On July 6, 2023, the US Patent and Trademark Office published two patent applications from Zwift:
- SINGLE-SPROCKET SYSTEM FOR A BICYCLE TRAINER (US-20230213087-A1)
- VIRTUAL SHIFTING FOR EXERCISE DEVICES (US-20230211208-A1)
The two patent applications are closely related. Not only were they published on the same date, but the technology they describe is meant to work together as one “system”, as described in the patent filings themselves.
This isn’t the first time we’ve heard of this system, either. It was first leaked by Zwift in December 2021, when the company said, “Z Cog: Zwift Wheel is built around a single cog design with virtual shifting, unlocking compatibility with all bikes from the box.”
What is this “Z Cog”, and why does virtual shifting matter? Let’s dig into what Zwift is developing.
One Sprocket to Rule Them All
The “Z Cog” is a single sprocket that replaces the rear cassette on a trainer, effectively creating a single-speed setup (physically, at least). See the Z Cog in Figures 2 and 3 below:
The Z Cog has angled sides to direct the chain onto the single sprocket even if it isn’t aligned perfectly. (A misaligned chain would probably be a bit noisy with this setup, but it would still function.)
To really understand how the Z Cog works, though, we have to understand its sister technology: virtual shifting.
Let’s Get Virtual (Shifting)
“Virtual shifting” may seem like a strange concept to cyclists who have only used “physical” shifting. If you’ve ever ridden a smart bike like the Wahoo KICKR Bike or Tacx NEO Bike, though, you’ve used virtual shifting whether you realized it or not.
Virtual shifting uses some a shifter/controller/button to control the resistance unit on the smart bike. Shift to a harder gear and resistance increases, giving you the same feeling as shifting to a physically smaller cog on a rear cassette. Shift to an easier gear and resistance eases up, like shifting to a larger cog on your cassette. As Zwift’s patent application says, “In such a system, the sensation of shifting gears is provided entirely through an electronic adjustment in the resistance of the flywheel.”
One nice thing about virtual shifting is it allows you to customize your gearing, as clearly seen in this in-game shot uncovered a few months back and discussed in our Zwift Leaks post in May 2023:
Most smart bikes today offer custom gearing configurations. Run a triple chainring in front, or a double, or a single, with whatever tooth count you desire! How many cogs would you like on your rear cassette, and how big would you like them? It’s all virtual, so the possibilities are nearly limitless.
Zwift’s patent application isn’t talking about smart bikes, though. It refers to a virtual shifting system that consists of a shifting controller interacting with a smart trainer, saying: “The control device and the associated trainer acting together may enable virtual shifting…”
The patent application even delves into the “feel” of virtual shifting.
That shifting may simulate the “Feel” of shifting as discussed more fully below. In particular, that simulation may be both for (1) the different levels of resistance associated with higher or lower gears on a bicycle in different situations and (2) the quick loss of power and resumption of power at a different rate, often with some clicks and snaps in between, while shifting gears.
Zwift also discusses auto-shifting in its virtual shifting patent application, which is a novel concept in the virtual cycling realm but quite common in auto racing games. Zwift says auto-shifting may be particularly necessary if a rider doesn’t have shifters, but it may also make sense for riders who simply don’t want to mess around with shifting. Zwift says it could also be used to help riders maintain a target metric like power, heart rate, or cadence.
(Auto-shifting to maintain a particular power output sounds a lot like ERG mode, although in this case riders would still feel the change in resistance on inclines and declines.)
Z Cog + Virtual Shifting Benefits
What are the benefits of Zwift’s proposed single cog + virtual shifting system, compared to a standard cassette with physical shifting?
- Multi-bike compatibility: you could place various bikes onto the same trainer without needing to change the cassette (perhaps a road bike with an 11-speed cassette, or a MTB with a 12-speed, or an older 8-speed commuter bike). Great for multi-Zwifter families or riders who want to train on different physical bikes.
- Simple setup: newer riders may be baffled trying to configure a smart trainer that works with their bike. A Z Cog in place of a standard cassette simplifies things.
