The REAL Story of That Single-Sided Carbon Fork

Jan 27, 2018 at 16:11
by Mike Levy  
PROPAIN TWOFACE


Well, I dun goofed up. It clearly won't be the last time, but this one stings a bit because I deprived a very clever man named Miloš Musil, @mmbike68 on Pinkbike, out of some well-deserved attention. I'm talking about the wild looking single-sided suspension fork that popped up on Spaziale Compositi's Instagram feed awhile back, a fork (strut?) that very much looked like it came from the admittedly strange Italian company. But it didn't. In fact, not only did I get the company wrong, I even flubbed the country that it came from - the Czech Republic.

Thankfully, the real story of this single-sided carbon strut-type thing is far more interesting than what I originally put together, so let's get this straightened out.

Fifty-year-old Miloš Musil originally built his odd creation six years ago, and back then it had 120mm of travel and was bolted to the front of Musil's 26'' wheeled RB Speedster (pictured at right). Until he broke the frame, that is. His new ride, a 145mm-travel Propain Twoface, has 27.5'' wheels and much more travel than the Speedster, so he had to bump up the fork's stroke to a full 160mm to balance things out. That's where it sits right now, but how the MM fork came to be is a whole other story, one that involves Musil using components from four different suspension brands - and a bunch of homemade carbon fiber - to build what you see here.
MM Fork
Musi's old RB Speedster with the MM fork set to its original 120mm of travel.

Musi started with an aluminum crown and tapered steerer unit from a Suntour fork and then bonded in the carbon-wrapped legs from RockShox. The two legs, which look like a single piece once they've been wrapped in carbon, are also joined at the bottom by an aluminum piece that ties them together and serves as home for the Enduro fork seals. The stanchions, also from a Suntour fork, are only 32mm in diameter, but they're both clamped by a massive, CNC'd aluminum lug at the bottom, and the titanium axle is from a Lefty. Talk about mixing and matching.


MM USD fork. Photo by Milo Musil.
MM USD fork. Photo by Milo Musil.
The fork's chassis is a mix of Suntour and Rockshox components, along with a few homemade parts and some carbon fiber.


Things are just as odd internally, too. Musil has kept the Suntour damper in the leading leg, but the trailing leg houses a Dual Air system from RockShox that allows for independently adjustable positive and negative air spring pressure. If you look closely, you can see the negative air valve on the CNC aluminum lug, and the positive air valve is at the fork crown.

As far as weight goes, Musil leaned more towards reliability than trying to shave grams - probably a smart approach when building your own fork - and he says it weighs about as much as a RockShox Recon, which is still under 5lbs.


MM USD fork. Photo by Milo Musil.
MM USD fork. Photo by Milo Musil.
The two separate legs are joined by an aluminum span that's home to a set of Enduro fork seals, and the whole thing is wrapped in carbon fiber to increase strength and rigidity.


MM USD fork. Photo by Milo Musil.
MM USD fork. Photo by Milo Musil.
Musil's completed fork looks wild, but it appears to be finished so well that it could have come off of a (strange) production line.


How does it perform? I'll let Miloš fill us in via Google Translate: ''The behavior is the same as a conventional telescopic fork. Thanks to the UD [upside-down design], it's better at lubricating bushings and seals, and inner legs are not contaminated from the shell. The fork has great torsional rigidity that's comparable, maybe even better, to Lefty, and it does not flex when pedaling or braking; curves can be ridden much faster than a conventional fork. Another advantage is that it is jednokorunková [single sided], so you can seamlessly mount tires on the wheel.''

I can't tell you if Musil's wild creation is any better than an off-the-shelf fork, but one thing that I am sure of is that, better or not, it's pretty freakin' cool. Much like Jean-Francois Boivin and his Insolent downhill bike, Musil has used a mix of existing components, carbon fiber, and ingenuity to build something that he couldn't purchase.


