# HELP - Ultegra 6800 11-Speed Groupset Config



## rscrant (Jul 15, 2013)

Hi,
I am asking for some help with choosing the correct 6800 groupset as I am not sure which Chainring Set (53-39, 50-34, 52-36, 46-36), Crank Arm Length (165, 170, 172.5, 175) and Rear Derailleur (Short Cage, Medium Cage) to choose.

I am going to put this on a 51cm Cervelo s5 and would like simple guidance on what to select.


Thanks in advance.


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## tranzformer (Dec 27, 2007)

Need to explain a bit more about where you ride/the terrain/if you race/fast group rides...etc. as that will help sort out the chainring set + cassette which will then determine your RD length. Crank arm length is usually due to personal preference with 172.5 being right in the middle for average height guys and 170 being for slightly shorter than average guys and 175 being for slightly taller than average guys.


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## rscrant (Jul 15, 2013)

tranzformer said:


> Need to explain a bit more about where you ride/the terrain/if you race/fast group rides...etc. as that will help sort out the chainring set + cassette which will then determine your RD length. Crank arm length is usually due to personal preference with 172.5 being right in the middle for average height guys and 170 being for slightly shorter than average guys and 175 being for slightly taller than average guys.


Hi tranzformer,
Thanks for your help.

Primarily road riding on flat to small incline/decline for fast-paced leisure and possibly to compete. Height is about 5'5"/165cm (51cm S5) with carbon wheels. The S5 is an aero high performance road bike so I want to complement this with the correct grooupset config.


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## rscrant (Jul 15, 2013)

Bump anyone???


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## Dunbar (Aug 8, 2010)

At 5'5" you probably want 170mm crank arms (most complete bikes your size will come with that configuration stock.) As far as gearing, with small hills you can go with the 53/39 and not suffer with the terrain in your area. You could also go with a 52/36 as a sort of "in-between" option too to give you lower gearing if you ever decide to ride somewhere with steeper hills. You might want to spec the "GS" long cage rear derailleur so you can install an 11-32 cassette if you ever go somewhere with steep hills. Even the 50/34 compact crank option won't slow you down (plenty of people race on them) but it really comes down to personal preference. The Ultegra 6800 crank allows you to replace the chain rings up front without having to buy a whole new crankset so I woudln't lose too much sleep over the idea of picking the wrong gearing.


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## rscrant (Jul 15, 2013)

Hi Dunbar,
Thanks for your help.

I will go with the 170 53/39 as you suggested.


Thanks.


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