Hello Vital MTB Visitor,
We’re conducting a survey and would appreciate your input. Your answers will help Vital and the MTB industry better understand what riders like you want. Survey results will be used to recognize top brands. Make your voice heard!
Five lucky people will be selected at random to win a Vital MTB t-shirt.
Thanks in advance,
The Vital MTB Crew
One more vote for looking at the system, so where the grips are in relation to the steerer.
The problem is that, aside from Bike Yoke ( @Sacki ) nobody publishes setback values of bars as far as I know. And bars have WILDLY different setbacks, even more so if the sweep angles are high. Bars aren't made to hit a certain point in space with a given setback. They are just bent back and up. A high sweep bar should be paired with a longer stem to offset this. QED, I ran a 70 mm stem with high sweep bars to get to a similar position with my hands to a normal bar and a 40 mm stem.
Then there's bar roll that gives another big variable to the table - ten degrees of backroll increases the setback by almost 10 mm for a 35 mm rise bar
You guys dont run adjustable stems ? It even works with both 31.8 and 35mm bars!
More on the topic here, too:
https://bikeyoke.com/media/6e/59/d6/1741646748/Handlebar%20geometry%20explained.pdf
Hard to do a real world test on this because bars aren't designed with setbacks - the sweep is pretty much determining where the grips will be.
Running the same bar on 2 different length stems, rolled the same, will be much different.
Run a different sweep bar (with a setback equal to the difference in stem length) on 2 different stems. The longer stem setup will need greater backsweep to get a similar setback, and feel much different.
And that is precisely, why stem length alone does not matter a single bit.
My sketch was just a little brain aid that helps do away with the myth that a longer stem makes steering softer and less direct. It's far from being cmparable to a larger diameter steering wheel (where you move around a much larger radius with your hands, e.g, on a car vs. lorry vs. tractor) as some people often reference.
You can see in the drawings that your hands will travel virtually the same amount between a 70mm stem and a 35mm stem with same handlebars at same turn angle.
The steering per se is not more direct or sharp with shorter stems. Of course, your cockpit is shorter/longer. That is what you can definitely feel. But the stem length itself does not sharpen the steering feel.
Not necessarily. You can make two handlebars with different sweeps and the same setback.
Exactly what I do as well.
I'm a little taller than most, grew up riding/racing road and XC, and I don't have a lot of super steep extended descents around me so I'm usually in the 40-60mm length, excluding the XC bike (which is still close at 70). Personally, I've always preferred a "pointy feeling" front end, and feel there's usually more time in nailing all the sketchy flat or blown out corners than bias weight rearward for the occasional steep section.
The ONLY comment I would have to this is to keep the setback as setback. Yes the setback directly correlates to the frame reach, but it's not a straight subtraction as the real reach depends also on the stack above the headtube (headset cup, spacers, stem), stem horizontal reach and, by proxy, headangle. And, as you also noted in the presentation, bar roll as well.
I don't see anything how you are handling bar orientation and the resulting bar roll, any thoughts on that?
Dang thanks for this detailed explanation, that makes a lot of sense
BUT THOSE TWO MILLIMETERS OF DIFFERENCE MEAN EVERYTHING TO ME
You just haven't experienced true "best or nothing" performance... besides, those two millimeters are going to ovalize your headtube.
Saying that 2mm of bar movement is not something a rider will feel is just wrong. Some beginners might not, sure. But expert riders who notice things like 3mm difference in stem spacers, brake levers being 1degree off, or lever reach being 1 click different (~0.1mm) will absolutely feel a difference in steering feel. And besides the radial movement of the end of handlebar, stem length changes the position of center of bar axis relative to center of axle axis, plus a tiny change in steering has a very noticeable affect on the orientation of the tire on the ground. The whole steering interface system is too complex to reduce to a basic 2d drawing, especially when you consider how (as others have pointed out) stem length will affect weight distribution onto the front wheel (which also creates feelings of over or under steering). That's why it's important to actually go try different lengths and see what feels best to a rider - not pick stem length based on a specific number in a RAD calculation or something.
Do people adjust their cockpits when it's time for thicker or more padded gloves? Or when they install thicker grips? Or when they ride with/without chamois?
lmao... people think it's crazy to suggest controlling for rad when considering bike handling characteristics.
rad takes into account stem length, so this kind of argument results in something that looks like:
x^2 + y^2 = r^2
I actually agree with you that some riders can feel a 2mm difference in bar position.
My comment didn't address what a rider can or can't feel, it addressed meaning. Meaning is the narrative that human beings attach to stimuli. Humans are, after all, narrative creatures. If I feel a 2mm difference, that doesn't automatically mean it's an important change. But if tell myself a story that the change is important, and if I believe that story, suddenly that change will become manifestly important to my bike riding and may even produce a measurable impact in performance.
My soapbox issue is that good or even decent riders can feel a lot more stimulus on a bike than they need to pay attention to. There are feelings we get from our bikes that are worth paying attention to, but a lot of it isn't. I think that the effect of stem length and bar position on steering feel is something that good riders can probably feel, but one that ultimately isn't important for performance, unless you're talking about a really wild or unusual setup.
