Trek-Segafredo disagrees with SRAM AXS gearing

[marciero]

Originally Posted by Mark McM

...
But SRAM also claims that they can achieve the increase in range without increasing the size jump between gears. This is the deception. Yes, the tooth differentials between sprockets are the same with both cassettes, but the ratio differences don't depend only on the tooth differential, they also depend on the absolute sprocket size. SRAM is just hoping that consumers don't catch the math fallacy behind the deception.

But that's just on the cassette side of the drivetrain. Because SRAM's chainring differentials are smaller than others, the AXS 2x drivetrain actually ends up with a smaller range of gearing than their competitors 2x drivetrains.

This. The single tooth jumps get bigger as teeth get smaller. This is why the jumps between cogs on, say, an 11-32 or 11-36 cassette go from 1 to 2 to 3 to 4 teeth as the cogs get bigger. But for the smaller cogs there has only ever been a one-tooth jump. This was not a big deal when 13t or even 12t was the smallest cog. No one complains about non-equal jumps between 12-13, 13-14, 14-15. I definitely notice it with 11t small cog. And now with a 10t...
For a 46t ring, the jump going from 11t to 10t is twice the jump from 15t to 14t. (The percentage difference is less than double, but actual ratio change rather than percentage change makes the most sense for comparison here).

When you think about it, the whole "closer ratios" argument that was a main justification for the cog arms race was mostly bogus, because smaller cogs were always being added. And now we have the addition of bigger cogs and one-by.

The only way around the increasingly big jumps at the high end with a traditional drive is to go with smaller chain pitch. It would also address the increased friction 10t. There is no way that engineers have not thought of this and dismissed it for whatever reasons.

Sheldon sure thought of it.

https://www.sheldonbrown.com/nanodrive/

[simonov]

Originally Posted by oldpotatoe

I also think, that in spite of the 2 teams in the pro peloton, the lack of a sram mechanical 12s road group is not grand. Does sram even MAKE a etap, 12s, rim brake group? Donno.

Yes. Yes, they do make an eTap AXS 12s rim brake group. Part of me wishes they'd update their mechanical group to 12, but other than the extra gear, I can't think of anything else I'd change about the current 11speed Force or Red groups.

[Mark McM]

Originally Posted by marciero

The only way around the increasingly big jumps at the high end with a traditional drive is to go with smaller chain pitch. It would also address the increased friction 10t. There is no way that engineers have not thought of this and dismissed it for whatever reasons.

Sheldon sure thought of it.

https://www.sheldonbrown.com/nanodrive/

Shimano kind of thought of it - but for single speed (track bikes). In the early 1980's Shimano introduced the Dura-Ace 10 track group which used a 10mm pitch chain which is about 20% smaller than our current 12.7mm (1/2") pitch chain. Since you only have one gear ratio on the track, riders tend to be pickier about exactly what gear ratio the choose, and the 10mm pitch chain allowed finer granularity in sprocket sizes.

Maybe the Shimano 10mm pitch chain will be resurrected someday.

[marciero]

Originally Posted by Mark McM

Shimano kind of thought of it - but for single speed (track bikes). In the early 1980's Shimano introduced the Dura-Ace 10 track group which used a 10mm pitch chain which is about 20% smaller than our current 12.7mm (1/2") pitch chain. Since you only have one gear ratio on the track, riders tend to be pickier about exactly what gear ratio the choose, and the 10mm pitch chain allowed finer granularity in sprocket sizes.

Maybe the Shimano 10mm pitch chain will be resurrected someday.

Ahh... And 10mm is such a much nicer number than 12.7! I've always thought it was some crazy coincidence that 1/2" became standard across manufacturers in the first place.

[merckx]

The Dura Ace 10mm track group was introduced in the 70's, maybe around 76/77. It was revolutionary, but never gained market traction.

[Mark McM]

Originally Posted by marciero

Ahh... And 10mm is such a much nicer number than 12.7! I've always thought it was some crazy coincidence that 1/2" became standard across manufacturers in the first place.

It's likely that the 1/2" became standard for bicycles not long after the roller chain was invented (late 19th century). Is there any other standard component dimension that's been in use for as long as the 1/2" dimension for chain pitch?

Now that I think about it some more, I wonder why a drivetrain manufacturer hasn't tried a different chain pitch standard more recently. Many times over the past few decades manufacturers have released a new component groups which is mostly or completely incompatible with existing component groups - for example, each time a new sprocket has been added to cassette, the manufacturers have insisted that you need to change the entire drivetrain, in which case there's no need to maintain the previous chain pitch.

From what I can see, it wouldn't take a lot of component changes to adapt a new chain pitch. Obviously, you'd need a new chain, plus new chainrings and cassette, but the chainrings and cassette could be made to fit existing cranks and freehubs. You'd need new pulleys on the rear derailleur, but I don't see why any other changes to the derailleur would be required as long as the diameter of the pulleys was roughly the same). And you could probably re-use the front derailleur if the basic diameter of the chainrings was the same. Which means you could keep the same shifters as well.

Since drivetrains have been moving to smaller chainrings and/or sprockets, a move to a smaller chain pitch would seem in line also. When is one of the component companies going to stand up and take this next obvious evolutionary step in the bicycle drivetrain?