213 Comments

  • + 265
 There's something not right going on here..
  • + 278
 Yeah... think it's cause we're only seeing what's left...
  • + 118
 There's only one side to this argument.
  • + 13
 @MrMediocre: because theres nothing to see right
  • + 107
 @MrMediocre: But do two lefts make a right?
  • + 63
 when you don't have anything right, there is nothing left to lose
  • + 24
 @mtbikeaddict: No,but 3 lefts make a right.
  • + 28
 He took away everything that was right with forks.
  • + 23
 Is this some sort of center left political statement from the Czech, seems very one sided.
  • + 2
 @wickedfatchance: Yeah... I know... make it a triple lefty! For maximum stiffness and "Enduroness"
  • + 13
 I hope the right half left on good terms.
  • + 1
 @teschenbrenner: True. Needs more centred support.
  • - 9
flag OnionRing (Jan 31, 2018 at 11:33) (Below Threshold)
 Won't buy. I always use the right side of single crown forks as Hat Racks. This thing would just ruin a nice Hat. The label said Unisex...
  • - 5
flag romkaind (Jan 31, 2018 at 11:41) (Below Threshold)
 Those two stanchions so close together, it seem so familiar?
  • + 10
 The stanchion's are further apart than a Fox 32 step cast so it must be stiff
  • + 0
 @MrMediocre: This is all about a right turned left...
  • + 0
 no ones got the right idea with forks these days
  • + 1
 I think ths is rockshox new syMETRIC fork Technology
  • + 1
 he should make righty not lefty.. again
  • + 1
 @JesseE: Indeed , double one...
  • + 6
 The NASCAR of forks
  • + 1
 two wrongs don't make a right, but three lefts do. I guess I need to patent the triple stanchion lefty. and call it the righty
  • + 1
 @teschenbrenner: not everyone.
  • + 1
 @mtbikeaddict: no... but three do...
  • + 1
 Hey, don't be so quick to right off this fork.
  • + 185
 Pink Bike: It'd be rad if there was a segment of DIY made bikes and parts every month or so!
  • + 35
 Agreed! A place for people like Milos to strut their stuff.
  • + 4
 FYI there's a 'Homemade parts' thread in the Mechanic's Lounge. There's some gold here and there, but you have to wade through lots of chain retention devices to get to them: www.pinkbike.com/forum/listcomments/?threadid=30987
  • + 98
 Not many people can roll something that bad-ass outta their garage after tinkering for awhile. Rad.
  • + 9
 My thoughts exactly.
  • + 13
 I think it's pretty dope, actually. Kudos to that dude. "Here's to the crazy ones.."
  • + 6
 And it's what we should expect from a guy who rocks a tire called the Mezcal
  • + 32
 How could a fender be attached? This is like a cool Frankenstein double Lefty or something... props for making your own parts...
  • + 4
 Burly version of lefty
  • + 6
 I'm pretty sure he'd figure out how to fit a fender if he wanted one ;-) Molding it out of carbon and drilling a hole in the bottom of the steerer for attachment would probably work?
  • + 7
 use a drill and some screws
  • + 5
 attach a fender like what motos do- they are mostly inverted forks. The fender would be right under the steerer; ie it wouldn't move up and down with the lowers
  • + 101
 This dude builds his own fork and here I am covered in a white liquid after three hours of trying to mount a new pair of tires.
  • + 92
 @scottay2hottay: dang, new tires get you THAT excited?
  • + 10
 @scottay2hottay: I'd see a doctor about that kind of arousal
  • + 0
 Whoa
  • + 6
 ' Hefty Lefty '
  • + 1
 @Pedro404: Drilling the carbon fibre chasis after-mod: what could go wrong?
  • + 1
 @CaptainSnappy: I don't know, which is why I put a question mark at the end of that sentence. In my head it seemed similar to drilling an internal routing slot in an aluminum seat tube, which is supposed to be okay, but I have no idea whether carbon would take drilling as well as aluminum does.
  • + 20
 now it´s time to produce a dual side two-legged beast with 220mm
  • + 11
 That would look like some futuristic shot gun from Halo or some thing, I wanna see that !
  • + 17
 Props for the DIY approach.
  • + 13
 Hi Mike,

actually, you translated it wrong, but you got the point.

"Another advantage is that it is single sided, so you can seamlessly mount tires on the wheel.""

Milos said it incorrect. In czech "jedno/dvou korunkova" means "single/dual crown". He just misspelled.
  • + 2
 translation is OK because single crown would not make sense in the sentence but i would say that Milos meant single side for "Leftyna"
just think how would single crown (normally expected as 2 legs) would help you with changing tires without unmout wheel.
  • + 11
 Man. I bet it's super stiff. Maybe someone will bring something like this to market. I would probably give it a go. Imagine the stiffness of a lefty (or better) but as light weight as a well made 32mm stanchion fork with all the same adjust-ability. I'd ride it.
  • + 5
 Surprised by the comments here. While the manufacturing is impressive, the engineering is awful. Lefty *is* stiffer than a conventional fork, but only because it uses a dual-crown interface. This strut doesn't, and that heavy mess of carbon under the head tube won't make up the difference. The use of a second tube is another substantial weight addition, but necessary here for lack of Lefty's needle bearings or square runner. Those telescoping tubes are subject to the same binding problem of any other telescoping design, except now it'll happen in a more obvious way under lateral loads. I don't believe his performance comments for a moment, even relative to the original pre-2010 Leftys (which weighed something like 3 pounds).
  • + 8
 Lefty is stiff also because of the square interface. USE also had a left side fork though I don't know how good it was. It was used for 4x racing so it must have been fairly good. It was designed to limit brake dive which may also have implied that it wasn't active when braking during a descend.
  • + 16
 Alex you don’t get it. This dude made a fork for himself. That’s pretty badass. What the hell have you been up to?
  • + 1
 @vinay: I tested a USE anti-dive fork once. It was active under braking - it was non-reactive to braking: you could roll along flat ground and hit the front brake and it would not compress like other forks. Quite a non-normal head scratching experience. I think it was only short travel but USE's point was that, because it was only reacting to bumps, and not brakes, that it was worth more when descending rocky trails where the fork has to cope with hits and braking. The downside to that argument was that when you were descending with no brakes, it was just a short-travel fork. I think that USE fork disappeared once LSC got better and no-one bought any fork under 100mm. The travel was limited by the 'linkage arm' thingy. The claim was less stiction/binding, but I didn't feel it. I think I was out due to price, but very tempted.
  • + 1
 @WasatchEnduro: Hence the second sentence about manufacturing. The surprising comments are from people who want a retail version.
  • + 1
 So if we put a dual crown on a 32/34/36 it would be stiffest of all? Then why don't they, maybe the turning radius interference is too big of a drawback...
  • + 8
 Nothing wrong with trying something different. It's not like is the new FOX 36 with a 28.99mm axle and it's the only option.
  • + 4
 Tgis is the kind of mind we need in mtb right now, someone who thinks outside the box. I love the looks of this fork and love that he uses the dual air design instwad of solo air.
  • + 3
 This could be a pretty cool design. The only thing I could imagine improving it would be a design with a tube on each side, instead of two on one side. Therefore doing the same task but in a better, more visually appealing, stronger version. The future looks bright. Just imagine a wheel, supported on both sides, being both physically stronger and visually more appealing at the same time. Fire your current industrial designers.
  • + 2
 Awesome right up here. I ride a lefty max PBR and know well the advantages of the single sided design. I think most of the lefty hate out there comes simply from the fact that they look weird to people. I can’t tell you how many times I’ve gotten asked “Aren’t you afraid the wheel will fall off?” Anyway... many props to this guy. This fork takes all the benefits of the lefty and addresses some of the main drawbacks. Namely that of tunability. Excellent craftsmanship there sir. This goes right along with the TED x talk I gave regarding the need for artisanship in an age of automation. Machine design and AI can never replace human design and hand skills when creating things that directly interact with humans. It takes a human to know what feels good and works with humans. Certainly this design could be placed into automated production. But the initial buildup had to be created by hand. Well done sir.
  • + 1
 I'm something of a TED talk junkie; can you direct me to where I might find this specific one? It sounds a bit like the counterpoint to this talk www.ted.com/talks/maurice_conti_the_incredible_inventions_of_intuitive_ai
  • + 2
 I'm always down for someone wanting to try something using skills I can't possibly possess and coming up with this. The personal learning and triumph aside, it's effectively a different take on a Lefty. Which is in the market, being sold. Maybe someone else takes interest and we have a Lefty competitor that ups the ante sometime in the future.

