Proto DM Stem from Cero Design

Mar 25, 2011 at 13:12
by Tyler Maine  
Cesar Rojo is the engineer and WC DH racer at Mondraker that helped bring us the Summum, now he's working on a new direct mount stem. Check it out! *Video added!*
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Cesar went from a medium frame in 2010 to the larger frame in 2011 in order to take advantage of the added stability found in longer frames. But he needed to shorten up the cockpit to make up for the added reach. Here is what he has to say about the project:

"After trying the stem out, having a longer bike makes it way more stable - what leads in more stability, but handling of the bike stays the same, I didn’t feel anything different. Having 10mm offset the handlebar almost turns from its center, so it makes the bike more direct, same as what you feel when you go from a 120mm stem to a 80mm stem. The difference is really huge.

It was a really big surprise how good the bike felt on the track. Mainly due to a longer bike, but feeling like you were riding the older shorter bike. I moved from a medium Summum to a large frame. I was riding a 62º head angle, 800mm front center and 450mm chainstay.

The stem at the moment is just a prototype done by our studio www.cero-design.com, it has an offset of 10mm, a weight with no bolts of 54gr and 68gr with bolts, stem and clamps. Uses 6 bolts instead of 8 bolts like normal stems and that is pretty much it.

Designed two weeks ago, prototyped last week and raced this weekend." - Cesar

From CAD to prototype in pictures:

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Author Info:
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Member since Mar 27, 2001
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138 Comments
  • 81 1
 I'm liking the no bullshit "Designed two weeks ago, prototyped last week and raced this weekend" approach.
  • 10 0
 MX style..nice
  • 1 0
 Siiiiick !!!!!!!!!!!!
  • 3 0
 make it for 888 too, please!
  • 2 4
 Not sure the length would feel too sweet, might make the front end feel a little short?
  • 21 7
 This is a bad idea, im doing machanical engineering myself, and all I see in this is Flex (4 Piece design meaning flex on threads) not the stiffs ( threads again) and putting a fair bit of stress on the crown threads.... (I know im gonna get neg props because there alot of ignorut people...
  • 1 4
 And it's weight without bolts... whack 20/30gs on that...
  • 6 0
 well i'm mechanical engineer too and the flex is not a matter if the part can handle it. Just the feel would be flexy.... Now is the timing to take the idea and build it stiffer! hahaha
  • 5 0
 **for first comment** with such a simple design there is no reason why it should take any longer than 2 weeks haha, theres probably almost no stress on this thing cuz all the presure is directed straight down or straight up, great design dont know why these havent come out sooner
  • 7 1
 @ DH-Til-I-Die, if theres gonna be flex here, explain all the other split clamp/4 piece DM stems out already, IE, deity, twenty6 ect, you dont hear people complaining about flex on those?
  • 5 0
 @ DH-Til-I-Die, In fact, stress on crown threads is less than any other design, simple moment/torque formula...
  • 2 2
 @billypopo , do you agree through one peice will always be stronger/stiffer? For instants... www.chainreactioncycles.com/Models.aspx?ModelID=49247 , that would be alot stiffer, and stronger. Im not ranting at this product but I've seen a Onepointfive racing stem like this just get completely wrecked.
  • 2 0
 I agree with mantasv haha it looks like a sick stem. clean and simple
  • 4 0
 All I know is that the guy in the video is phucking fast! Eek
  • 2 0
 @ DH-Til-I-Die I do agree with you that the stem in your link is way stronger, since it's a one piece. But for stress in crown threads and crown, this design is 'better' than any other 'normal' integrated stem...
  • 3 0
 at DH-til-i-die... this stem reduces the eccentricities (look that up in your text book) from 40/50/60mm to 10mm and likewise reduces the torque and moment loading in the stem... therefore... less stress, less strain i.e. flex... and/or less material required i.e. lighter. This design almost simplifies the loading to straight compression and tension.. so, pay attention in class, because this is a great idea.... and remember the first principal of engineering: KISS
  • 20 0
 That would be a beautiful addition to any double crowner,inherently strong,as light as a feather,and nice and simple.Lovely component,well done Cero Design,best of luck with it.
Gringo. Drool Salute
  • 12 0
 yeah? i bet if it sells its stupidly overpriced.
  • 2 0
 its unique..... greed will be involved for sure.
  • 1 0
 its not all that unique tho, its been done before, just not with as little material its about a few £'s worth of metal and like a £100 pricetag more then likely.
  • 7 0
 I raced with a similar setup on a Rotec PRO DH in the late nineties. It worked really well. Nice to see someone exploring that concept again. Maybe this time it will catch on. Now if only someone would make a frame long enough for a six foot five rider...
  • 4 0
 moto style....i'd love to try this out.
  • 4 0
 XL v-10 carbons are huge, im about 6'2 it might have been alittle big but it felt so good to be able to stretch out on a dh frame for once.
  • 2 0
 Love it!
  • 2 0
 x2 6'4 here and its a bit hard to find one long enough... The XL jedi works but would be nice a tad bigger...
  • 3 0
 I am dealing with this right now I want a 29er with a 26 inch toptube and one of these stems, with 800mm bars. I am sick of mountain bikes for midgets.
  • 7 0
 You've obviously all forgotten the Azonic Zero stem that came out years back. Not as neat or light, but it was a 0mm length well before this. This is hardly groundbreaking stuff - it's only appeared now for another round of testing - it won't take off, just like last time.
  • 3 0
 yea, its been done many times
  • 1 0
 Sure marzo used a smiliar style for its monsters
  • 8 1
 Almost centered. Big Grin
I've started riding bicycles after mx bikes and after that I was wondering why do bicycle stems have any offset?
I like this one. It simply gives a better control I think.
  • 5 1
 i agree with you i am riding a supermoto and riding bikes too, and this stem is like an mx stem, so coool, and i think it provides good handling
  • 4 4
 It seems to be going the opposite way of the mtb trend though. That will raise your bars pretty high. seems like low bars with a low rise stem is what people want. This will raise your bars an inch or two it looks like.
  • 1 0
 Less raise on handlebars and your problem is solved. (Though todays DH bars are almost flat)
  • 2 0
 Or integrated bar mounts on the triple clamps.
  • 2 0
 @ climbingbubba....... it also going with the trend with super short stems....so if ther that bothere....upside down handlebars Razz
  • 4 1
 They should make a top crown that has the bottom shape of the stem carved into it so all you need I the top piece. That way you can Solve the problem of too much rise and you can also have only have the weight
  • 2 0
 Actually there isn't really a trend for shorter stems in mtb. they have been staying around 40-50mm for quite a while. The new trend is drop stems and low rise bars. Running zero rise bars and a drop stem would be a full 2" shorter than the stem above.

