ARC8's Prototype Downhill Bike Uses a Sliding Shock Mount

Dec 1, 2023
by Matt Beer  
ARC8 Downhill bike prototype

ARC8 is a boutique brand based in Switzerland, best known for eye-catching paint schemes on their carbon XC and trail bikes, but recently at the Craft Bike Days, they brought along an alloy prototype with 200mm of travel. Massive plates support the front triangle while housing a sliding mechanism that actuates the shock.

ARC8 Downhill bike prototype
ARC8 Essential Mountain Bike Connection Winter - Rupert Fowler
The sliding bars are used to control the leverage rate and the two plates, which are bolted to the front triangle, allow for faster turnarounds when testing various pivot locations.

Similarities between the raw finish and suspension mechanism might draw you back to Yeti’s Rail-series of bikes, but this isn’t ARC8’s first go with a sliding shock. Their shorter travel bikes, the Evolve FS XC and Essential trail bikes use a production version of the system.

Jonas Muller, part-founder of ARC8 went on to explain their design ethos, “The main features are the two plates that are bolted to the down tube and top tube which incorporate all the suspension points and the BB. This allows us to independently change any suspension characteristic or geometry number by changing those plates, which are relatively inexpensive water-jet cut parts.

The current pivot locations and rail system produce a rising rate that is linearly-progressive. Along with the plated mounts, the rail system allows ARC8 to tune the kinematics.

The geometry on this prototype in particular has a 465mm reach, 622mm stack, and a 62.5-degree head tube angle. It’s also rolling on dual 29” wheels with 450mm chainstays and a 25mm BB drop - standard numbers according to Jonas.

bigquotesIt is really simple to individually tune travel, progression, anti-squat/anti-dive with that system. In current form we have 200mm of rear travel, but anything is potentially subject to change with this project. Jonas Muller

ARC8 Downhill bike prototype
ARC8 Downhill bike prototype

ARC8 Downhill bike prototype
Bjorn Aeschlimann of Dead Rabbit Bikes built this prototype in Switzerland using 7005 alloy on the welded sections.

ARC8 admits this layout isn’t necessarily their best work because the bike is far from production. As it stands, the design team has decided that this is the optimal construction method to reach their goals.

There’s no timeline for the development of this bike and since it’s still a fresh idea, pricing and availability isn’t on their list of top priorities yet. A final version will likely look entirely different and may not follow suit with the rest of ARC8’s bikes using carbon construction either.

Will ARC8 have a World Cup downhill team in 2024? Racing is the main focus of this project and a creating team is something they would like to build towards. They’ll be drawing on a past World Cup winner to provide feedback in the meantime.