Kinda like how Rockshox, Fox, Suntour, Manitou, DVO et al all have their take on bi-stanchion (I want credit for this word) and are trying to be better than their competitors. All of these forks (DVO comes to mind) come from people who dreamed them up or were working for one and left for another because they thought they could do it better.

I particularly like this design as it appears you could service it with "regular" tools and service kits. I'd give this thing a try for sure.
  • + 2
 There are industrial linear bearings that utilize a stepped profile to keep the inner race clocked correctly at all times... perhaps using that instead of the smooth round tube would limit rotation of the stanchion and therefore reduce the common torsional weakness of traditional forks (without depending on the axle). The "ribs" of the stanchion would also add rigidity (like 80/20 extruded aluminum beams). The Lefty's square profile did the same thing to some degree, but square tubing is more prone to buckling along its flat surfaces than tube is along its curved surfaces. The type of tube in my example would be super stiff but a bitch to keep sealed, you would have to utilize shaped seals, but in a dual crown configuration with enough overlap to use 2 bearings per side it would be insanely resistant to any angle of deflection.
I'll be more than happy to test ride the prototype, Mr. Musil!
  • + 1
 While this is really cool and innovative, what problem is being solved here? Are they severe enough to warrant this solution? What problems arise from this solution and do they out weigh the problems being solved? Is this a solution nobody was looking for?
  • - 3
 It’s amazing, but it just doesn’t follow that a one sided fork can be as stiff as a two sided one at the same weight. If quickly accessing the tire were of paramount importance then maybe you’d have something... but it’s not, so it’s only a novelty.
  • + 6
 @Rasterman: Would this be in your professional engineering opinion or is that claim based purely on "this one only has one side and two is more than one so two must be better" logic? Do a bit of research and you'll find that a Lefty is stiffer than a conventional equivalent.
  • + 3
 No theres actually a bit more than just mounting a tire. A huge positive to upside down forks is weight. I mean unsprung weight. You have less mass moving when the suspension compresses. This is why the RockShox RS1 was made. Makes for a smoother ride. DVO attempted this for aamw reasons but the overall weight reduction wasnt good. Heavy fork in general. High end motorcycles use this suspension for a reason. One extra positive is that this man used more readily avaible parts. If it specd Fox and rockshox components and such, rebuilding it would be a easy thing. The fall through with the Lefty SuperMaxx was that it took months sometimes to repair because of special parts. As far as rigidity. This would be stiffer. If you remove an axle from a normal fork you can flex the legs easily. With this fork, trying to flex any of the parts would be hard because of how tight packed and less bridging material there is. Hoped this helped Smile
  • - 3
 @Kamba6: Correct, and mainly because of the square stanchion and roller bearings. Imagine how stiff this set up would be with those implemented!

