Electronic & Hydraulic Shifting (Di2, Ui2, customisations)

Yeah, I thought I'd seen it done so went looking...

https://mariposabicycles.ca/2021/09/09/mariposa-feature-all-road-bike-with-shimano-grx-xtr-di2-mullet/

Both our gravel bikes are 2x so if I wanted to go lower gears I'd probably just try Roadlink with a 46T cassette. Actually, the grrl's cassette is worn out so I might just buy a 46T to try it out...

There's no reason why couldn't run road shifters and MTB RD&FD if you wanted to go 2x. The MTB front derailleurs only word with small chainrings though, so you'd be limited on gearing. I imagine that with all things Shimano the figures they give are conservative and you could probably get away with slightly larger rings than they suggest for MTB FDs. I doubt it would work happily with standard or compact road chainrings though.

That's a good point, I forgot Shimano did MTB front derailleurs!

You could use that two speed hub thing with an ostensibly 1x mullet setup to get an effective 2X?

Isn't the whole point of all these new fangled 14-speed cassettes with 9T top and 53T bottom that you get all the range an actual human can use with jumps that keep you well within the powerband? In which case, why do you need to complicate things with a second set of changeable gears?

I hate on 11t cogs for their chordal action inefficiency... 10t and 9t are far worse.

Not to mention the fact that it makes for even wider jumps between gears, right where you're fighting the wind almost entirely, which resists with the cube of your speed.

You want smaller gaps at speed, but they keep making them bigger! Such poo.

The only way around it is bigger cogs and more chainrings. Instead of continuing to worsen the dish on rear wheels and make chains thinner, we could have all the range we want, nice and close, if only road triples were still a thing.

I even came up with another possibility, using 38/50/52 rings (due to the maths, that's about the only good choice for this) for a half-step setup.

It can use a double crank; the 38t only needs to be inboard of the standard inner position by a mm or two, while the 50/52 is probably best made as a single part, with a narrow gap between them, centred on the standard big ring location. FD could be the same as a double one, but would require a specific cage (the extra travel is within normal adjustment range).

Of course, it'd only make sense as electronic.

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I hate on 11t cogs for their chordal action inefficiency...

So do I, but we're howling in the wilderness. Track riders have only just come around to using big sprockets, and they only have one to worry about.

I guess when the manufacturers have sold everybody 1×10T-50T, there will be a miraculous "discovery" of science and they'll try to sell everybody 3×14T-28T again. Probably 15-speed cassettes so at least we'll get back our true straight-through clusters 😀

They'll probably pinch my half-step idea (added to my post above via edit)

Richard Gate had a "somewhat bodged" 3x setup on AMR.

I like the idea but having to remember that you can't change into the extremeties isn't something I'd like to play with. I can imagine many a thrown chain or worse.

I'm pretty happy with 30/46 w/ 11-42 on the gravel bikes, though I'm tempted to see if a 46T will work.

On the MTB I've 30 w/ 11-51T or whatever Shimano is. I wouldn't want a bigger ring on the front and it's rare that I'm 'that' bothered about spinning out the 30x11. Just coast bro!

Chordal efficiency worries only apply to racers where everything else is already optimised. The differences are tiny.

The differences are tiny

In Watts on a dynamometer, yes. IIRC, the difference between 48/12 and 64/16 on a track bike (straight line, bushed chain, clean and oiled) is between 1W and 2W. The feel though; all that horrible vibration gone.

wipes half kilo of dust off chain

As far as chordal action goes,

1. It's the principle of the thing. It can be specced (not even redesigned, really) to be more efficient, so why not?

2. Like tester says, yuck. I want my cogs to approximate circles, not polygons.

3. A bigger reason to put more metal in your drivetrain is to reduce wear. It's certainly the main reason I hacked OSPWs into my RD-9070 cage; holds like 3% more chain. Bike weighs 6.14kg btw, so not gonna break the weight bank...

4. But the main reason small cogs blow chunks is the huge gaps between them, which get comically large below 12t in relation to what's actually desirable at high speed.

If you want to maximise your speed for a given effort, you need close ratios. Otherwise you're either going a bit slower than you could, or trying harder by spinning or stomping.

This is the Di2 thread. Extreme cross-chaining doesn't happen here.

As for talk of triples, a few years ago I wrote the Arduino code to shift my half-step triple using RC servos, was a piece of piss to rule out extreme crossover.

I can imagine many a thrown chain or worse.

There's the rub (or rather lack of it)! Di2 thread!

What would a Di2 triple be like? Come on Shimano...

How long do folks give it before 1x is yesterday?

There's a very good reason front derailers were a thing, and it wasn't all about range.

What would a Di2 triple be like?

They do an XTR one

I thought so, but not relevant to road.

Anyway, I want my double and a half

Hey.

You know all those super-ingenious folks on YouTube who reverse-engineer all sorts of kit, who CAD and CNC all this super cool shit?

We need one of those guys to crack Di2 so we can really get hacking. I saw somewhere that one bloke made a start on it, roughed out the basic functions.

I want to see a YouTube channel with modern full-bore DIY pointed at bikes. Someone bust it out!

This is the Di2 thread. Extreme cross-chaining doesn't happen here.

You say that, but I still can't get my partner's setup to do the Semi-Auto shifting, ie. automatic prevention of small to small. :)

I like my FDs.

42-32-24T

Does Di2 work with it? Is there a 3x Di2 FD?

Just put on a bigger chainring? (And use SRAM cassettes instead of Shimano, they have much more linear ratio gaps)

Your gears should be so that in a full gas flat sprint (1500W, 65kph) you are in the 13 or maybe the 12. The 11 or 10 is for descending at 70-80kph when you are are putting out much less power, aerodynamics is much more crucial and you are focusing on cornering and following the wheels.

No one can be bothered with half-step triples and shit in a race situation (TTs excepted perhaps)

use SRAM cassettes instead of Shimano, they have much more linear ratio gaps

I've just bought a couple of SRAM cassettes (fucking SRAM!) because (I think) they are all steel, whereas the Shimano cassettes have the two lowest gears in aluminium which wear out before the rest of the cassette.

If anyone knows where to get the lowest three cogs on a Shimano MTB cassette as a spare part, I'm all ears.

I don't think so. Has anyone done mechanical front and Di2 rear? I think that would be cool and would be useful for when chain drops happen so can feather the chain back on.

The cheaper Shimano (Deore)cassettes are all-steel and the intermediate ( SLX) have just the largest in aluminium

I've seen downtube shifter FD combined with STI rear (didn't Lance do that?) but not sure about mech FD and Di2 RD. Not a bad idea though. But I really don't want to add mech stuff back into my life. The Bokeh is getting the 1x RD but 2x cranks and FD. It should work, as that's what I've got on the Tripster already.

So I've just ordered SRAM for no reason? Bugger.

UNCLEAN!

All steel: Shimano Deore CS-M6100 Cassette 12-speed - 10-51 Teeth
1 alu sprocket: Shimano SLX CS-M7100 Cassette 12-speed