105 Chainset with Sora Cranks + BB?

[Sam Kennedy]

I currently have Sora Cranks and a UN-25 Bottom Bracket.
I have spotted some nice 105 cranks, but I don't know if they will work with my 8 speed chain + cassette, or if they will be compatible with my bottom bracket?

Anyone know?

Here are the cranks: http://www.chainreactioncycles.com/Models.aspx?ModelID=2647

 

[ianrauk]

Your Sora and UN-25 are square tapered aren't they? The 105's are Hollowtech. If you get the 105 cranks you will also need new bottom bracket cups.

Edit: The crank you linked too is an Octalink so you will need a Octalink bottom bracket like this

 

[MadoneRider1991]

those 105 arnt hollowtech

 

[andy_wrx]

Yes, you'll need the Octalink BB.

I just put one of these on my Allez, used as Winter bike, as it was probably cheaper than getting a new set of rings for the Spesh-branded Sugino cranks that were on it.

It'll work fine whether you are running 8speed or 9speed.

I found the cheapest place I could get a 105 BB was Wiggle http://www.wiggle.co.uk/p/cycle/7/Shimano_105_5500_Octalink_Bottom_Bracket/4000000771/ - you want the 109 for a double, 118 fits a triple
CRC were, very unusually, this time dearer than Wiggle

Any road Octalink BB will do, Ultegra 6600 or DA 7700, although they are dearer - but don't get a MTB one as they are Octalink V2 with different length splines and won't fit
- i.e. those ES25 and ES51 CRC have for £5 and £10 unfortunately won't do...