@Rasterman It sounds like you don't quite have a good understanding of dynamics or fork design... if that's the case it would probably be a good idea that you don't comment on things like this...
  • + 3
 Upside down forks have a unique and great feeling of their own, I've rode bikes with Shivers and a Foes with Curnutts and the front wheel feels almost weightless,feels so easy to pick up the front wheel and place it it down precisely and the way the wheel tracks the ground just feels so unique and so good.
  • + 2
 This is amazing because it is a stiff upside-down fork which can actually have up to date damping (unlike Lefty). The problem with lefty is that they had to squish a proprietary damper and a spring into one leg. The problem with bicycle upside-down forks is that they are not torsionally stiff. So yeah, this thing actually solve a couple of problems Wink
  • + 2
 @chillrider199: I would check the statement about the DVO Emerald being heavy. I replaced a Boxxer Team (2016) with an Emerald and they were (near enough) the same weight - and the emerald out performs it in every way.
  • + 1
 @ermoldaker: Oh, I thought I just heard that it was heavy from reviewers and such? Maybe Im wrong.
  • + 2
 @chillrider199: Unsprung weight on MTB forks is a myth. Pick up a set of 40 stanchions in one hand and lowers in the other and you'll see I'm right. Maybe in motocross, but not MTB. Also, wave a fork in the air and wave a front wheel in the air: which contributes more to unsprung mass? Half the fork weight? Or all of the wheel?
  • + 1
 @millsr4: that's not an inclusive attitude to others in the community. People come to the comments section for a variety of views.
Belittling people is just trolling. Only one suspension expert on here, he made those forks.
  • + 0
 @yeti-monster: You must not spend much time on here... trolling is standard especially when someone doesn't know what they are talking about! Just ask @WAKIdesigns Wink It sounds like you are a bit too sensitive for these comment sections and maybe the internet as a whole...
  • + 1
 @millsr4: I commented as I have never seen anyone tell someone else on here don't post comments because they don't know anything.
Waki provides intelligent alternative views and encourages and engages debate. Again never heard him say don't post comments.
You lose your respect for others in this community just because you have been granted anonymity on the Internet.
  • + 1
 @yeti-monster: Take a chill pill bro... I said maybe he shouldn't comment on things like this if he doesn't have a proper understanding of it, I never said he shouldn't comment in general. I was even fairly polite in my response with no name calling or really even being rude. He was answering someones question that he does not have actual knowledge about... this is how misinformation is spread and also how we ended up with our current orange president over here...
  • + 1
 @iamamodel: First, counting a wheel is a bit silly. Regardless you need one. We are studying a fork. Not a wheel. Second, thats a downhill fork. They are heavy. Regardless. When you think about AM and XC forks, they can be improved. Why do you think Fox did their new 32 lower casting? And Sram has the RS1. It makes a difference in ride quality and the way the suspension works all together. Regardless if there is a wheel, youre still shaving weight for improvement.
  • + 1
 @chillrider199: I used a DH fork as an example as you can't disconnect the crown from the stanchions on a single crown fork to do the experiment. I add the wheel because, right side up or upside down, any decrease in unsprung weight will be negligible once you add the weight of the wheel. Talk to a fork manufacturer (I have) and they will tell you USD for MTB has nothing to do with unsprung weight and more to do with oil on seals. Fox's StepCast design was to accommodate a narrower chassis, not reduce unsprung weight (try finding Fox mentioning unsprung weight). Unsprung weight DOES matter (ask anyone with a Rohloff hub), but USD in MTB makes no difference because forks are already hella light.
  • + 1
 The problem being solved I suspect is simply boredom. He got bored, wanted to make himself something cool, problem solved.
  • + 3
 i had to blink when i saw the first photo !! I've been up late the last few nights and honestly thought i had double vision. nice innovation though, interesting concept
  • + 5
 Looks very good for a homemade part. Kudos Salute
  • + 1
 So he's got 64mm of stanchion there.
Why not just cut down an MX coil spring fork? You've got a damping cartridge and spring in both fork legs, so you can pick either and go to town. I think one 49mm stanchion would be plenty for a mountain bike
  • + 4
 With all due respect to the fun of trolling, this looks like a better idea than lefty and it’s bearings
  • + 2
 When I come to the comment section to see WAKI's trolling and am genuinely impressed that he likes the forks! good man!
  • + 3
 Meanwhile the engineers at cannondale working on the single crown lefty are explaining to management why they were beaten to the punch
  • + 5
 Thumbs up for creativity and efforts!
  • + 4
 Looks like two lightsabres
  • + 4
 Like a double barreled/over under shotgun...
  • + 1
 @mtbikeaddict: That would be a sick name. The “Over Under DBS” (Double Barrel Shotgun.)
  • + 1
 @chillrider199: Yeah... Cane Creek has the DB Double Barrel Shock or something... But Double Barrel Shockgun would be cooler. Or shotgun... not sure about that pun...
  • + 2
 @mtbikeaddict: well punned...errr, penned. whatever
  • + 1
 Im all for innovation. The mountain bike industry desparately needs game changing innovation for sure. Its long over due. However, this is doing something just for the sake of doing it. Completely pointless.
  • + 1
 I must correct the article "jednokorunková" means single-crown in czech. The lefty is double crown. That is why it's special and different. Btw. One sided is "jednostranná"in czech.
  • + 2
 It seems that if one person makes something new everyone on pinkbike loves it, but if a company does, everyone hates it
  • + 1
 True that. At least he used existing standards.
  • + 2
 Strangely,
I’ve seen the exact opposite! People, usually the …spoiled brat’s variety, demonstrate hate when the see something new / homemade / personalized…
The usual words are:
“Kill it with fire!” (Sometimes followed by the most copied, “it looks like a session”!!!)
As for the companies, there IS a great difference. They are supposed to provide mass produced products that will work along with other so we might have a working bicycle. When the various companies introduce strange new sizes and more, they owe first, at least out of respect for the client, to sit down and agree on the new standards.
The rest of us (people), we are free to create. After all these creations made our sport what it is today…
  • + 2
 @uncajohn: yeah....I hadn't scrolled down to the hidden comments. What a bunch of miserable bastards. What have they built today?
  • + 1
 @yeti-monster:

