First Look: ARC8 Essential - A Light & Aggressive Trail Bike

Aug 15, 2022
by Dan Roberts  



ARC8 have been around for a few years now, but they're still a relatively small brand. That didn't stop them from raising some eyebrows back in May with the launch of their Evolve FS, a bike that blended a very low weight with properly aggressive geometry for the bike's short travel.

It didn't take a clairvoyant to see that the Evolve FS heralded a new direction for the brand and that their other bikes might just follow suit. The next bike to receive a makeover? The Essential.

The original Essential was the bike that launched ARC8 and was developed way back in 2016 as an aggressive trail bike for the time. But it also saw a lot of time in XC races thanks to its low weight.

Essential Details
• 29" wheels
• Carbon fiber front & rear triangles
• Slider suspension
• 120mm - 130mm rear travel
• 130mm - 150mm front travel
• M and L sizes
• 1800g frame weight (claimed, size M, without shock)
• Bike Pricing: €4,399 to €5,299
• Frame Pricing: €2,199
arc8bicycles.com
The new iteration keeps that same idea but leans on all the learnings from the development of the Evolve FS to drop the frame weight while upping the aggression of the bike.

Seeing as the Evolve FS and new Essential were developed almost in parallel, there's a lot shared between the two bikes. We dove a bit deeper into all the details behind the new Evolve FS, and so the new Essential, in our First Ride.





ARC8 Essential Mountain Bike Connection Winter - Rupert Fowler
The surface area in the mainframe and rear triangle was dropped considerably to shed a bunch of material and weight.
ARC8 Essential Mountain Bike Connection Winter - Rupert Fowler
The slider suspension system allowed more weight to be dropped by being a smaller package than a link long enough to give the same smooth leverage ratio curve.

Frame Details

The new Essential runs on 29" wheels front and rear, and instead of being fixed in its travel, ARC8 wanted to give some adjustability to the bike's intent and shape via the front and rear travel.

Rear travel can be between 120 - 130mm by changing the shock stroke and fork travel can sit anywhere between 130 - 150mm.

With the bike's light weight and aggressive chassis as a foundation, it allows the Essential to be built up as something with more of a focus on shooting up the hills while still being pretty capable on the downs, or something that swings more in favour of the downhills without compromising the uphill ability too much. All the while having the same light, direct but aggressive flavour in all the guises it can be built in, something that we experienced when riding the Evolve FS.

That lightweight chassis comes about from all the same developments as the Evolve FS. Frame surface area was significantly reduced in both the main frame and rear triangle while also eliminating pivot hardware by way of a flex pivot out back. And the slider suspension design played its role in eliminating weight too.

The compact slider design shaved weight when compared to a link long enough to get the same smooth suspension curves, while bolstering stiffness enough that ARC8 felt they didn't need a seatstay bridge.

ARC8 Essential Mountain Bike Connection Winter - Rupert Fowler
The mainframe is moulded in one piece and with a closed surface where the main pivot will eventually go. It's then post machined to make the window where the chainstay enters into the frame.
ARC8 Essential Mountain Bike Connection Winter - Rupert Fowler
The Essential uses the flat mount brake standard. Bolting the caliper directly to the frame, it uses a 180mm rotor. Adding in the adapter bumps it up to a 200mm rotor.

ARC8 Essential Mountain Bike Connection Winter - Rupert Fowler
The slider itself runs in polished and hard anodized rods, Norglide bushings and SKF seals to keep the dirt out. It's also a very simple component to disassemble and maintain.

ARC8 Essential Mountain Bike Connection Winter - Rupert Fowler
There are two mounts to take water bottles or essential gear for your ride, all protected from mud and debris on the inside of the mainframe.
ARC8 Essential Mountain Bike Connection Winter - Rupert Fowler
The top build uses the Faserwork, ARC's in-house component brand, Baselerstab combo as well as internal headset routing by way of a custom Acros headset.

The slider suspension design is a single pivot layout and uses a 230mm long shock that can deliver between 120mm and 130mm of travel by changing from a 60mm stroke to a 65mm. This results in very low leverage ratios, as normally this length stroke would be used to develop 150mm to 170mm travel bikes. Again, this is a concept carried over from the Evolve FS and means that very low pressures are needed to achieve the correct sag.

The Essential was designed with air shocks in mind, but can accommodate those with piggy backs for builds that are more descending focussed. But, if you find more fun in blasting up the climbs it's also possible to use a remote shock lockout on the Essential.

Other frame details carried over from the Evolve FS include the threaded bottom bracket, room for up to 2.6" tires and flat mount disc brake mount, that works with 180mm rotors out of the box or 200mm with an adapter.

There's room for water and gear storage via the two mounts on the downtube, mounts for an upper chain guide and space in the frame for a whopping 38 tooth chainring, on a 55mm chain line.

SRAM's UDH is out back and all cables are internally routed. They enter via the headset, and that's all that will be said about that.





ARC8 Essential Geometry

Geometry & Sizing

The Essential comes in two sizes, M and L, which actually line up closer to other brand's L and XL sizes in length. As is with the Evolve FS, ARC8 found that they could fit a wide range of rider heights and styles with just two sizes and so dropped the S size. The M size is quoted as good for riders between 160 - 178cm, with the L size for riders between 178 - 190cm.

Reach is 465mm for the M and 495mm for the L, both based around the 561mm axle to crown of a 150mm travel fork. Dropping the fork travel lengthens the reach.

There's a 64-degree head angle up front, which carries on ARC8's new philosophy of properly aggressive geometry for short travel bikes. Running a shorter fork will steepen the head angle.

In the middle there's a 40mm bottom bracket drop, which should equate to around a 330mm bottom bracket height depending on the tires. Dropping the fork travel will drop the bottom bracket height, but the shorter travel at the front is likely paired with shorter travel at the rear, stopping the bottom bracket from getting too low when riding.

