Shimano chainring design with gaps between every other tooth

If the recent silent freehub design we found is any indication, Shimano is looking at ways to reduce noise, friction and drag in some creative ways. And perhaps this chainring design, which we found in yet another patent application from the drivetrain giant, is even more creative despite its utter simplicity.

Want to reduce weight? Cut drag and friction? Easy, just remove every other tooth. But not just any teeth, only the narrow ones from a narrow/wide design. Which is even more odd coming from Shimano since they don’t currently offer a narrow/wide chainring, though they have patented shiftable narrow/wide ring designs. And, we’ve heard from one source (but can’t verify) that Mr. Shimano was the first to patent a narrow wide chainring design all the way back in 1978, albeit for agricultural purposes. Yes, you read that correctly: Shimano may have been the first to patent a narrow/wide chainring design, and they did it almost 40 years ago.

Here’s how this could work…

Shimano chainring design with gaps between every other tooth

The patent application states the design could be used to reduce the weight of the chainring and reduce the likelihood of missed shifts. The weight savings is obvious, but there are a few tricks to save more than just the weight of the missing teeth. Images below show cut-outs on the teeth as an option, and the filing mentions a sandwiched design of using a hard candy shell (iron, titanium) over a lighter (alloy or resin) interior.

Shimano chainring design with gaps between every other tooth

Beyond weight, the focus is on performance, with mention that fewer teeth could improve shifting performance. There’s not a deep dive into why or how it would improve shifting, and not all iterations are even designed to accommodate shifting. Figure 3 shows a non-shifting design with square edged tooth shapes.

Shimano chainring design with gaps between every other tooth

The teeth are, however, shaped to facilitate the chain gliding on and off the teeth. But for shifting, the teeth get chamfers (222) on the leading and trailing edge, top to bottom. That’s shown in Fig. 5 and Fig. 6.

Shimano chainring design with gaps between every other tooth

It’s particularly interesting that this seems to be the focus of the design. Specifically, the filing reads: “Further, the bicycle chain is less likely to fail to engage the sprocket teeth due to less number of the sprocket teeth in comparison with a conventional sprocket.” Perhaps this primarily refers making it easier for the chain to lift off of a ring and start towards the other one.

Shimano chainring design with gaps between every other tooth

For settling onto the big ring when shifting up, there are a few additional features shown that either claim to or we suspect will aid in helping the chain settle into place. Fig.7 shows an intermediate tooth (317) that would be narrower than the others and designed to catch the inner chain links, and it would all be timed with pins to encourage the wide links to settle onto the wide teeth.

Shimano chainring design with gaps between every other tooth

Fig. 11 shows a cutout, which they note can take any shape, at the base of the tooth intended to reduce shock by allowing it to flex (Imagine a fish’s tail. Not a dolphin, a fish.). We interpret this as shock from a chain shifting onto it under load.

Shimano chainring design with gaps between every other tooth

Switching back to what we presume are single ring applications found on so many modern mountain and cyclocross bikes, another iteration shows a support platform (960a) at the base of the tooth. The chain’s outer link plates would rest on it as it settles onto the tooth, providing additional stability. This could mean a proprietary chain-and-chainring design meant to work together. A recess (20, shown on all images) presumably allows a straighter path and plenty of mud clearance for the inner links.

Shimano chainring design with gaps between every other tooth

So, could this work? Well, Shimano’s not known for putting out any product that hasn’t been dialed to near perfection. But, we reached out to several other chainring manufacturers to get their input.

Brendan from Wolf Tooth Components said “The narrow teeth definitely help. They’re less critical to chainring retention, but they do help, particularly on smaller chainrings where you have fewer teeth engaged at any given time. And they’re particularly more important on smaller chainrings for driving a load. Because smaller rings have fewer teeth engaged at any given point, each tooth is handling exponentially more load. So, the narrow teeth would improve chainring durability.”

I spoke with another brand that wished to remain anonymous but concurred, adding that it would also likely cause faster chain wear because only the outer (wider) chain links are being used, so they’re pulling double duty.

Regarding durability comparisons, most aftermarket narrow wide chainrings are machined from alloy, which wears faster. This includes virtually every aftermarket ring from Wolf Tooth, Race Face, OneUp, etc. Shimano’s high end chainrings’ teeth are hardened steel, titanium, or cold-forged aluminum, all of which are much more durable.

Shimano chainring design with gaps between every other tooth

The patent application mentions multiple materials molded together, using steel or titanium for the outer tooth profiles (430, 434) for long term durability and an inner part (432) of the ring from either alloy or a resin material, the latter suggesting a carbon fiber or composite spider is in the works…similar to what’s used in their high end cassette cluster or XTR single chainrings.

Shimano chainring design with gaps between every other tooth

That dual material layering could make this design durable enough, particularly if it’s reserved for road applications that don’t need as aggressive chain retention but could really benefit from reduced friction.

