Cut a 73mm BB to 68mm?
 

Well, can I? I've got a Dirt Research/Tom Teesdale Kenai frame and the English threaded BB shell measures 73mm. I want to fit some latest generation 10 speed, 7800 series, 2007 Shimano 105 cranks to it and use its English threaded 68mm integrated on this frame. What'll happen if I face it until it all fits?

Thanks,
DG1

Possible chainring/crankarm clearance problems, chainline problems. If you want to run a triple the FD may bottom out on the ST before completing the shift to the inner ring.

Apparantly, the new 105 crankset fits a 70mm BB in order to work with Italian threaded shells. Do you think that means I can get away with grinding to 70mm on the English shell? 1.5mm on either side doesn't seem like much and shouldn't mess my ankle/chainwheel clearance, at least I don't think it will. So, let's say I'm only going to run a double, think I can get away with it?

DG1

I think you could, but it sure would suck to have it turn out wrong. Not fatal to the frame though, there are always BB spacers to bring you back to 73. I hope you don't plan on doing any grinding, use the correct facing tool or have it done. This is critical.

+1 on that. You'll have problems with it becoming loose if it is not properly faced. The lockring will not be secure, and then you run the risk of of stripping the locknut when you tighten it because it will not be seated properly.

No! English is 1.370" X 24 tpi left and right hand threads, Italian is 36mmX1mm right hand threads only!

Let me ask a more fundamental question, why do you want to install 10-speed Dura Ace cranks on what is obviously an MTB frame?

If I read Sheldon's chart right, Italian bb shells are larger diameter than English, so the 70mm option is out. Youll likely find chainline/clearance issues, anyway.

Hehe.

My other thought exactly...

Thanks for the warning. My thought though, isn't to actually install Italian threaded cups, I'm just mulling over exactly how far to face the shell and what the widest I can get away with might be.

DG1

For the same reason people make fixie mtb's: because you can. Consider the downhill, or possibly the old cruiser conversions, as the beginning of the evolutionary chain. Somewhere between mtb, cyclocross, then road is where this bike will fit. A bombproof NYC bike that's geared too high for most offroading, but can do it in its sleep anyway. Think of it as a cyclocross bike, growing up from an mtb, instead of down from a tourer.

DG1

[Wrong info]

beat me to it...

No. They refer to the width of the BB shell. You could grind it down, but I can't see it being a good idea. you would need to make sure it's exact and the shell is faced properly, then make sure the FD can still reach all of the chainrings.

Now that's an interesting turn of events. Just measured an old Italian made Lemond team frames bb width and it reads 70mm, the width of the Dirt Research reads 73mm. Birdy in the corner: 68mm. These three measurements certainly lead me to believe that I've covered the examples and that they match the definitions of Italian 70mm (Lemond), English MTB 73mm, and English road 68mm. Guess I'm off to Sheldon's....

DG1

Am I the only one confused here? It sounds like an interesting project, though.

I'm wrong on the diameter thing (sorry), but I just went downstairs and measured my "68mm" shell. It's closer to 75mm axial. (Obviously it's not the diameter, which is closer to 35mm).