What’s a Good BB for my new Crank?

Dear Lazyweb,

This weekend, I tried to replace the crankset on my Trek with a shiny new Sugino XD2-600 I scored on sale from Velo Orange.

I got the new one on yesterday, and then discovered that no amount of front derailer adjustment would let me shift into the the big ring. It also wanted the pitch the chain off the little ring onto the BB shell.

It was almost as if all three rings were sticking out too far from the frame. So, I guessed my bottom bracket spindle must be too long.

So, I measured the distance between the downtube and the big ring with the XD2-600 installed. It was about 45mm.

Then I put the original crank back on, and the distance was about 40mm.

Perfect, so I guess my bb spindle is about 10mm too long, 5mm on each side. (Assuming the original setup was right to begin with.)

So, I measured the bb spindle. It’s 123mm long(!!!) This seems ridiculously long? I measured it twice, just to be sure, but it was 123mm both times.

I’m guessing that means I need a 113mm bb spindle, which according to Velo Orange, is what Sugino recommends for this crank.

Rivendell sells this crank, too. They say that it wants a 107-110mm bb, unless you have bowed out stays (which I don’t), then you’d want a 113.

I’ve never really fooled around with my bottom bracket before. So, do I want a 110, or a 113, or am I splitting hairs that needn’t be split?

2 thoughts on “What’s a Good BB for my new Crank?”

  1. That 123mm BB is the one I had for the long XT cranks that got bent in the crash. Do you still have the BB that came off your bike before we replaced the cranks? It’s almost guaranteed to be shorter. If you get a new one, either 110 or 113 should work, but I’d go with 113 if you’re running a 135mm rear hub.

  2. Yeah the one in there now is the one you gave me.

    I went out and measured the old one that came original with the Trek, and it’s 122.6mm. So both have basically the same spindle length. Really weird.

    I guess I’ll order a 113 and see what happens.

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