Im not saying the stem above is a bad idea, I was just pointing out that its not what the current trend is. For taller people it would be awesome but for shorter people it could cause a problem with weighting your front wheel in corners since it will be up to 2" higher.

Oh and why the negative props above? don't like when people actually point something out that makes you think?
  • 4 0
 Bahhhhh Noobs listen to Miff and everyone else on here- there's been tons of these stems in the past decade. Learn about Motorcycle chassis in relation to weight distribution, rake and trail settings and design spec and typical rider position- Bike's have varying amounts of stem length to deal with the fact that they are operated entirely differently, with different chassis weight, geo requirements and needs and how the machine handles 'in space'- These stems have been around for ever, personal pref really, but there is a reason you typically see a certain amount of stem length on bicycles, and it has everything to do with 'physics' check it out sometime. Nice design though.
  • 1 0
 Wow... finally someone who knows what they're taking about. Zero-length stems are OLD NEWS and they didn't work back in the day. I had one for about a month and got so sick of the horrible handling that it went bye bye.
  • 1 1
 They didn't work back in the day because people were riding short frames! The benefits of this stem only come into play when you have a longer toptube eg by sizing up in frame size. Sheesh didn't you READ THE WHOLE ARTICLE! I have a Specialized Status 2012 frame and run a 17mm (ajustable from 0-22mm) stem on my shiver DC and can tell you it works GREAT!
  • 1 0
 The TT on the frame I had then was VERY long as was the WB of the bike... didn't work. Sorry, it's physics, not an OPINION. I under stand the science behind clearly you don't... SHEESH don't you read posts you respond to???? I'm not saying the bike will explode beause of the stem, I'm just saying you loose steering stability and as speed and forces increase it gets worse... Read the post above mine, he and I get it, you don't...
  • 1 0
 Well then it doesn't work for you and thus your opinion. I like having a 1210mm wheelbase with a 17mm stem that is my opinion. However, the longer the wheelbase the more stable the bike in a straightline=FACT. My bike is way more stable at speed and still super agile due to the increased agility provided by the short stem. Is there a point when it becomes too long i.e. starts to affect other aspects like riding tight singletrack? Sure, but it's not around 1200mm maybe +1300mm i.e. closer to MX wheelbases.
  • 3 0
 Flex what Flex, give me a break..e speculation at its best again... Stiffer if anything. HELLO.