That said, I think the effects of body position and the relative position of a rider's center of mass on the bike are both really, really, really important for bicycle performance, and stem length affects both of those (via adjusting the effective reach of a bike). I just don't think it significantly affects steering dynamics.
Well, I watched the video linked in the first post and I felt I needed to correct some things.
In the video it is being said that you "sverve" around the steering axis rather than rotate around it.
This is just plain wrong, hence my picture in my original post.
Maybe this picture makes it more clear.
It does not matter how long your stem. Any given point on a handlebar rotates in a perferct circle around the steering axis.
It's just that simple.
Again, I am not saying that different stem lengths can not feel greatly different on one and the same bike wiht one and the same handlebar.
But it's not that your hands are suddently "sverving" around the steerer axis rather than rotating.
They still are.
And it's also not like the hands are suddenly having to do more movement to get the same turn angle. And sorry, but no you do not notice 2mm more travel of the end of the handlebar (that's not even where your hands are) on a 30° turninf angle. On a trail. In the heat of the moment. And neither do Pros.
One will notice a lot things feel different with a different stem length, but your hand moving 2mm more is most likely not one of them.
Do with it what you will. I just wanted to give a little fuel for the discussion.
I don't entirely disagee with some points menitoned in the video. But it is very dramatized.
A tenth of a millimeter? Are you Rain Men aware that we’re taller in the morning, our dominant arms are like 1.5% longer, and we’re only symmetrical from across the street?
there’s no way!
I dont think this has been answered, but ignore if it has: how much do you actually rotate your fork when going fast? I know I do rotate, but I’m also leaning the bike over and steering with my hips. I’m pretty sure that I don’t turn more than 45*, but 20*? 10*?
Good question. I watched the Asa helmet cam from Hardline, and this low speed section had the most handlebar turn of any section on the track (other than when he's cranking whips in midair on the big jumps), and it's only for a split second. This looks like maybe 35 degrees? Everywhere else it's more like 5-10 degrees, even on berms.
Do you know anyone who makes handlebars?
I would genuinely like to make handlebars in the US.
Sorry, no. Not in the US at least...
I think changing dimensions messes with body positioning more than "steering-feel" hence this video:
https://www.youtube.com/watch?v=apyTlND9Cuo
It seems like the stem in this video reflects the difference between the basic geometries of xc and dh bikes.
Just like any bike, going +- 20% stem length from stock is digestible and can help with fit. 1-2cm of comfort and CG shift closer to the front contact patch seem more relevant than the numbers shown for the radius and arm swing angle.
I hate to be the "normie" :D But he proposed stem shape was here before, yet almost everyone is on 35-50mm across trail and dh bikes for the past what? a decade? Rulezzman's illustrations seem blown out of proportion. Race teams do every and any shit to make riders faster. I think such a low-hanging fruit this was crossed off of their lists many a times.
I don't claim to understand the subject fully, but as a bit of a cockpit component collector myself - across both road mtb bikes for 20 years. My observations are: going towards extremes addresses more and more specific issues, while getting increasingly shit everywhere else.
Steering is quite a discreet movement, 30 degrees is quite a large steering angle, how much do you turn your bars to initiate a turn into a berm? Stem and bar companies bloody love us all when you go oh I’ll just get a 5mm +- stem, oh I’ll get higher bars blah blah. Where your hands are is about COG / weight transfer and this then relates to stance and it relates to suspension setup…. I would love a bike fit where you jump on a bike they tell you all this or to just capture what I’m riding now. My bike feels “balanced” what does that mean?
I'm pretty sure testing wild things (like reverse stems) would require a holistic approach, so an adapted frame for example. If you have a really short or even a reverse stem, do you need a really long rear centre? Or just a shorter front centre? Do you achieve the latter with a steeper headtube angle maybe? etc.
What we are using now in regards to stems works for us now for the frames that we have now. 50 mm stems don't really work on 15 year old bikes.
Short stems were tried in the past when bikes where tiny and that's why they didn't stick. Nowadays you can size up and run a short stem without any problem. You get stability from a longer bike and added agility from your cockpit making that long bike handle well. Pros as well as brands don't tend to test limits, they are rather conservative. Minnaar took years to finally get on a bike for his size and yet he didn't grow a mm taller in 20 years racing.
When I started diving deeper into all of this bar and stem geometry when I designed our bars, I built myself a handy little tool to play around with cockpit geometries that takes bar roll into account.
Stack and Reach is taken into account, depending on bar roll, but I have not yet found a way to calculate the sweep angles, as a function of bar roll. Either it's very complicated or I am just not seeing the forest for the trees. Brain gets mushy after some time of trigonometrics, espoecially in excel.
But it's quite fun to play with.
That is some crazy excel sorcery lol impressive!!
I had no idea so many people were running 60mm stems in 2026. I thought since like 2020 50mm was the absolute max with 40 and 35 being most common.
What sort? Doom bars is in abq, out of steel or ti, there’s Mone down in silver city too.
Butted aluminum bars.
Made like these:
https://youtu.be/EICpmw1avR4?si=5XmfNquVgRP85DNr
Post a reply to: Stem Length