Joe Bender-Zanoni wrote
>
> There is one part of Jobst's analysis that is very flawed.
> Campy says to set them up dry and that is where the chainline is
> correct. If you grease them, they slide up further on the taper.
Joe, with all due respect, they don't slide up there by themselves. Unless I'm missing something, seems like the only way a crank can go too far up the taper is if the mechanic keeps on wrenching after the point where the crank is just right. Ya gotta know when to say when!
The torque required to get it there is less with grease, but it is more predictable and repeatable than dry. Especially since "dry" almost always has *some* lube, varying amounts, unless it was specially degreased, which nobody does. The tightness of the press fit is the same in either case for a given chainline, being determined by the geometry of the pieces and their modulus of elasticity; only the tension on the bolt, and the torque required to get it there, are lower when the taper is greased. This is not a bad thing.
Those that say they've seen cranks ruined by grease: aren't you leaving something out? Namely the other side of the coin - you really should be adding "...and I've *never* seen a crank ruined that was assembled dry". Otherwise what you're saying is, you've seen cranks ruined both ways, but you don't attribute the failure of the dry ones to their being dry. Without some more scientific inquiry, I'd say this is illogical. I've seen more ruined cranks that were assembled dry than were greased, but I don't attribute this to anything other than the fact that more cranks get assembled dry. Whether they get ruined or not has to depend more on other factors, notably overtightening.
Mark Bulgier
Seattle, Wa
USA