Square, ISIS or Octalink drive?

[Willie_B]

I am building up a bare OZ frame and would like some bottom bracket info. Back when I stopped riding the only choice was square drive. Now there is ISIS and Octalink, both of which I know nothing about. What do I need to know to make a good decision? This will be just a weekend fun bike for an older  rider. Looks to be harder to find a square drive that will fit compared to how many of the other types. Thanks.

[Old Proflexer]

my 'square' drives still function just fine -

guess being of the older set myself - associating with 'square' isn't all that bad

if the old one's still work - there's no need to replace

OP

[shovelon]

I too am a square taper guy. I like the adjustable chainline. Lots and lots of used cranksets out there and they work great for me. Phil Wood makes the best square taper in Titanium.

As far as Isis I think American Classic makes the best.

[jeffhop]

stay away from isis theyre nothing but trouble, i used to have gxp outboard bearings on my oz with a truvativ chainset with no issues, ive also had a square taper bb in 5 frames that is still as smooth as a babies bum, octalink is generally better than isis but still no where near square taper regarding longevity.

[Willie_B]

So it sounds like it's still ok to be square. That's cool dude  .

[willem]

None of the above...

Broken a few square tapers.
Hated one ISIS.
Octalink a little too unusual.

Completely taken in by the last two external BB systems I've put in.
And they're getting cheap, too.

[shovelon]

None of the above...

Broken a few square tapers.
Hated one ISIS.
Octalink a little too unusual.

Completely taken in by the last two external BB systems I've put in.
And they're getting cheap, too.

You monster you!

[DugB]

I'm running an XTR M952 crankset on my 4000, with an M950 needle bearing bottom bracket (their lightest Octalink BB). I love the combination! This older XTR stuff can be picked up cheap these days and works amazingly well. I've got full XTR M950/M952 on the 4000, bought it all in the slightly used range, and the resulting bike is a fast shifter (I'm using Magura hydraulic brakes). I might opt for a new bottom bracket, though...that's a part you don't want failing on the trail. Seriously, if you go Octalink try to find a new M950 bottom bracket...or an M952 if that's all you can find (a true cartridge design, but slightly heavier).

Just my experiences. I've never had a problem with square taper either, and still have an old ook Brothers crank I'm waiting to install on my 856, if I can ever find a light square taper BB in the correct length.

- Doug :-)

[Willie_B]

Like this DugB?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250369903628&ru=http%3A%2F%2Fsearch.ebay.com

[DugB]

Yes, but ideally cheaper...and longer. For some reason the Cook Brothers crank seems to have the square taper receptacle embedded deeper into the crank arms than other cranks...so I'd need like a 117mm or something like that. I actually have a standard steel BB spindle downstairs that worked with it on one bike...I may test fit it with that, then look for a lightweight version if it works.

- Doug

[Carbon_Angus]

None of the above...

Broken a few square tapers.
Hated one ISIS.
Octalink a little too unusual.

Completely taken in by the last two external BB systems I've put in.
And they're getting cheap, too.

You monster you!

count me in as one who has also stripped a square taper crank. ISIS has been fine for me, now i'm sure a taper would be okay, too.
i wonder if any one style puts more stress on the BB shell or if it just installation of the BB into the shell?

[willem]

Y'know OP... I think you hit on my favorite feature of the external BB's. They seem to put less stress on the frame/BB shell.

Like all BB's they put lots of working stresses on the threads, but a good deal of the stress is translated to the outer surface of the shell. I know I sound like a XBB salesman, but these things are really adjustable and change out quickly. (Every dealer has like a hundred wrenches they got for free from Shi_mano - just ask for one...)

For some reason I had five or six pedal strikes last Saturday, but with the XBB's I never worry about cracking the crank arm at an overstressed corner of a square taper.