There's a 76-degree virtual seat tube angle on both sizes that when combined with the seat tube offset gives a 71-degree real seat tube angle. That's a bit more difference between the virtual and real angles than the Evolve FS, meaning that if your seat is above or below ARC8's designed seat height, there will be more fore or aft movement from the seat.

Seat post insertions are 245mm and 265mm for the M and L sizes respectively, which isn't bad at all. But if your preference is to fit really long droppers then it's wise to double check.

The Essential uses short head tube lengths, like the Evolve FS, at 100mm for the M and 115mm for the L. That means the stack heights are low for a 150mm travel fork, but this is something ARC8 have always done, with a bit of a focus on being able to get the bars low for an aggressive climbing position, if that's your preference.

Chainstay lengths are also short, by today's standards, at 430mm on both sizes. But again, this is in keeping with ARC8's philosophy of having a short back end on all sizes for utmost maneuverability.





Build Options, Price & Availability

The Essential is available in two full builds as well as the frameset, all available in September of this year.

Builds with piggy back shocks, like the XT build, come with 130mm rear travel. Builds with inline shocks, like the SLX build and frameset, come with 120mm rear travel.


Essential XT - Fox 34 Performance 140mm fork and Float X Performance shock. Shimano XT drivetrain and brakes. Newmen Evolution A.30 wheels with Onza Ibex 2.4" tires. Faserwerk Baslerstab combo. Bikeyoke Revive dropper. €5,299.

Essential SLX - RockShox Pike Select 140mm fork and Deluxe Select+ RT shock. Shimano SLX drivetrain and brakes. Newmen Performance 30 wheels with Onza Ibex 2.4" tires. Faserwerk Rockstock bar and Handschmeichler stem. RaceFace Aeffect dropper. €4,399.

Essential Frameset - RockShox Deluxe Select+ RT shock. Across headset. ARC8 rear wheel axle. €2,199.






178 Comments

  • 143 2
 My electrician just upgraded my house by routing the mains connector handily in through the waste water pipe! I couldn't believe it, right through the toilet! you can't even see any wires now and we can will all the old holes in.
  • 92 1
 "They enter via the headset, and that's all that will be said about that."....you think so, just wait for the comments....Smile
  • 73 4
 GTFO with that flat mount...
  • 25 3
 Yep, total deal-breaker. No way I want roadie two-piston brakes on my trail bike.
  • 8 1
 Yeah, I don't get it. There are like next to no options for calipers...
  • 15 4
 @litany: Formula Curas do the job as well as any lightweight four pot
  • 7 2
 Magura and Shimano have flat mount.
But still, they are 2 piston calipers. Fine for XC, questionable for "aggressive trail".
  • 18 7
 @Hexsense: The Formula Cura are 2 piston and more than enough for heavy DH bike & eBike use. Piston count doesn't matter, and more pistons is usually worse (more complex, more fiddly, more expensive); better to just oversize your pistons rather than adding more.
  • 3 0
 Kinda funky having a flat mount rear and post mount front.
  • 3 0
 At least you can readily get a flat mount adapter for post mount calipers, although it is bulky as heck
  • 6 3
 @wburnes: Yeah, come to think about it, friction forces do not rely on surface area; this makes sense, since when considering a static braking force, a larger surface area will exert less pressure. Less pressure equals less braking force per unit area. I guess larger pads really only allow for a longer pad life, since they are under less pressure. But typically, 4-piston brake pads are only 20-30% larger than 2-piston and often much more expensive, so maybe only necessary for extremely long and aggressive descents.
  • 3 0
 It's a good look, a flat mount caliper on a show bike that already has a visibly overheated rotor!
  • 8 0
 @cosmicCnidarian: First, post mount are better than flat mount at heat dissipation, then 4 pot has a number of advantages over two pot that aren't pure power related. Again, they're bigger and dissipate heat better, offset size pistons allow them to naturally toe in the pads to tune out any resonance or juddering and they can be less tall than a 2 pot with the same piston size, which means they have a smaller cutout and less flex.
  • 3 0
 The main problem isn't the "2 pistons vs 4 pistons" i think, but when you buy a new pair of brakes... They DON'T come with 2 different mounts...... So you're screwed again and have to buy them one by one.
  • 4 2
 @wburnes, @cosmicCnidarian I guess that physics was not your favourite subject. Hydraulic brakes works exactly as a simple mechanical leverage, where the ratio of piston area gives you the leverage. So with the same brake level the caliper with more area gives you more force, simple as that. Last time I checkes most 2-piston braked had about 20% less area then 4-piston brakes.
  • 3 2
 @lkubica: The point of wburnes' comment was that companies COULD make the the caliper pistons larger (like in the formula brakes) giving the same mechanical advantage as 4-piston brakes. I then agreed that pad area doesn't really contribute to friction force the way people intuitively think it should.
  • 2 1
 @cosmicCnidarian: Yes they COULD do that, but as said above there are numerous reasons why they usually don't.
  • 5 1
 @cosmicCnidarian: Raced AF world cup course on single piston XT's and don't remember any problems other than bite point wandering... so Im gonna call BS on 4 piston being noticeably better. Maybe these guys just brake too much... nah... commenters are sick!
  • 2 0
 @wburnes: I've got Cura 2s on my Murmur and they're well good. If anyone has any doubt check Paul Astons youtube reivew.
  • 2 0
 @Grosey: do you weight 100 pounds or something?
  • 4 1
 @smgishot13: just remember, all of the steepest, gnarly, ridiculous lines/trails where rode a long time ago on v brakes or cantilever. Quit complaining.
  • 1 0
 My thoughts exactly - mtb or bust mfer.
  • 3 1
 @robway: If someone offered you a V brake bike now, how often would you ride it?
  • 2 0
 @cosmicCnidarian: Even same force, same area but apply on different contact shape change braking power.
Grab rotor by F unit of force at the outer disc edge brake the bike more efficiently than grabbing the rotor by F unit of force at the rotor center.