And that’s the missing part of the conversation. The patent filing has no mention of reduced friction, and friction creates drag and robs power. Fewer teeth theoretically mean less friction, and that could end up being the real benefit of such “toothless” designs. Add that to the new rear hub design we spotted and you could have a dramatically more efficient road transmission.

One concern discussed with a competing brand was chainline and derailment issues when the chain is on the upper or lower extremes of the cassette. The further from 0º the chain rolls onto the chainring, the larger the lateral displacement in relation to the wide teeth, which could lead to an increased likelihood of dropped chains.

Regardless, it’s a very interesting concept that shows how the venerable bicycle continues to evolve and advance.

26 COMMENTS

  1. Does tooth load really grow “exponentially” as chainring size decreases, purely due to reduction in engaged tooth count. I’ll have to calculate that one. At a fixed torque input, it would seem to be a linear relationship. Removing teeth from a fixed size ring, would also seem to result in a linear increase in force across the remaining teeth.

    • LOL! I was thinking about that too as I read it. Truthfully, per-tooth load decreases hyperbolically as the tooth count increases.

    • I would say that the load on each tooth increases more because the mechanical leverage is increased as the chain ring decreases in size than it has anything to do with the decrease in engaged teeth.

  2. I’m not smart enough to have an opinion about the feasibility of such a chainring design, but this seems like something I’d wait for production, then a year or so of consumer use and reviews before I’d buy into it. Especially if this gets branded as “Dura Ace 9900” or something, with it’s commensurate price tag!

  3. @Teilchen my thoughts, too.

    Some other thoughts. Shimano has a better single ring tooth profile than narrow-wide. NW is popular because any shop with a CNC machine can churn out rings from aluminum in it. Shimano’s single ring solution involves actually sort of hooking the chain rollers. Four links of chain engaged on a Shimano single ring can support substantially more weight than the crankset itself. 4 links engaged on a narrow wide can’t support any weight.

    Shimano expressly doesn’t want a narrow-wide solution because the wide teeth wear the piss out of the side links.

    This could just be a protective patent for stuff that’s is or was in development and testing.

    • Really? It’ll wear an aluminum ring out way before the side plates. You should also be replacing your chain, long before any of that minor wear would actually damage your chain.

        • Use a belt-drive then.
          There are pluses and minuses to everything. The taller toothed 1x rings don’t feel as smooth, narrow wide wears your chain and chainring… wait? All chains wear out chainrings!!! If it mangles your plates after 1500 mountain biking miles, who cares if you probably needed a new chain at 500-800 miles.

          • Belts incur a double digit percentage loss of power while chains keep it under 5%. Shimano has engineered a system of chain retention that grips chains BETTER than narrow wide, and wears LESS than narrow wide. That’s a win on all aspects. There are no other arguments for narrow wide.

          • You don’t actually know until you use it. That said, belts stay cleaner than chains, they weigh less, they don’t really wear. The wins seem pretty big. Sure, IF this works, chain wear will be better (where it doesn’t even matter since you’ll be replacing before then anyway) but chains still don’t last nearly as long as belts.
            I’m not a belt user, just stating that this doesn’t really solve much of anything

  4. Um… I worry about the fools who don’t replace their gear when its worn. I have people come into thw shop with mangled chainrings thinking they just need a new chain. Or an adjustment. Not an issue for people who regularly inspect/maintain their drivetrains but lets be real… Seems like a good idea in many other ways though.

  5. It’s called skiptooth. More recently, SRAM had their openglide design, but it was also used on the big cogs of many old freewheels

    • Exactly what I was remembering (though I didn’t think it was nearly 20 years) – the shape of that chain – it must be something they are working on currently to have discovered additional feature: quiet

    • meant to reply here – – – Exactly what I was remembering (though I didn’t think it was nearly 20 years) – the shape of that chain – it must be something they are working on currently to have discovered additional feature: quiet

  6. This is really nothing new. Ever seen an inch-pitch chainring? Some of the first bicycles designed, way back in the last century, only engaged the chain on the wide links on both the front chainring and rear cogs. Quality multi gear freewheels as recently as the ’80s skipped teeth on the larger cogs. Check your history books.

  7. I see this as a way for Shimano go patent various iterations of the “wide” teeth of a narrow/wide ring without showing a narrow/wide ring. Otherwise, I don’t see how removing teeth could improve chain retention. The whole idea of the narrow/wide rings is that it doesn’t allow enough lateral movement of the chain from one tooth to the next. Here, the allowance more than doubles.

  8. Yawn. The friction and weight savings this technology affords are miniscule compared to the benefits of shimano’s soon to be released motor-powered groupset. You can have your 0.003 watt savings with this stuff, but as for me…MOTOR ME UP!!! RAWR!!!!!!

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