ARC8 Downhill bike prototype


Author Info:
mattbeer avatar

Member since Mar 16, 2001
352 articles

75 Comments
  • 117 2
 Yeti 303 2023
  • 8 1
 Beat me to it.
  • 27 1
 naild it... it worked great on that bike, I'm sure it will also work perfectly here and will never be impacted by frame tolerances or dirt/grime.
  • 2 10
flag itslightoutandawaywego (Dec 1, 2023 at 13:54) (Below Threshold)
 2nd’d!
  • 5 1
 ARC8 bringing it back to 2003 baybayyyyy
  • 1 1
 Yeppp!
  • 5 2
 Switch infinity and Beyond!
  • 49 2
 The really big question is when does the Christmas advent start... Been waiting all day for it to pop up, still waiting!
  • 24 0
 Looks like it has gone the way of the Fantasy League.
  • 19 0
 @nozes: the same like "comment of the year"
  • 6 0
 I'm still waiting to see if I won
  • 3 0
 @bushbush: this was our year for sure! tup
  • 4 0
 where is the photo contest?
  • 2 1
 @mikelevy care to comment!?
  • 9 0
 Chances of winning stay the same.
  • 34 8
 Some shocking technology at work here
  • 8 8
 I will have to slide my mind around this one
  • 4 3
 Are cheap plates the best to have a test at your new recipe?
  • 1 2
 @fautquecaswing:
If you give your patrons food poisoning, the flatware will be the least of your worries. Smile
  • 2 2
 Let's hope it's not cracking technology like some of their other bikes en.brujulabike.com/frame-break-bottom-bracket-area-pure-power
  • 11 0
 There's something when it comes to desing and manufacturing. The two-plate construction is stellar in its simplicity while having the suspension pivots and BB all in the same plane and accurately dimensioned as well.
  • 1 0
 I found the idea interesting too first. I agree with you on the fact they are in the same plane as long as the plates are not screwed on the rest of the frame. I am not sure how precise the frame mounts could be accurately welded to the frame. Even if they are perfectly placed on the jig, they may not longer be well align after welding.
  • 1 1
 @labourde: I think you are looking at it backwards from an alignment standpoint. Since the top tube is only welded at one point(the headtube), the big, accurately machined plates can probably slightly flex the top and bottom portions of the frame into alignment with themselves. And all the mounting points for the suspension are located on the plates, so if anything this suspension system is probably more accurately produced than a tube frame with all the pivots/shock mount points being separately welded to the left/right sides of a round tube. Thats just how my brain visualizes it being produced, who knows
  • 1 0
 @labourde: Indeed!
  • 2 0
 You can also weld on oversided mounting points and machine them after welding. Not sure how many manufacturers do this, but its the only way to archieve good tolerances.
  • 1 0
 @endoplasmicreticulum: If you put your mind to it, you can archieve anything!
  • 12 0
 They just announced their race team is sponsored by Loctite.
  • 41 36
 "a rising rate that is linearly-progressive"

Who writes this shit? Linearly progressive? That's the definition of oxymoron. It's also redundant, the rising rate part tells us the ratios change, don't need to add progressive unless it curves, except if it's linear then it doesn't curve...

And rising (shock) rate is never used in mtb anymore (needs a very very rampy air shock or high HBO force), unless they're using that term from the wheel's perspective, but then the -gressivity wouldn't be progressive, it would be regressive.

A _flat_ line is constant, a straight line is linear, a line that curves towards the end rate is progressive (or regressive depending on if it's a rising or falling rate, and from which perspective: shock or wheel).
  • 54 1
 They mean the suspension is progressive, but the line of that progression is straight if you were to plot it on a graph from the first point to the last.
This is something many bikes strive for, if you follow Neko's Frameworks project this was a subject of importance he wanted to achieve.
You could have two bikes with the same % of progression but how the curve from 0mm to end travel can allow them to feel very different from each other.
  • 21 2
 It is indeed poorly worded, he probably means that the rate of change of the leverage rate is constant, or a quadratic leverage curve
  • 11 0
 @Mike-Rogge: Thank you. Calculus is useful as it turns out
  • 7 2
 It IS a thing, we just don’t refer to it in that way usually…

A coil shock is linearly progressive actually, as the amount of force required to compress it increases, but at a linear rate… equaling your straight line graph.
  • 14 1
 A suspension expert writes this stuff, my tinfoil homie! Progression can occur in a curved way or in a more linear way on a graph. Like the curve of any eclipse, this can vary. This is in reference to the shape of a line on a graph. In this case, the author is saying on a graph the line ramps up in a straighter, less curved way for a progressive frame.
Something tells me the author has a VERY good understanding of what both progressiveness and linearity mean....But that's just my ¢¢
  • 1 0
 @SonofBovril: If the force increases in a linear fashion, we call it a "linear" spring (probably ever since Hooke came up with his law hundreds of years ago). If it increases faster than linear, we call it "progressive", slower than linear "digressive".
If we then wanted to describe how the progressive it is, we might encounter that the spring ratio (Force/compression) increases linearly. One could then call this "linear progressive" as in the article, but we could also talk about the motion ratio and say that it increases which I find a lot more precise.
  • 3 0
 Short, exposed bushings not in line with the centreline of the shock feels to me like a recipe for friction and therefore uncontrolled extra damping. I absolutley see benefits of some aspects of this but simple sliders don't seem like a good idea.
  • 15 13
 Big fat nothing-burger.

Destined to be another 'innovation' that has no measurable benefit. Remember the Yeti sliding shock, cannondale driving the spring and damper via different links, um... what else in the innovation graveyard?
  • 2 0
 Yeti sliding anything?

