Di2 6870 Ultegra 50/34 upgrade to 52/36 on a cannodale synapse ?

Ahh the op didn't say he was running a FSA crank, the way he worded it seemed like he was running the Ultegra crank

In that case you need the FSA chain rings to do the conversion

52t for £55

http://www.chainreactioncycles.com/fsa-super-t-road-compact-n10-11-chain...

36t for £22

http://www.chainreactioncycles.com/fsa-k-force-abs-super-road-n10-11-cha...

Quote:

11 speed Ultegra Di2 chain rings can be upgraded to 52/36

If it's stock, you don't have Ultegra Di2 chain rings; you have FSA Gossammer Pro. Ultegra won't fit without changing the crankset. I've upgraded mine to a Cannondale Spidering whilst keeping the stock Si crankset is it's supposed to be stiffer and lighter than the Ultegra. The spidering costs £100 almost-new from eBay. You can get them for £130-£160 new if you look around. Only problem is that you can only use them with crank-based power meters... That and the number of sizes is basically just compact and standard I think. Here's a 53/39 http://www.cannondaleexperts.com/Cannondale-SpideRing-Road-Chainring-Sta...

In terms of changes, you'll need a longer chain and you'll have to move the front derailleur up but otherwise it's fine. You do, however, need some specialist tools (a tool for removing the chainring's lock ring and another for removing the crank) and they are pretty expensive; £50 for the both if you're lucky, £100 if you go for the branded ones.

I think what pastaman might have been saying is that the Cannondale already has a higher top gear than the Kuota. Of course you can go higher but you're also better off than you were.

According to gear tables 50x11 is actually a higher gear than 52X12... so not sure where you're coming from on this?

http://www.bikeradar.com/road/gear/article/what-is-a-compact-crank-38845/

"I cannot get enough top speed that I would like with a 50/11"

Really? On the flat?

Wow.

The Ultegra di2 groupset uses the same crank as the mechanical groupset

The 6800 crank uses the same 110 bcd for all size chain rings so you can fit any combo you like, unlike the old 6700 crank where you had to buy a whole new crank set

Your chain may need to be made a little longer but that's about it

Chain rings can be bought but its often cheaper to just buy a whole new crank set and sell the old one on to recoup some of the cost

For example a 52t chain ring is £89

http://www.chainreactioncycles.com/shimano-ultegra-fc6800-11sp-double-ch...

A 34t chain ring is £22

http://www.chainreactioncycles.com/shimano-ultegra-fc6800-11sp-double-ch...

So a combined cost of £111

A complete crank set is the size you want is £120

http://www.chainreactioncycles.com/shimano-ultegra-6800-double-11-speed-...

So £9 more but it leaves you with your old crank set to sell on which you should easily get £50-£60 for it

I've never done it personally (as many will have here) but I was watching one of the GCN videos earlier this week where they rode up some stupid climb on a compact with a 11-32 cassette, then cycled down swapped the front and rear over to an old school 53/39 and 11-25. Then did it again.

The video shows them simply taking off the rings at the FD and swapping them for different ones.

You may have to also replace the chain too if this is as easy as it sounds.

Hope this helps. Sorry it's not conclusive.