BB shell width for a cross bike

[zennmotion]

A buddy decides to jump on a cheap Aluminum Ebay frame to try out cross, has scrounged old parts to make a raceable frankenbike. Cool. Until the build- turns out the bottom bracket shell is MTB standard 73mm. And he has a nice Ritchey compact road Octalink crank and (Ultegra-V1) BB. Just for giggles we tried to install, the drive/spider side is actually fine, it fits with sufficient clearance everywhere. But the non-drive crank arm rubs against the left BB Octalink cup. He really doesn't want to invest in a new MTB crank and BB, and a road crank would be best for this bike anyway- and the ritchey set is like new. So among the options is to shave 5mm off the BB shell to bring it to a road standard 68mm. It looks like a shop with the right facing tool could shave off 3-4mm on the non-drive side of the shell, but only 1-2mm off the drive side- without making the spider uncomfortably close to the chainstay (this is a cross bike and will see mud build up so need a greater margin) Is it smart to ask a shop to remove more material on one side than the other? Is there a simpler solution?:help: Looking for insight before making a potentially frame killing error-

[pakora]

It sounds like you're in a similar situation as me - I race a Kelly Knobby X, and Chris Kelly built his bikes around an XTR group, which means that the stays are weird and expecting a mountain crank (and subsequently chainline), though these bikes have a 68mm shell.

The general workaround there is to run a wider BB with a road crank and just live with a chainline that's a little off. Functionally in cross racing, I find there's more than enough other things to worry about (like mud, sand, clumps of grass and other riders getting stuck in my chain/cogs) that it's not a problem.

Obviously with Octalink V1 you don't have many BB options - I'm running an XTR crank, and I couldn't use either a 109.5 (bottomed out) or a 118 (chainline so far off on the big cog I couldn't not drop it). My solution was to run a single ring on a XTR 112.5 bb (XTR were V1, the rest of the mountain stuff were V2). XTR bbs also came in 116.

I'm not sure whether all are, but all of my XTR bbs are for a 73mm shell and have spacers to run them on a 68.

That's a LOT of words heh but I thought I was the only person with this problem. You have to REALLY want to run that crankset it seems. Switching to a square taper and figuring out an appropriate spindle length seems easier and cheaper (and doesn't rely on scouring ebay and classifieds for 1999 mountain bike parts).

[zennmotion]

It sounds like you're in a similar situation as me - I race a Kelly Knobby X, and Chris Kelly built his bikes around an XTR group, which means that the stays are weird and expecting a mountain crank (and subsequently chainline), though these bikes have a 68mm shell.

The general workaround there is to run a wider BB with a road crank and just live with a chainline that's a little off. Functionally in cross racing, I find there's more than enough other things to worry about (like mud, sand, clumps of grass and other riders getting stuck in my chain/cogs) that it's not a problem.

Obviously with Octalink V1 you don't have many BB options - I'm running an XTR crank, and I couldn't use either a 109.5 (bottomed out) or a 118 (chainline so far off on the big cog I couldn't not drop it). My solution was to run a single ring on a XTR 112.5 bb (XTR were V1, the rest of the mountain stuff were V2). XTR bbs also came in 116.

I'm not sure whether all are, but all of my XTR bbs are for a 73mm shell and have spacers to run them on a 68.

That's a LOT of words heh but I thought I was the only person with this problem. You have to REALLY want to run that crankset it seems. Switching to a square taper and figuring out an appropriate spindle length seems easier and cheaper (and doesn't rely on scouring ebay and classifieds for 1999 mountain bike parts).

Thanks for the thoughts, but a different spindle length, whether Octalink or square taper, wouldn't solve the problem because it's the Non-drive arm that's in contact with the shell- the spider is actually fine. I'm thinking that if I cut down the BB shell asymmetrically (more on non-drive side) it would solve the issue- there seems to be a little more material on that side that can be removed without cutting into the fat toothpaste Tig welds. I'm just concerned that there's something I'm not considering properly- I don't know what I don't know and I don't want to just hand it to a shop just yet as cutting is irreversible. I doubt I'd notice a couple of mms of asymmetry- smaller Q factor on L than the Right. Right? Anyone?

[Mr Cabletwitch]

If you got a 73mm bottom bracket you would be fine aside from some minor chainline difference. If you do shave the BB shell you should shave equally on both sides. The only reason its the non drive side that is rubbing is because the drive side is attached to the threads so it doesn't move because the shell is too wide the non drive side doesn't stick out enough.

[pakora]

heh what I mean is the only V1 Octalink bbs with a 73mm width are XTRs.

[oliver1850]

Another option that might work would be the ES51 VII BB with a Tiagra crank. ES51 is still available new for 73 shells in the 113 mm length that the Tiagra uses. I have a new Tiagra 175 if you're interested.

[zennmotion]

heh what I mean is the only V1 Octalink bbs with a 73mm width are XTRs.

Yeah, gotcha, thanks. Am I just a luddite who thinks that BBs never really got any better after Octalink? Scratch that---- better after square taper? Back in the day, I knew pretty much everything that a civilian needs to know about cranks and BBs. Then Email and the interwebs and Lance ruined everything. Sheldon Brown, Rest in Peace:beer:

[zennmotion]

Another option that might work would be the ES51 VII BB with a Tiagra crank. ES51 is still available new for 73 shells in the 113 mm length that the Tiagra uses. I have a new Tiagra 175 if you're interested.

Thanks for the ideas, but ideally I'm looking for a permanent solution with some different options that allow a standard road crank- ie cutting the shell if that doesn't eff up the frame in the process. Is your Sirer still in mothballs? Post a pic if you ever built it, a bit of an odd frame that would be cool for somebody-

[oliver1850]

Well, the Tiagra is a 130 BCD road crank, not that bad looking, especially if you replace the black rings with nicer silver ones. I have a stock one on my Zurich. Here's one with 38/46 rings:

http://www.ebay.com/itm/Shimano-Tiagra-crankset-with-38-46-cyclocross-chainrings-175mm-/171131702114?pt=US_Cranksets&hash=item27d83e8b62#ht_58wt_1178

The Sirer is still sitting here. I wanted to build it for my Czech friend to ride, but he's moved to Milwaukee and hasn't been here this year. Still contemplating a repaint.