Race Face SIXC Carbon DH Crank Review
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Race Face SIXC Crank Details • Purpose: all-mountain/downhill • Hollow core carbon construction • CrMo steel axle and pedal inserts • Removable granny spider • Weight: 646 grams (w/ BB and 36t ring) • Lengths: 165, 170, 175mm • BB options: 68/73mm, 83mm, BB92/BB107 Press-Fit, PF30 conversion or BB30 conversion • Manufactured in Canada • MSRP: $599 USD (36 tooth single ring), $649 USD (24/36/bash guard) | Light And Strong? If you can justify the cost of these, you're likely the ideal user. Maybe not the ideal option for riders who are on a tight budget, the $549 USD (w/ a single 36t ring) SIXC cranks are a high-end component intended for riders who want some of the lightest and strongest arms out there. Practicality has met it's match. Weekend warriors on a budget, bashers, smashers, and crashers, and anyone with a financial plan best suited to canned beer need not apply. Race Face has engineered the SIXC cranks to be the ultimate packaging of strength and weight by utilizing a hollow, layered carbon fiber design. These are built to surpass the stiffness and strength of any other material, all while doing so at a significantly lighter weight. They are strong enough, in fact, that Race Face has no qualms about them being used to downhill racing, let alone the burliest all-mountain riding that you can likely subject them to. And that is exactly what we did with them. From shuttle runs on the track, to sessioning hidden super-booters in the forest, we've put these lightweight carbon cranks through the ringer. Below, you can find out how they fared. |
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Downhill Approved - 83/165mm Options
With carbon at the forefront of bike technology these days, the industry's push to gain consumer confidence outside of the realm of spindly cross-country components has resulted in a barrage of new era composite designs that largely eliminate the need for excessive reinforcement for use in heavy-duty applications. Just like the interior of a carbon bike frame, the SIXC cranks utilize a hollow molded design, created by a proprietary process developed by Race Face. Layers of carbon fiber laminate are laid into shape by hand around a cromoly steel axle and pedal insert, with the lay-up then put into a machine that applies heat and pressure to mold the carbon into it's permanent shape. Afterwards, all unnecessary material is removed.
The SIXC's intent is immediately apparent in the basic components of the crankset - it is the only carbon crank on the market to utilize both a steel axle and steel pedal inserts. These hard-wearing cromoly components provide a robust platform for bottom bracket bearings, as well as for long-term durability at the pedal interface. While the crank is designed for dual-ring use, the removable small-chainring spider allows for ample compatibility with most any chain guide, and the updated 4.5mm thick chain ring tabs should be burly enough to shrug off even the worst abuse. Adequate testing in the aggressive all-mountain department has led Race Face to produce the SIXC in downhill crank spacing and lengths for 2012, with 83mm and BB107 options in 165mm lengths now available.
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 Trade in your granny for a single ring, or vice versa. With the granny ring spider removed, the versatile SIXC cranks offer ample clearance for a variety of ring mounting options. Race Face's 8mm bolt-on design with self-extractor cap proved handy, and once mounted, these cranks stay put - we had no issues with the arm arms coming loose. |
Achilles Heel
While carbon has proven that its structural rigidity and fatigue life can surpass that of its aluminum counterparts, it is generally agreed upon that it falls short of aluminum when it comes to abrasion resistance. One-time impacts are not going to cause damage to the carbon crank, but gradual wear over time definitely contributes to a carbon component's failure. Through shuttle scars and crash damage, abrasion creates voids in the carbon strand that create an opportunity for catastrophic failure in the event of overloading the component. This, aside from the initial cost, is perhaps the only deterrent to most riders for recreational use of such high-end componentry.
With that in mind, Race Face created the nifty Crank Boot to help protect the ends of the crank from abrasion due to rock striking, and recommends use of the boots at all times on the carbon crank. The boots also fit SRAMs XX and XO carbon cranks. For riders who heel rub their shoe on the crank arm, Race Face recommends protecting the crank faces with clear 3M protective tape to help mitigate wear to the crank arm.
