The OP has multiple opinions to weigh and I hope whichever path he chooses works out for him.

ericm979

I'm in the ISIS doesn't allow for decent bearings camp. You can research ISIS and find industry luminaries who say the same thing.
Although the SKF looks like an interesting solution to the problem.

The best regular ISIS BB I found when I was running ISIS is the FSA Platinum. It uses double row ball bearings, well spaced on the BB axle. Other ISIS BBs I have taken apart have their single row bearings well inboard. I still only got 8-12k miles on the FSAs but that was easily double the single row BBs.

The SKF looks like it'd be good. The AC has a poor reputation for reliability.

The OP should make sure that it's really the BB that is the problem, and not something else like a loose crank arm.

RJM

That SKS is a great bottom bracket. If the bike's worth it, I would get that one.

canam73

I would buy a modern crankset before spending that.

merlinextraligh

I concede there's an issue with the bearing size with Isis BB's, and writing on a clean sheet of paper, you wouldn't choose an isis crankset/bb today. But there are serviceable ISIS BB's, and even if they wear out a bit quicker, you can replace a bunch of them over the next few decades before you'd recover the cost of a new crankset.

blarnie

And yet you have no idea what you're looking at or why but you will be able to "fix" it with tools around the house.

AbsoluteZ3RO

Which is the same place I was when I learned how to do all of my own repairs. Short of taking a mechanics class, isn't this where everyone starts?

deacon mark

I would buy a new crankset with external bearing bottom bracket. You can get a shimano 105 for less than 150$ and be done. This will be the best option and you have a better crankset.