Or skip to the full paper here. On glance-through, looks quite impressive on all fronts from theoretical modelling to simulation to experimental validation. I'd have to read far more carefully to catch any gotchas, and that might take me quite some time as my engineering background is not in gear transmissions. Would also want to read the first few references which claim independent findings of ~99% planetary gear efficiency in other (automotive, aerospace) applications.

I will give intitial credit in an age of decreasing bike industry whitepaper quality (see the hookless thread for some dismay there) that the whitepaper gets initial high marks for nerd cred. Though as mentioned, have yet to run the fine-toothed BS-detector through it all.

99.8% efficient at 1:1 ratio, so a locked hub same as a normal one. 99.2% when the internal parts are actually spinning. I'm not a fan of stating these numbers in such a way, as they are largely speed-dependent and not nearly as power-dependent. 1000W up a low speed hill climb is going to make any setup look incredibly efficient, percentage-wise. A 100W descent is going to make the best system look horribly inefficient.

In the white paper it more clearly states these numbers in a more digestible way: 2.49W loss when the hub is 'active' v. 0.52W when the hub is locked. It makes a lot more sense when stated like this. I'm taking them at their word for the testing numbers as food for thought, but obviously it would be good to have third party testing as well.

The tests shown were on the order of 10min in length, presumably in laboratory conditions. My worry with this setup is not the initial performance, it's the tiny gear teeth and their wear rate, especially if any contamination is let into the hub. There's 6 tiny teeth taking the entirety of the load that are going to wear out, contamination is going to get in, etc. I'd be more interested in an efficiency test after 1000 miles of road riding.

https://acrobat.adobe.com/...aVerb=group-discover

I struggle to see how this is "better" than 2x.

You lose the weight of the front derailleur but gain the weight of the classified, so a wash. One less chainring however.
You save a few aero watts for no front derailleur but you lose 2.5 when hub is active, very close to a wash, maybe slight savings
Since you are 1x up front, you have very slight loss in chain line efficiency, probably taking back the previous savings
You have a custom cassette. No big deal but definitely not a pro

I think shifts are cleaner than shits on the front derailleur so a slight advantage there.

Currently a proprietary shift button but they say this will be resolved.

You bring in maintenance and wear unknowns.

Extra cost.

What am I missing ?

Well supposedly the larger ring is more efficient than the smaller ring, along with the ability to have a 12t sprocket and still have gear range

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That's a pretty low bar for drivetrain cleanliness.

You're not missing much. 0.52w needs to be taken off the 2.49w as the cost of gearing since it is from the main hub bearings, which are present in any hub.

But other than that, it's wider gearing on 1x shifting under load.

I agree with you. Not a lot of benefits for most TTs.

I agree with this, it's kind of cool but I just don't see much of a benefit. I'd add to your list that you're going to get inevitable chain drops on 1x without a chain catcher. Adding the chain catcher probably negates most of the already scant aero savings from getting rid of the FD.

I'm also pretty skeptical of their efficiency claims.

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I'm not sold that it's any better than 2x, TBH it's probably worse. But it's a cool idea and may be worth refining. I'm not buying one anytime soon so it's enjoyable to watch the progress from afar, same as most World Tour level tech.

The proposed theory is that unlike true 1x the gear in this can be selected to keep the chain as centralized as possible on the cassette. There's a theoretical perfect shifting order that minimized drivetrain losses, but more realistically a rider is staying in one chainring (or hub setting, in this case) and only moving with large swings in speed.

One other issue (a nit pick) is that the chainring ratio is fixed. It's not unusual to see wide chainrings (53/32) for mountainous races and narrow spacing (55/42) for flatter races.

My big question is what is the ceiling for this tech? FD and 2x tech is basically optimized. If you optimize this hub can it surpass traditional 2x? I would bet that yes you can make a hub more efficient but at the cost of longevity.

It doesn't make any sense at all unless an input power and speed is provided. 2.49W at what power and speed? Graphs are better for this type of thing.

Here they are.

It is provided. That was at 300w and 30k.

fwiw, the one bike I don't think I've ever dropped a chain on is my 1x catcherless MTB. Granted the MTB probably has an RD that takes up slack far more aggressively than anything but late-model gravel 1x. I have a catcherless 1x TT bike as well, and don't think I've dropped a chain in a long time.

I'm starting to think the Classified hub makes good sense for MTB and gravel. You can run a tighter 1x cassette, and still have the bailout option. And in my new riding area in the High Sierras, I'm learning I need that. This past weekend I hit a legit mile straight at 20% gradient and higher, topping out at 28% according to my Garmin.

For road and TT, I agree, I'm sceptical right now.

Also makes great sense for higher-end commuter, cargo bike stuff.

I mean it wasn't provided in this thread. I'm being a bit snobbish. This forum goes back and forth where some people say that aero efficiency should always be expressed as Cd, not "Watts." and rolling resistance as Crr instead of Watts I've come to mostly agree with that even though I understand that "Watts" is more immediately understood by many. Also think that drivetrain efficiency should be first expressed in percent, than expanded upon as needed, like Classified did.

I'm just picking those because it's the numbers they used for their top line "99.9% efficiency". There is something I missed before, that the testing only goes up to 35kph. I suppose you could argue it's testing the little ring scenario only, but those lines of load-dependent power loss are going up very quickly.

I'm sort of lost. What is "top line" efficiency? I also don't see "2.49W" either in the whitepaper linked in the OP or the technical paper I linked to. Where is that listed?

Are we talking about the (second from) top line of the graphs?

They went to 60kph and 700W in predictions. Just posted the graphs. This should cover most road scenarios. They did not experimentally validate all the way out there, but the validation range they covered looked solid.

It's possible there could be reality vs. model separation in those other areas.

I'm pulling the 2.49w and 0.52w from Fig 7 and Fig 12. I'm guessing that's where they got the 99.8% and 99.2% efficiency numbers. I'm calling those top-line as they're the most prominent in the press-release type original paper.

I'm not doubting their extrapolated model of efficiency, just noting that they cut off the 0.686 ratio graph at 35kph when it was going upwards fairly linearly. They sell it pretty well though "Finally, simulations in the 0.686 ratio were carried out until ground speeds of 35 km/h; beyond these speeds the pedaling efficiency rather than drivetrain efficiency becomes the limiting factor for cycling performance."

https://www.hambini.com/...m-technical-details/

Figures can't add up, but they can be made up.

Well, you could expect a 5 year old to make numbers up.

I guess he can get a pass on small chainring = big chainring efficiency, because that's only around 0.6% difference for the same cog. But he's got a big error on the single stage planetary gearbox efficiency.

3T makes a Strada that comes stock with a classified hub. If i was buying a road bike today it would be fairly high up on my list. I live in Oklahoma. It's pretty rare that i shift into my little ring, and even more rare in any sort of race. I like the way the solid 1x chainrings look.

So for me, it would give me the ability to use a cassette with smaller gaps than something like the XPLR cassette, i'd still have good efficiency during racing in the locked configuration, but on an easy ride or if i travel anywhere with climbs i would still have an opportunity to shift the hub into an easier gear. I'm not opposed to losing a few watts in that scenario in order to have a bike that performs well in all other scenarios.

In this scenario a more economical decision would be to buy two wheelsets, one with a tightly spaced cassette for racing and one with wide spacing for climbs. The most economical would just be to buy a second cassette for travel to hilly places, but that has an extra 5 min for every trip to swap cassettes.

This makes the SRAM 1x aero crank more attractive for road riding. However, I wouldn't want to take the AXS chain efficiency loss. So does anyone know if you can use an AXS chainring with a Shimano chain/cassette?