Help with Math - 8-spd hub/BB/Cranks



st caoimhin

New Member
Apr 24, 2007
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I'm nearly ready to start ordering a drive-train and building up a sweet work bike. I have it mostly under control, except for the BB/CS and how they'll create the appropriate chainline. I have one full build under my knickers: a fixie conversion that was pretty straightforward as far as how my brain wrapped around the numbers. This one I can't seem to figure out at the moment without dropping more money on experimentation. I have top-notch shops in the area, but every time I ask the couple I have relationships with about my wacky bike ideas they are unsure since most of the work in the area is either basic maintenance or high end racing gear. Internally-geared hubs mostly seem to come as complete bikes, not pulled out of thin air!

Here's what I have and what I wish to do:
- Free(as in from a drinking buddy :D ) No-name Alum MTB frame - 135 rear spacing - 60cm back from the rear of the BB shell the chainstays measure ~82cm across and 10cm back it is ~10.5cm(sorry, I'm unsure about how to measure this best) - Vert. dropouts with replaceable derailleur hanger.

- Truvativ Hussefelt SS crankset(from a parted out mountain bike) with Isis-splined BB(113mm as spec'd for 48.5mm chainline??(hard to tell, it's not labeled but that's the number from Sheldon's BB data). The spider is actually set up for two chainrings and it appears the 48.5 is for the inner ring.
- Older Campy(Chorus?) Double crankset(I have no info about BB size or chainline)
- Phil 103mm BB, but this was meant for a track frame I am slooowly building up and I didn't think it would work for this anyway.
-Singleator-type chain tensioner

The plan is to build it as an Xtracycle with an 8-spd internal geared hub, either Shimano Nexus or Sturmey-Archer that I will have my LBS build for me. I'm leaning towards the S-A for price, though I hear the shifter is cheesy. Both take a 45mm chainline I believe.

It's my understanding that a Phil BB would give me plenty(??) of chainline adjustment to fudge it a bit, but I can't really drop all sorts of cash at the moment unless it will make any headaches go away super easily. It's already getting upwards of my stretched budget. I just need to get it rolling and think about upgrades later.

So, please help me if you can. Should I use one of these cranksets with a ???mm BB? Just the matched truvative CS/BB?. Can the chainline be tinkered with on the hub end? I can't find any real info the net. If I sell a few more quarts of my blood I could probably spend another hundred on a decent, sturdy crankset and lower-end BB. Would that be best?

Please bear with me as I learn, and let me know if I am way off course or just need a light smack on the noggin. I'd love to figure this out soon so I can schedule some time at a shop for the wheel-build and BB/HS installation and have this ready in a few weeks if possible.

Oh, and Hi everybody. I'm new here :)