Nothing. That's why they hate new & different things.... This guy is creative, that only makes him a... minority.
Mr. Milos.
If you're going to answer questions, you have to do some seriously filtering. Your design and craftsmanship are, at least, superior.
Thanks for sharing
  • + 2
 If two legs on one side is good, three must be better. I don't really know what this project accomplishes but I like it!
  • + 1
 This is fantastic!
And, yes. If you can, you ought to do! After all that’s how the whole mountain bike sport stepped into existence…
Great work Milos…
  • + 1
 Anyway here’s the link to that talk if anyone cares to click. It features guitars and Mtb design as examples. youtu.be/0MfOFYXQo0s
  • + 1
 Oh, thanks. I was looking for it above. please disregard.
  • + 1
 I seriously doubt it is stiffer than a Lefty with that single crown. Great looking effort though. As for that RB monstrosity, it needed to break. Appalling!
  • + 3
 Mad respect for building it ur self!
  • + 3
 Damn. That is pretty cool. Props to Mr Musil for building that!
  • + 2
 Love the uniqueness and creativity, even if it's not functionally superior. Fit and finish is impressive.
  • + 2
 Curious, can anyone enlighten me as to what the black thing between the brake caliper and stanchion is?
  • + 2
 Looks like a cyclocomputer mount www.mmbike.cz/foto/kola-2011-068-jpg
  • + 2
 that propain ib one sick looking ride. me likey
  • + 1
 "That looks awesome...A NAAAAHT"

-Borat
  • + 1
 "We need to introduce a new front hub standard, we need to make the forks people made themselves obsolete" -SRAM
  • + 1
 custom frames are cool, but when I see a custom suspension part, I just loose it! soo wicked
  • + 1
 Wouldn't mind seeing that replicated on the RHS too. 4-stanchion fork would be rad!
  • + 2
 love it kinda reminds me of the late great John Britten
  • + 1
 This fork and the Insolent Dh bike are one of the most exciting new creations for a while!
  • - 2
 Is this overblown lefty supposed to balance the weight of all the components on the right right side? If there's two pistons, why not make it symmetrical and have the other piston on the other side of the wheel, just like 99% of all shocks? Kind of makes you think when Darwinism is going to occur for the Lefty. Hell, make it 3 or 4 shocks on one side to make it super plush FFS!
  • + 2
 ale błotnika za huja nie podepniesz Razz
  • + 2
 Well you're still misspelling his last name a bunch of times, it's MusilSmile
  • + 1
 Thanks for that – it appears to have been some kind of funky autocorrect function. All corrected now.
  • + 1
 @alexcgevans: Also, in the google translated part, "jednokorunková" means single-crown, not single-sided. Single-sided makes more sense in the context though.
  • + 2
 THis is pretty cool, I don't care who you are
  • + 3
 Marvelous!!!
  • + 1
 Super innovative new way to waste carbon!
  • + 1
 Somehow, this fork feels like a women with 3 tits.
  • + 1
 Join the club of unnecessary developments. belong to the fashion world.
  • + 1
 Smoken that 64mm squish squish!
  • + 2
 PropainSmile
  • + 1
 As cool as these look....I don't understand what the point of them are?
  • + 1
 what? april fool's day already.
  • - 2
 People making their own parts is always awesome, I do wonder tho what kind of a person looks at a lefty bike and thinks: "This would look better if it were even more lopsided!"
  • + 1
 Looks good, where's the fender mount?
  • + 1
 Yeah okay, it looks well made, but why?...
  • + 1
 Two rights don’t make a good fork but they do make a good airplane
  • + 1
 Looks awesome! Great to see people thinking outside the box
  • + 1
 Any plans for 29+?
  • + 1
 Looks like a lefty.
  • + 1
 Oh, but why?
  • + 1
 Love it!
  • + 1
 Wow awesome.
  • + 1
 looks like a false leg
  • - 2
 So I glanced over the article...

But two stanchions on a single sided fork?Why!
  • + 8
 Stiffness
  • + 2
 I haven't found the exact answer, but I assume it has to do with positive and negative chambers, the same way the left and right stanchions on a normal fork perform their own duties. Since he borrowed parts from other manufacturer's, I assume this was easier than going with one stanchion and getting too technical.
  • + 5
 Same as a normal fork, one houses the spring and the other the damper.
  • + 2
 Because the biggest issue with lefties is trying to have a good reliable spring, and good reliable damping, is next to impossible while maintaining high performance in just one tube. Leaving two tubes makes a lot more sense, since the industry has spent so long refining damping and springs for that size of space(independent tubes).
  • - 4
flag takeiteasyridehard (Jan 31, 2018 at 8:32) (Below Threshold)
 I don't see why people downvote you, it's a legitimate question if you haven't dealt much with lefties....fyi they suck because manipoo makes the internals, and they are too complicated to be good at anything for too long, and a pain to service, requiring proprietary poo tools....
  • + 2
 Theoretically, since the stanchions are connected both at the bottom and the top, it should be as stiff as a fork with one 64mm stanchion. Or am I just making things up?

