radiocontrolhea

Ok i'm having a really hard time figuring this out. I just recently purchased an Alien frameset and i'm now looking to purchase a crankset, bottom bracket and hubs to obtain a perfect chainline. I have searched and done research on sheldon's site as well as these forums and cannot figure it out.

I am going to use sugino 75 cranks but have realized that hatta swan BB are 109mm long and the Sugino 75s are 109.5mm.

I am thinking of going with dura ace hubs, but will this provide for a perfect chainline?

calv

.5mm difference? Don't worry about it, man.

mihlbach

You are talking about 0.5mm. Thats barely macroscopic. Cogs vary in thickness more than that. Plus its not likely that your frame is aligned correctly to that degree of perfection. When you pedal your bb sways back and forth much more than that. Worrying about half a mm chainline difference is pointless.

TejanoTrackie 

Yes, and furthermore, over time the crank will pull inward on the square taper spindle as it is repeatedly removed and
retightened, changing the chainline. Far more important than exact spindle length is that the correct taper type be used, which in this case should be ISO.

radiocontrolhea

i guess wehre i'm going from here is i'd like to understand the concept of it.

calbob76

The concept is the spindles being such a small difference in length basically means they are about the same once on and in use

Scrodzilla

The "concept" of .25mm per side making no difference at all isn't really difficult to understand.

radiocontrolhea

Found out that both these bottom brackets are practically identical with a spindle length of 109mm. The source I used had posted a spindle length of 109.5mm for the SG75 BB. Guess this setup with either bottom bracket will result in a 42mm chainline up front.

Scrodzilla

Do you hear that? Baby Jesus has stopped crying!

seau grateau

Sure.