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Cannondale used to make these shocks for mountain bikes and they were pretty common when I rode as a kid. It seems like they have completely phased them out of production. What caused this? Is there something inferior about this technology?

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    Note that Specialized has introduced a similar system with their "Future Shock" arrangement on gravel and endurance road bikes.
    – MaplePanda
    Jan 26 at 19:03

3 Answers 3

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Cannondale still makes them. Under the form you present, they are only found in urban E-bikes. On MTBs, they evolved into a different form.

One drawback of this design is that the travel needs to be shorter than the head tube length. But MTBs evolved towards longer travel and needed to shorten the head tube to have good geometries. So Cannondale moved the mechanism out of the head tube and created a single leg design now known as the "Lefty" fork (mostly found on their high-range products).

More info here

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  • Seems to me that the longer lever arm on the single shock absorber would also make this design shorter-lived/less reliable/heavier. The fact that it's still used on urban bikes but not MTBs would be consistent with that, with MTBs much more likely to take many more and much harder hits to the front wheel that would try to bend the entire fork backwards. And also forward - urban bikes won't be doing many landings that would tend to bend the front fork forward. Jan 26 at 15:33
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    @AndrewHenle you are in fact wrong -- the surface area on which the forces act is somewhat larger than a traditional fork and the needle bearing system is totally different (and patented) and hasn't yet been copied by anyone else. I believe the maximum travel of the classic headshok is 80mm which is now considered rather a short travel. This is why the design evolved through the Moto FR fork to the Lefty, which all use the same needle bearing system.
    – JoeK
    Jan 26 at 18:47
  • @JoeK So? That doesn't preclude the longer lever arm being another reason for going to fork-mounted shocks. Given the pivot point for the shocks on these would be the bottom of the head tube, and the pivot point for a fork-mounted shock is MUCH closer to the axle, these shocks would need at least twice the surface area because the side forces on the shock from the much longer lever arm would be much higher. Jan 26 at 19:16
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    @AndrewHenle thankyou, i'm sure you've made a great point, though when you read through the designers interview notes and the history, it doesn't look like your speculation is the real reason. It might be though!
    – JoeK
    Jan 26 at 19:23
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It is a little difficult to give an answer that distinguishes between the pros and cons of the concept and any untapped potential it might have versus Cannondale's implementation of it.

With its very precise array of needle bearings on a non-round telescoping section, the Cannondale design is successful at being smooth and slop-free, but it's way too expensive and maintenance-intensive for its own good and the benefits it provides. Problems never really went away with how susceptible the design is to tears in the boot, which has a critical role to play in keeping contamination out and lubrication in. If the boot becomes compromised, things go south very quickly and a rebuild is often needed, to an extent where normal riders simply need more margin for error. The tight tolerances that keep Headshock largely free of perceptible slop also make it very easily affected by contamination. Headshock mostly exists/existed to be cute and tell a good visual story on the sales floor. On a practical basis its combination of low travel, marginal damping control, and high maintenance needs were too little benefit at too much cost compared to a conventional fork for mountain bikes and to an appropriately sized and pressurized pneumatic tire for utilitarian/road-going ones.

I won't speak too much to what's good and bad about the design in more abstracted terms. The Cannondale design sacrificed a lot to be very smooth and very free of slop when everything was working right, and also had a lot of proprietary tool, component, and support access hoops to jump through. It's possible to imagine someone taking the concept in a different direction, but difficult to imagine the result being clearly better than just using the right width tire at the right pressure. Note that the period Headshock arose in was basically the apex point for popular tire tire sizes being too narrow for almost every application in cycling, and of the dogma that higher tire pressure is usually better.

Suspension fork designs with one telescoping element like Headshock and Lefty are unaffected by increased stiction when the front wheel is side-loaded, as in cornering. That this is true to some extent compared to a conventional fork is provable and undeniable, and Cannondale loves to make a big deal about it, but the importance of it is highly debatable since loads on a bike track largely in-line while cornering, a fact you can read about in various technical work on bikes but that's easy to work around in marketing material because it's not completely obvious. Going over technical terrain at speed (mountain bike racing) it's not too much of a contrivance to say this effect provides some advantage, but it's a stretch on utilitarian or on-road bikes.

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  • I've heard a lot of the same comments/concerns about Lefty, mainly the bearing construction and maintenance, whether durability is more important than functionality, etc. Good points!
    – ebrohman
    Jan 27 at 0:17
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Other answers have covered some technical pros and cons. I will add the original Cannondale company was forced into bankruptcy about 20 years ago and broken into pieces auction off to various buyers, whoever bought the name and bicycle intellectual property started new design and production halfway around the world with completetely different motivations from the original company. So your question is sort of asking why Joe stopped making(or did not restart) Bob's old product.

(The bankruptcy was a disappointment. They had just released a new line of motorcycles[R&D was the reason for taking loans], and they were getting great reviews but they hit the market a few months too late to improve cash flow in time to pay the bills and the creditors were rather inflexible.)

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