What's Going On With Commencal's Prototype DH Race Bike?

Jun 9, 2021
by Dan Roberts  
Behind the Commencal Title Image


Yesterday, Commencal pulled back the curtain, or should I say removed the blanket, on their new DH race bike, a prototype in the purest sense of the word.

This prototype looks to be allowing Commencal to test out their ideas for the future of their DH bikes at the pointiest end of the sport. If I had Amaury Pierron and Angel Suarez, to name just two of the racers aboard it, available to give my ideas as much of a testing as possible, you wouldn't have to ask me twice.

While there is a lot going on, and we'll get to some of those interesting changes, there are a lot of similarities with the current production bike. Commencal says that they've used lots of the same tubing to make this bike, which makes sense. Tubing moulds can be expensive and with current long lead times for everything down to washers and bolts it's good to use what you already have. And they do have quite the portfolio of bikes to pick and choose frame parts from, which is likely why some of the forged parts actually look quite finished. Maybe that or someone was burning the midnight oil when doing the 3D for this bike.


The new race bike.
Commencal Supreme DH 29 - 27 Photo Kifcat Shaperideshoot
The current production model, in mullet guise.

What's New?
Where we do start to see the changes is in the big CNC parts that go into making the suspension system. And that suspension system is quite the talking point of the new bike.

The production Supreme uses a high single pivot design, with two links used to actuate the shock. The shock is attached to the downtube at about 45°. The idler pivot is connected to the swingarm, meaning that its position, and influence in the suspension, is going to change as the bike goes through its travel.

This new bike, however, moves two steps away from a single pivot design and is a six-bar suspension system, closest to a Stephenson I linkage system. Some other notable six-bar designs include the Atherton bikes and the much mentioned Felt Equilink design, whose name is being thrown around in the comments and forums, as this new Commencal sits closest to this layout.

The new bike uses a six-bar suspension system, in a Stephenson I layout.
Commencal Supreme DH 29 - 27 Photo Kifcat Shaperideshoot
The production bike uses a high single pivot with a linkage-actuated shock.

Easily recognisable in the system once we overlay the kinematic are the seat stay (dark green), chainstay (yellow) and rocker (light green). Where things get interesting though is in the addition of the link between the chainstay and mainframe (blue) and the dog bone link (purple) between this aforementioned chainstay link and the rocker.

One other point to note is that it looks like the shock is connected to the mainframe. There has been some speculation that it might be floating, and connected to that lower chainstay link. But that link rotates clockwise at quite a rate of knots, so connecting the shock to it would mean that the lower shock mount would too migrate around quite quickly, requiring more compression of the shock from the rocker link to account for this lower shock mount movement. It does however have a flip chip on that lower shock mount to move the mount forwards and backwards, adjusting the progression of the system.

Commencal DH Race Bike Kinematic
Overlaying a more visible kinematic drawing might help you see all the links and pivots, and then imagine how they work as the bike is compressed.

As the rear wheel sees an impact, the whole seatstay part is going to begin moving up. This is going to push on the rocker and start it rotating while simultaneously pulling on the chainstay. This chainstay pull is going to start to rotate that small chainstay link. This then means that the purple link, connected to both the rocker and chainstay link, is going to be pulled up by the rocker but also pushed up by the chainstay link.

This purple link is, like all the other links really, a key link in the system. Remove it and the rear wheel would move around freely without ever rotating the rocker or compressing the shock, all the while still technically connected to the mainframe of the bike.

It's also an adjustable link. When we see flip chips in a bike to adjust the geometry and suspension, all we're doing is changing the geometry of the link that the flip chip sits in. For the purple link, that geometry change is the change of its length. And with it the whole bike changes its geometry, and so too the suspension. Extending the purple link pushes the rear wheel downwards, steepening the head angle, raising the BB, lengthening the reach and shortening the chainstay. Shortening the purple link has the opposite effect.