2 round pistons put a circular/square pressing area on the rotor.
4 smaller round pistons, 2 side by side change the pressing area to a more oval/ rectangular which is wider around the rotor outer edge and less deep into the rotor center.
  • 2 0
 @robway: I did race my first Megavalanche in 2001 with a Avid tri-align v-brake on the front and a Grimeca disc brake on the rear,with a 135mm rotor...which of course heated up and blocked the wheel on those long descents.
Good times!
  • 2 0
 @Hexsense: Funny enough, it still doesn't matter. Friction force is strictly (Coefficient of Friction) x (Normal Force). That's it. Even if pads were super flexible, the total amount of force applied would stay the same. Plenty of other things can affect the amount of friction force put on caliper pistons, however. Stiffer housing, stiffer lever bodies, better heat dissipation, and greater mechanical advantage can all serve to increase the the amount of force applied through the brake pads.
  • 1 0
 @wburnes: pistons count doesn matter, but with more pistons, the pads are bigger (longer), and that matters.
  • 1 0
 @cosmicCnidarian: bingo! Have a Bell’s
  • 2 1
 @cosmicCnidarian: You missed his point completely. Braking on the wheel comes down to torque from the rotor. So if a 2 pot pad puts the same force on the rotor over the same size contact patch, the 4 pot caliper will still produce more torque. Same principle as putting on a bigger rotor, just on a smaller scale.

Also, since you mentioned stiffness, I'll say again that all else being equal a 4 pot caliper is stiffer than a 2 pot caliper.
  • 3 1
 @wingguy: How does the 4 piston caliper put more torque on the rotor? Torque on the rotor is (rotor radius)*(friction force). Friction force, in this case, is (coefficient of friction)*(normal force). Going to a bit larger pad is not the "same principle as putting on a bigger rotor, just on a smaller scale". As I've said before, the SIZE of the contact patch doesn't matter. Friction force doesn't care about area.
  • 1 0
 @cosmicCnidarian:
Rotor radius* friction force.
There, the radius isn't a constant value. It's a gradient between outer most edge of the pad to the inner most edge of the pad. Normally we average it out and consider the center point of the pad as the radius where the force apply.

Now, consider two pads of the same area. One is square and tall (2 big piston pads), another one is wide and rectangular (4 piston pads) which one have center of the pad closer to the outer edge of the rotor, hence more effective rotor radius?
  • 1 1
 @cosmicCnidarian:
Also, reread my post above. I have tried to emphasize "SAME AREA" but it seems to escape you. I'm not talking about the area difference. I keep the area constant but change the shape of force application surface from a more square-ish to a more rectangular-ish shape, where it hug around rotor outer edge better. Putting less force on the inner area of the rotor and more on the outer side of the rotor edge.
  • 1 0
 @cosmicCnidarian: I don't know the inner workings of brakes super well, but I do wonder that with the added pistons, that equals more brake fluid volume. Would it be possible that with more volume moving the 4 pistons vs the 2 pistons, that can change the mechanical advantage from the lever?
  • 2 0
 @cosmicCnidarian: Ok, so I was thinking about a pad that took full advantage of a larger single piston, it would be squarer and extend further towards the centre of the rotor, changing the average torque. In reality you’re right, the pads will almost certainly be the same height as 4 Pot but smaller. I’ve just checked an XT 2 pot pad vs a 4 pot pad and it’s literally half the size for (I assume) almost the same total piston area with all the wear and heat management implications that come with that.

Plus the additional advantages of stiffer callipers and natural toe in that comes with 4 pot.
  • 3 0
 @Hexsense: Brake pads have very similar pad heights, which is why it's easy to use most pads with most rotors- the pad height lines up with the braking surface! I think if you measured pads from a bunch of different brakes you'd find the center of height to be very similar for all of them.
@Spencermon: This is a great point you brought up! Indeed, the mechanical advantage of a hydraulic brake is partly determined by the ratio of (Master Cylinder Cross-section Area)Frown Total Piston Area). So putting a lever with a small bore with a caliper with large pistons will increase the force, but you may have more brake rub since the pads won't move as far.
@wingguy: It's cool that you had both brakes to compare, I didn't realize the difference in size was that big!
  • 1 0
 @robway: fk yeah ! and remember those Cannondale CODA discs. We rode those as well ! Im surprised we survived .... along with those of us who had those original Magura Loise horror shows fitted. We only complained once we discovered modern 4 pots :-)
  • 1 0
 @Voxran: which company provides two brake systems in the box? You buy two brake systems for your bike. One for front one for rear. No problem. Problem solved
  • 1 0
 @cosmicCnidarian: there is no really. Friction is independent of surface area. Physics fact, not bike industry physics, physics physics as in Isaac Newton , nils Plank kind of physics
  • 1 0
 @Hexsense: no it’s not unless the pad shape is designed to have its centre of area at a great radius. Even if it does it’s a polony skin further out giving a polony skins worth of extra leverage. The biggest gains is in the having bigger pistons in the caliper and small pistons in the master cylinder. This increases the hydraulic leverage ratio. This is all that matters.
  • 2 0
 @wingguy: . The only way the 4 piston will produce more hydraulic mechanical advantage is if the area of the little pistons exceeds the area of a single large piston design
  • 1 0
 @golefty: Who are you talking to? I didn’t say anything about mechanical advantage.
  • 1 0
 @wingguy: to you. You went on about pad shape hocus pocus. The only thing that will make a difference is mechanical advantage which is not guaranteed with 4 pistons
  • 1 0
 @golefty: You said hydraulic mechanical advantage. I said nothing about that at all. The pad shape thing was explaining someone else's statement.
  • 1 0
 @nace: I don't want them on my road bike either! It's bad tech that was jammed down our throats. Maybe necessary for road bikes to transition to disc brakes but... I don't want disc brakes on my road bike!
  • 1 0
 @smgishot13: 190, so basically same
  • 57 2
 looked good until the headset routing. While the sliders look good, I feel that they should be nearer the bottom bracket to really give them agood mud and chain lube coating, and you wont attract the right sort of dentists without a kashima coating.
  • 19 2
 Ive stopped reading after the headset routing
  • 5 1
 same for me - also every time I see Acros headset I see a ton of maintainance :-(
these headsets barely last one dry summer
  • 42 0
 I'm here for the headset routing comments.
  • 15 1
 ARC8 out here using the most proprietary shit they can do and then proceed to add that headset routing? i've seen canned spaghetti with a neater look than that
  • 12 0
 What are these companies doing about keeping the brake and derailleur housing from touching the steerer tube?