- Customized gearing: as mentioned above, with virtual gearing riders could configure their chainrings and cassettes to be anything they’d like. This will prove especially helpful for riders on mountain bikes who would otherwise spin out when sprinting on their physical gears. It would also greatly expand capabilities (and improve the experience) for riders using simple single-speed bike setups.
- Less wear and tear: if you don’t need to physically shift or use a rear cassette, those components will last longer.
Compatibility
Zwift’s Z Cog patent application states that the design is “compatible with most direct drive trainers”. Their virtual shifting application seems to indicate that the virtual shifting would be done by the game software itself, meaning that both the smart trainer and shifting controller would be paired to the game software, and all virtual shifting signals would run through the game software.
This means that, in theory, Zwift’s virtual shifting system could be made to work with any smart trainer. It could be generically set up to simply add/remove trainer resistance with each virtual shift, or perhaps a more trainer-specific implementation could be put into place by each trainer manufacturer, utilizing a Zwift API and the manufacturer’s knowledge of their own product’s abilities.
Our guess is virtual shifting will roll out on the Zwift Hub trainer first, but Zwift will share the virtual shifting API so other brands can implement it if desired.
Timeline
When will we see it? That’s the question everyone asks whenever we see leaks from Zwift.
The truth is, we don’t know. Zwift’s official statement doesn’t clarify timelines:
Zwift remains at the forefront of innovating the indoor space. We are continually developing new products and features designed to benefit the indoor cyclist. We will only comment on new innovations when we are ready and therefore will not be commenting further on these patent filings.
With Zwift’s Play controllers now released, we wouldn’t be surprised if virtual shifting was added to their capabilities before the year is out.
Questions or Comments?
Share below!
How would shifting work? I suppose you need Zwift play to shift or how else would this respond to my SRAM red manual shifters?
Yes, I suspect the buttons on the outer edges of the Play’s – which currently only function to +/- the workout bias (during workouts) would be the perfect candidate to have these buttons mapped to act as shifters…
Absolutely, however, I am interested in how it will work – considering there are two buttons and you ideally need four (chainring back and forth/cassette back and forth). I assume there would be a difference between press and hold?
With virtual gears you don’t have the limits of real-world gears.
So to have the range of a real-world 2 x 11 setup you don’t need a virtual double chainring – you could have a single chainring running a “virtual cassette” of any size you like – so it could be 1 x 22, or 1 x anything.
You could, but I expect they’ll try to mimic real world shifting. We’ll have to see.
I’d probably have thought the same until a few weeks ago, when I started looking to swap the groupset on my old mountain bike. Then I learned that all top-end mountain bikes now use 1x systems, so “real-world” for MTB is going towards one set of shifters.
While Wahoo went with real-world shifting on their bikes, as everything Zwift does with tech seems to be about making it simpler for entry-level riders to get onto it, I can’t see them using two sets of gears. But as you say, we’ll find out one way or another soon enough! 🙂
I think it’s pretty obvious now that the side buttons on Zwift play will act as virtual shifters, time to grab the device before it’s out of beta.
Also, I am quite interested what the pricing for the “virtual cassette” is going to be – my guess is €99 at the very minimum.
