That’s really weird gearing. What does he need a 56-teeth front chain ring for?!? Professional time trialists run that kind of gearing, although they do that for efficiency, not because they need a 56:11 top gear.
And at the same time the same person needs a 34:42 low gear?!? That doesn’t make any sense to me.
Well, whatever floats your boat.
I think it might be so he can pedal during longer fast descents when the speeds go over 35. So he doesn’t spend 50% of his endurance rides coasting downhill.
Is that really necessary? A 50:11 at 100 rpm would do the job.
Where I live there are few safe descents where I can safely let it rip beyond that speed, and I rarely if ever spin out. I tried a 52:11, too, and I can think of two, three descents where I can make use of the extra gearing. Plus, at speeds beyond 60 km/h I’ll typically let gravity do the hard work for me.
It’s probably not necessary but I know he generally likes to pedal closer to ~85rpm so the bigger chainring would help him stay in that range. Also, where he lives there are a decent number of fairly straight descents that average 4-6% so you could safely pedal at 40+ mph.
Wasting energy at that point…anytime I hit 35+mph on a descent, I just coast and tuck. Having done IMMOO twice, I always passed other riders who were pedaling on the descent.
He has his training bike set up like that. I don’t think he’s got that wild gearing on his race bike. So it’s not about going as fast as he can but so that he doesn’t spend 5-10 min of each hour coasting downhill because he ran out of gears.
I just pointed it out initially to say that you can get away with some pretty wild gearing if you want to and you are a bit clever with it. Not that it is the best or most practical thing to do.
I do not have a Venge, but I have run 52/36 and 11-32 on Dura-Ace Di2 9100 (hydraulic version). It shifted fine. As others have said in this thread, Shimano is a bit conservative in their maximum gearing specifications. It worked fine, though I’m not sure I would run it daily unless I lived in the mountains, just to make sure I wasn’t putting unnecessary strain on the RD.
Late reply, but… Do you have to change your chain when you swap cassettes? I’m looking at picking up a 52/36 with a 11-28 cassette bike (medium cage Ultegra), but want to swap the cassette for an 11-32 or 11-34. Hoping to not have to change the chain (almost certain with the 34).
It depends.
If you sized your chain for maximum chain wrap (small + small + pull chain so there is tension and not slack), then no. The easiest say to tell, put the bike into the small cog and the small chainring, and look at the derailleur position, and then pull the chain off the chainring so that the chain is dangling. The movement of the derailleur should be really tiny. It should just be 1 link worth of movement.
If you sized it for the shortest chain (big + big + 2 links), then yes.
I would only change chains if it’s worn and needs replacement (or close to replacing), or you need to add links.
@iamholland Thanks. Sorry for the confusion, but I was replying to @bolton who said he had this setup (52/36 with 11-28 and 11-32 cassettes) and said he switches them. I was wondering if he got away with using the same chain when switching and if so, how long it is.
it’s a generic question. but if you only want to know what @bolton does, then that’s fine.
many people do it, not just @bolton. People even change wheels with different cassettes on the wheels, or have different cassettes on their trainer vs their riding wheels. 
No, I don’t change the chain. It’s cut for 11-32 cassette and I use it with 11-28 daily basis.
thanks.
Yup, I do too with my trainer (11-28) , 28s (11-32), and 40s (11-32) but my current bike’s big ring is only a 46 - not a 52. Bolton happened to describe the exact ratio scenario I was looking at. Thanks for your help.
Swapping the cassette is pretty easy if you have the range on your rear derailleur. 52 in the front and a 32 in the back will get you up most things.
I have found this site useful on the question of changing chain length for different gear sizes. Look up the geo chart of your bike in mm, select the correct options in the drop-downs, and I have found it to be accurate.
http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html