That purple link has two mount points too on the rocker. Seeing as the link is floating, and not fixed to the mainframe, then changing its mount point on the rocker is going to adjust how much rotation and at what point for the rocker and chainstay link as the rear wheel goes through its travel.


The dog bone link, that connects the rocker link and chainstay link, is adjustable in length.
The idler is now mounted on the mainframe as opposed to the production bike, with the idler mounted on the swingarm.

This new Commencal also changes the idler position too. A large plate, bolted to the mainframe, now holds the idler, meaning that its position doesn't change through travel like it did with the old bike. That means the interesting span of the chain to take into account when analysing the anti-squat is just from the idler to rear wheel. The span between the bottom bracket and idler has no effect, given that the two points are connected to the same frame member. The idler position is also much lower than the production bike, closer to the chainring.

This idler mounting change likely came about as a result of the other, more important, drivers of the frame. The seat stay has moved up quite a bit, and there are no other frame members in the vicinity that are favourable to connect the idler to. Idler stability is a big point - lots of bikes with single shear bolts on the idlers tend to suffer from problems. Lots of the designs with double shear, capturing the idler from both sides, fare a lot better under the high chain loads, especially if you're one of the racers sprinting with gritted teeth mid race run.


Why?
Well, this is the trickiest but also the most entertaining part. Speculating, or playing Sherlock Holmes, as to why Commencal has gone down this route is always good fun.

Firstly, they wanted to create an instant centre that they could manipulate. On a single pivot bike the instant centre is the main pivot, so it's a physical fixed point in space. On the production bikes the idler is fixed to the swingarm giving some freedom in designing the anti-squat characteristics of the bike. But things like the anti-rise were simply a by-product of the main pivot placement. That gives the production bike very high anti-rise figures and there isn't much Commencal can do about it.

Making the instant centre a virtual point gives them much more freedom in deciding its location in space and so, the anti-squat and anti-rise characteristics of the bike. That freedom, along with the construction of the bike, may have led them down the path to have the idler mounted on the mainframe.

The design still retains a high pivot, with it being way up there for the majority of travel. It does migrate downwards throughout travel, almost following the line of the shock, before dropping really low at the very end of travel. That does give the axle path more of a vertical trend, if you will. While it might never travel forwards of its starting point, it does begin to travel back towards it from about half way on.

Perhaps this was intentional, as one notable point of the truly high pivot bikes, like the production Supreme, is that completely rearward axle path. While it does mean that the axle path allows the wheel to move with a little more ease with the vectors of the oncoming impacts at the rear wheel, in the rebound stroke it actually moves pretty damn quickly back at them at a very aggressive angle. This might go towards explaining why the true high pivot bikes need a lot of rebound damping, especially high-speed, to control the fast returning wheel smacking into the oncoming impacts. It's often magnified too, with these bikes requiring a lot of spring to handle the bikes active tendencies, exacerbating the amount of spring force pushing back when deep in the travel.

Commencal DH Race Bike Kinematic With Bottom Out ICs
The kinematic at bottom out is added, in grey, along with the instant centres for each 10mm of shock compression, which show just how it migrates downwards from its initial high location. It also accelerates as the bike approaches full travel, getting lower much faster than at the start of travel.

While I can try and draw out the kinematic from a side on photo, the sensitivity of kinematics to small changes means that the exact pinpoint numbers on the suspension are very hard to nail down, especially with this short link design. But the general theme is there, and that's something we can report on. As this new bike goes through its travel, the instant centre drops down, slowly at first but then speeds up towards the end of travel. This slow change to quick end stroke drop off is a common trait of short link bikes, as the short links rotate around quite an angle. And with the six-bar design, that lower chainstay link really begins to accelerate as the bike nears the end of its travel. At the end of travel the instant centre might actually be getting pretty close to the ground.

It's also possible to see that this design yields a progressive leverage ratio. The movement of the wheel relative to the shock is quite a lot at the beginning of the travel, meaning a lot of wheel movement for a small shock movement. The two begin to get closer to 1:1 as the bike goes deeper into the travel.

