Right now i have a Specialized Strongarm II crankset on my bike. It uses the square taper. I am using the Shimano LX Square Taper. The size is 68x110. I also only have 8 speed in the rear but I have a mega 9 Deore LX front derailleur. Now if i want to upgrade to LX hollowtech crankset i know i will have to upgrade the BB. Since the splined BB's only come in 68x113 and larger will this create any problems. Also, the crankset is mega 9, will it affect the shifting or chain rubbing since i know there is 8 and 9 speed cranksets. And which splined BB from shimano do i need to be compatible and once again will the diff from 68x110 to 68x113 make a difference?
Scott Gambler, Scott Ransom, Kona Bear, Bianchi 928 Carbon/Chorus, C'Dale Rize4
The problem you might run into will be that the angle of the chain wil be greater which could cause it to drop off the chain rings. It can also cause more flex in the chian stays when pushing big gears. The shifting will also be affected in back. But then again, you might not have any of these problems. As for the mega9, I believe that they are designed for 9 speeds so you should not have a problem. I run different length bb on my dh rig depending on the size of the chain ring I am using and have found that 3mm did not make much of a differance. It did however take just a bit longer to adjust the rear derailer. Lastly, the longer bb will set your pedals farther out from where they are now.
Hope this info helps.
9 speed are just slightly narrower, the spacing is the same on the chain rings, but a 9 speed cassette is the same with as a 8 speed, so the cogs and chain are narrower to fit 9 in the same place as 8...
Using 8 speed rear with 9 speed fron is less of a problem than the other way...
But shifting will be less crisp, if you mix it up.