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Cero Design 10mm Offset Stem

Cero Design 10mm Offset Stem

James Renwick James Renwick

Cesar Rojo, ex-World Cup racer, man behind the Mondraker Summum and all round good egg, just beamed over the latest on his 10mm offset stem. For those not in the know, that’s about as short as it gets, so short in fact that Dirt Ed Mike Rose reckons it looks like the one on his Rotec downhill bike from ten years ago.

Cesar talks us through the details and his thoughts behind the design…

With a longer bike it feels more stable but the handling of the bike stays the same. Having a 10mm offset, the handlebar almost turns from its centre, making the bike more direct, in the same way you’d feel a benefit moving from a 120mm to 80mm stem.

Weighing in at around 68grams it’s about half the weight of the lightest integrated stems.

It was a really big surprise how good the bike felt on track. I’d moved up to a large frame but by using the 10mm stem it felt like I was riding the shorter, medium Summum frame. The rest of the bike was set up with a 62 deg head angle and 450mm chainstay.

The stem at the moment is just a prototype done by our studio cerio-design. It has an offset of 10mm, weight with no bolts of 54grams and 68grams with bolts, stem and clamps. We use six bolts instead of 8 bolts like normal stems.

Designed two weeks ago, prototyped last week and raced this weekend at the Gouveia MAXXIS Cup:

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  1. John

    Azonic used to make something simaler but obviousely alot heavier.

  2. Rory Beirne

    Looks good, would be nice to try med with 40mm stem vs. long with 10mm stem.

  3. flozza

    wow that would give you way more leverage! i think?

  4. Jan'imal'

    well i like it

  5. Norbert

    Its a good idea but most of us folks who already have our bikes built cant get a frame one size up so it will feel really akward. Not to mention people with no acess to wc tracks would rather have their bikes shorter, not longer. Still its a good idea if you look for a new bike and live in an alpine area. Cesar is a cool guy and Im sure it is a great idea for some of us who manage to find a deal on a large 😉

  6. Meat Ball

    Way too short, would make steering feel awful. 40mm stem is perfect and still short enough to give quick steering.

  7. Cesar

    @Norbert. For sure your not going to change your frame right now, but I think will be the future. Is one of those things that doesn’t look like are going to make a difference, but they really made.

    @Meat Ball. Why you think will make steering awfull? Is just the other way around, makes it way better, much more direct. On your 40mm or 50mm (most common) stem your not turning from the center of the handlebar. With a 10mm you are almost doing it, what means less movement on the sides of the handlebar and you need the exact same amount of force as the steering momentum just depends on handlebar width. Hope I was closer to let you ride my bike and change your mind 😉

  8. Tim

    “Designed two weeks ago, prototyped last week and raced this weekend at the Gouveia MAXXIS Cup”. How cool would that be – I need a new stem, what shall I get… I’ll just design one, be ready in a couple of weeks. Sorted.

  9. Trialsben

    Good idea, hope it will provide the same direct feel of steering and grip that I get on the motorbike and should also help with centralising weight on the bike. The only problem I have with it though is that I’d like to have some longer top tubes on dh bikes for us tall guys. I already run a large frame and I would struggle to find another dh frame with a top tube atleast 40mm longer than that, especially with the slacker headangles now-a-days shortening reaches. I would much prefer to run a 10/0mm reach stem as above and have a looooooonger top tube and front centre on my bike but there isn’t anything out there to fit the bill at the moment!

  10. Tim

    @Meatball, I used to have one of those Azonic Zero reach stems that John is talking about on my Shaun Palmer Specialized. It was great, I only got rid of it because it weighed so much.54g – can’t grumble at that!

  11. Lew

    is this the start of a ‘one size fits all’ dh frame?
    i think im right in thinking that thats what you get in MX already…
    could mean that as sizes are more limited in different choices of size, it will mean the differences between geometry designs and suspension systems should become clearer…also with angle adjust h/sets and moving dropouts, and stand-over height getting lower and lower its starting to make more sense of a move in the one size direction….could be interesting to see who does it first….Cesar?

    right enough of internets, its sunny and im off work! woo!
    bye! im off riding :)

  12. Spooky

    I thought that if you were running the bike so long and slack you’d want a longer stem to help keep the weight over the front? Do you not understeer quite badly with the set up Cesar?

