SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.



Kinda looks like a bike now
Originally uploaded by jimgskoop
Kinda looking like a bike now...still having some issues with the cranks/BB. Thoughts/advice?


Blogger Tarik Saleh said...

Cool! I have half the crank on and everything covered with phil grease, including myself. I would run the crank as is, I can't tell if you can have the left crank arm any closer than it is now...

6:38 AM  
Blogger blackmountaincycles said...

The reason why you have so much room is your crank and chainline are for a mountain bike frame where there would be a fat 2.1 tire which would push the chainstays out closer to the rings. In effect, the rings are where they are supposed to be relative to the centerline of your frame based on a 135 rear hub. That, and the rings are on the small side compared to a road triple, contributes to the effect that there are gobs of space between them and the chainstay.

That being said, I would bet that those cranks also give you a pretty wide q-dimension (tread). That bike is begging for a set of old forged Ritchey Logic cranks.


7:17 AM  
Blogger Jim G said...

Hi Mike,

Yup, I know that the cause of all this airspace is the combo of MTB cranks on a road frame. The chain line is to specification, but the alignment with the cassette could be better, IMHO. And as you said, the Q/tread is quite large. I'm wondering if I should try a shorter BB, and if so, which size (I only have a 107 on hand)? I also have another (non-Shimano) crankset I might try...

10:53 AM  
Blogger blackmountaincycles said...

You could try a narrower bb. UN-54 comes in 107 or 110. The bb shell is 68 otherwise it wouldn't have fit on Steve's alignment table.

I think there are a couple of factors contributing - it's essentially a "road" frame, but with mountain bike rear hub spacing. The stays are welded to the bb shell pretty far to the center line of the frame. If the frame was 130 OLD, your chainline would be narrower and the gap between the rings and stays would be more what you are used to.


6:09 PM  
Blogger Tarik Saleh said...

OK, almost caught up, I think I have everything but cables, fenders, rack and a star nut on, pics tomorrow...

10:58 PM  

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