X-Fusion Prototype Details• Single crown, inverted design
• Travel: 160mm
• Air sprung
• Uses twin-tube HLR damper from Vengeance
• External adjustments: rebound, separate high and low compression, air pressure
• Weight: 4.3lbs (
claimed, prototype)
• Availability: TBA
• MSRP: TBA
X-Fusion's stock has been on the rise ever since riders began to catch on to the impressive performance of their HLR damper-equipped Vengeance fork. Admittedly the underdogs in the suspension biz, the Vengeance equalled, if not surpassed, the performance of more expensive offerings from the competition. While the Vengeance's travel has been upped to 170mm, X-Fusion has also been working on another project that slots in the same realm: a 160mm travel inverted fork for the aggressive all-mountain crowd.
Anyone who has ridden an inverted single crown (remember the single crown Shiver or Dorado?) knows while there are advantages to the upside down layout, torsional flex is simply too much of an issue to make the chassis a contender. Having said that, talking to X-Fusion at Eurobike gave us the impression that they are quite confident in the prototype's stiffness, with them also admitting that there is some internal trickery going on within the tubes that greatly ups the fork's rigidity, although they wouldn't go into detail.
Time to speculate? Of course. The fork employs a standard sized 20mm thru-axle, as well as somewhat average diameter stanchion tubes, and we're betting that it also uses a typical dual
bushing layout inside of each leg. The answer, we think, lies in an interlocking shape on the upper portion of the stanchions (hidden from view within the upper tubes) that mates with the upper tubes. This arrangement would greatly reducing twisting under torsional loads, allowing X-Fusion to build an inverted fork that approaches the torsional stiffness of their burly Vengeance, but without the added weight that would usually be required to meet that goal. X-Fusion was mum on the topic, and we're simply making an educated guess, but this design would be one of the few ways of building a 4.3lb (claimed) inverted, single crown fork that is stiff enough for aggressive riders. There would obviously be challenges when it comes to having the shaped sections slide smoothly within the upper tubes, but we're betting that X-Fusion has come up with a remedy for this.
Why would X-Fusion, among others, pursue an inverted design, especially when it presents such a design challenge? It boils down to less unsprung weight (
mass not supported by the suspension) that allows the suspension to react quicker to impacts, with another plus being that the fork's lubrication oil is likely to spend more time around the seals and bushings, thereby keeping the fork running smooth.
The prototype fork is fitted with X-Fusion's HLR damper, the very same unit that has proven itself within their high-end Vengeance offerings. External adjustments include separate dials for both high and low-speed compression, as well as a rebound adjuster at the top of the fork. The twin-tube HLR damper has shown to be among the best out there, leaving X-Fusion with the task of designing a new inverted chassis and dropping the HLR unit into it. When will we see a production version of the inverted fork? Will it actually make production? We don't have the answers to either of those questions, but we're crossing our fingers that we get to try it on the trail at some point soon.
www.xfusionshox.com
www.cyclingnews.com/features/photos/new-suspension-bits-plus-more-parts-for-road-and-cross/11902
gallery.mtbr.com/showphoto.php/photo/36026/size/big
If these are as stiff as X-fusion claims, they could be onto something. They have tough competition from the 36 Float though.
Well considering inverted forks were ridden the hell out of in the original Rampage comps, and many people ride gnar daily on them.
Questions? www.pinkbike.com/video/14844
I can guarantee 99% of pinkbike doesn't go big. Sure these guys aren't "pro" big, but they still hack it more than the majority.
Speaks for it's self. USD forks are epically strong.
i completely forgot about the new lefty
Build it, I'll sell my 2011 Float 36 RLC.
Are you listening FOX? and maybe XFusion will sell me internal parts so I can work on it myself...
I'm more of a motorbike guy and when I got back into pushbikes a couple of years ago I was confused by all this talk of USD forks being flexy. I guess maybe for a given weight they could be, but when ultimate stiffness is concerned a RWU design cannot compete with an USD layout.
In motorsport, performance is more important than weight. I think it's the same with DH. The big boys should all be doing USD. So what if it weighs 500g more? If it works better and looks better people will still buy it.
Street forks are pumped so stiff that they only move under impact, it isn't going to make your commute to the skatepark easier. DJ, maybe.
The average rider could get away with it. 4X, yeah why not. But a Fox 32 doesn't last a month under a rough street rider. Is this fork 32 or 36mm stanchioned? If it's 32mm it will snap like a noodle.
Not saying people are buying them, because who would, but you can still get them.
Even if they weren't though, it would still be a pretty big risk coming out in the bike world with only inverted designs.
AWESOME, but a risk.
Magnesium cast lowers are so light that there would be little to no difference in performance, especially when you add the weight of the wheel and, especially, a DH tyre. I was going to write an article on this subject and, well, riding got in the road but what contact I did have from a fork manufacturer put the advantage down to oil on the seals, not unsprung weight. I can forward you that email if you like.