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| Wrap it up! Race Face's Crank Boots solve the issue of carbon abrasion at the tip of the crank by providing a soft bumper for impact protection. The boots, available in several colours, fit other brands of crank as well. |
Quality Control
Race Face is proud to be able to design, develop, and produce the SIXC carbon cranks in their Vancouver, Canada, facility. This gives them complete control over the process, which is important with such a labor intensive and complex product like the SIXC cranks. They also conduct in-house testing, running through all CEN tests and a handful of proprietary crankset torture tests to be sure of the product's strength and quality. In the case of an incredibly high load (picture 3000lbs) they feature a designed-in 'safe failure' at the spindle that prevents the arms from separating.
 | The fatigue life and strength of carbon fiber is incredible. We've run industry CEN fatigue tests to 10 and 20 times the industry standard without them failing. - Race Face carbon engineer |
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| Above, the SIXC crank starts with a thin sheet of raw carbon fiber mat which is then stamped into pieces to be wrapped around the steel axle and pedal insert. The molded crank is then machined for chainring tabs. We weren't allowed to show you the lay-up or carbon molding because Race Face's process is proprietary and unique, but lets just say it's really cool to see this kind of ingenuity being employed domestically. |
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| Stages of Race Face Race Ring chain ring: raw aluminum plate; tools of the trade for the CNC operator; metal dust; chain ring being flipped after machining of the first side; scrap metal; laser engraving; final product. |
| To make manufacturing feasible in North America we employ a lean manufacturing cell operating at very close to one piece flow. Inefficiencies and wasteful processes are clearly visible, allowing us to continuously improve our processes over time. This is in stark contrast to typical large batch manufacturing techniques found overseas. - Race Face carbon engineer |
On The Bike
Mounting the SIXC cranks proved to be a breeze. Once the BB cups are installed in the frame, the cranks bolted right up with a single 8mm bolt. Shims on the crank axle allow for 3mm of spacing adjustment for setting the chainline, but ours were bang on right straight out of the box. The initial installation is much easier than what was required of Race Face cranks in the past, with the spindle to crankarm fitting being a pain free process. With our 83 x 170mm SIXC cranks mounted up on the big bike, we were ready to put them to the test.
Admittedly, we were initially a bit frightened to send it aboard the carbon crankset. But After a few runs the SIXC arms proved to be no less stiff than the hardy Atlas FR crank, so we totally forgot about the structural support mechanism and were able to focus on the trail. Other than nearly half pound difference in weight, there is no noticeable difference between the SIXC and the Atlas arms in use, which says a lot of the lightweight cranks' prowess. In fact, the SIXC cranks may actually feel slightly stiffer, but we're not sure if that's for real or just in our head. Regardless, the fact that the SIXC cranks can equal the stiffness of the heavier aluminum arms is impressive.
Maybe it's the gloomy weather and gritty trail conditions of the North Shore, but whatever it is, Race Face has figured out how to build a quality bottom bracket. With twice as many balls in each bearing cup compared to the competitors, the rugged Team DH bottom bracket endures downhill punishment despite any trail conditions. These bottom bracket bearings glide smoothly and freely without the need for ever adjusting the crank.
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Rock chunking, crashing, and shuttling leave only marks of character on an alloy crank. However, carbon doesn't fare as well. Scratches and gouges to the carbon arms produce stress risers immediately, and start to abrade the fiber. Even with the crank boot on, we managed to chunk the non-drive arm slightly behind the boot while grinding through a rocky trail section (seen middle, below). Whether or not this proved a fatal blow will only be told in time, but for now it doesn't seem to have any affect whatsoever in the functionality or stiffness of the crank. Rider beware though, carbon does take more care, so choose your components wisely.