Now why Commencal chose to use six-links to make their instant centre a virtual point instead of using four, much like the GT Fury and DH/enduro bike that we've spotted recently, is a little harder to speculate on. With the added freedom that the increased number of pivots and links bring, they also up the complexity, weight and potential for problems. One question that pops up is that with designs that are sensitive to small changes in pivot placement, how much can Commencal guarantee that what they're riding is matching up with what they designed? Aluminum construction can yield bigger tolerances in angles, lengths and pivot placement. But perhaps they're using some validation process, like 3D scanning, to understand exactly the bike that is being ridden.

Perhaps that added freedom is exactly what they are after and gives them the tools to explore all the ideas that they have for DH racing, and perhaps for their next generations of all their bikes. There is also a fair bit of adjustability in this bike, so Commencal has even more tools to test out a lot of different bike setups in one bike and with very short spaces in between runs to make the changes. With the added freedom of all the instant centres that a six-bar design gives that gives Commencal a lot to play with and learn from, perhaps feeding that into their later production bikes with suspension systems that are a touch simpler.

Amaury's bike has a rocker with two mount points for the dog bone, along with what looks to be a lower and further forwards idler position.
Whereas Angel's rocker only has one mount point for the dog bone and a very different silhouette. The idler looks to be higher and further back too.

There's also noticeable differences between Amaury's and Angel's bikes, with the rockers being very different and Angle only seeming to have one mount point for the dog bone link, whereas Amaury has two. The idler position is also very different in relation to the seat stay tube, Angel's is very close indicating that it's higher and further back. While Amaury's is lower down and further forward. That freedom in design of the suspension system that the six-bars are offering is perhaps giving Commencal the tools to fine tune and adjust to suit the rider's preferences and needs.

The beauty of this bike is that Commencal can do exactly what they want to, test ideas out at the highest level. As some of you have questioned, isn't there a UCI rule against this? Well, prompted by that very question a while back, our own James Smurthwaite researched to see if he could find this rule that means a brand has to eventually be selling what they are racing on. No such rule could be found and it seems to have been uttered by a brand owner once and the rumour started spreading.

But this is all just speculation from a bunch of photos. We'll likely see a lot more of the bike from more angles in the coming days now that the veil has been lifted, along with seeing if the fairly radical changes that Commencal have made add up to a winning combination. DH race season is on and I am as excited as a kid at Christmas.


142 Comments

  • 185 1
 You show me a cat shooting lazer eyes, I click. It's science
  • 7 0
 My thoughts exactly
  • 24 0
 Came for the cats as well. Left mildly disappointed. Lazer:cat ratios are suboptimal.
  • 16 0
 @VtVolk: how do you think the welding is done?
  • 1 0
 i missed the synthesizers. and space.
  • 2 1
 We must keep the likes right where they are!
  • 67 1
 Dan "Delivers" Roberts. Always on point and interesting to read your stuff!
  • 12 0
 This is the kinda shit I come to pinkbike for
  • 2 2
 @gtill9000: #metoo
  • 1 0
 absolutely!!!!!!!
  • 62 0
 so would you say it's more of a squish squish or a boing boing?
  • 16 0
 A man of many technical words I see.
  • 11 1
 I think the main benefit of the revised suspension system is that it allows for a full squoing.
  • 2 0
 Hopefully squish squish on the landing and boing boing off the lips
  • 2 0
 There are many ways to make the shaft go in and out...
  • 3 0
 @takeiteasyridehard: Your mother knows.. :-)
  • 13 0
 From the UCI rule book:
§ 2 Technical innovations
1.3.004 Except in mountain bike racing no technical innovation regarding anything used, worn or carried by any rider or license holder during a competition (bicycles, equipment mounted on them, accessories, helmets, clothing, means of communication, etc.) may be used until approved by the UCI.
§ 3 Commercialisation
(§ introduced on 15.10.1Cool
1.3.006 Equipment shall be of a type that is sold for use by anyone practicing cycling as a sport.
Any equipment in development phase and not yet available for sale (prototype) must be subject of an authorisation request to the UCI Equipment Unit before its use. Authorisation will be granted only for equipment which is in the final stage of development and for which commercialisation will take place no later than 12 months after the first use in competition.