It seems to me to be an easier way to manufacture a "lefty" without having to figure out how to package a spring and damper in the same leg and still achieve rideable stiffness.
  • + 2
 Torsional stiffness. If you had one it would try and rotate around inside the single tube without having to revert to a "square in a tube" design like a Lefty. If you're trying to adapt normal telescoping fork parts and not just re-make a Lefty this is one way to go about it. Also makes it easy to separate the damping from the spring like in a conventional fork. Kudos to the builder, it's a novel solution.
  • + 1
 @takeiteasyridehard: that's a good point, rather then have an overall complicated internal for a single stanchion.
  • + 2
 @tigerteeuwen: lefties are not complicated, have you ever taken one apart?
  • + 2
 @takeiteasyridehard: rubbish! check your facts, they are not complicated at all.
lots of companies have made internal damping for lefties, not just manitou! easy to service, the telescopic action runs on bearings so they don't wear like conventional forks do. they are stiffer, lighter and stronger than conventional forks..
  • + 1
 @MortifiedPenguin: Just spitballing and assuming circumference=stiffness, it would be more like a single 45mm stanchion because the cross sectional area of two 32 mm stanchions (not accounting for wall thickness) is close to the cross sectional area of a 45mm one. Imagine one 43mm leg from a honda CRF(except its probably way thicker inside)
  • + 1
 @Deoratwo: Makes sense. But I would imagine 2 thin walled 32 mm tubes would be lighter than 1 thick walled 45 mm tube.

Either way this does seem like an easier way to build a "lefty." Which begs the questions, why did the lefty get built in the first place? And why do we need any easier way to make one?

Awesome project though.
  • + 1
 without a keyway one round stanchion will spin, two bonded will not spin, without a keyway. leftys have notorious bearing problems, this sidesteps the issue in a simple and effective way.
  • + 2
 @lifted-d: bearing problems? Like what? I have had no issues in over 15 years, do my own servicing on them, easy!
  • + 0
 @baggyferret: yes I have taken one apart. There are certain versions which are more ridiculous than others. You obviously haven't acquired the taste for proper suspension performance. Lefties leave much to be desired. And now when they need serviced, you usually send the thing back to cannondale...lame. I guess you're lucky you like yours and can easily service it. That is not the case for all of them. I'm not the usual lefty hater who has no experience with them...I have taken them apart, and I have also ridden one. They suck. They are plenty stiff and light though.
  • + 3
 @takeiteasyridehard: so where's the difficult bit? I have 4 different versions in use right now, also i have other conventional forks, there is no comparison, by saying 'they suck' doesn't explain anything, normal forks twist, normal forks wear coatings off stanchions, normal forks have stiction because of the bushings, lefties dont suffer any of this, so why do you think they suck? Im not trolling, i use both lefties and normal forks, lefty rules in everything, simple engineering proves this
  • + 3
 @takeiteasyridehard: you also said only manitou make internals for lefties...wrong! Google it and you'll see, you mentioned bearing problems, what bearing problems? Im happy to hear your views, but facts only..
  • + 3
 @baggyferret: I haven't ridden a recent Lefty so hopefully it's fixed, but I owned 2 in the past and they lost travel due to bearing migration on big hits. It could go for weeks with moderate hits and not have a problem, but a single big hit and it would lose travel, and I'd have to take the top cap off and forcefully top it out to regain travel.

I also had friends with Lefties and they seemed very hit or miss. Some worked great with little maintenance forever, but others needed constant maintenance. I think the product required tighter tolerances than CDale could deliver at the time. Plus, while spring and damper service was the same as any other fork, bearing maintenance was a royal pain in the ass when needed. Hopefully they've fixed the issues, I'd love to try one again.
  • - 1
 @baggyferret: I never mentioned bearing problems, even though other's did. I don't know why you are so sensitive about this. They suck, it's my opinion. From experience. Get over it.
  • + 2
 @baggyferret: genuinely interested in this discussion. Had no experience with lefties. I can't see why the damper and spring in one leg is an issue either .... Are all our rear shox not this design?
Why is this design not universally accepted, patent issues?
  • + 1
 @dthomp325: appreciate your time replying decently, yes i have heard/experienced bearing migration, i don't mind doing a quick 'reset' the latest lefties don't have this set up.
Again, what you say is true, some lefties are trouble from the get go, i have been lucky, but we must remember that there are a lot of lefties out there, from an engineering perspective they are the 'rolls royce' of front suspension. Bearing maintenance is a simple gaitor up, clean and smear grease, much easier than replacing stanctions, bushings and seals on regular fork, and much cheaper! The huge benefits and cost saving in the long run make the lefty a wise investment, especially if you ride as much as i do!
  • + 1
 @takeiteasyridehard: not sensitive just dont like people spreading nonsense. Maybe they suck because you didnt set yours up property, if you look at the superior quality and design of the lefty, its clearly a better design, not cheap to make but built for performance and long life. I get over everything with my lefties Smile
  • + 2
 @yeti-monster: there is no issue, there are people that just dont like the 'look' of lefties (which i get) so they seem to project hate without investigation.
You get it, rear shocks perfect example.
Lefties run on needle bearings, two square tubes so no twist, super sensitive, very smooth, no stiction, massive stub axle so stiff and strong, dual crown.
Yes again, patent power! there are adapters now so lefties can be used on most frames.
  • + 1
 @baggyferret:

> yes i have heard/experienced bearing migration, i don't mind doing a quick 'reset' the latest lefties don't have this set up.

