Specialized Granted Patent for Linkage Fork Design
Specialized has been granted a patent titled "Simplified gas spring setup for a trailing link cycle wheel suspension," which relates to an air spring design for a linkage fork. The inventor is Dave Weagle - the same Dave Weagle behind dw-link suspension (among many other designs) as well as the Trust Shout and Message linkage forks which we've already reviewed. The design of the fork depicted in the patent is very similar to the two forks Trust developed before the company ceased operations in April 2020, citing a lack of cash brought on by the coronavirus pandemic. The main thing which makes this patent so interesting is that the applicant is Specialized Bicycle Components.
According to Weagle, when Trust closed their doors an intellectual property portfolio was put together and then sold in order to cover the company's liabilities. That means Specialized now has the patent on the design Weagle created, and can implement it however they'd like, or even put it on hold until the right opportunity comes up.
While Weagle's name is on the patent, he's not involved with Specialized's plans at all, and wasn't able to shed any light as to when (or if) this design might hit the market. Given all of the time and effort that went into creating the original Trust forks, he said, "I'm just happy it didn't get completely mothballed."
The fork described in the patent looks a lot like the Shout and Message forks from Trust Performance.
Specialized have history of developing their own in-house suspension. Who could forget the 2007 Specialized Enduro with its Specialized-branded shock and 150mm-travel dual-crown fork? Not to mention their Brain inertia-valve technology used in their cross-country bikes. So perhaps "The Big S" is planning on developing an in-house linkage fork based off of Weagle's designs. The Trust Shout and Message both showed potential, but had their faults, not least of which was the hefty price tag. Perhaps with the capital, scale and expertise of Specialized, the full potential of the linkage fork will be unleashed at a more reasonable price point.
Could Specialized be working on innovative in-house forks? It wouldn't be the first time.
The fork has a damper and an air spring in one side and a (larger) air spring in the other.
As for the patent itself, the fork described shares a lot with both of Trust's forks. It's a trailing link design, meaning the axle sits behind the main body of the fork, and moves in an arc that curves back and then up as the fork compresses. This means that in the middle of the travel the fork offset is shorter than at the start of the travel, which results in greater steering stability (trail) when the fork is compressed. It's a four-bar linkage, which makes it possible to adjust the amount of anti-dive to help it resist compression under braking compared to a telescopic fork.
The fork has a damper in one leg, which sits below an air spring that operates in-line with the damper. A second air spring is housed in the opposite leg. The two springs mean the rider's weight is held up at both sides of the axle, which reduces the twisting force on the axle compared to a single spring. This is important given there's no arch to help keep the two dropouts from moving interdependently of one another, so if there was a spring in only one leg, the wheel would exert a twisting load on the fork chassis .
The shock absorber has a damper below an air spring using the same shaft to drive both the damper and spring piston
The piston area of the air spring in the non-damper side (B-B) is larger than the damper side (A-A), helping to balance the compression forces from the damper.
All the above is shared with the Trust Shout and Message, but the patent underlines that the springs in each leg are not identical. The unit containing a spring and damper is referred to as the shock absorber, and the spring in the other leg as the spring unit. The spring unit has a larger piston area than the shock spring. This is to increase the spring force on the spring-only side, compensating for the damper on the other side, which adds its own force depending on the compression speed. The idea is to make the forces more equal on both sides of the axle, at least at some compression speeds: "the first gas piston area (110) is less than the second gas piston area (111), which allows for a more equal force output between the shock absorber (44) and the spring unit (48 ), which helps to distribute forces more evenly in the linkage and avoid the detrimental results of angular wheel displacement."
Patent documents are written to keep the inventor's options open, but it sounds like the spring-only side will have around 25-30% more piston area, so providing that much more force for a given air pressure. "In some embodiments, the second gas piston area is between 2% and 300% larger than the first gas piston area ... In other embodiments, the second gas piston area is preferably between 15% and 100% larger ... and even more preferably between 25% and 30% larger than the first gas piston area."
Presumably, they could achieve this by increasing the pressure (by around 25-30%) in the spring-only side, but the patent focuses on ease of setup. The different piston areas balance the forces at the same pressure, so the user doesn't have to do any calculations. In fact, the patent suggests the piston areas could be fine-tuned so they offered the recommended spring stiffness when set to the same pressure (in psi) as the rider's weight (in lbs): "The disclosed simplified wheel suspension assemblies are designed to use a first gas piston area and second gas piston area that are sized so that when the suspension assembly is installed on a cycle, the gas pressure inside the shock gas spring 92 (for example when measured in PSI (pounds per square inch)) is equal to a recommended or predetermined pressure that produces an optimum ride for the user's body weight (for example when measured in LBS (pounds))". So for a 160lb rider, just inflate the springs to 160psi and go ride.