Motos [dirtbikes] have been doing this for years plus 40 odd.

Good on Cesar, looks great to me.

As for same old nothing is new but that doesn't mean someone can't revisit older ideas or work with the concept and create new ones.

All bikes have round wheels too doh!

As for sizing, stem height et there's so many variables comes down to individual rider setup! which most people here seem like they have no idea of!

Many people I see on bikes have too long a stems and to small a frame, this will be a good step, maybe not for everyone but thats great because there are so many stem and frame options out they're, and that for me is whats good, options,

Now I could run this on a large frame instead of a medium I'm looking at, go zero stack reducer headset, low set Boxxer crowns low rise handle bar 780mm.

Instead of a Medium frame with a 50mm stem, longer front tri gives more stability, more power through legs for pedaling less pitch while flying across terrain which all adds up to moar speed!

Good work guys Euro's are really stepping it up imo.
  • 7 0
 hello moto
  • 6 0
 Marzocchi also had a zero stem on the monster and superT models.
  • 1 0
 Hmm, comments challenging the viability of new designs are deleted? Nice open-minded conversations you strive to keep here, PB.

As a mechanical engineer and component designer myself, I believe I'm qualified to make such assumptions. Anyone can make a pretty part in CAD....let's see some abaqus finite stress analysis models.
  • 1 0
 I don't think a single comment was deleted on this post over the weekend, so I am not sure what the complaint is. Are you looking at the comments in Time or Score order?
  • 6 1
 reminds me of the marzocchi DM stem that they made years ago.
  • 1 0
 yea, this looks like one thats been on a bit of a diet Razz
  • 1 0
 had one on my shivers
  • 2 1
 Yeah, and weren't they on the JrTs of all things? Like reinventing a really old, worn out, been done before wheel...
  • 2 0
 Its Nothing New! Specialized has been working on this concept with the SX trail stems at 30mm. All SX trails have very long wheelbases and the 2011 is even longer with the medium size at almost 47 inches.
  • 3 0
 I don't think you guys are fully getting the concept. It isn't just about the stem, it's also about going up a size in frame.
  • 1 0
 I agree. Large frames are awesome (I'm 6'4" haha)
  • 2 0
 when, where can i get one of these!?! totally seriously, if anybody knows of a way to get this stem please let me know. i realize its still proto, but holy hell that thing is dope!!!!
  • 1 0
 if you really want one let me know Graeme, i have a buddy who has a machine shop, i can design one and have it made for you..
  • 1 0
 i was thinkin about drawing up something similar but with a 2 or 3 piece design to make it a little more rigid. would like to try one out. curious on how snappy the response is at high speeds now that you eliminate that much more forward leverage of a typical 50mm length...
  • 1 0
 This is great little piece! When people can´t decide frame size, just go larger and adjust reach, just switching stem. Or when only large/small frame is available. Large is too big and small is too small problem is now solved, just go larger. Just like on road/xc bikes.
  • 1 0
 Not that it is a big deal...but no more leaving the steer tube long so you can sale the fork later...cut to fit.....but still is bad ass that it is all moto look.....bet its super sweet and stiff
  • 1 0
 I hadn't even thought of this... I'd rather not cut to fit cause i'd like to transfer my fork between frames. But I guess it's the compromise.
  • 1 0
 U can allways put some spacers under the second crown,directly on the headset cup...
  • 1 0
 This is a possibility... but you can only go as high at the stanchions will allow... Ahh well I have single crowns anyway Razz
  • 1 0
 Great work integrating the bolts for dual purpose there, i would be worried about bar rotation in a crash with such a small surface area however. Then again, you could just not crash ;P
  • 3 0
 with the sweep of the bars wont that mean your hands are actually behind your fork?
  • 1 0
 wow that guy is pinned but i dont like the idea of the stem gotta have abit of length in the stem, id like to try it and c what its like but i wouldnt want to buy it anf find i dont like it
  • 5 1
 so mx style, i like it..
  • 1 0
 Is possible to place this into Go-ride flat crowns from 888? couse they are originaly for 25.4 bar and theese looks really nice.
  • 1 0
 looks good, i guess it jus personal preference where you want your bars. but for the moto feel, this is good. i would give it a try
  • 1 0
 yea i think if DH bikes were to go to this they would have to have a longer top tube. even my 28mm straitline feels awkwardly short.
  • 2 0
 Not longer top tubes just the same small seat tube on all frame sizes. Then you just buy the right length reach/stack for you. This is effectively what the Summum has already.
  • 1 0
 And Summum is a hell of a bike...
  • 2 1
 what was always in my head is now here. i thought it would be ridiculous to have this kind of stem but here it is. im not crazy after all, LOL!
  • 5 6
 Yo thats too light and minimal design. I'm sorry but rather bash this company than see another rider down for the count because he wanted to shave 3 ounces off his front end. There's a fine line between being a weight weenie and reckless endangerment. Do your self a favor and buy a real direct mount stem and don't worry about saving such little weight at the expense of your grill or ribs. That whole idea about switching your bike up to a large to compensate for this redicilously short stem is garbage. Couple millimeters isn't going to do as much as more push ups will for your front end control. Leave your setup alone and get in shape!
  • 5 2
 go look at a dirtbike and come back and comment about design and weight.
  • 3 11
flag shishka (Mar 25, 2011 at 19:57) (Below Threshold)
 Yo shut up about dirt bikes. Anyone who can afford a dh bike can easily buy a dirtbike. THIS IS ABOUT DH BIKES, and people I've personally seen break ribs as result of flimsy direct mount stems. I'll be the one chugging by on my beastly dh bike while you pick up the pieces!
  • 2 2
 um... it the other way round, try switching to this stem to compensate for the reach on a large bike.....

