Sy Reene

That'll only happen if the bike makers can figure out a way to integrate it into a proprietary 1-piece bar/stem unit.

Kimmo 

See that first kink in the curve at third gear? That's where the 2t gaps and 1t gaps meet. If I'd plugged in a really wide cassette with a 4t gap at first gear, you'd see three of those kinks, specifically intended to curve that line down. This is mostly due to the effect of aero drag, which rises at the cube of speed.

But due to the limitations imposed by the half-inch pitch, as soon as aero drag starts to really kick in, you're into the 1t gaps and widening ratios, which I'd really like someone else to acknowledge is actually quite a bummer.

Voila, 38/50/52. You're welcome.


It works on a double's Q factor, because you only need a cassette-like gap between the big rings; the inner has been moved inboard by about the thickness of a chainring, and the outer is outboard by pretty much the same amount. A standard FD has enough throw, but it needs a cage designed for this, and obviously you'd want CAD shift ramps and gates on the big rings. The two big rings should probably be integrated into one unit, which would be expensive, but the good news is there's no reason why you shouldn't design the rings to fit on standard double cranks.

Say Shimano came up with this; a retrofit kit for a Di2 bike would be the chainrings and FD, and a firmware update. That's it.

You could have it set up any number of ways; toggle between normal shifting with minimum front shifts and half-step mode, or maybe normal mode by default with another shift button for when you want that in-between gear, for instance.

I'm getting blue in the face telling you guys this is the biggest bit of low-hanging fruit left. Sooner or later, it will happen.

HTupolev

Few people will acknowledge this because almost nobody actually cares. Even spacing-concerned roadies rarely get bothered by jumps up to 10% or so.
The fact that power loss from aero drag increases cubically with speed doesn't really affect this. It compresses the speed distribution for flat-ground riding, causing people to spend a lot of their time in a small speed range, which can make it more "worth it" to put tight spacing in that area than in other parts of the range. But it doesn't really increase the degree to which the legs care about a particular gap on a moment-to-moment level: a 13% gear jump feels like a 13% jump at 15mph and at 25mph.

And on most road drivetrains that have big straight blocks, few cyclists are spending much time in the smallest cogs where the 1t jumps are biggest. Even when they are, if they're not bunch sprinters it's often in soft-pedal situations where gear jumps aren't felt as badly.

That might work okay for the two larger rings, but if you're actually shoving three chainrings into the space normally occupied by two, you're going to end up with an extremely steep relationship between the inner and middle chainring. It's going to be tricky to produce good shifting even if you can solve the FD geometry issues.

The other way to solve the q-factor problem is to just bring the NDS crankarm inboard. Tons of manufacturers did that back in the day, and almost nobody noticed that their pedaling stance was offset to one side, even though the discrepancy between sides was sometimes a centimeter or more. The issue is just that 2-piece cranks generally don't offer lateral crank arm adjustment.
I have an old bike with a 142mm q-factor triple, it's awesome.

It might not just be an issue of throw or cage shape, but also the shape of the arc that the cage moves on. I wonder if really optimal results would require something like a Huret Allvit-style parallelogram inversion.

Kimmo 

IME when I'm cruising along in the big ring, I feel like the available ratios sometimes restrict my speed a little - I'd like to spin a slightly taller gear, but the next ratio is too steep to get on top of and stay there without more effort than I care to expend. I can't understand how it's not obvious that the ideal would be a CVT, if it wasn't for the inherent inefficiency of such systems.

The gap between the inner and middle rings is the standard 10s chainring gap, from memory. Or maybe I squeezed it a tad to the 11s gap. I put a fair bit of thought into the chainring spacing before I specced the spacers, and nailed it first try - the chain is quite happy on those rings I reckon. Once I raised the FD to clear the middle ring, shifting was consistent with plain rings and a too-high FD; I was pretty sure shift gates and a proper FD cage would complete the picture.

The arc the cage swings through is a relatively negligible factor, IMO - the critical thing is the cage shape, which just needs to take that into account.

Kimmo 

I thought ljsense 's post was very imaginative.

I just watched the Pinkbike Grim Donut vids about future MTB geometry, and figured since MTBers don't mind complicated stuff, that maybe dynamic geometry might one day be a thing for them... they already have dropper posts.

HTupolev

I experience that sometimes on my 50-34 11-28 Shimano 2x11, but that's due to being caught between the 15T and 17T cogs. I'm never particularly bothered when I'm in the 13-14-15 range.