I've seen housing that's sized too short or long routed on the outside of a frame come into contact with the fork crown or frame and it can cut right into the metal over time. Now it's on the inside and potentially touching the steerer.....sounds like a bomb fuse that's lit and you just don't know how long the fuse is.

Add into that an egress for dirt and water to enter that area, no thanks.
  • 4 0
 @sprockets: there is no control in the design process, so you end up with very poorly designed bikes. Anyone designing something should have worked out the failure points and designed accordingly. Nuke proof and virus have been handing out plastic sleeves to go over the steerer to stop the cables sawing through the steerer.

Would be interesting to see how acros and bike companies would fair in a court of law if someone were to be injured through hose failure or steerer tube failure.
  • 4 0
 It doesn't look that bad, on the edge of the headset, so not through the stem, not that far off from going through the sides of the top or down tube. Personally I'd prefer lines run externally, but I've given up making that a need.
  • 3 0
 @nurseben: I’ve had internal routing on my bikes for probably ~6 years now. I was finally at the “Internal routing is actually okay” point.

Then I got a Chromag. All external cables. Had the whole bike built in about 45 minutes and it was a joy to do so. Massive whiplash back into the external routing camp.
  • 31 6
 That color scheme does it for me. Hopefully sponsored riders wont have to slap an orange fork on it.
  • 14 16
 Sponsorship is designed 100% to showcase a sponsored rider's equipment. Orang is Fox's signature color (red Rockshox, green DVO etc etc.). Reminder that almost ALL products are available in signature colors along with black or similar non-loud colors.
  • 17 1
 on the contrary, I think an orange fork would look pretty good on this bike, but to each his own.
  • 12 16
flag swagner2 (Aug 15, 2022 at 9:51) (Below Threshold)
 @bman33: You really needed to post this?
  • 7 12
flag bman33 (Aug 15, 2022 at 9:55) (Below Threshold)
 @swagner2: not at all, but neither does there need to be a post in almost every article that mentions Fox specifically or talks about color preference. No one seems to realize that black is always available nor understand how sponsorship works.
  • 9 2
 meow meow meow I don't like bright colors.......
  • 21 0
 Seriously, what is up with the headset cable routing craze? No one is biting, and it is neither "cleaner"/"less cluttered" nor is it a maintenance advantage. Loved the look and premise of this bike but hard pass with trying to shove that headset routing garbage on us.
  • 12 1
 Cheaper than molding in ports and tubes
  • 8 1
 Cheap to manufacture
  • 2 0
 @BillT999: Ah yes, so true...
  • 8 9
 It’s a trend like 29’er wheels, it will die out eventually…
  • 2 11
flag Worley1 (Aug 15, 2022 at 22:12) (Below Threshold)
 How often do you change your headset bearings? If it’s more than once or twice a year You should be worried and at the same time change out your cables and re bleed your brakes? Almost like that’s what manufacturers encourage as standard maintenance
  • 1 0
 @Worley1: the headset definitely gets more water in it. Mine had rust pitting on it after 4 months on my Scott spark. Sold the bike. Headset cable routing is dumb and lazy of the company.
  • 22 1
 Ooooo flat mount, extra stanchion, and internal headset cable routing
  • 1 16
flag Worley1 (Aug 15, 2022 at 22:10) (Below Threshold)
 Ooooo you definitely ride blues on a 180mm super enduro bike and have someone else do you maintenance
  • 4 0
 I've got an older reverb that I cant seem to bleed that would be perfect for this build.
  • 3 0
 @Worley1: someone with a mechanic wouldn’t care about these little things…
  • 18 0
 Say it again with me: Faserwerk Baslerstab.

Faserstab Balserwerk. Stabwerk Baslerfaser.
  • 13 0
 Fasterstab Ballworks?
  • 7 0
 Fastest Blwerb
  • 5 0
 Tasrfase Breklrsew
  • 3 0
 Werkfaster Ballstaber?
  • 1 0
 Werkfaser stabfaster
  • 15 0
 Internal headset routing… stop reading when I realised it.
  • 14 1
 This is the way, if you're going to do a slider. Its lighter and better looking than the Trek Supercaliper, with double the travel. Shame about that cable routing.
  • 1 0
 I'd like to see a little cover for it and the Schock to keep them clean. Idk why this and drivetrain fairings are not standard or at least widely available for MTB (and for road bike aero gains).
  • 3 0
 @wburnes: So back in the day forks all had those bellow-style covers, and it was quickly discovered that bare stanchions are better, as the coverings just hold dirty grease against the sliders. Cannondale found this out with their lefty too. Yeti had a bike with single and dual sliders, and they also came to the same conclusion.

