Component(gearing) upgrade question

Question

I'm a long time ultra-runner turned triathlete so please bear with me. I'm looking to upgrade to Shimano Ultegra 11sp components and currently I'm running on the stock components which are Shimano 105's 11sp. I'm riding a Fuji Norcom straight which is their performance tri bike. I just want to make sure that I purchase the correct parts ahead of time so I can take them all in to get installed on my bike. I have the following parts needed on my checklist and want to make sure I have everything before making this purchase. If you see that I need anything would you please let me know? Thanks!

1. I wont need to buy front or rear calipers because I have trp brakes which are hidden behind the fork and the backside of the frame. I also wont need the levers because I have vision shifters on the ends of my aero bars.
2. I will need the Shimano Ultegra 6800 11-Speed rear derailleur
3. I have a choice between the GS Medium Cage Rear Derailleur 11-speed or the Short Cage Derailleur and am not sure what the differences are. Any help here?
4. Ultegra 6800 crankset 11-speed
5. Ultegra 6800 11-speed cassette
6. Ultegra 6800 SM-bottom bracket
7. Shimano 11-speed inner chainring bolt set
8. Shimano Ultegra 6800 outer chainring bolt & cap set

Anything else you all see? I'm purchasing from this site: http://www.trisports.com/shimano-ultegra-6800.html

Answer 1

In terms of the rear derailleur, you will need to determine the capacity you need.

To do that, add together the teeth in largest rear cluster and largest chainwheel to get the max teeth you have. Then add together the small rear cog and the smallest chainwheel to get the min teeth you have. Subtract the min from the max. That is your capacity needed.

You can then go on to the Shimano site and gets the specs for the derailleur you are interested in to see if it has enough capacity. You will also need an 11 speed chain cut to fit.

Answer 2

Nice shopping list. You'll need a new chain too - theres no saving putting your existing used chain onto brand new everything else.

Personally I'd go for the long cage because it allows more difference between smallest and largest cog in the cassette. As an all-purpose rider I want a 12~28 or 12-30 cassette with a triple on the front.

However as a tri rider you might never do climbs, so flat-land speed would be better developed using a corncob cassette, where the tooth count changes by 1 between cogs - you could have 11-22 in steps of 1 tooth for optimum cadence.

Finally, 105 is still good, so don't shelve it. You could consider putting it on a training bike, or passing it on to someone else. I still ride a 3x7 speed road bike!