chainset/Bottom bracket upgrades

goddamnit_76

Hi All,

I'm looking to upgrade the chainset/ Bottom bracket on my Allez from the original tiagra.

I was thinking of buying a 105 chainset (Octalink Double 5502) but I'm not sure which BB would go with it and my bike as I can't seem to find any info on sizing for the BB anywhere.

I am assuming that the Octalink 5500 BB will fit, but am lost as to which size to get.

All info for the bike can be found here.


would these be decent/ worthy ugrades for my bike?
Any help would be appreciated.

Naonope

redddraggon

So you want to go from a Hollowtech 2 Tiagra chainset to an old 105 octalink chainset, I'd call that more of a downgrade than an upgrade.

Nout wrong with the Tiagra chainset.

maddog 2

yep, depends on what Tiagra you have. The older ones are pretty hefty so the 105 would be an improvement but you should really go HT2 as it's way better than the older designs.

goddamnit_76

ok, That'll be why there are some good deals on the 105 then. Looks like I'll stick with what i have for the time being.
Just for future reference, could someone point me to a link that explains what the different sizes mean for BBs?

sungod

this is a useful reference, no longer updated but covers what you need...

http://sheldonbrown.com/bbsize.html

also, there's shimano's compatibility chart...

http://bike.shimano.com/publish/content/global_cycle/en/us/index/tech_support/tech_tips.download.-Par50lparsys-0025-downloadFile.html/01)%20Drivetrain%20Compatability%20Chart.pdf