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Pinkbike's take:
 | While aggressive riding and lightweight components seem contradictory, the SIXC cranks promise both. Lighter than the Atlas alloy crank and just as stiff and strong, they provide a sturdy platform for experienced aggressive riders. The SIXC's sport a beautiful, yet subtle look that commands attention on any bike. We're also head over heels for Race Face's single-bolt crank mounting design, which proves to be trouble-free time and time again. Although capable of pursuits in freeride, Race Face recommends the SIXC's usage for all-mountain riding and DH racing, and we couldn't agree more. The only reason we leave the SIXC arms out of the freeride and everyday downhill use genres is it's susceptibility to abrasion. This is a crank for those riders who take great pride in their rig so they can enjoy a flawless ride every time. Take care of your bike and it will take care of you. -Brad Walton |
www.raceface.com
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Maybe the rubber end cap reduces the effect of the impact energy below a critical value. If so, this is what I'd like Race Face to tell me and to prove to me. Not just state the rubber end cap is to reduce abrasion. Agreed abrasion is a porblem but less so than damage tolerance
Perhaps the error is in Pinkbike interpretation?
As far as weight goes, Middleburn cranks are the height of aluminium design: cranks 416g, Ti BB approx 150g, 36T G-ring 37g = 603g, lighter than this SIXC. Carbon is not the solution. And for those who doubt, I'm sure there's many on here who would vouch for Middleburn for DH use.
Perhaps the error is in your interpretation.
Being an "aerospace stress engineer specialising in carbon composites" I'm surprised you have such little respect/interest in the strengths of carbon fibre, not to say that these cranks are any better then middleburns, but carbon parts continue to get better and better with innovation in productions methods and resins, aluminum is going to become a heavy alternative soon enough. PS lets not throw around big words to try and make us look smart, I smell the BS miles away
I still disagree with the statement that, "one-time impacts are not going to cause damage to the carbon crank".
Carbon products will get better. But it doesn't mean they will be the best solution for all applications.
P.S. I can't really see any big words in my reply.
As for Middleburn cranks, I don't see those as a fair alternative. You could easily compare them to RF's Next SL crank, and they would be nowhere as stiff. But Middleburn for DH use? Not for me.
RF also had this to say when we toured the facility: "In the case of an incredibly high load (like 3000lbs) they are designed to fail at the spindle leaving both of your feet still firmly planted on the bike. That 3000lbs of load is huge…that is more than the curb weight of a 2012 Honda Civic."
the carbon fibre itself is such quality that it is resistant to impact damage just like aluminum, more likely better because of its flexible characteristics. all the boot is doing is cushioning the impact, especially with sharp object the true killer of carbon fibre.
PS where do you work as an "aerospace stress engineer of carbon composites"?
if you understand anything about the aerospace industries, they work to considerably higher standards of design, engineering, material selection, manufacturing and quality control than the bike industry could ever dream of, especially when considering composite materials
when you have 350 aeroplane passengers lives in your hands, you make sure things are done properly, otherwise large lawsuits and criminal investigations ensue
the bike industry (if you have actually worked behind the scenes in manufacturing and warranty) is a joke with regards to its manufacturing standards, in comparison to aerospace or automotive
I have been working in the industry since 1991 in many guises including shop sales staff, mechanic, workshop manager, owner of a frame manufacturing company, warranty manager, etc.
there is some absolutely horrific Carbon Fibre composite frames and components coming through the bicycle market, often the lower-end of the market with extremely dubious quality of material and manufacture
some very respected composite engineers (aerospace, automotive working for Williams F1, etc.) have openly stated on bike forums here in the UK that carbon fibre has no place in either crank sets or handlebars on mountain bikes, but is a fantastic material for bicycle frames
RF also had this to say when we toured the facility: "In the case of an incredibly high load (like 3000lbs) they are designed to fail at the spindle leaving both of your feet still firmly planted on the bike. That 3000lbs of load is huge…that is more than the curb weight of a 2012 Honda Civic."
