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Discussion Starter · #1 ·
Getting a new 105 5800 crankset (just bought a 4iiii Power meter!).

Currently am running a 11 speed 11-28 53/39 setup. I've been fine with the extended 4-6% grades here in CO with the 39/28 with a cadence somewhere between 75-90, but anything steeper, my cadence drops and I have to get out of the saddle and mash.

I'm trying to determine if I should get the 52/36 or 50/34 as a replacement crankset. My only concern on the 50 chainring is that I'd spin out on the many downhills. It's pretty frequent that I'll hit 35+ coming down from the mountains, but then, of course I need to get up those mountains in the first place :)

Thoughts from those who live in mountainous regions?
 

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Forever a Student
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50/34 is my vote. If you're spinning out a 50x11 on a descent it's time to just aero tuck.
 

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I guess it depends on how comfortable you are on the long climbs and how long your steep climbs are. I ride in the Blue Ridge, my longest climb is 12 miles @ 5-6 %, the really tough stuff 10-15+% is rarely longer than 1/4 to 1/2 mile. My climbing bike had a 50-36 with 11-25 rear. I recently changed the crank to a standard 50-34 Campy 10 speed compact (previously was FSA) but really haven't noticed much difference, the 25 cog is still bailout gear and luckily don't get on to it that much.

I just replaced my climbing bike with a newer one that came with Campy SR 11. It has a standard crank, but I'm looking to replace it with 52-36. I think that's the sweet spot, the 50t does leave a lot to be desired on a long descent. FWIW I consider myself an OK but not great climber. 165 lbs.
 

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'brifter' is f'ing stupid
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Sounds like you need 2 things:

50/34

Learn how to pedal a tiny bit faster.

The difference between 50 and 52/3 is VERY small. 2mph to be somewhat less than exact at 90rpm. 50/11 @ 90rpm is around 32mph. At 100rpm it's nearly 36.0. At 110 it's almost 40mph.
 

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Bianchi-Campagnolo
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I use 50/34 and 12-29 in the French Alps. So what if I cannot follow the 90 kg guy on 53x11 when we zoom down from Col du Lautaret towards Briancon at 80 km/h +? We stop for a laugh together down the road anyway.

Back home where we don't have much more than 6% anywhere and then for only a short duration I'm fine with an 11-23. And I've never lost a wheel using 50x11.

YMMV and all that. That descent from Lautaret is completely non-technical, as opposed to almost anything else in the area.
 

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50-11 at 100 rpm is 35.7 mph.
52-11 at 100 rpm is 37.1 mph, not a huge difference. It's the same as 50-11 at 104 rpm.

Here's a chart of 34, 50 and 52 chainrings at typical road cadences. The 50 chainring moves the shifts down by less than a half shift.

View attachment 317092
 

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Banned Sock Puppet
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Another vote for 50/34.
 

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52/36. Aero tucks do you no good if you're aero tucking out the back.
Two fallacies in this statement:

1. If you're on the back, your tuck is even more effective as you draft

2. 50/11 @ 100 rpm is nearly 36 mph, and at 110 rpm is 39. You will be faster in a tight tuck than pedaling. A tight tuck cuts aero drag by 33%.
 

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Two fallacies in this statement:

1. If you're on the back, your tuck is even more effective as you draft

2. 50/11 @ 100 rpm is nearly 36 mph, and at 110 rpm is 39. You will be faster in a tight tuck than pedaling. A tight tuck cuts aero drag by 33%.
Man many times when I'm tucking in the back I'm finding myself moving up the guy's in front arse that I have to sit up and move into the wind to slow me down or risk ramming the guy in front. IME, I ride a compact 50x11 and I have rarely been ever dropped out the back in a group, and I'm feather weight. They key for me is accleration, i.e., when the guys in front accelerate, I also accel and go with them always keeping in touch of their slipstream, and this usually happens at speed slower than 30 mph (and you can't say you spin out at under 30 mph on a 50x11). So it's about the accleration for me, and once i'm on their slipstream, it's more of a matter of modulating speed by moving in and out of the slipstream so you don't ram the guy in front! This is for a non-technical wide open road descent.

For technical descents, then it's not about speed anymore but skills, i.e., guys with lesser skill around curves risk being dropped, but man.. are we racing here or riding for fun? Why are people so hell bent on spinning out descending mountains, for what?? so they can get down 10 seconds sooner?!
 

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Two fallacies in this statement:

1. If you're on the back, your tuck is even more effective as you draft

2. 50/11 @ 100 rpm is nearly 36 mph, and at 110 rpm is 39. You will be faster in a tight tuck than pedaling. A tight tuck cuts aero drag by 33%.

One reading failure on your part.

Out the back is not on the back.

Having been out the back at 40 mph, tucking gets you further behind than pedaling, and then your day is done. Plus at a max effort like that, every rpm matters.
 
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