may i suggest reading lessons?
  • 3 5
 Obviously sarcasm is beyond your comprehension but you going to be aiight. I was commenting on how stupid the concept of switching a frame to suit a stem was. Be my guest to waste all your money on new frames, stems , hairpieces, viagra, whatever floats your boat. Anyone who has been in this sport as long as me has already seen this product come and go. Many companies have produced short 0 offset stems and nobody wanted them. All of a sudden some little company puts a stem out and you guys jump on it like it going to turn you into pro status.
  • 2 0
 Except no ones suggesting switching frames to suit a stem..... Funny you talk about other's lack of comprehension. Pot, meet kettle.
  • 3 0
 & where does cost of bikes come into this? You are bashing a prototype stem, A PROTOTYPE.
  • 1 3
 Did you watch the video? They were suggesting this stem would make you want to switch up to a larger frame for more stability at high speed. I think they definately high over there. You guys stroking them a little too much but they appreciate it. Bottom line nobody wants a short ass stem.
  • 2 0
 The market disagrees 100% with you.
  • 1 0
 the stem isn't anamazing idea, it makes sence only using 6 bolts, but that's about as unique as it gets. Forget that tho, that track looks awsome!
  • 3 1
 Why does it take us soooo long to borrow from dirtbikes?????
  • 1 0
 Not really a whole lot to look at here. Minimal machining, simplistic design, questionable integrity.
  • 2 0
 Still no production for this piece alone ?
  • 2 0
 I'm all about it! I like where their heads are at.
  • 2 0
 idk about having it in two pieces like that.....
  • 3 0
 Same here, I don't think it's the fact that it would be flimsy/unstable.I just don't like the aesthetic quality to it.
  • 1 3
 hahaha found you
  • 1 0
 I'm glad to hear this is nothing new. I thought it looked to simple and sensible to not have been invented a long time ago.
  • 1 0
 Gamut created something rreeeaallyy similar awhile back. same idea and pretty much same design
  • 1 0
 Will this be available the Marzochi 888? I had already think to make one of those stems but good someone had think that Smile
  • 2 0
 retro. my buddy had an old marzocchi one of these a ways back lol
  • 1 0
 There is suspensions with the stantions too up, could they touch in the bar?
  • 1 0
 why not? my 450f has this style stem. might as well stick it on the dh bike too
  • 1 0
 CHECK THIS STEM..... MX STYLE ZERO OFFSET ALMOST ..... www.pinkbike.com/photo/6515942
  • 2 0
 Looks weird. I like it.
  • 6 1
 looks so good, and i have actualy thought before why don't they do it like that.
  • 1 0
 I would rather the bike...........
  • 4 0
 Thats not even a stem, its a DIRECT MOUNT.
  • 6 0
 Reminds me of my moto.
  • 12 0
 Wondering when they would adopt 20+ years of moto tech for dual crowns.
  • 1 0
 Smart and easy ! I love it!!!
  • 1 0
 Such a moto style to it, i like it.
  • 1 0
 so simple....suprised no one thought of that before
  • 1 0
 reminds me of old Rotec ages tho...
  • 1 0
 So .... "a few" monthes later.