"what im getting at is im hearing alot of unnecessary, overly complicated engineer talk" the guy did say he was an aerospace stress engineer ..... Could explan it? I'm a fabricator and when we get plans of a job its in that unnecessary engineering language..... when All I'm bothered about is measurements and tolerances
Yup i understand that, but talking like that on a pinkbike news page...looks like hes pasting every sentence straight off wiki
"Maybe the rubber end cap reduces the effect of the impact energy below a critical value" - translated "maybe the rubber end cap stops impact damage"
I ride a carbon frame, but there are 4 or 5 areas I don't want carbon: bars, stem, cranks, pedals, fork legs or stanchions, hubs, spokes, seat post, and seat.
heres actual laymens terms for you= Under impact or stress carbon fibre can crack/seperate internally which will lower its strength, hopefully the rubber end cap protects it enough.
your whole statement had nothing to do with facts gathered from the product, you simply stated how carbon fibre usually fails, and then state RF should tell us if the rubber end cap is going to stop any damage the crank might endure...
what im guessing you couldn't grasp from the article is that the cranks without the rubber end cap is going to be strong enough as it is to take the abuse its designed for. the rubber end cap will stop wearing down of the epoxy which eventually will lead to weakening of the cranks, it will also lower/spread the impact energy should you hit the cranks on a rock etc.
so mr.aerospace engineer specializing in carbon composites, what was it again that you cant seem to grasp with the rubber end cap or strength of the cranks?
the point of carbon fibre is to design it so it will never fail not to design it so that after failing it will still work...
what do you mean by a one-time impact? an impact with the ability to cause internal damage to these cranks will be enough to crack/bend an aluminum crank. Carbon fiber has been proven to create better strength then aluminum, its only real limit is its design and the quality of the materials. It seems people are so biased about carbon fiber because it can fail in a hidden(though internal cracks can often be heard) or extreme manner, though if well designed this failure will happen at considerably higher loads then what will cause an aluminum product to fail, and yes aluminum can fatigue and crack internally aswell.
yes you can if the damage is from a chip on the surface, he would be checking for cracks growing from it.
the customer complained that the crank set has started to split / crack around the chain ring bolt mounting holes on the crank spider, I could clearly see this
SRAM have asked us to send this crankset back for warranty inspection, as it was only 2 months old and used for road riding, and no evidence of any crash damage or mis-use
we also recently had a Trek Madone (carbon fibre road bike) where the customer was hit by a taxi in London, and knocked off his bike
the front wheel was buckled, but more concerning was that the frame was 9mm out of alignment despite NO visual evidence of any damage to the Carbon Fibre layup. Trek UK informed me that their rejection rate for the Madone is 2mm, and 9mm indicated a serious internal lamination failure
customer was offered a new Trek Madone by the insurance agent of the Taxi company
Mr Radride, what you're saying is that the crank is strong enough on it's own to take an impact without a rubber end cap? Maybe so, but sounds unlikely to me. If you're really certain, let me give your carbon cranks a good whack with a hammer then let me push you off down a steep hill!!
and trying to link that to all carbon parts not being capable of enduring impacts as well as other materials. not to mention the bullshit job title you threw in for credibility.
I am confident my cranks can take a hit without internal damage, look at all the X0 cranks being used on DH and in DH WC. Is that not evidence alone of their strength?This rubber boot is just one more step in the direction of creating stronger designs
@hampsteadbandit All sound like design, and/or production faults(most important design elements of carbon fiber). Taxi crash is really not the fault of the carbon but I do admit its biggest faults is that damage can be hard to detect, after a crash that bad though damage would probably be expected.
well this is the main issue with Carbon Fibre - without access to NDT (for example X-Ray) it can be near impossible to detect catastrophic damage?
bikes will get damaged, it happens, but its always easier with cromoly steel, aluminium alloy or titanium alloy to see the damage from a large impact as you will see ripples / bulges and paint flaking in the tubeset
the way the Trek Madone I mentioned, had "hidden" damage despite our alignment tools telling us otherwise, was a little concerning
for a customer without access to a quality bike shop with alignment tools, they could visually inspect their bike after a crash, proclaim it undamaged and then suffer a serious injury if the frame then failed during a high speed descent
with increases in the use of carbon fiber im sure damage detection devices will be available in the future, either that or higher strength designs/materials
agree with your comments
personally? I am riding a carbon fibre mountain bike (2012 Specialized Stumpjumper Expert 29er) and have full confidence in the quality of this frame knowing first hand of Specialized's reputation for engineering and manufacturing, plus industry leading warranty backup
however, I would not consider a carbon fibre crank set, or handlebar, nor seat post...