The ideal for gear spacing obviously is CVT. But it's an issue that's subject to diminishing returns.

Kimmo 

Right; that's why there isn't a drop bar shifter for the NuVinci - the ratio advantage is much less than the drop in drivetrain efficiency.

But here's the key point - it is an improvement, and it's big enough to be perceptible. And at this stage of the game, it's doubtful there's any other improvements to make that'd be big enough to be perceptible, except dropped pedals. The latter would finally kill that stupid interface that Jobst Brandt hated so much, he came up with a way to transition the industry to a tapered seat. I'm almost surprised that Shimano hasn't pinched the idea yet for Dura-Ace, given how they refine that group with such a fine-toothed comb... (backwards compatibility for non-tapered pedals is achieved with a split collet). But yeah, the tapered seats, although an eminently sensible improvement (which would also eliminate the need for a left-hand thread on the left, if it wasn't for backwards compatibility), beyond making just that interface much nicer, would merely serve to address crank fatigue failures initiated from fretting damage at the pedal eye (happens a bit on high-mileage cranks to this day, I believe), allowing for less material in that region. The sort of thing you'd definitely have in a clean-sheet ground up redesign, but not really worth the trouble in the real world, despite the nastiness of a crank failure.

But my gearing idea is another story; it just needs someone at Shimano to throw my specs into their CAD software, come up with the rings and FD cage, plus a few lines of code, and bam, there's a whole new headline feature that can easily be marketed as a perceptible improvement. With graphs and everything.

Having thought a bit more about how to shift it, I'm thinking a good logic would be to shift through the range a cog at a time, only shifting the front as necessary to continue through the range (same as Semi Syncro but with a third ring for the topmost gear), until a third or fourth input tell the system to go up or down half a gear (on the small ring these buttons would just give a full gear).

Come on - who doesn't want to see how well Shimano can electronically shift a triple? They died just before electronic shifting properly kicked off - what's the bet triples are on the shelf as one of the last things they can bust out as anything halfway close to a game-changer? Part of the reason triples got the bullet might have been to allow for refinement of electronic front shifting in a simpler context...

HTupolev

I actually don't think that indexing was all that big of a gain in and of itself. The thing is, SIS included a number of improvements that facilitated light-action non-baulky shifting, it wasn't just clicks in the shifter. That this happened to facilitate indexing was a huge marketing win, and was crucial for the integrated shifting that would come half a decade later. But for the shifters at the time (downtube and bar-end levers) I think the fixation on clicks belies the real advancements.

I've found that friction shifting with modern derailleurs and cogs and chains feels pretty darn good, very non-finicky. On my gravel bike with bar-end shifters, I keep the rear in friction mode even though the shifter is able to index the drivetrain: friction mode has a much lighter lever action which just feels really nice and allows me to comfortably use my pinkie for upshifts.

Racing Dan

Or a set of smaller chainrings that put you into the "1t jump" range of an ordinary cassette.

Bicycle Gear Calculator

Kimmo 

Aside from the basic notion of making a half-step triple easy to shift electronically, the second element is the 38/50/52 combo (if you plug all sorts of numbers into a spreadsheet, you'll see this is special sauce; the 1/2" pitch combined with the scale of a drivetrain means this is the only combo that gives you such a nice gear curve). The third element is the chainring packaging with the two big rings jammed close together (possible because they're nearly the same size). And on a double crank, because there's no granny, and the width increase doesn't necessitate wider Q.

Can anyone tell me if this third element has already been done, back in the day, in whole or in part? Two big rings close together, and a small ring, on a double crank?

HTupolev

I think you're missing what Kimmo is saying. The half-step isn't being used to replace 1T jumps. It's being used to split the 1T jumps in half, because Kimmo thinks that the 1T jumps aren't tight enough.

Kimmo 

Yeah, Hyperglide was necessary for indexing to work properly; previous attempts sucked. The biggest improvement it brought was nearly always allowing the chain to change cogs without disengaging and jumping over the teeth; it helped the chain really bite on a larger cog for very reliable shifts to lower gear, and safer shifts to smaller cogs while accelerating, which was a boon. It definitely allowed indexing to do its thing, which allowed for the final fundamental improvement to the road bike: dual control.

Kimmo 

They're tight enough for many. Many folks also don't want a 39/53... doesn't mean there isn't a market for it.

If you admit a CVT would be better if only it wasn't inefficient, you effectively admit my totally practical proposal has merit.