  13. Cesar

    @Trialsben & @Lew. I think is time to think about one size fits all, like motos, for me what i really see is to type of bike. Like a really race ready with more extreme geometry and another more to go around, but not to focus anymore in sizes

    @Spooky. People is even riding slacker than that. I had no problems of understeer I got used to ride a bit more in front of the bike in the past and 62º for me just feels great. I though I had to probably go back to 63º with the shorter stem, but it felt so great on the first run even on a super flat track like Gouveia that decided to keep it that way. Bike is so fun like this!

  14. Spooky

    Awesome…. I have a Sunday and am going to make it a bit slacker (63.5) so will run with the stem i have at the moment which is a 40mm to see how it handles.
    Its good to have someone like yourself commenting on things like this, maybe you should start testing bikes for Dirt themselves as you know how to put down on paper what the bike is doing etc.

  15. Dirt HQ

    The old Rotec I had that was mentioned at the start did have a stem just like this on it, I’m pretty sure with no reach at all. For sure it was a different feel and look, but I really liked it. Just for the record, the Large sized Rotec did have a good sized top tube. This will work for some people on some bikes. Just ask Carmichael, Bubba and all that lot.

  16. Tim

    The azonic hammer!


  17. Cesar

    @Mike. Found a picture of the Rotec!

  18. miik

    Controltech also made a stem similar to what you guys are talking about. very minimal reach. was a clamp-on style not direct mount. was a brick of a thing.

  19. Graeme

    This looks really cool, getting more and more moto as technoligy and riders progress!!! How would I be able to get my hands on one of these, I’d be pretty keen on riding this stem, going with an XL turner DHR to start and this would take the Turner’s handling to the next level for sure!!!

  20. gareth

    Marz’ did these a few years ago as well(ok, a fair few years ago….). They were for the Monster T2-type forks. It worked really well on the super monsters that I had on my bike at the time. very responsive to any movement. You’d need a longer, larger frame though as if your riding a tight/short one, You’ll notice that it becomes very twitchy at speeds.
    The old ideas always come back to the fold. Sometmes they just made their appearance too early.

  21. RRP

    I don’t understand all the emphasis on the weight of this stem, if it requires moving up a frame size, and therefore more than negate the weight savings.

  22. diggerythedog

    you would have to the steerer tube cut the bare minimum!

  23. the bear

    I run a straitline 28mm direct mount stem on a large giant glory 2010, I’m 6’2″. It handles confidentially, although yes you do have to lop off the steerer as you would with this stem. short stems can interfere with the high of the bars too; as I found out. A longer 50mm stem would allow me to run the bars lower as the sanctions / rebound dials aren’t in the path of the lowered bar. Where as with the 28mm stem the bars make contact at a high point. Each to their own though.

  24. Chris Waddup

    Using two of the bar clamp bolts to fix the stem to the yoke saves weight even if you have more offset than 10 mm. This is what I made for my Boxxers in 2006.

  25. Norbert

    Cesar you are right that on future frames it’s a great idea. The only thing that worries me is national races. In here some of the tracks tend to be super tight. Normaly I have nothing against going 1 size to long even with normal stems but on the tight stuff it might be a chore.
    Though the tracks change in good direction so maybe when new frame time comes that won’t be a problem. I need to borrow a straitline stem from my friend and check if I feel a 22mm differance.

  26. Ben

    One size fits all? No thanks I’m 6’6″ how is a frame that fits me going to fit some kid who is 5’4″ or vice versa?

  27. tumble

    Might have limited popularity in Australia. Most riders over here run their clamps low on the stanchions because of the flatter nature of our trails. Not possible with this product.
    Nice looking kit though. Love the way people are “thinking outside the square” with new products.

  28. Frederico

    some more pics of the old Rotec:


    Very moto, very cool.

    I personally run a 0/10mm marzocchi stem on my shiver and I think it’s perfect. I like the long frame + short stem idea. And as for tighter stuff that’s what adjustable chainstays are for as well as the cane creek angleset! One bike to do it all!

  29. jonny

    good idea, makes sence

  30. Cesar

    @Norbert. Yes national races are a bit more tight, but it doesn’t make any difference I rode this week the bike on a few places where I normally ride my 100mm bike and that bike is enought there but this one rides really good even if its super flat.
    @Ben. Same way a moto does I guess 😉

  31. Ben

    @cesar motos arn’t the same as bicycles though, no matter how much some people seem to want them to be. thats like saying cars only come in one size. bikes come in more than one size for a reason, bigger people need wider bars and longer bikes becasue we’re bigger and smaller people need shorter bikes and narrower bars because they’re smaller, bikes just arn’t big enough to offer in one size fits all.