Switch infinity isn't dead, but it's also only there because of patents
  • 51 1
 You're right. People should stop innovating so nothing ends up in the graveyard.
  • 14 0
 The sliding shock mount isn't really the coolest part of the bike. The swappable plates that are cheap(ish) to manufacture and can easily alter any kinematic or geometry number are far more interesting. The 303 didn't have that.
  • 1 5
flag flattire (Dec 1, 2023 at 17:23) (Below Threshold)
 @ljblk: If its ends up in the graveyard, was it an innovation? Or just marketing folks trying to sell you new stuff?
  • 1 0
 Kona’s air over coil?… shit… that was last month
  • 2 0
 @ljblk: the graveyard of mtb innovation is basically Stephen King’s pet cemetery: you just thought it was afu and dead….
  • 6 0
 tesla cyber bike
  • 3 0
 Standard geometry numbers for a medium sized frame. I really like it, I just hope it comes with more reach in an XL version.
  • 4 0
 Exterior Floating Piston, for extra friction!
  • 3 1
 Externally-routed cables Smile Much better than the Cable Tourism on some of their other bikes...
  • 3 0
 name it ARC 170 and use republic colors Smile
  • 3 2
 …absolutely not new - this is funtionally a Nicolai Trombone clone. A World champ DH bike from 1995…
www.mtbr.com/threads/what-model-is-this.694529
  • 2 0
 A love all these new prototypes and projects that have been coming out lately!!
  • 3 0
 Purely on aesthetics that’s a great looking frame
  • 1 0
 The purpose of the Sliding Shock Mount was to control leverage ratio. Still no leverage ratio graphs, like in many other reviews.
  • 3 1
 Finally space for 36 inch rear wheels
  • 3 3
 I'd love to see a compression video for this one... Assuming that the sliders run to the sides of the rear tire beneath the seat stays?
  • 1 1
 The tail ends of the slider rods appear to be fixed to what would typically be the seat tube of the bike, though the plate construction in this area means there is no actual 'tube' making up the triangle. I could see the construction style making this confusing, but the rods are fixed and the tire should never make contact with the 'seat tube', just like on your regular linkage bike.
  • 1 0
 @banjobiker789: To me it looks more like the sliders are attached to the frame where the seat tube would be like you said, but then that the rods run backwards through the sliders as they compress the shock. I'm sure I'm wrong though which is why a video would be helpful to visualise how this thing works!
  • 2 0
 @banjobiker789: I would have just said that the seat stays push the shock on sliders up the fixed rods (Which wouldn't be overly revolutionary). But I can't see how the seat stays have 200mm of travel on them as they look like the first weld point on them would impact against the frame within 50mm!
  • 4 0
 @bunjiman82: They don't have to move 200mm the shock is likely a 70-75mm stroke shock.
  • 1 0
 The photos of the DH bike aren't ideal to see what's going on there. Just take a closer look at the photo of their XC bike and you'll see how the rods are fixed in place with a shock mount sliding along them. Just like @Spencermon points out, that end of the seatstay itself must only travel the distance of the shock stroke, and there is certainly 70-75mm before it would run out of clearance and run into the plate.
  • 1 0
 It’s only a matter of time before PB slo-mo bucks it to flat; for your pleasure…oh, and science
  • 2 0
 "innovation"
  • 4 3
 "smart comment"
  • 2 1
 I like it, if it looks good it will ride good!
  • 1 0
 "hey, I've seen this one!"
  • 1 0
 What, no room fir a water bottle?
  • 1 0
 As something to look at at least it’s glorious
  • 1 0
 Craaaaasy brah, its like a yeti but “not?”
  • 1 0
 Looks awesome! Reminds me of the old yeti’s
  • 1 0
 i know at -40 air shocks get stuck down.
  • 1 0
 3 stictions are better than 1
  • 1 1
 Looks cool but how many people are really gonna buy it?
  • 1 2
 Did y’all see the start of the WC XC race in which the entire bottom bracket separated from the frame?
  • 2 0
 Yea, but it was a crash.
  • 1 0
 Are u Yet?







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