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GALATIANS 2:20
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I have always had triple or single chain rings until now I just got a Specialized Epic with a Double Chain Ring. Any tips on which ring is your go-to ring and methodology or strategy or differences to using the double chain ring?
 

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aka Taprider
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Small chain ring with big (low gear) cogs, and big chain ring with small (high gear) cogs, to improve chainline and drivetrain efficiency and durability
Or for climbs that have many flat to even downhill straightaways followed by steep switchbacks, then pick a middle cog and just shift with the front for quicker big jumps in gear ratios (Shimano's front pull side swing derailleur shifts better than and faster than even the newest 11 and 12 speed rear derailleurs to make big jumps in gear ratios )
 

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2017 Transition Smuggler XL
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Small chain ring with big (low gear) cogs, and big chain ring with small (high gear) cogs, to improve chainline and drivetrain efficiency and durability
Then you can only go very slowly or very fast. The biggest problem of double front rings is that the most needed gears result in crosschaining.
 

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These days with the influx of 1X drivetrains you hear everyone talk about how fast you can jam your way from one end of the cassette to the other as a key aspect of how they perform. Back in the days when 2X and even 3X drivetrains were the norm it was actually consider more efficient and better technique to hang out in the middle range of your cassette and use your front rings when you needed to quickly dump or gain a bunch of gears.
 

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Take a look at your chainline; if cross-chaining from the big front to big rear isn't too bad I'd think of it as a 1x with a bailout (small front ring as the bailout), and just use the small front ring for super steep climbs (or horrible mud where you need tractor gears). I've watched a couple of videos about testing power loss from cross-chaining big to big, and assuming those videos are somewhat accurate, the wattage loss is negligible, just a couple of watts at most. My primary race bike came as a 2x, I raced it that way for a while and eventually converted to 1x, I liked it as a 2x, but the bike lost about a pound converting to 1x, and assuming that a pound of weight is worth more than a few watts, it's probably better to take the weight savings (in the xc race forum anyway).
 

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aka Taprider
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Power (equivalent to drive train efficiency) is more important than weight
from Climbing Power Calculation
70 kg rider 10 kg bike 20% grade 1km climb 200 watts (assuming granny-gear climb for non-elite rider near the end of a marathon race) = 14 minutes 36.6 seconds
take away 500 gm = 14 minutes 30.6 seconds
or
improve efficiency by 2 watts =14 minutes 27.6 seconds
but you are not riding a singlespeed so there is still some sideways chain deflection with 2X and 3X, so
improve efficiency by 1 watt =14 minutes 31.8 seconds
but are you really saving a pound to go 1X since you will need a heavier cassette, a heavier narrow/wide chainring, longer cage rear derailleur

Anyway, small changes in wattage (from your fitness, tire rolling resistance, drivetrain, aerodynamics etc.) are equivalent to big changes in weight/mass/grams
 

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Elitest thrill junkie
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Does this mean I've traveled back in time? I hope so!
 

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Power (equivalent to drive train efficiency) is more important than weight
from Climbing Power Calculation
70 kg rider 10 kg bike 20% grade 1km climb 200 watts (assuming granny-gear climb for non-elite rider near the end of a marathon race) = 14 minutes 36.6 seconds
take away 500 gm = 14 minutes 30.6 seconds
or
improve efficiency by 2 watts =14 minutes 27.6 seconds
but you are not riding a singlespeed so there is still some sideways chain deflection with 2X and 3X, so
improve efficiency by 1 watt =14 minutes 31.8 seconds
but are you really saving a pound to go 1X since you will need a heavier cassette, a heavier narrow/wide chainring, longer cage rear derailleur

Anyway, small changes in wattage (from your fitness, tire rolling resistance, drivetrain, aerodynamics etc.) are equivalent to big changes in weight/mass/grams
I weighed the bike before and after, - I found my old notes: it was 13 oz, so I did exaggerate a bit. The stock cassette is 11-42, when I'm not broken I can climb most anything with a 32 11-42, so I just kept the stock xtr der and cassette. You make a good point about the time lost per those watts, so I think it would be important to consider how much time a person is spending in the 'inefficient gears' during an average race, in my experience the biggest gear on the cassette isn't used for very long, usually just a short 'extra steep' section. ccm: have you seen those Zipp ads on youtube?, claiming 40w savings on cobbles from their tubeless hookless road wheels?, that's some real savings!
 

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aka Taprider
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from the example above 1 watt is equivalent to ~380 grams, so 13 oz barely beats that
40 watts!? compared to what or is that compared to watt? Difference between an Icon and a Minion is probably about 20 watts (for trail-ish versions and not the vastly different carcass types)
 

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It’s been a few years now since I’ve ridden a 2x11 drivetrain bike outdoors! It’s been 1x12 since the end of 2019 for me. I had 38/26 tooth front chainrings with a 10-42 tooth cassette.

I would try and stay in the 38 tooth big ring as much as possible whilst riding, using the entire rear cassette including big chainring/ largest rear sprocket if necessary.

I had two main rules with the 2x shifting. If I was starting a steep climb, where I knew I would definitely need to drop onto the little ring, I would anticipate and do the front downshift onto the inside chainring when I was 3 sprockets from the largest rear sprockets, not when I was in big chainring / largest rear sprocket. The reason for this is it’s a less extreme chainline reducing the chance of the chain coming off the front chainring on the downshift.

The other main rule I had was to make sure I was on the big front chainring for descents, particularly anything rocky or with g-outs or compressions. The reason for this is that on a wide range 2x11 drivetrain there’s significantly more chain tension on the big chainring than the smaller little chainring, reducing the chance of the chain being bounced off mid descent.:)
 

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I wrote cogS plural
by that I mean up to 2/3 of the cassette per side, which would result in less cross chaining than 1X
My experience is that most of the time I use gear ratios from the middle of the range. Take a look at this gear calculator https://www.gear-calculator.com/ and select some 2x setup. You will see that to get medium ratio you either must use small front and one of the smaller cogs from rear or big front and one of the bigger cogs from the rear. In case of 1x or 3x setup chain is much straighter for those ratios that you use most.

Another thing I didn't like about 2x setup (compared to 3x setup) was the fact that I had to use front derailleur more often. With 3x I was on the middle chainring most of the time and used small chainring only for deep ascents and large one only for tarmac.
 

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I think the epic rear suspension is tailored to small chainrings, if you use the bigger ring you will mess with the anti-squat, unless the brain accounts for this. In any case, in practical terms you shouldn't care about your chainring preference just for the suspension performance. I would try to stay in the bigger chainring as much as possible for two reasons. Higher efficiency and less wear, just once exception though, if you are on the big chainring I would avoid using the last 2 rear rings as must as possible.
 
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