What's up ? Some production ?
  • 1 0
 Won't it make the handling very, very twitchy?
  • 2 1
 you mean "direct" in marketing terms?
  • 7 1
 As race bikes get slacker head angles and wider bars, going with a shorter stem is a viable solution to bring back the steering response that was lost in the process.
  • 2 12
flag jason21218 (Mar 25, 2011 at 14:14) (Below Threshold)
 This type of stem slackens the steering even more.
  • 3 1
 learn some basic geometry and then maybe you'll understand better how your bike works. but if you not interested forget it
  • 7 1
 Actually no, basic leverage. The shorter the stem the less "twitchy" the steering. The longer the stem, the shorter the movements you need to make to turn, in other words, that's why spanners for large bolts have long handles. Small movement at the users end, big movement at the wrench end. The shorter the stem, the more you need to turn the bars for the same turn. Thus, less twitchy. The steering response would be regained with wide bars to counteract the short stem.
So go for a short ass stem and wide ass bars.
  • 5 1
 I thought the long handles for spammers for large bolts are for generating enough torque? The further the perpendicular force is acting from the pivot, the larger the torque/moment. And I don't think the 'small movement at user's end, big movement at wrench end' is relevant here. If you're considering the angular movement, both the bolt and your hand move/rotate for the same degree, but the longer the spanner, the larger the distance you have to move your hand to make the same degree (picture a circle with a greater circumference due to a larger radius). So it's actually 'big movement at user's end, big torque at wrench end'. I think longer stems do have a stablizing effect, because when you're initiating a turn with a longer stem, your action is both tugging in one end and pushing pushing out the other, PLUS pulling the bar laterally to one side, while with a shorter stem you're just doing the tugging and pushing, so it's gonna feel more twitchy. But it's gonna be ok when we're talking about crazy slack headangles, and I do like short ass stems and wide ass bars. Smile
  • 1 0
 looks stiff, strong and light! not too sure on bar placement... look likes it could make the cockpit a bit cramped. Worth a try forsure.
  • 1 0
 Seems like the idea the moto guys are doing for years.
  • 1 0
 dh bike is not slalom one..not comfort on speed parts
  • 1 0
 soooo when does it hit the market and can we order early Smile
  • 1 0
 a stem like that would be feel so well! and the style is almost FMX
  • 2 1
 Thats silly. go back to the design program.
  • 1 1
 it was rubish when Azoinc did it back in the 90's and it will be rubish now!
  • 1 0
 YESSSSSSSSSS!!!!!!!!! FINALLY!!!!!!!!
  • 1 0
 Those look sick!! Sooo want them
  • 1 0
 nooo! they have done before me!
  • 1 0
 Finally. I've been waiting so long this kind of stem.
  • 1 0
 MX style! Did any say that yet? lol
  • 1 0
 thats cool, a moto stem, i like what these frenchmen get up to
  • 1 0
 Cool
  • 1 0
 motooooo
  • 1 0
 MX design, realy nice
  • 1 0
 sweet bike and vid
  • 1 0
 Awesome, !
  • 2 2
 So badly getting cad now after those sick/sweet/AWERSOME cad pics!
  • 1 0
 Looks clean.
  • 1 0
 Sikkk love it!!
  • 2 1
 SO. SHORT!
  • 1 0
 KISS rule ftw.
  • 1 0
 simple, yet genius cool







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