I would like to see this and be able to use my gates carbon drive setup without spinning out the gears. Smooth and quiet with no maintenance or chain lubricants. Eliminate a miss shift
I don’t know why they’d need to share the API with other trainers. They could implement it like other platforms with virtual gearing do and just send a signal to all trainers to increase/decrease the resistance. On a different platform, the virtual gearing is described as adding the equivalent of X% slope (from 0-9 by 0.2% increments) to whatever slope you are riding, and I just put my drivetrain in an efficient gear and use the +/- buttons on my keyboard (because no equivalent of Zwift Play) to change the virtual gearing as I go up or down hills or… Read more »
That’s why I wrote what I wrote above. “This means that, in theory, Zwift’s virtual shifting system could be made to work with any smart trainer. It could be generically set up to simply add/remove trainer resistance with each virtual shift, or perhaps a more trainer-specific implementation could be put into place by each trainer manufacturer, utilizing a Zwift API and the manufacturer’s knowledge of their own product’s abilities.” While a “generic” implementation by Zwift would probably work decently, letting manufacturers “dial it in” so it works optimally with their particular trainer (since each trainer adjusts at different speeds, has… Read more »
Ah, must have speedread through and missed that bit. I just have memories of Wahoo saying that they were going to make the Climb able to be used by other trainers who wanted to build that into their firmware (and some Neo’s being made with the ability of their freehubs to rotate to support that) only for that sharing never to materialize. Not that I ride a Neo, but that (and similar incidents in other non-cycling tech areas) made me a bit pessimistic about Zwift saying, when it first cam out that they’d share the data if other platforms wanted… Read more »
Could the Z Cog not be an ANT+ relay of sorts?
You pair the the Z Cog to the Play controllers and directly to your trainer similar to how you pair the Climb or Headwind to a Kickr. Then you select the Z Cog as your “trainer” in Zwift/Rouvy/etc.
Now you have virtual shifting in all apps (and a lot more failure points for drop outs…)
If you are riding and another person in the family wants to ride at the same time, you still need two trainers. In reality, most households only have one person riding. This could be a niche group, but ultimately most people want their own set up, and don’t like have to swap bikes frequently. Did they do market research on trainer sharing?
I’m in a toxic relationship with Zwift. I don’t like the stuff they do put out on the software side, like no local gradient and no live segments on longer climbs but I do like the hardware stuff they offer like Zwift Play and now this. So I hate their personality but I love their body. 😅
LOL.
What do you mean by “local gradient”?
Useful upcoming gradient with colors like they do in climb portals but everywhere.
There’s the sideview in the top right corner that shows the gradient on your current route. It’s small but on a decent sized screen gives enough of an idea of what’s approaching.
Would I be right in saying that this full Zwift hardware setup is not going to be compatible with other platforms
Auto shifting with virtual gears? Why even have this fake shifting at that point? Just get rid of gradient simulation/resistance changes. You’ll be pedalling along, then hit a hill, you’ll feel a virtual gear change and then just keep pedalling at approx the same resistance. So it’ll just add some random “clunks” in your pedalling.
You still feel the gearing effect though. I have a kickr bike with virtual gears and it feels exactly like physical gears, so much so you forget they’re virtual once riding. The ‘auto’ would simply mean someone can presumably set a cadence/power point at which it shifts gears instead of you pushing the lever/button, so you go from harder effort/slowing cadence to easier effort/faster cadence. This is very different from simply pedaling at the same resistance with the odd clunk to simulate changes.
But why would I want to feel gears if I don’t have to? Should we include stop signs and traffic lights and cars passing you too close to it feels more real on zwift too?
Will the Z Cog be chain only or also be available for the Gator belt ?
Chain only, far as I can tell.
In June I had to contact support regarding a new gearing UI element. They told me I had erroneously been added to a group for the feature. I assume now this was virtual shifting.
The UI element looked like this
Very interesting!
I’ll be interested to see how/if this affects me as I ride and race on a single gear most of the time.
This week indieVelo just introduced virtual gearing, works with any trainer. Hoping Zwift adds this soon, would be great with Zwift Play controllers. My bike has Ultegra R8000 mechanical shifting, would like to avoid wear/tear, and sometimes I wish I could shift faster in races :). But I seriously hope it will work with any trainer and not just the Hub. I use a Saris H3 that works perfectly, no interest in replacing it.
Looks like this chap has some sort of early access to the virtual shifting:
https://www.youtube.com/watch?v=lsg3-4SPWPM
I think he’s just on a Wattbike – they’ve shown gearing in game for years. (Or maybe another smart bike? I know the KICKR Bike does not… but the NEO Bike recently started showing it.)
Oh, I wasn’t aware of that! Makes sense!