As I read it, 1.3.006 does NOT make special exemption for MTB, the way that 1.3.004 does.
  • 3 0
 and the reality is that, as long as you make a new "prototype" before the 12mo is up, you are golden. see also: Intense Loophole
  • 1 0
 So they have to make it for sale with in 12 months, even if it sucks?
But how likely is that?
  • 1 0
 @aljoburr: It's never been a rule that's been enforced.
  • 13 0
 Really going out of their way to make sure people don't say it "looks like a Session"
  • 3 0
 I'm from the future. Everyone there says everything looks like a Fury.
  • 8 0
 "As the rear wheel sees an impact, the whole seatstay part is going to begin moving up. This is going to push on the rocker and start it rotating while simultaneously pulling on the chainstay. This chainstay pull is going to start to rotate that small chainstay link. This then means that the purple link, connected to both the rocker and chainstay link, is going to be pulled up by the rocker but also pushed up by the chainstay link"

Sounds cool but I think I'll just wait for a video of the suspension compressing.
  • 3 0
 Honestly that's all we need to see to understand. That coloured graph helped a lot, but come on. Video. Please.
  • 2 3
 isn´t it basically a vpp with a rocker?
  • 2 4
 @Gimli: Looks like a ?????
  • 14 0
 @Gimli: Actually you mean a DW Link with rocker (both links rotate same direction, whereas with VPP the links rotate in opposite directions). Regardless the answer is no. With VPP or DW Link the seat stay and chain stays are static in respect to one another. If you want to say something mildly discouraging about this I'd instead opt for "looks like a Horst Link got a DW Link knocked up, but since they lived in Alabama they couldn't get an abortion" Personally I think it's rad (the suspension that is, not Alabama).
  • 2 0
 @nzandyb: > Alabama


that's an odd way to spell Saskatchewan
  • 2 0
 @conoat: let's split the difference and say Alaberta
  • 2 0
 @nzandyb: nice!
  • 11 0
 What just happened???
  • 27 0
 i learned exactly nothing on how this suspension works. always happy to see lasers though
  • 6 0
 This reminds me when once upon the time I thought I can read (and understand) "Ulysses" by J.Joyce
  • 2 0
 @pakleni: I'd say about the first 80% of it is mildly understandable. After that the progressive dissociation from reality Joyce experienced (from his encounters with opium IIRC) start to show up and the book gets harder and harder to read.
  • 1 0
 @pakleni: I’ve read the first three pages at least a dozen times.
  • 10 0
 My bike is orange.
  • 1 0
 @calgarytrev they made room for a water bottle with the new suspension Wink
  • 2 0
 @kylar: We all did, my friend, we all did
  • 9 1
 Laser cats FTW
  • 5 0
 and still you can't get a shark with a fricken lazer on its head!
  • 2 0
 @neimbc: sharks are much more dangerous than kittens, cats probably know what to do with their lasers so they don't blind plane pilots and stuff. Common sense, SMH.
  • 2 0
 @imnotdanny: cats are way more evil than sharks.
  • 2 0
 @parkisatool: true, they would probably wield their superior intelligence to do ill in the world
  • 5 0
 “tekmology is whack” Smile
  • 2 0
 Booyakasha
  • 1 0
 whagwan
  • 5 1
 tekmeowlogy?
  • 9 0
 There’s this bloke round where I live, Rainbow Jeremy, who reject everything to do with science.
  • 2 0
 @dan-roberts: and check dis - he don’t have a telly
  • 1 0
 He ain’t even got a tele
  • 2 0
 @diegosk: He lives in the house though?
  • 2 0
 Is it good? Is it wack?
  • 4 0
 @Mondbiker: No, he ain't got no techmology. You can check his website!
  • 5 0
 I see space for a water bottle lol
  • 3 0
 Same. Ultimate über-Enduro bike! Or Bike Park bike. Throw a FitLock bottle on there. Also looks to be Burrito cavity on the downtube.
  • 2 0
 I came here to make the same comment. Hopefully an internal dropper is possible too. Sign me up for one.
  • 1 0
 @Afterschoolsports: Would smash! (into a pile of rocks)
  • 1 0
 This new DH bike looks fantastic! I'd love to own one. If only two peasants would be complementary with it, so that they can keep it clean and all lubed up for the next day ride. And Oh yeah they should also iron my shirts...
  • 1 0
 @dan-roberts: How similar is this new design compared to what the Canfield Bro's were doing with the Jedi back in the day? I'm sure it varies in someway's but is it close in concept?

