Longer Chain Moving from Compact to Semi Compact?

[SpideRaY]

I have just changed my compact 50/34 6800 ultegra 170mm cranks to the newer semi-compact 52/36 8000 ultegra 165mm cranks, I also had to upgrade the front mech something to do with the inner chain ring being closer to the bottom bracket. See shimano tech docs the new 8000 front mech is so much easier to set up btw.

Everything was going well until I adjusted the high and low screws, I have a 32t rear cassette and I had already used a chain length calculator to see if my chain would be long enough I presumed that it would have 55 links however when I tried the 52/32 combination the rear mech was forced towards the bottom bracket and the chain caught in the front mech. Never presume upon checking my chain is only 54 links so it appears that it's 1" to short for the new 52t front chainwheel. Sadly I don't have any extra 11 speed links as this is my first 11 speed bike so I guess I now also require a new KMC 11 speed chain.

Never assume it makes an ASS out of Uand ME.

 

[Ajax Bay]

This is why I think that the practical large/large plus one link (1") is safer than calculation and counting. Your LBS may let you have some spare 11 speed links; and use a second quicklink.

just changed my compact 50/34 6800 ultegra 170mm cranks to the newer semi-compact 52/36 8000 ultegra 165mm cranks,

OT:
What's your motivation/reason for going to 165mm cranks?
Do let us know how you get on with them, in comparison to the 170s.
Think that you could use the 'old' 34t instead of the 36t to keep your lowest ratio the same. Which I'd expect you to appreciate with 3% less leverage on the cranks.

 

[SpideRaY]

I am 5'6" ridden 170mm cranks for 5 years however I'm now almost 50 and have started having a few left knee problems on longer Audax 200km+ rides so I was recommended to go to 165mm after a recent Retül Bike fit. I also reduced my stem to 75mm whilst using the 170mm cranks on a few shorted rides which also felt better only time will tell.

I also forgot to post that I had also swapped out the 6800 36t from the semi-compact and put in a new 8000 34t so I now have a 52/34t after reading about having the best of both worlds on this bike test review website @ http://biketestreviews.com/having-the-best-of-both-worlds-gearing

Ajax, I will let you know how I get on. I will purchase a new 11 speed KMC chain this week as the one that's on is a Shimano 11 speed I hope that adding 2 more links from 108 to make 110 in total will stop the problem not that I ever intentionally cross chain big to big but you never know.