The patent goes on to claim that "The disclosed wheel suspension assemblies can be designed to be lighter in weight, lower in friction, more compliant, safer, and perform better than traditional wheel suspension assemblies ... [and] also reduce stiction and increase stability during braking, cornering, and shock absorption, when compared to traditional wheel suspension assemblies." These are similar to the claims made of Trust's forks, although the Message and Shout were a little heavier than their telescopic competitors at the time.
Finally, the patent suggests the fork may be particularly suited to e-bikes, so perhaps that's where the fork will end up, if we ever see it: "E-bikes are heavier and faster than typical mountain bikes. They are usually piloted by less skilled and less fit riders, and require a stronger front suspension to handle normal riding conditions... The beneficial caster effect described above with respect to the disclosed wheel suspension assemblies is an important improvement over traditional wheel suspension assemblies and reduces some of the drawbacks of E-bikes."
Disclaimer
I haven't read or heard anything about this other than the patent documents themselves, so I don't know anything about it other than what I can glean from the publicly available patents. I've reached out to Specialized for comment and clarification but so far haven't heard anything back.
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it a…never mind.
I liked a lot about the Message, but it also could feel pretty harsh over rough ground or high-frequency impacts, and we mountain bikers are used to the supple smoothness of traditional suspension. Specialized would need to improve on that, for sure, and maybe do a hell of a marketing job...? I'm interested!
"so efficient"
So Mike, rumor has it you guys had a Motion E13 + in your grimy lil' paws ... what did you think of it?
Imagine the love child of a Motion fork and a Trust fork
FSR stands for Future Shock-Rear, from back in the day when Specialized had their in-house Future Shock fork on some models. #themoreyouknow
I ride a Message and Shout fir a season plus, had a Motion E13+ for two months.
For big hits I liked the Shout best, for flowy smooth terrain I liked the Message best, but for all around I’d put my money in a Motion.
That Motion has a very cool damper, it’s harder as to turn by hand, and it’s not that sophisticated, but it works well and it’s zero maintenance for years.
Consider the Wright and complexity of the linkage forks, a leaf spring, torsion spring, or coil spring is a better bet. The Motion leaf spring was solid and functional, easy to set preload.
Maybe Bike Monkey would let you have it again now that you’re well?
Nevertheless I still like the brand and this fork is a perfect match for high pivot designs on the rear if you want active, sensitive suspension. Just have to have the right damping so it doesn't dive or move too much when you don't want it to.
Although personally I think you should just get a an xc bike at that point, but apparently the gravel crowd are willing to jump whatever hoops they can to remain apart from mtb as the whole Sram Xplor range points out
Buying the rights to the Trust IP saves them a considerable amount of time in R+D and testing, as they have a product that has been manufactured and proven, but might need further refinement, as this new filing indicates. It's shaved years off their development cycle and might have even saved them money, depending on the cost of the portfolio.
What they do with this fork is the big question. I think Levy is right in saying that aftermarket Spec products, save for basic accessories, are not widely-adopted enough to make this a viable aftermarket product, but I could be wrong. Based on the language in article, I'm going to guess that it shows up on Enduro-ish eBikes first as a way to firmly distinguish the eBike category from its non-electric forebears. It makes salesfloor and catalog marketing easier when you can point to a big visual difference in something and do the "you see, eBikes are like THIS while other bikes are like THIS."
As for my own bike. I like linkage forks and I hope this does go aftermarket at some point, but with Spec's track record on that, I will not hold my breath.
That's not what the marketing department says!
Right after it: "In many cases the electric parts are large and unsightly"
Some Electric Trolls here won't be happy......
"The disclosed wheel suspension assemblies are particularly well suited to E-bikes. E-bikes are heavier and faster than typical mountain bikes. They are usually piloted by less skilled and less fit riders, and require a stronger front suspension to handle normal riding conditions. E-bikes are difficult to build, requiring the challenging integration of motors and batteries into frame designs. In many cases, the electric parts are large and unsightly."
Anecdotally, I've found on steep downhill they're the same speed but on less steep they're slower. All of my top to bottom DH times on eeb vs analog the eeb is always a tad slower.
Also, who cares about the patent. Companies take over patents all of the time.
T-Mobile Pink is another similar example. I'm going to guess that McDonald's Yellow and Red are also covered, but I don't have to time to look that up right now.
Because that is what Specialized is know for, right?
(Yes I own a new Enduro… Comp)
Surely this is offensive in this day and age! hahahaha.
The objective, rational side of me said: "It actually works, and does so very well."
The subjective Pinkbike forum fanboy who shoots his mouth off first, does his homework second says, "Hell naw, I ain't riding that, my bikepark bros would totally dis me."