Also, of any place on your bike least likely to get mud & spray on it, I'd say under the down tube is a good bet.
  • 12 0
 Headset cable routing and flat mount brakes. No one wants this crap.
  • 2 0
 I bet many clueless riders with money do
  • 9 0
 @kanioni: You've ridden in Switzerland then...
  • 11 1
 Looks good, but I'm really not on board with flat-mount calipers on MTB's.
  • 4 0
 What doesn't look good in a press release is blued rotors
  • 1 0
 @therealmancub: I've wondered if there's something about the Magura Storm HC rotor design that makes it extra susceptible. It's the only model I've ever discolored, personally. The Centerline I had before it in same diameter showed no evidence of heat.
  • 3 0
 @AndrewHornor: I LOVE that blue discolouration. Reminds every one I'm just a Joey and pleases non biker fashionistas
  • 8 0
 So a 160 cm person and a 178 cm person are both suppose to fit on the same frame size? Please do post two pictures of that.
  • 5 0
 495 reach, 64deg HA and 430mm chainstays ? Lol wtf are those are on about ? I tried their Extra with similar number and 435mm CS and it wasn't great at cornering to say the least, that one will be even worse lol.
  • 23 0
 antiquated idea that short cs = nimble, when in reality a balanced cs length will rip corners faster.

also, f*ck headset cable routing.

i like the idea of this bike - light, minimalist shredder (i like the aesthetics, too); unfortunately fails on a couple points.
  • 1 0
 @xy9ine: If you want to talk about balance, it is better to compare front and rear center rather than reach and chainstay length. Obviously there is a relation, but if your reference is a bike with a longer fork and/or longer headtube, it may affect your expectations of how this bike will ride. My bike has a 1214mm wheelbase with 415mm chainstays, so basically the chainstays are just over one third of the wheelbase. I'm happy with how it is balanced. Something similar seems to go for this bike (also a rear center just over one third of the wheelbase) plus of course this is a full suspension bike so as it sags in its travel the rear center will grow and the front center will get shorter (whereas I am on a hardtail).
  • 5 0
 @vinay: I actually use rear and front center, having the habit of looking at bikes I know that 495mm of reach with 64HA will not have a F/R center ratio that I consider suitable. If you want to go even deeper, ideally you should consider F and R center and ratios at SAG as these will differ wildly from static geometry depending on axle path, travel, HA etc. Either way this geo is rubbish and the Extra geo size L is also rubbish. When I got to try it it really did everything I was expecting it to do and confirmer my theory that a good cornering bike should have a F/R ratio of 1.80 or below at SAG. But it will take time before the industry moves on from their short CS bs.
  • 1 1
 @Balgaroth: Just did the math. At sag (25% for a 120mm travel fork, 63deg HA) this F/R ratio is over 1.89 for my bike. I need to fully bottom out to get below 1.8! Cornering is fine to me. I can oversteer, understeer and I can find the sweet spot in between. What does matter I think is where you put your foot on the pedal. I used to have the ball of my foot over my pedal axle and I could just get away with that on my 16" seattube DMR Switchback. I wanted a low top tube and was willing to accept that the frame was short. Once I moved on to Catalyst pedals and shifted to have my midfoot over the pedal axle, I basically shifted my whole bodyweight forwards by a couple of cm and suddenly the oversteer got out of hand. That's why I eventually moved on to a bike with a relatively short rear center and modern wheelbase (and still have a 400mm seattube). I understand it may not be ideal for some, especially those with a different foot placement or those who sit down as they ride. But for me it is perfect. Just did the math on this large sized bike here (with a 140mm travel fork at 25% sag) and the f/r ratio is similar to mine. I haven't even taken the rearwards shift of the rear axle into account as I don't know how much it is. But yeah, I think I could get along just fine.
  • 1 3
 @xy9ine: Right, which is why all the bikes that are used for nimble riding have short chainstays ...

Keep in mind it's the rider 90% of the time, so maybe you don't ride the same tech in BC that I ride down here, but down in the southwest we ride stuff that can't be plowed.
  • 4 0
 @nurseben: personal riding style & trail type play into these things for sure i've ridden a variety of bikes with reaches in the 490-495 range paired with chainstays ranging from 420-445mm, and it's the longer stay bikes that have the best overall handling (for me) - and the trails i frequent tend towards tight tech jank. of course, one man's opinion, yrmv.

what i have a bigger issue with is one size fits all chainstays (ie, ignoring balanced geo). if your marketing spiel claims a tight cs for nimbility, who specifically is this claim directed towards? what's short for a size large rider is not for a small frame rider. do they optimize for the median size rider & say too bad for everyone else? it's just being lazy and/or cheap, which is disappointing when so many aspects of bike design are heavily nerded over.
  • 1 0
 @xy9ine: On my bike (a BTR Ranger hardtail, 26" wheels) the chainstays do grow proportional with the size. 405mm for XXS and XS all the way up to 425mm for XXL. I've got large with 415mm. They do this with for their 27.5" wheeled frames too though it stays a constant 426mm for their 29" wheeled frames. Apparently it is hard to get it shorter because of the big wheel. On full suspension bikes it gets harder as customers all want the same amount of rear suspension travel and characteristics, regardless of size. Some brands (like Norco) manage to do this by simply keeping the rear triangle the same but shifting the pivot and shock locations in the front triangle. This is something more brands could do but arc8 here got themselves in trouble as they shoved the rear triangle inside a cavity in the front triangle instead of brace it from the outside. There are other reasons I'm not too excited about that (covered in a different discussion under this article) but this is another one.

