There is some play in an ISIS BB that I can't eliminate. I pulled off the crank arms and tried to tighten the BB cups. They were tight. I tightened down the crank arms and there was still some play. These things aren't really serviceable so I take it that the only fix is to buy a new BB.

Still I'm a little surprised. First, this is a newish BB without a lot of miles on it. This is the 2d ISIS BB on this bike; the first one died when it was fairly newish as well. Second, there shouldn't be any play in this right? The BB turns nicely. There is no creaking noise when I ride. But there is clearly side by side play in the BB. What gives?

are you sure the play is the bb? i have found that isis splines tend to get worn out more so than square taper. you could try driving the spindle left or right while it is install in the bike and retightening the cups

The spindle moves up and down. I'm not sure what you mean by driving the spindle left or right. It's pretty much fixed isn't it in relation to the cups?

literally hammer on the spindle to move it left or right. in this case i would knock the non drive side towards the drive side. i do this to cheap stock square taper bbs but hit them the other way because they are too tight new. sounds like the bb is worn out though, hard to say without seeing it. isis bbs are not the most durable things

If the BB cups are tight and there is play in the spindle, the BB is toast. ISIS BB's were not very durable and that is why they were quickly replaced by external BB's (which still aren't very durable). The Race Face ISIS BB's were some of the worst for durability. The best I found were the FSA Platinum for price and durability.

I figured the BB was toast but I certainly didn't get a lot of life out of it. Good to know about the FSA platinum as I am looking for a replacement. I have one other crank (low mileage) with a Shimano octolink BB. I think when it goes, I'm dumping the crank and getting something with a more durable BB.

Don't equate Octalink with ISIS. I have two bikes with Octalink bbs (one a 5500, 105 level and the other a 6500 Ultegra) and both have been extremely durable. The 6500 has over 36,000 miles and is still in fine condition. The 5500 is still relatively new with only about 6,000 miles and operates like new.

ISIS was a public domain design and they were made by numerous manufacturers in a huge range of prices and quality. The poor ones were very bad and gave the whole design a bad name.

This is useful info as well. The octalink BB I have is a good one as well (XT quality for a triple mtb crank) so I'll see how well it holds up over time. I'll source out a good quality ISIS BB for my other bike; it's worth trying to find a good one to see how it holds up over time.

This is a useful discussion of ISIS BBs: https://weightweenies.starbike.com/fo...hp?f=3&t=60539

If you have ISIS and want a BB that will last a very long time buy SKF. Not cheap but certainly worth it.

Or just buy a couple spares. They're only about $10 on eBay; that's cheap enough not to bother worrying about it.

I have had xlnt performance with these:

SKF
Stronglight
DEDA

The SKF looks great but it runs $150. The Stronglight doesn't appear to be as widely available in the states (I tried googling it) but I suspect I could source it eventually; the Deda looks good at app. $40. Still I've run through 2 of these in fairly short order. I'm thinking maybe it's just time for a new crank and BB. I've seen the SRAM Apex Cross crank going for under $150 with a BB. That might just be a better long-term solution.