...because I simply don't trust carbon fibre for those applications, having seen first hand carbon fibre crank sets, handlebars and seat posts suffer complete failures in minor crashes or failing from scratches caused by crashes / poor installation (notch sensitivity, like glass!) or from abrasion (wear and tear caused by mud)
I have also not found enough of a performance / cost benefit over industry leading crank sets from Shimano, or regular aluminium alloy finishing kit from Easton and Thomson
as an example, Easton's CNT handlebar was 3 x the price for a 30gm weight saving over their EA-70 bar
I do also see where your coming from not liking some of the smaller carbon parts, but I do think that there are carbon bars, cranks, and seatpost that will be as strong as aluminum, though much much more expensive usually.
Give carbon a few years and I think we will see some huge gains in strength from better manufacturing techniques and materials.
well this is the really interesting thing about using Carbon Fibre on bicycles
without doubt it is stronger and tougher than any aluminium alloy, when done right, it also has infinite fatigue life if not over stressed
however, and its a big however, it requires much more care during installation, and suffers from undetectable damage after impact
as a first hand example, a few seasons back, a young rider I sold an Easton CNT DH bar to, slammed into the dirt during a DH training session, catching his left grip fully in the dirt, but with no noticeable damage to bars, stem or forks.
a week later he was riding a mild track and his handlebar suddenly failed (sheared) right where the left brake lever clamp was bolted to the bars - Easton told us (when we sent the bar for inspection) that the edge of the brake lever (Shimano Saint disc) had caused a "notch sensitivity" during his first crash, leading to the bar failing on the next ride with no warning
without any doubt I trust Easton when they tell me their CNT DH bars are 3x stronger than their Havoc DH alloy bar (which I run) and the CNT bar is also lighter, but the "real world" abusive nature of mountain biking is what puts me off the CNT bars, and my example of the young rider is far from uncommon in the MTB world with bars, seatposts and even cranks
"Carbon composites deform purely elastically in their response to stress. Its does not yield like metals.
A handle bar is basically a tube that is clamped at the stem. It also has numerous other components clamped to it. All of the edges of these clamps are stress risers. A normal alloy bar will yield locally around a stress riser and thus reduce the stress riser. This cannot happen in a carbon structure so the stress riser will always be there.
Added to this most people don’t properly torque their bolted components absolutely correctly which will only worsen the effect. Add to that dirt and grit that can get under the clamps and the stress risers only get worse, add more scratches and crash/uplift damage etc and it still just gets worse.
Even if you do take care in correctly bolting on your brake levers to the correct torque you could have a crash that twists them slightly round the bar, suppose there’s a tiny bit of grit involved as well and you’ve now got a scratch on the bar surface right at a stress riser. Not good. A handle bar that suddenly goes without warning can lead to a very nasty injury. I’m not saying that this will definitely happen only that the chances are much higher. Why take the risk?
In terms of vibration and comfort carbon bars should win outright, but for durability on a DH bike a good alloy bar that has been shot peened will but a much wiser choice.
It’s obviously your personal choice but me, as composite materials engineer and bike rider, I would never put carbon bars on a mountain bike."
Put it this way, if you've got enough money to afford a lovely carbon AM or DH frame, you wouldn't want to hang shite parts off it, would you? You'd want the best- and this is it.
I'm not sure carbon will come down in price in the future, rather everything else will go up. I'd imagine that in a few years time once carbon parts become the norm, they will seem much more competitive.
It's already happening with frames: The Yeti SB66 Alloy is £2k, and the brand new Carbon is only £600 more. It seems like a lot at first, but when you're already spending £2k on a frame, that extra £600 isn't a great deal for all the benefits that carbon brings.
Put simply: You don't get Ferrari parts at Ford prices.
And no, I am not just defending an expensive purchase - luckily these came with the bike that I bought. If they were shitty, I would call them out as being shitty.
up mint and still look new. They may be a little pricey but WTF isnt.
Pinkbike is confusing at times.
ps I didnt buy these cranks as planned earlier this year because I wanted to let other riders beta test them. But anything that requires booties (more consumable crap and inconvenience) has put doubts in my mind. I put down some serious wedge on other, high end, first-year components. I think I'm doing enough consumer beta testing on behalf of the MTB community this year.