I think, for brands who stick with a constant rear center across all their sizes, they'll probably sell most bikes to people of a length for whom that rear center is a good fit. There is little point moaning about a brand releasing a frame that doesn't happen to work for you. Hopefully there are others that are. And otherwise of course there is always the custom option.
  • 1 0
 @vinay: there is a point, if nobody points about the weaknesses of a design (like CS that are way too short for big sizes) then there is no chance that a brand will one day decide to release some bikes with appropriate geometries. If nobody complained about dwarf size front triangle and steep HA we would still only have 390mm of reach and 67deg HA on a size L enduro bike. But since I got tired of waiting indeed I went custom tho I'd prefer to just be able to order a bike that is standard and would ensure that I can flip it easily 1 or 2 years later. My current custom hardtail has 450mm CS, 470mm reach and 63HA static, it corners like a dream while being on 27.5 wheels.
  • 5 2
 Quote:
"
The mainframe is moulded in one piece and with a closed surface where the main pivot will eventually go. It's then post machined to make the window where the chainstay enters into the frame.
"
Is this really what they've done? Do I understand correctly that they actually cut through the laminate to make room for the chainstays, so that they now have free edges in the front triangle near the bb area? If so, what have they done to avoid delamination to start right there? You don't want to be the rider who has to guinea pig a gravel ride on one of these.
  • 3 0
 Yes, they did. But they are not the first to do so. Müsing does that since 2019 with their Petrol carbon frames (www.muesing-bikes.de/de/bikes/fully.html). And I never heard that there is any kind of problem with those frames because of that.
  • 1 0
 @juuro: Müsing frames are Arc8 frames are Chinese frames
  • 3 2
 @juuro: Well, if they get away with it, they get away with it. But it is bad practice in composite production unless maybe if all fibers are oriented in the same direction (UD). If you have free edges of a composite subject to a load, the fibers will try to reorient in the direction of the load which near such an edge will be parallel to that edge. This implies that if fibers have different orientations, they'll try to rotate with respect to each other and the matrix (the glue/filler between the fibres) will crack. This crack can then grow between the layers. I don't have much experience with carbon fiber bike components but I have ridden with Magura 2007 Marta and Louise brakes with carbon brake levers. These levers were just trimmed and polished at the edges. A hit from a fall could start a delamination there. For subsequent carbon brake levers, they used a braid so there were no longer any free edges and the leverblades got much more robust.
  • 4 0
 @vinay: Bad practice doesn't necessarily mean bad product. I agree it's not ideal to cut fibers, but it's possible it facilitates manufacturing in other ways, potentially leading to a better overall product. For example, a lay-up without cutting fibers might require sharp bends that could result in voids or internal stresses in the fibers, maybe it would force the designer to create a different and less efficient shape, or could require more expensive molds when spending that money elsewhere would've produced a better overall product.

It's always possible to just add extra material to compensate for something that compromises strength. Over a small area like this, we're looking at only a handful of grams.

I'm not saying the ARC8 is or isn't a better product for the choices they've made, just that the overall picture can be complicated and we shouldn't be too quick to condemn a design for cutting fibers. And yes, the area of cut fibers should be monitored closely, and the company should receive a giant serving of "I told you so" if it becomes a common failure point.
  • 9 0
 Edge seal. That's what we typically do in aerospace. Cutouts are done all over the place.
  • 1 2
 Well yeah, agreed it is possible to keep the delamination in check with enough reinforcement. We've been guilty too of trimming carbon composites, then taping them off with a piece of UD tape. Having it this close to the main pivot worries me a little but I suppose they should have tested this too. It just strikes me how people get upset about a flex pivot and not about this.
  • 3 1
 @vinay: People get upset about what they can see, feel, or understand. A flex pivot is easy to see and forcing a material to flex can cause it to break. Material management is difficult to see and understand.

On the topic of reducing stress in this area, the main pivot width could've been increased. The surface of the frame extends only to the edge of the BB shell, when it could've extended to the outside of the BB or even the inner faces of the cranks.
  • 1 1
 @R-M-R: Yeah, there is a little to bit to gain on the non-drive side, but not much on the drive side. To do away with those weird jumps (from the two chainstays sharp towards that central block and the sharp disjoin and join between bb and seattube) I would have thought it were better to keep the rear triangle on the outside (holding the bearings) and the front triangle in the middle. Indeed in my case it is the join between the two chainstays that becomes a bit of an afterthought I and I would do that below the bottom bracket for lack of a better place. It won't look as clean hence it will never sell Wink but it feels more structurally sound.
  • 6 0
 @vinay: I estimate there's at least 20 mm to gain, and I wouldn't be surprised if it's 30 mm. I've seen frames where it could be double that. We're talking 50% to 100% increases in bearing spacing. Unrealized opportunities like those are why I don't get too stressed about a few cut fibers, 63% vs 67% fiber:resin ratios, T700 vs T800 carbon, etc.

And we haven't even got started on the sketchy things some factories have been known to do, like increase cure temperature until it destroys the resin to save a few minutes, simplify the lay-up to fewer than half of the original number of pieces (including some enormous ply-drops), omitting glass layers at bonded-in aluminum pieces - it's a terrifying list of corner-cutting.

If ARC8 has properly designed for their manufacturing process and will do proper QC - and I've heard no reason to doubt them - some cut fibers is nothing to worry about.
  • 1 0
 @R-M-R: Alright, I wasn't aware of these practices in carbon production. It is something you've just got to trust right, as a customer. Luckily I ride a steel frame and I've got a builder I can talk to if I have questions (BTR fabrications) so I'm not expecting anything weird. And then indeed for this Arc8, if all else is good and the frame keeps up for as long as it is supposed to, then it is good enough indeed.
  • 1 0
 @vinay: Yes, carbon is a challenge for bike brands to QC, let alone consumers. Metals also have their share of invisible problems, though, like weld quality and heat treatment. Problems are most often caused by the design. I often tell people the hierarchy is design > manufacturing > materials.

For consumers, the best indicator is failure rate. Some brands have a higher rates than others. Some failures come in waves, like a specific point where a tremendous number of frames break that probably indicates a design issue, or a "bad batch" that might indicate the factory started cutting corners, since many factories will keep slipping in dodgy changes until their client calls them out on it. Some brands seem to always be having all sorts of problems: alignment, cracks in various locations, mysterious delaminations, etc., which may suggest a company that doesn't take QA & QC seriously.