  32. Cesar

    @Ben. Bikes need sized to better fit body kynematics in order to pedal positions and optimize the performance of the rider. Downhill is about the performance on the track, going thru turns, jumps, not about pedalling eficiency, that is why the geometry is so important if a mid size bike turns great a L size won’t be as good, so if you are tall you have two options Use the bike the bike that turns so badly or use a bike that you be a bit more stretched like on a motorbike the same person but be able to ride faster.

    If this person is going to do Cape Epic on the DH bike then things will change as I don’t think a good geometry (for riding the bike fast downhill) will make a diference as a good riding position for perfect body geometry will be ;).

    Hope you get my point. I’m not telling all bikes need one size, I’m just telling for downhill need in the end, because only will be one size that will be the optimal. Proportion from front wheel to bb and bb to rear wheel, the others this proportions will be different, that is why i think one size is the way to me.

  33. kenny g

    Why do houses have 4 walls and a roof? Torsional flex. 4 piece designs by pass a simple engineering fact. You are assuming that the clamping surface can has enough torsional rigidity and will not move under load.

    Just saying that this is not a motorbike, these are not set apart 4 plus inches into a massive piece of material. Our bearing surface is so close together, 2 piece designs is best.

    Quit chasing grams truly the amount saved in the weight war is not so great that compromising on a part that keeps your bike steered safely is worth it.

    My two cents only and I’m not saying this is a crap design just pointing out a known fact. I’ll go hide in my 4 wall house now.

  34. Cesar

    @Kenny g. Not really sure what you mean about 4 walls. But to my mind comes Eiffel Tower, skyscrapers… None have roof or walls (structurall walls). Golden Gate but tell you that I might understand you wrongly.

    But don’t be worried this stem is stiffer than most ;). I even ises bigger metric bolts than most stems :). So colums are pretty solid inda house.


  35. Ben

    @Cesar “Use the bike the bike that turns so badly or use a bike that you be a bit more stretched like on a motorbike the same person but be able to ride faster.” I’m not really sure i understand that. do you mean that a short bike is better or a long bike as surely the long bike would turn worse and be more stretched out? and how can you make the pint about nimbler shorter bikes being better when the bike you designed is ridiculously long and slack?!

  36. Cesar

    @Ben. Sorry my english is not that good. What I meen is what makes good a moto gp bike (as an example of single size and also I worked there so I know a little about that) is the position of the front wheel, the rear wheel, the axle of swingarm, the seat…

    If you look to Pedrosa and Simoncelli probably they are 30 cm diference in heigh and they ride the exact same bike. I’m sure Simoncelli can get a bigger bike if he want but then the performance of the bike will be comprosimed. So he will be faster stretched on a bike than on a longer bike… To me is the same on a Dh bike… From size to size this changes, motogp, motocross bikes doesn’t have sizes because all geometries doesn’t work the same way if you make it longer on front end.

    I am 178cm tall and riding a 1255mm wheelbase bike and to me feels way better than my M size and this bike if you ask in a shop will tell is crazy long for me, but works for me not because is my exact size using what a manual will say, it is because the bike performs so great on the track.

    About what you said from handlebars, Minnaar is riding a narrower bars than pretty much any dh rider in the world. You theory is big guys wide bars, small guys small bars and I think there is a single guy now riding less than 750mm bars.

    Hope this makes it more clear 😉

  37. Norbert

    Cesar don’t worry. I’m still very curious about the product. I’ve been unintentionally shortening my bikes every new frame so I’m biased. I know only one track where a large would really suck ass because of some crazy tight switchbacks (under 1m turn radious) but for the rest I like longer feeling bikes. Extra stability is allways welcome. Though I’m still afraid I’d loose the playfulness. Have you noticed it by going large? Is the bike harder to whip and throw around.

    btw. What’s about the ex-world cup racer comment on the start of the news. I though when reading RM that you will race a bit this year.

  38. Ben

    @Cesar i appreciate that one size would stop geometry being messed up by having a super longfront end, why not make the rear of the bike longer as well? then offer a long and short size? and the bars are just personal preferance obviously, but have you ever seen a 12 yar old try riding a bike with 780 bars its just ridiculous and it cant be comfortable

  39. the bear

    straitline DM 28mm stem without bolts weights in at 90g. with 8 bolts 135g. for what its worth.


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