There was another one recently that you still haven't covered.
So when you post this will you cite PB since you are obviously copying them if you post it now?
Ain't that the truth!
( jokes. I actually liked the way the Trust looked)
If there would be better practical solution like then the tradional for design, the enduro, motocross, motoGP, superbike...every motorsport would used it, but all of them uses the traditional supsension type.
Nice try from Specialized, but it will be a big failure IMO
What do you do if no one trusts your design? Paper over people's worries by calling yourselves TRUST, of course. (That said, I was and am enthused about these forks.)
Linkage forks are similar although this one has multiple internal damper pieces.
If you want to see the potential positives a linkage fork has, see this article:
m.pinkbike.com/news/review-six-months-on-structures-wild-looking-cycleworks-scw-1.html#descending
Quote from article: "The linkage suspension on the front of the SCW feels impossibly smooth throughout its travel, almost enough to make me think conventional forks are filled with a 50/50 mixture of sand and maple syrup for lube"
1. All telescopic MTB forks are by necessity nearly identical (many of them even use the same SKF seals in different diameters for example), whereas there's a huge variety of possible configurations and executions of a linkage fork, so even the term "linkage fork" is about as generic as saying "bike frames". Some frames have very few issues, some have many, it depends on the details of the design and execution, so it seems reasonable to expect the same variations within linkage forks, and tarring them all with one brush isn't likely to be accurate.
2. There's a ton of telescopic forks on the market that are sold at enormous scale that all have to deal with all the issues mentioned (with varying degrees of success), so we (as a market/industry) have seen exactly what does happen, whereas with linkage forks that don't really exist on any large scale currently all we'd be doing is speculating. I don't think it's really reasonable to say that linkage forks necessarily have more things that can go wrong though - my telescopic forks have usually required more maintenance than my frames' linkages + shocks, but a couple of less-than-ideal frames and shocks have been the opposite too. A well built linkage fork might be the most reliable fork out there, but a less well-built unit might be a total POS too.
I think what @mdinger said is pretty accurate though (and having ridden the Structure I'd agree that it straight up outperforms telescopic forks). I'd love to see someone do a stand-alone linkage fork well, but I think it's a lot harder than a telescopic because you have way more variables to balance, and even if you got the performance, cost, weight, reliability etc right, 90% of riders still wouldn't be interested, partly because of healthy skepticism, partly because of unjustified cynicism, and partly because it's just kind of jarring to try to get your head around a bike that looks that different.
We have many tens of thousands of hours on our WTF Linkage system, and stand behind it with more confidence than ever. It's tough, smooth, slack when you need it; steep when you need to maneuver, and best of all has no bushings, seals, oil, springs, or dampers in the fork at all. Many of our bikes have thousands of hours on original frame bearings. We also know with zero doubt which suspension type requires more service, and it's not ours.
Nice to see Specialized pick up the Trust patent, and we hope they'll release models with linkage forks as optional.
That being said, we are *extremely* confident in what we're doing at Structure and have big plans for full-linkage bikes of many model types in the future (apologies to the haters)
If you increased the stiffness of the bearings, wouldn't the need to have springs on both sides reduced? Like if it was built as a single sided lefty for example.
Spesh like doing their own suspension forks/shocks for one reason only - cost. Buying the intellectual property from a failed venture just underlines this.
- Trust me: We Can!! And if we put a "BRAIN" sticker, it'll be another grand!!
patents.google.com/patent/US5899478A/en?oq=woodside+terence
I'd put it on if there was no weight penalty and no price difference. Which means I'm safe for... ever.
"E-bikes are heavier and faster than typical mountain bikes. They are usually piloted by less skilled and less fit riders, and require a stronger front suspension to handle normal riding conditions... The beneficial caster effect described above with respect to the disclosed wheel suspension assemblies is an important improvement over traditional wheel suspension assemblies and reduces some of the drawbacks of E-bikes."
I don’t think any of this true - less experienced rider and faster??? There a lot of us who ride both. It’s a different sport let’s start with that and it ain’t dirt biking - it’s just a new thing one day people will get it and not make stuff up, until than faster and ridden by novice jk.
The only reason you’d ride a heavier bike is because it doesn’t matter:
1) an ebike
2) a downhill bike
It’s okay to be a good rider on an ebike and either be out of shape or injured, but don’t pretend that skilled healthy fit folks ride ebikes cuz that ain’t the truth.
Trust forks (I’ve owned both a message and a Shout) result in LONGER trail, thus more stable handling.
It’s a lot to wrap your head around, but google some of the explanatory articles from 1-2 years ago.
They were REALLY onto something. I hated to see Trust fail. : (