As you said, it's the results that matter. If the performance, price, features, weight, etc. all check out, all that matters is that it doesn't break. Wouldn't matter if it was made from PVC pipes and duct tape if it somehow delivered the results. That said, you're right to be cautious about certain things, like cut fibers, small or single-shear pivots, sharp angles, long unsupported sections, etc.
  • 3 0
 I'm no engineer, but can someone explain to me how these single pivot "slider" rear suspension systems work?

The rear triangle is pivoting at the bb, fixed at the rear axel, so shouldn't it need to rotate downward at the slider mech when engaged? Doesn't that pressure turn into friction at the slider and stress on the upper seat-stay?

I just don't get how the natural "arc" in the rear triangle movement can be converted into a linear movement along the slider vector without another pivot (say at the hub)?
  • 15 0
 I'm no engineer but pretty sure bending is involved
  • 6 0
 I’m no engineer either but I believe the “pivot” is flex and engineered into the seatstay. The carbon is laid up to provide low(er) resistance to flex in the vertical axis. As for the pressure on the slider I assume it’s built tough enough to be ok with that.
  • 9 0
 Yes, the whole point is that the seatstays flex, same as most XC race bikes out now. They save weight by eliminating the need for a pivot near the rear axle, since in most designs that pivot only rotates a few degrees anyway.

The slider carriage thing isn't rigidly attached to the stays, they both can rotate around the shock mount bolt (the stay bends in an arc, not an S-shape). Yes it will create some off-axis forces on the slider, but probably not enough to be super noticeable (probably much less than a telescoping fork or Yeti's Switch Infinity sliders, for example). The force on the slider is directly related to the stiffness of the stays, so the easier they are to bend (looks pretty easy by design), the less they cross-load the slider shaft.
  • 17 1
 I'm an engineer, but I'm off duty now. Pretty sure there is magic involved.
  • 1 3
 @bkm303:
@B-foster
@browner

Thanks all, that makes sense... or rather... I believe what your are saying to be true and thanks for clarifying.

Despite their sexy hardtail looks, I can't see this design sticking around for years... seems destined for catastrophic failure. Some poor lycra wearer impaled by a snapped seat-stay.
  • 3 0
 @browner: I'm an engineer (albeit not a structural engineer...), bending is definitely involved

@vinay I'd guess is that FEA is used extensively in designing this bike, which is in fact magic

@bhuckley there are plenty of flex-stay designs out there, from 2005-ish alloy trek fuel EX's to the current supercalibre to the new stumpy. As long as robust fatigue considerations were made (fatigue can be surprisingly overlooked in engineering generally) and good engineering practice used I think it should be fine
  • 2 0
 @bhuckley: yeah what @IsaacWilson82 said, a ton of xc bikes use a flex stay, transition, giant, last bikes, trek, canyon, Scott, cannondale and almost certainly a load more. If anything the slider looks like it causes fewer degrees flex than some of the rotating links out there, but I could well be wrong there
  • 1 0
 @bhuckley: the last bikes one is even and enduro bike with a flex stay
  • 7 1
 I'll chip in. I design bikes. Others have given good feedback, so I'll largely echo their statements.

All frames flex. Thin tubes / plates flex more readily (some thin seatstays aren't hollow; it's more common on road bikes). These seatstays will flex upward as the suspension compresses to follow the path of the sliders. It's not much flex over such a long structure as the rear triangle. I'm not the slightest bit concerned about this amount of flex in such a long section of CFRP.

Yes, there will be off-axis forces on the sliders. Yes, this creates friction. If it works for telescoping suspension forks, it can work in this application. Unclear how well the execution works, but execution is a separate issue from concept.
  • 1 0
 @IsaacWislon82: @vinay: FEA is brute force, analytical formulas are magic
  • 3 0
 @ak-77: Well yeah, but with complex shapes you'll probably have to do so many simplifications that the magic may not be too accurate anymore. Like what happens to the fiber angles when you lay a weave over a double curved surface? I think FEA as well as analytical formulas have their place and it would be a missed opportunity to only rely on one of the two.
  • 1 0
 @vinay: I certainly didn't imply you should rely on only one of them. I prefer elegance over brute force but elegance can only get you so far
  • 2 0
 @ak-77: Yeah, agreed there. I think FEA allows you to work out the details but the analytical approach is what guides you to the viable concept. Both as my teacher used to say, garbage in = garbage out. Always be aware of the opportunities and limitations of the tools you're using and be aware of the simplifications you made in your model.
  • 2 0
 For reference, this is 200g lighter than the specialized stumpy frame. That one is roughly 2000g without the shock. No snack box, but very impressive.

Is anyone else intrigued by the Chadyang tires on the display bike? I'm guessing Arc8 is a Chinese company or they would slap on some 'standard' rubber.
  • 2 0
 Swiss company with Chinese made frames
  • 1 0
 I have a friend riding their Extra and who is pretty close to the people at Arc8 and from what I understand they are all friends with local Suntour antena (in Freiburg I think) which also work with those tires which are from the same parent company than Maxxis, I haven't had the chance to get my hands on these tires yet but I will as soon as my friend can get more, even there supply is problematic.
  • 3 0
 "The surface area in the mainframe and rear triangle was dropped considerably to shed a bunch of material and weight."
Honest question: Is this marketing newspeak for "we build the frame with smaller tube diameters"?
  • 2 0
 “There are two mounts to take water bottles or essential gear for your ride, all protected from mud and debris on the inside of the mainframe.”

Marketing regurgitation for: there’s room for one bottle in the frame, and an additional mount for accessories. Please use plural “bottles” only if it fits two bottles.
  • 2 0
 Light weight, acceptable pricing, modern geo, flexibility in use, Shimano SLX or XT groupsets? Yes please!

(Has a closer look...)

