ISIS bottom brackets

[marathon marke]

I left the cycling scene a couple decades ago, back when the tapered spindle BB was the norm. My 2005 Felt F65 has an ISIS BB with internal cups. If I wanted to get a new BB, is there an ISIS version with external cups? If so, is there a disadvantage to this? The reason I'm asking is because with external cups, wouldn't that bring my crankarms out further from each other than with internal cups, this increasing the Q-factor?

 

[TexPat]

SKF makes the only ISIS bottom bracket that lasts in my experience.
Internal bearings have a much better reliability rate, so stick with what you've got. Don't think there is any other option, anyhow.

 

[brianf7]

FSA Platinum is a very light hollow BB they come with 10mm 13mm and 17mm wide
Your cranks are same Q factor as most external BB cranks some are wider.

Not a lot of difference in waight
No if you want external BB bearings you need full crankset.

 

[Bustedknuckle]

I left the cycling scene a couple decades ago, back when the tapered spindle BB was the norm. My 2005 Felt F65 has an ISIS BB with internal cups. If I wanted to get a new BB, is there an ISIS version with external cups? If so, is there a disadvantage to this? The reason I'm asking is because with external cups, wouldn't that bring my crankarms out further from each other than with internal cups, this increasing the Q-factor?

No. ISIS is for systems with 2 separate crank arms, bolted onto the spindle. External cups by and large, are bearings only with a 2 piece crank, spindle integrated into the crank arm. In addition, if the cranks went that far out your FD wouldn't work anymore since the rings would also move way out.

 

[marathon marke]

Thanks for the helpful replies.

TexPat: I've had a difficult time finding a source for SKF. Also, since I need a new crankset too, does anybody make an ISIS crankset of middle-range quality, something like an Ultegra?

 

[Notso Swift]

Well if you need cranks at the same time there is no restriction to going to external BB as long as the cranks and BB match the thread type you will be fine

 

[marathon marke]

Well if you need cranks at the same time there is no restriction to going to external BB as long as the cranks and BB match the thread type you will be fine

I was under the impression that the internal/ISIS bearings were better (longer lasting) than external. Aren't the bearings in external cups smaller? That made me consider sticking with ISIS if possible.

 

[Aapjes]

I was under the impression that the internal/ISIS bearings were better (longer lasting) than external. Aren't the bearings in external cups smaller? That made me consider sticking with ISIS if possible.

The bearings in external cups are larger than in ISIS. If you really want long lasting, you should go for square taper. ISIS and octalink were later innovations which introduced a bigger spindle for extra stiffness, but only smaller bearings would fit internally next to that big spindle. That is why the bearings were moved externally, so you could have a big spindle and large bearings.

Given the low price of external BB's and them being pretty much standard, I think it is really not worth the bother to get anything else. Just make sure your BB is faced.

 

[Bustedknuckle]

I was under the impression that the internal/ISIS bearings were better (longer lasting) than external. Aren't the bearings in external cups smaller? That made me consider sticking with ISIS if possible.

Just the opposite. Teeny bearings inside a BB shell when mated to a big, oversized BB spindle made for high failure rate of ISIS and Octalink, WHY shimano started the outboard bearing 'standard.

 

[marathon marke]

Aapjes and Bustedknuckle, thank you for clearing that up for me. It makes sense now.

And since I'll be off my bike for a week or so (due to a back injury from snow shoveling), I think I'll take my bike into the shop this week to get the BB faced, and then just pick up a new crankset with external BB cups. Again, thanks for your help, guys.