This "less unsprung weight" is passed around in this article as if it is a proven fact, but I am yet to see the proof.
You guys all drank the marketing koolaid propaganda that the MTB suspension world promoted to keep R&D costs down. I have ridden so many different forks since I started riding in 1982 (not a typo) and cannot understand the sheep mentality in believing the crap. Fox's latest leaked prototype was just more of the same. How many Dorado owners complain they have poor tracking on their Dorados? None. They just smile when people clamp the wheel and turn the bars claiming excessive flex.
Shiver DC: 1lb heavier than a Fox 40,
white brothers: 2 lb's heavier,
Dorado: had to use carbon fiber uppers to get it to a decent weight,
Foes F-1 XTD: I couldn't find a weight, but I believe it's heavier too.
It's worth the extra weight, in my mind: been riding a shiver for almost a decade. But lots of people look at that number to exclusion of all else.
As for flex, the one's I have expienrience with could all have been made stiffer with some design tweaks that were obvious to even me, so I'm not surprised that they might be able to make this work.
motos have plastic guards on the stanchions, on a mtb because there is no engine sound , those guards will flap around and make some irritating sounds!.
hah made me laugh on that yz450 you should try the roost from a kx500R (not a fun being behind of, but kickass being on one!), other than two wheels, handlebars and a chain moto's and mtb have nothing in common, so please do not compare them!.
Again - 2001 Shiver SC was inverted, had 4" travel and a lockout > Ten. Years. Ago.
And keep your bike stored upside-down kids. Keeps the seals lubed and slickery.
The point is still, by removing the middle arch of a standard single crown fork, you lose considerably more torsional stiffness than any "internal trickery" can make up for. I would have to actually see big weight savings in unsprung weight to even think about going the inverted route. Granted, I haven't ridden anything USD since the Shiver days... but I did own and ride both the single and double crown Shivers for long enough to know that they were ok, but yes.. noticeably flexy in hard corners and rock gardens.
Because you've had good enough bleeds, and good enough seals in your brakes that it didn't affect you doesn't mean that storing your bike in a manner that can leak air into the circuit is smart thing to do. Fork seals leak oil and make a slight mess if they dry out, air in your brake lines can cause your brakes to fade or fail at a critical time. your choice.
Or get an inverted fork.
The main point was about the loss of torsional rigidity from removing the middle arch of a conventional fork. I'd be more than happy to demo a U/D fork, and would be happy if it would change my mind. But until I see enough feedback saying that it is truly different than what has been hashed out in the past, I'll hold off on saying carte blanche that it 'will be my next fork' because it looks sexy. Having seen enough BS gear come and go, I want shit that works at least as well as claimed and lasts reasonably well with proper service.
It's giving me nostalgia for my old Shivers... ahhh. Just need some stanchion guards, maybe the old Shiver ones would fit?
Unsprung weight is the second advantage. There is less moving weight which allows the wheel to respond to bumps quicker.
There is less overhang at the axle, making hanging up in ruts, clipping rocks or roots, or stumps less likely.
You can use a smaller stanchion with the larger upper with the same rigidity. This results in less stiction from the seals and the bushings. Expensive coatings are not as needed, and SHOULD result in a lower cost in the final product. This also reduces the overall weight of the fork.
Disadvantages:
Slightly more torsional flex. This is only noticeable when trying to push a large object out of the way with the front wheel, (or twisting the fork with the wheel held stationary.) In rock gardens, the inverted design actually tracks better as the wheel can have slight motion under loads that won't be felt by the rider. Tracking is much improved because of this.
Closer tolerances are needed than a traditional design. Since the design is more rigid, loose tolerances result in binding. The fork on the 1992 Suzuki RMs had this problem. KTM 48mm forks in the early 2000s had this problem (from flexy sliders) as well.
Loose seals will weep sooner than a traditional design, as they are bathed in oil. This has been mistaken for shorter seal life, but they wear the same a conventional forks. You are just made aware by the weeping.
What DVO does with that strange contraption arch at the bottom, is only making the list of features longer - but it cannot stiffen the fork in any significant way. You can place a hemisphere there, and not much will improve, as it is the number of braces and their placing along the length of two rods that contribute to the stiffness of the whole structure. You don't see many electric line masts made of thick rods, with few braces in between - what you see is masts made of thin vertical elements with lots of bracing between them.
The only saviour of USD single crown forks might be the use of composites: a monopiece steerer, crown and upper tubes, all formed in a shape counter acting flex forces. It would look kind of like broad pants in officer shoes. Maybe that is the future, who knows? I'm all for it! But in such traditional form as this X-Fusion, it just can't beat the standard fork with arch.
Srsly, any ``internal trickery`` that might employed will never make up for the torsional stiffness that is lost by removing the middle arch. I am all for less unsprung weight but not at the cost of a fork that feels like a bowl of overcooked ramen noodles.
And as for better oiled bushings and seals - here`s a completely not-so-secret secret - keep your bike upside-down when you`re not riding. Your fork will thank you for it!