Only 2 sizes for riders between 160 and 190 cm? Hmm...
Flat mount brakes? Why?!
Through headset cable routing? OK, NO F-ING WAY! GTFO!
  • 3 0
 As a 178cm rider, thank you for making me OCD and post the same question in multiple versions on every forum about "which size".
  • 1 0
 I might be alone on this, but I dig the internal routing. This probably comes from appreciation of custom motorcycles in which great pains are taken to hide all the cables resulting in a very clean look. I know it's a maintenance pain, but I still like the way it looks. Interestingly, not long ago, everyone was raving about how the AXS allowed for such a clean looking cockpit. We're fickle.
  • 1 0
 Apart from headset size, single chainrings, droppers and thru axles.... I feel like the bike instustry should have stopped like 14 years ago, in 2007, with models as the Pitch Pro...Bikes were made with much more common sense and aimed at the amateur ripper. WTF honestly needs electronic shifting, live valve,INTERNAL ROUTING, electric motors...Sad how they always succeed in turning something pure into pure business.
That said bike looks cool and has some good bits (in my opinion) like the spot on geo and looks, flex stays and rear shock guide.
  • 1 0
 Good to see you're still with PB, Dan. I've got a couple of questions about the ARC8 and I'd like to hear your input as an engineer:

- Do the bushings for the sliders look reasonably well sealed against dirt ingress?

- How would one go about aligning the sliders in the frame after a rebuild? Seems like the slightest deviation from the perfect angle could ruin the suspension performance.

- Any thoughts on ARC8's custom/proprietary rear wheel offest? Is there any tangible real-world benefit and would it really be worth having to re-dish the rear wheel?
  • 1 0
 Looks good. Really interesting geometry and that slider suspension system. Really long reach and long wheelbase, slack head tube angle, and low stack height. It would be interesting to ride.
  • 4 0
 Looks awesome... apart from that cable routing Frown
  • 2 0
 Intriguing looking bike. Too bad they effed up the CS length. 442 mm CS on a size L DC bike is what I'm in search of. That Wasp looks pretty dang good.
  • 1 1
 This bike bike, with 120mm rear and 130mm front travel, would be perfect and all i need in my area. I could live with the flat-mount rear brake, as there are strong enough 2-piston rear brakes with 180mm rotors. But the headset cable-routing is a turn-off.

What I like to see is manufactures offering a M/L size. Almost every DC/Shorttravel Trailbike released during the last few years is either too short in size M and too long in size L for people with 180/84cm body-measurements. I'm in no way going back to -600mm top-tube-lenghts with 70 or 80mm stems on mediums, nor do I want to be strechted out with a 650mm top-tube, almost 500mm reach and a wheelbase of 1259mm for large.

BTW: €3,299 frame prizing for an Evolve FS but "only" €2,199(=€1100 less) for an Essential!?! Is this a typo??
  • 1 0
 The only brand I know with a M/L is Trek. Perhaps Specialized too but the jump from S3 to S4 seems kinda big.
  • 1 0
 @Curtuscd: Yes, thank you. Trek Top Fuel in M/L seems to be a perfect fit for me. The only other frames with almost similar measurements (+/- 615mm toptube and +/- 470mm reach) is the Arc8 Evolve FS size M, Banshee Phantom and YT Izzo in L.
  • 1 0
 As someone who uses an adapter with post mount caliper to use mtb brakes on a gravel frame and avoid buying new flatmount calipers, wtf is a flatmount caliper doing on a mountain bike??
  • 3 0
 That’s a good looking bike.
  • 3 0
 Why is that stem back so aesthetically satisfying
  • 3 0
 Flat mount on a trail bike lol
  • 1 2
 Given the same weight, since 65mm and 60mm shocks only differ in the travel reducing spacers, why would you want less travel? If you want the short feel, you set up the long shock with enough pressure to get the equivalent sag (in mm instead of percentage), maybe stuffed full of volume reducers if really want extra support when deep in the travel, and get a pretty similar feel but with some insurance for the spicy stuff.
  • 1 0
 The whole article is about how light the bike is...can you tell us what it weighs? 1800 grams for the frame *without* the shock isn't a whole lotta information.
  • 2 0
 ^that sounded (was) rude, sorry! Meant to ask if there's any more info available to make it easier to compare, or where they were heading with the builds. I had missed the comment from Faris, that's impressive. Really interesting bike and great review, thanks!
  • 2 0
 What type of mountain biker is this bike specifically targeted at?
  • 26 0
 The Cervelo rider that’s needs more than a gravel bike
  • 1 0
 @somebody-else: it does appeal!
  • 3 0
 Up-country riders
  • 2 0
 looks mint...do it all bike
  • 2 0
 Really nice looking bike!
  • 4 2
 So it's a canyon spectral 125?
  • 2 1
 Well no. Cause A it’s an arc8 and be it doesn’t have 125mm travel
  • 1 0
 This bikes looks awesome. We’ve got geometry figured out, the next evolution for trail bikes is cutting weight.
  • 2 0
 That's a very pretty looking bike to these eyes.
  • 2 0
 That main pivot would sand itself apart where I live
  • 2 0
 Onza tires, not "CHAOYANG"?
  • 2 0
 They must really hate their customers
  • 1 1
 OMG a Pinkbike review that calls out the difference between actual and effective seat angle geo. A momentous day! Well played Dan Roberts.
  • 1 0
 Shaving so many grams on the frame then not offering a top notch building for 8K or so...
  • 1 0
 Interesting that it’s built with DT Swiss suspension that isn’t an option.
  • 2 0
 Does anyone know if these will be aviable soon for us in America?
  • 1 0
 Nevermind the weight savings, the sliders allow for so much water bottles!
  • 1 0
 178 cm height.. M size to low, L to big... :/ Isn't IT?
  • 1 0
 Aggressive trail bike .... why?
  • 2 0
 So that it's good at nothing
  • 2 2
 Look how thin the seat stays are, rock strike, 1800-is-this-covered?
  • 1 1
 Is that a Tsukihime reference?
Below threshold threads are hidden





Copyright © 2000 - 2022. Pinkbike.com. All rights reserved.
dv65 0.023786
Mobile Version of Website