I want lower (sub 1:1) gearing on my next drivetrain but also a decent range, reasonable spacing between gears and still be reasonably light.
While looking at different combinations of components, I noticed that:
- 1x options were not nearly as light as I expected, mostly due to the huge cassettes needed for decent range.
- On 2x, large cassettes were killing my weight compared to "standard" road setups (50/34 compact double with 11-28 cassette).
- Shimano GRX setups gain weight in all the components, partially negating their gearing benefits.
At this point, for a lark, I threw in some randonneur type cranks and the old heavy bottoms brackets that go with them, and noticed the numbers coming up not that much worse than modern drivetrains.
Furthermore, I found that some rando cranksets can be made to come with super small chainrings. One manufacturer I looked at went down to 42/26(!), and pairing this with an Ultegra 11-28 met my criteria and was the lowest weight combination. I'd love to buy an Ultegra 42/26! Just imagine what that would weigh!
So, why don't more people use smaller chainrings? Or the flip side to this question: why don't drivetrain manufacturers offer them?
Is this just the standard reason that "the bike industry is driven by racers"? Or am I missing some obvious physical thing that makes smaller chainrings inferior? Should I just give up and become a retrogrouch?
This answer seems claims that smaller cogs have more friction, but it doesn't seem like it would be a lot more, considering we have "small" cogs on most of our cassettes.