I'll probably stick with my nasty, rubbed, heel-polished, battle worn, scarred Saints.
they are amazing
"My wife borrowed my bike after folding the front wheel in the rocks in heart of darkness, and catrwheeled the mojo in the same spot."
My wife is a novice rider. It was her first trip to a real mountain, rather than the local river valley we had locally.
"My wife borrowed my bike after folding the front wheel in the rocks in heart of darkness, and catrwheeled the mojo in the same spot."
So she borrowed your bike but first folded the front wheel on it?
As far as todays "kids" lacking reading skills, re-read my original reply. The part about me having a nine year old, I am probably older than you!
And I still have yet to see any real rocks on HOD!
That's what happens when manufacturing is kept in Canada and the USA, INGENUITY.
So don't ride the parks you say? Well AM riding isn't any cheaper. An aluminum nomad frame (this isn't "keeping up with the jones") is nearly $2,000 + another $1500 of bottom line parts... Find me many sports that ask that kind of up front price for something you will likely be replacing in 5 years. And when you get into it, adding in $3000 frames, $500 cranks, $1000 forks, the price becomes insane.
Dont lie to yourself... This sport is damn expensive.
In terms of Aluminum vs Carbon cranks... it's not like an iPhone vs a Blackberry where everyone loved their crackberry until they tried the iPhone -- there's just so much more useful features along with the elegance of design and ease of use that separate the two. I would say carbon cranks (although beautifully designed) has not created a sizable gap when comparing the 2 in terms of the problems they solve or the benefits they provide. They both do the same thing relatively well. So right now it comes down to cost for most riders.
Having worked at bike shops, I still have yet to see a carbon part fail like that. I have seen full carbon road forks fail at the steerer that had grease in that area, but it's hard to say if that's why it failed. It's always been a crash with heavy front impact. For the most part, carbon withstands alot of punishment, so maybe the "voids" are blown a bit out of proportion.
I also did a stint of my working life doing fiber glass repair. I wonder if a gel coat would help with the "normal" wear? It would add a few grams, but would absorb some of the scratching and heel rubbing. I've seen jetskis beached 100's of times before it needs a new gel coat.
The first thing I brought up was concerns of abrasion related failure.
Don't remember his name, but the guy was saying the crank is so overstrong/overbuilt that it would take a lot more than a single smack on a rock to put the crank out of service. If I understood correctly the outer layers are for protection of the structural layup underneath....He basically brushed off the idea of the crank failing. When I asked "what if it does fail?" he said, "then we will send you a new one". Good enough for me!
More impressive is the crank is a little over a full pound lighter than the the current Saint setup!
Expensive...Yes...So is the V-10 carbon it is going on!
I don't know if you're doing that type of riding, but like above, deburring the stem and seat clamp area will help any type bar last a bit longer. Under heavy load an aluminium bar with a burr at the clamp can fail. Might have to also look into heavier parts. Instead of a 200 gram bar, try a 250 gram bar. These usually have a thinker center butt.
I'm around 250lbs and get about 5 years out of a carbon bar before I replace it. I replace it "just in case".
you can find these exact same phrases about steel-alloy ;-)
Ruktion is proper material choices and design decisions and priced right. Stamped steel chainwheel, aluminum cranks with steel inserts, steel axle, screwon bb with decent bearings, easy to shim, thin coat of matt paint. Most everything done right.
Carbon, unlike steel/alloy wars from yesteryear, is not the right material in this application.Score it and you loose strenght. Score aluminum and nothing happens. Scratch aluminum, sand, paint, done. Scratch carbon, off to the shop, buy new. Hit a rock and your day is done.
But then again - I also have 2 Raceface sets in use. A 12 year old Rf just retired. They make very decent cranks.
No thanks, it feels better without one.
I don't think you will ever see this on the new SIXC cranks. I ride them in Whistler and have had no issues whatsoever
If that chunk is fatal then they aren't worth $150. Time will tell
any ways its sick that they are still here today and these cranks look glorious