The fix is quick, no big deal, but the thing that sucks is you lose travel on big hits and either have to finish your ride with less travel or pull to the side of the trail and fix it.

> Bearing maintenance is a simple gaitor up, clean and smear grease, much easier than replacing stanctions

I'm not sure you've actually performed this service. The Lefty has 4 sets of bearings, each of which has 2 races. All 4 bearings and 8 races will fall on the floor in a heap when you drop the lowers to gain access to these for maintenance.

Now you have to measure all of the races with a micrometer, since they all have different thicknesses depending on the tolerances of your specific fork. You regrease them or order new races and bearings and are ready to put them back in? I hope you wrote down the exact position of each of the 8 races, because the fork won't work properly if you accidentally swap a 0.025" race from one side of the fork with a 0.020" race from the other side.

Ok, you remember to write everything down and have carefully positioned each of the 8 races in the correct place, now you find that you don't actually have enough fingers to hold all of this together as it's reinstalled into the fork, and you have to call a friend for help.

Granted, bearing maintenance intervals are long, and this service is infrequent, but when it needs to be done it is a giant pain in the ass, no doubt about it.
  • + 1
 @dthomp325: dude, too deep! the losing of travel is minimal, no issue when riding. the end.

the bearings and races DO NOT NEED STRIPPING FOR MAINTENANCE, if/when the lefty develops fore/aft movement then this can be done simply. nothing 'falls on the floor' unless you have no idea as to what you are doing. i'm not going to waste time explaining, you can make this a big deal or if you are mechanically minded it all makes sense, i won't be asking you to rebuild my motorbike engine! lol.

tools are available for complete rebuild or just make use of elastic bands and a balloon, RTFM (read the flipping manual), a little thought before hand goes a long way and saves you calling on friends!

difficult for some people, a piece of cake for others, depends where you are skilled.
  • + 1
 @baggyferret: The bearings and races need to be dismantled for maintenance any time contamination is introduced, for example if the boot rips (on the old forks) or the seals die (on the new forks). There is no other way to remove contamination from the bearing assembly.


It is significantly more difficult than any maintenance on a traditional fork, which don't require "elastic bands and a balloon", and even if you've done it before and successfully remove the bearings and races, you still need to carefully record the position of all 8 races due to the different thicknesses. It's not a "piece of cake", I worked in a CDale shop in college and have performed the operation dozens of times. Most shops in the US won't even do it anymore, they will send it back to CDale instead.
  • + 1
 @dthomp325: routine maintenance isn't a strip down because of water ingress due to ripped boot! I'd not ride with a ripped boot in the 1st place. Lets see how you fare replacing bushings in the oh so wonderful normal forks. Compare like for like, the lefty is head and shoulders above the rest. If mechanic work isnt easy maybe you chose the wrong field to work in. You seem hung up with bearings and races that if maintained property will last 10 years or more. There's plenty of places to get a lefty serviced check on google, you're being silly now.
  • + 1
 maybe the newer ones are better, but from extensive experience as service manager at a large mountainbike only shop in BC. They don’t stand up to use and abuse from our customers. The lefty alone is the primary reason we no longer carry cdale. Seriously
Nearly a 100% failure rate with our customers that ride often and aggressively. Not happy people.
  • + 1
 @lifted-d: interesting, so what was 'failing' on 100% of the lefty units?
100% failure rate goes against my over 15 years of lefty use, not to mention countless others, if 100% of lefties fail, surely Cannondale would of stopped producing them? The older models are renowned for being reliable, there is a great lefty following for good reason, even being used on fatty bikes, I've covered thousands of miles on my Ti litespeed with a lefty...maybe your workshop was setting the lefties up wrong and CAUSING the 100% failures..
  • + 0
 @lifted-d: so you've been a pinkbike member since 2007, a service manager at a mountain bike shop BUT YOU HAVE 2 FOLLOWERS.....hmmmm, something fishy about you...2 FOLLOWERS....why only 2 followers? Did you ruin everyone's lefties? lol
  • + 1
 @baggyferret: why would you correlate followers on pb with anything? And the staff was trained by cannondale back in the day. the bearings failures were often accompanied by damper or air spring issues. generally junk from all angles. Also in more recent times (2015) a friend of mine tried to run an endure season on one and it barely lasted 6 weeks before damper failure. I warned him, it failed, no surprise.

