Gearing

• Dirty chains might make these issues even bigger for us than the immaculate chains that were used in tests.
• Many of us have been looking at smaller front chainrings, but this does lower the efficiency of your drivetrain.

• use a regular freehub body and 11-46 (or bigger) Shimano style cassette, rather than Sram Xd body and 10-42 cassette: they are cheaper, but more to the point here, you will have a 10% bigger front chainring/cog combo for each ratio, helping to keep drivetrain efficiency  up.
• Consider setting your chainring slightly inboard of stock chainline if possible. This will improve efficiency in  the middle gears of your range, where you spend most time, and make it worse in the smallest cog(where you spend little time and aero drag is a bigger factor).

• look at using a bigger cassette, before getting smaller chainrings. IRD has an 11 speed 12-36 cassette that could be a great option for many gravel riders. Let’s say your road bike had 11-32 cassette and worked well for you. Swapping to this cassette would give you across the board 10% lower gearing, while slightly increasing drivetrain efficiency. Only after doing that, if you wanted lower still (larger wheels? Longer rides? Deep gravel) do you start dropping to smaller chainrings up front.
• run the smallest big chainring you can get away with. The longer you can stay in that big ring, the better your drivetrain efficiency, and the less front shifting you have to do. In general, you won’t lose much total time occasionally spinning out  at a 10% lower top speed, but you will lose much more total time riding in your granny ring for a larger part of the ride, since you are running smaller cogs/chainring and cross chaining them too.

I like reading those articles, but when I’m most worried about chain line, I just jump on my track bike, LOL.

I think anything bigger than a 46T chain ring is just silly.  I can do anything I want on that.  Guess I don’t spend enough time at full power going down mountains.  Still at 40+mph I think pedaling starts to do more harm than good.

Certainly using bigger cogs and cassettes increases the efficiency of your drivetrain. 

HollyBoni wrote:With a 10-42 my Rival 1 rear derailleur regularly turns into a bush.

I’m a fan of big rings, but I use small ring (36t) because that puts me in the section of the cassette where the gaps are small.  With a big ring most gravel bikes are going to have big jumps.  I’m more concerned about the efficiency of my legs vs my drivetrain. 

After much sole searching, I went out of my way to get 2x for the gravel bike.  I don’t shift much, but the chainring I need for a long solo gravel ride is much different than for a fast paceline on the road.   I get tired of manually chainring the chainring based on the ride I’m doing that day.

• first 200km, before broadcast,  they had a tailwind and averaged 50km/h.
• Later they tended to be riding around 42km/h on the attack’s/chase group on the final flat headwind section.
• On the steepest sections of climbs they were at 13 km/h
• the sprint finish they hit nearly 60km/h.

chas wrote:I’m a fan of big rings, but I use small ring (36t) because that puts me in the section of the cassette where the gaps are small. I’m more concerned about the efficiency of my legs vs my drivetrain. 

Slim wrote:@NoCoGreg...

Since we are on this topic, have you considered replacing the 50t big ring with a 48 on that bike as well?  Since you say that is mostly used on flatter terrain, you wouldn’t miss the 5% lower top end right? Or is it used for racing, where you have to sprint on the flat at high speed?

NoCoGreg wrote:Want another reason to go with a 2X setup? 

https://www.velonews.com/2019/05/bikes-and-tech/gear-issue-friction-differences-between-1x-and-2x-drivetrains_493185

Slim wrote:As I mentioned above, I was ready to switch back to 2x  on my next gravel bike, due to the drivetrain efficiencies and smaller gearing steps offers by the 2 system, But when I went to buy my Warbird last week, only the Apex 1 was in stock in my size, so I am still on 1x, 

Since I am stuck with the 1x, I am trying to maximize efficiency by using a Shimano cassette (11-46) vs a SRAM Xd cassette (10-42) of the same range.
I wish they had compared this set up as well, and that they had used an identical chain.
Using the 11-46 cassette means that in the middle and harder gear combos, efficiency is identical to the 2x (since it would be the same size chainring and cog and according to the test, the 1x chainring is in the same location as the big ring of the 2x).
That would leave only the easy gearing (far left side of graph) where the 2x is more efficient. Even there the difference would be smaller than it is now, because the cog and chainring would bigger.

I would look something like this, where I drew in a hypothetical 53`x11-46 1x system(which would have the same gear range as the tested 48x10-42, since everything is 10% bigger).