Just trying to see how ahead of the curve Lance and Chris really were - that was a sic bike for it's time. I know I wanted one!
  • 3 1
 This bike is sexy af! Never thought I’d want to own a DH bike again after selling my TR450, but this, this is making me reconsider. This is one beautiful bike.
  • 4 0
 soooooo..... the bike go fast?
  • 2 0
 Regarding the rules of riding a non-production bikes... I thought there was a time frame of 12 months that a prototype can be raced. Maybe that's only from the roadies...
  • 1 0
 That's what I was thinking... are there rules similar to say WRC where you have to have a production version of what you're racing?
  • 1 0
 Yeah its a rule but uci doesn’t enforce it. Busier loosing their credibility on meaningless bs.
  • 2 0
 @parkisatool: UCI selectively enforcing rules? That never happens..LOL
  • 3 0
 UCI changed the rules 3-4 years back about a bike needing to made in a production run to punters.
  • 3 0
 How hard would Isak smoke everybody if UCI riders had to fabricate the frame they would race on by themselves?
  • 1 0
 Starting the idler pulley trend and continuing to push it forward, while also keeping a straightforward and seemingly easy to maintain bike like the furious in the lineup. I'm impressed
  • 1 0
 @dan-roberts any thoughts on the cloth on the seatstay bridge? It looks out of place like it might be hiding a bolt that can disconnect the bridge to give the rear end more flex
  • 1 0
 I'd suggest it's just to prevent metal to metal contact with the seat tube at full travel. But I've been wrong before....
  • 3 1
 I sure do feel like Dw and his DW6 suspension is gonna have something to say about this.
  • 1 0
 They’ll probably read the notes from the Giant/Maestro court case and tweak it just enough if they do release to the public
  • 1 0
 I think the spacing between the 'secondary' links (DW6 has them tucked very close together behind the BB), deliberately high IC, and use of an idler are probably enough to avoid legal stuff (though I'm nowhere near an expert on that sort of thing)
  • 5 0
 @theshortestcharles: You may not be an expert, but don't sell yourself short... you're a Pinkbike Commenter!! I pretty sure anything you say (type?) can be used as evidence in a court of law.
  • 1 0
 Please note that european brands (YT, Canyon, Rose, Radon,...) were able to sell FSR bikes (in Europe) before specializeds patent expired as european patent office stated something like "different suspension designs basically do the same thing (compress a shock during an impact) a bit differently so they are more like a variant and not really an inovation and therefore cannot be patented". EU intelectual property laws are somewhat different compared to US, and we know Commencal is not primarily US brand. And btw this is way closer to Felt Equilink design compared to DW6.
  • 1 0
 @winko: I am going to just throw out there that they layouts are identical save for the “equilink” portion not being on dw6. Felt’s pivot on metal bikes is above the rear axle, not below like dw6 or com. Save for a little lower link trickery in wheel path, it may be something dw6 solved that commencal needed the link to achieve from a stability POV. Either way it doesn’t matter if DW’s claims on patents cover something ludicrous like a specific virtual pivot path or layout, still wins in a court of law. I.e. knolly lawsuits on seat post to bb location.
  • 1 0
 While both designs are 6bars, there is a whole world of difference on how they work. DW6 mounts both lower links to the mainframe, so their combination "guides" chainstay, while commencal mounts one on the frame and second connects to the upper link. So except of both being 6bars I see very little similarities. I doubt this would hold in US and no way it would hold in Europe (principle is identical to the Felts equilink so it is not really new and can therefore not be patented in Europe). And Knolly droped that lawsuit and didnt even bother issuing a comment because they probably realised how pointless whole deal was.
  • 1 0
 What this will all come down to is how good are Myriam, Amaury, and the rest of team at working with their mechanics/engineers on setup.
  • 4 0
 Not in stock - TYPICAL!
  • 1 1
 Uh.... It's a PROTOTYPE.
  • 2 0
 @rosemarywheel:

What is this? A prototype for ANTS!
  • 2 0
 Great article and nicely written, but needs improvement in the Lasercat section
  • 1 1
 Maybe the cycling industry never played hockey?
A mullet is little up front and lots in the back.
Not the other way around. You are running a reverse mullet with a big wheel up front.
  • 5 0
 But it's business up front and party in the back. I'd argue 29 is business (front) and 27.5 is party (back). So mullet is accurate.
  • 1 0
 Nice graphics Dan! That's some good overlaying from the profile shot. Look at that axle path, damn vertical, just like I guessed, haha!
  • 1 0
 This is the right amount of pivots. I'll accept no fewer.

Actually, I take that back and recommend applying n+1 here.
  • 2 0
 Where are the dogs with fricken laser beams attached to their heads?
  • 2 0
 Look like Atherton Bike !?
  • 1 0
 The last gen was a super winning bike - they must be really confident in this design to replace it. Can't wait to watch!
  • 1 0
 You thought the 6 bar was hard to understand? Wait till they come up with an 8 bar.
  • 2 0
 I just realised I need DH bike again
  • 1 0
 Just one? Wink
  • 1 0
 @rosemarywheel: yeah, no more space in bedroom
  • 1 0
 So it's a take on DW-6?
Also what rear axle are they using? Better be 148! How long are the CS; 470?
  • 1 0
 If I was going to have sex with a bicycle, it'd be this one. Hot damn, that's sexy
  • 1 3
 "Now why Commencal chose to use six-links to make their instant centre a virtual point instead of using four, much like the GT Fury and DH/enduro bike that we've spotted recently, is a little harder to speculate on."

Not super hard, obviously this gives them even more control over the instant center.

Pretty sure weight is not really a major concern for something like this, it's all low, and even with a beefy alloy frame, it's probably not going to be anything insane with modern parts.
  • 1 0
 Looks very cool.
Too bad there's nowhere near me that would be worth riding a DH bike ):
  • 1 0
 Hey Scott... good job hiding the shock inside the frame, but I think it's more important to focus on this.
  • 1 0
 That's the Felt Equilink design found on the Compulsion with an idler and more adjustability.
  • 1 0
 I'm Mr peirron will make it go super fast!
  • 2 0
 hi felt!
  • 1 0
 Whether you like it or not commencals are fast whatever they come up with
  • 1 0
 A very informative article, indeed.
  • 2 0
 Great breakdown!
  • 1 0
 just like a Suzuki RM250 from the '80s.,,with one extra link.
  • 1 0
 That thing will be fast as fuck.
  • 1 0
 So... is it faster than a basic 4 bar horst type setup?
  • 1 0
 Looks like a session and a demo
  • 1 0
 "The idler pivot is..."

Idler _axle_?
  • 1 0
 and all this tech, still makes you no faster
  • 1 0
 Felt suspension anyone? ;o)
  • 1 0
 We just needed that pic. Thanks
  • 1 0
 And no water bottle gussets in the front triangle Frown
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