so whats your deal? lefty idolizer? own a cdale shop? you don't seem to have a grasp of the overall picture, even if yours have been flawless, I am not the only one with bad experiences with these.
  • + 1
 @lifted-d: if you had so much to do with riders/bikes then its only natural to chat with them on here, there is nothing to suggest what you are saying is true, nothing to back up your claims. I have over 10 lefties, and i ride more than most pro's and have been riding fulltime over 10 years, photos show im active, friends will vouch for me, if lefties were as bad as you suggest then where's the proof? I recon you are trolling.
You have been on pinkbike 10 years, 2 followers, it doesn't add up, you probably bought an abused lefty and couldn't rebuild it and that sent you on the lefty hate mission. I am a trained mechanic, welder, painter, panel beater, engineer, health and safety inspector and lots of other things, i find lefties to be very well designed, light, strong, stiff and easy to work on. From an engineering perspective, they are fantastic. I say it like it is and i can back up what i say, you say lots of stuff but offer no proof. I am still using a DLR 2, original bearings, smooth as silk, lefty max 140, original bearings, only done 1 damper service, perfect, i run a speed 110 on my rush, done damper service and air spring, perfect, also speed 110 on my litespeed i built for touring, rode through 8 or so countries on that bike, all weather etc. Show me some repair receipts, back up what you are saying!
What are these 'bearing failures' you keep on pushing? The air springs take 5 mins to strip and fit new o rings, the dampers take under an hour to strip, rebuild and refil with oil, i really can't see your problems, hence my comment about you trolling. Prove me wrong.
  • + 1
 I would never buy a pos like a lefty! And I have no reason or need to offer proof to you or anyone else. Maybe you ride a lot, good for You. doesn’t make me wrong about my experiences regarding lefties. And with corroborating stories in this thread as well as else where on the net, who sounds more legit? You who own 15 lefties and have never had a problem? Gtfo
  • + 1
 @lifted-d: You as good as admitted you are talking crap. 2 followers in 10 years, now i see why. Lol.
  • + 0
 Whats with your follower fetish?
Guess I’m not a social media mogul like you. I’m glad you have had a terrific experience with your lefties. There are
Plenty of folks out in the world that havn’t, that is all @baggyferret:
  • + 1
 @lifted-d: but TWO followers in TEN years.....no-one wants to hear your non-sense....get it? lol!

you've never owned a lefty but have lots to say about them....stop posting ffs.
  • + 0
 Seems you take yourself very seriously. Could you offer documented proof that your fleet of lefties have never had any failures that were within the recommended service intervals? If not then I guess your spewing an equal stream of rubbish as to the reliability of these forks. You make me laugh. Taking yourself and your forks so seriously, I bet all your followers are very close and dear friends of yours. Get a life@baggyferret:
  • + 1
 @lifted-d: people like you bring out the worst in me. i just say things as they are... i've got no need to lie, i use normal forks and lefties, the lefties need less maintenance, they are lighter, smoother and last a long time, the normal forks have issues as i described earlier. if you ever come to Wales i'd be happy to take you out riding, you can use one of my lefty equiped bikes and see for yourself how good they are. if you piss me off i'll leave you there lol! trying to derail the discussion wont work.
  • + 2
 @baggyferret: sounds like a sweet holiday invite, can I come if he doesn't?
  • + 1
 @tigerteeuwen: lol, i'm sure we could come to a deal, you live and ride in one of my favorite countries....tup
  • + 1
 @baggyferret: thats a nice offer and someday id like to ride there, I have ridden older lefties and they were nice enough, though I only did 'shop rides beginner intermediate' and never owned one. I think one point to note is that your experience is statistically sort of n=1 ten times over, whereas my observations are n=100's plus. you may infact set yours up well for your riding style, the hundreds that went out the door from the shop were 'set up' to average set points but its no secret that often customers adjust their settings. we had no control over that aspect of use.
As for 'leaving me out there' lol I think i'll be fine thx. I've been riding mtb since 1984 in Vancouver, I haven't seen everything, but there isn't much that phases me either. my relative silence and lack of followers is likely that In the shop days I would look for trends and product opinion info. there is shop politics to avoid on the web. and this thread is an example of some of the bs that was always best left alone.
  • + 1
 @lifted-d: you have pointed something out that does make a lot of sense, i am fickle, after years of restoring sports/racing jaguars for very wealthy collectors, i have developed a zero tollerance to 'good enough' set up's, i must have things as close to perfection as possible, again, i agree with your views on 'customers' that fiddle with their stuff once it leaves the workshop without any knowledge of what they are doing and that could well be where the problems arise..maybe my OCD with my bikes has been the reason i don't get failures..
wow, some of my early videos of 'dangerous dan' and the boys in vancouver suddenly flashed before my eyes, what a place that is..and you ride there, i have always dreamed of going there, this is one of the reasons i love pinkbike so much, seeing all of the world through other bikers eyes in their edits etc...Wales has a lot to offer the mountain biker, where i ride mostly, is miles from others, only logging roads to get into the heart of the forests and soo easy to get lost or hurt..love it!
  • + 2
 @baggyferret: you like Lefties and vintage Jaguars? I think you might have some type of masochistic mechanic complex.
  • + 2
 @dthomp325: lol! you could be right....i don't mind a bit of pain either....for the record, lefties are better made/designed than the 1950's racing jaguars..
  • + 0
 Why tho???
  • - 3
 Kill it with fire!
  • - 1
 Frankenfork
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