It's not a must-have improvement for almost everyone; I'd argue we've seen all those, with the final ones being definitely dual control, probably clipless pedals, and I'd argue the dual pivot brake (finally being able to lock the front wheel was a bigger deal than the better wet braking of discs IMO).

Joearch

Excellent post. For the most part amazing ideas. Fun to read.

Racing Dan

Imo, rather than brute forcing a expensive "every conceivable" gear solution, I think most would be better off looking at some telemetry and adapt their gearing to their particular use case. Lots of phone app based solutions to this out there. - Ride your favourite routes and daily commute and record your speed and cadence to get a sense of your real speed and adapt you gearing accordingly. Lots have 52/36 + 11-28 to have (in their mind) lots of fine gradation 1t gear jumps, but never realise they actually never (or very seldom) use the the 14t and thus never use any of the 1t jumps.

Kimmo 

I'd say it's too elegant and simple to call it brute forcing: the extra cost over a double is one chainring.

Racing Dan

And DI2 to be practical. No one is going to put up with a mechanical 1/2 step system, no matter what they claim on the forums :-)

Ghazmh

I thought 2 things were the cats meow.

1) Treks speedwing pivoting aerodynamic cover for front brake calipers. It saved the rider from the horrible aerodynamic drag of a brake.

2) Zipp Biogimmickery whale tail rims. As if resembling a walrus when dressed in black spandex isn’t enough Zipp will sell you wheels that resemble whales tails. At a particular angle of wind yet to exist in real life going 40mph they will make you faster.

Kimmo 

This is a thread about future tech...

HTupolev

I have multiple bikes where I take advantage of mechanical 1.5-step systems.

No half-step, though, so maybe you're right.

Racing Dan

Sure, and its not 3 x 10 either (im betting). The proposed setup has about 15(!) chain ring shifts from one end to the other not to mention the bottom gear is about equal to 34/21. The amount of front shifting would drive you nuts unless you ran it in manual mode, in case of DI2, to prevent it.

https://ritzelrechner.de/?GR=DERS&KB=...N=KMH&DV=speed

HTupolev

Nah, the most is the 3x8 drivetrain on my gravel bike. 48-38-24 paired to 11-13-15-18-21-24-28-32. It's basically a classic wide-range mountain triple, but the two larger chainrings 1.5-step the cassette: it's got a low-end of about 19", but also a top-end of 113", and I get get close-ratio shifts when I want them in the road cruising range. Obviously "close-ratio" in this case is normal close-ratio, not what Kimmo is talking about.

This being said, I'm not sure that you're being fair. Front shifting isn't intrinsically dramatic: it's dramatic because modern 2x front shifts are usually huge, and also require lots of compensatory rear shifting. Small front shifts won't necessarily drive a person crazy, because they won't necessarily feel much different from rear shifts. Even the 10-tooth jump between my two larger rings on the gravel bike is considerably less disruptive than the 16-tooth jumps on modern road bikes, which is why I don't take much issue with doing it frequently. Sometimes I even do a front shift in place of a rear one, if I'm in a situation where I feel like having a single somewhat-bigger-than-normal shift. With appropriate FD and chainring design, and Di2 control, the 4% 2-tooth front jump that Kimmo is proposing could potentially be extremely subtle.


Yeah, it's definitely not a drivetrain that would be remotely suitable for my riding, even if I were to end up liking the ultra-tight half-step feature. Far too high on the bottom-end.

Racing Dan

I cant see it happening, but if you like it then 3x7 is more than adequate for a road bike.

Bicycle Gear Calculator

Or IGH + 3x chain rings or 3x cogs.

https://ritzelrechner.de/?GR=SN5E&KB=...N=KMH&DV=ratio

Or a 420% 3x9 with shallow chain angles.

https://ritzelrechner.de/?GR=DERS&KB...N=MPH&DV=ratio

cybirr 

Has anyone mentioned ABS for road bikes? There are prototypes out in the wild right now. I'd imagine our MTB and e-bike friends will go for them first. Then, like disc brakes, they'll migrate to road bikes.

wphamilton

I brought that up in an earlier thread like this one, and it turns out that something very similar to ABS already exists and isn't even that complicated.

By a clever arrangement of cables, when the back wheel stops turning - skidding or flying - the front brake eases off. You'd be a little scared of the mechanics (if something malfunctions I have no brakes or they lock up?) which I'm supposing accounts for it never being adopted. That's a great idea for the future tech though.