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I'd think simplest way to do it would be create an equation for start and end points of the straight bar section as a function of roll angle. Those two points define the axis of the straight bar section so should be pretty easy to find the angle of it relative to whatever plane you want. I believe the easy check for whether or not the equation works is a roll of 90 degrees should result in a down sweep angle that equal to the back sweep angle before the 90 degree roll.
I just filmed the Push Nine One video on a 60mm stem and it worked fine.
Damn, I'd straight up touch a stranger's wiener, to get a copy of that spreadsheet !
We need Reece or Cahal to test the 0 stem on their regular frame size with 470 chainstays and then on a frame size up with 445 chainstays.
Spent a season on a 500 reach bike instead of my normal 475 and the body position part of the handling equation wasn't the issue due to the higher stack and 35mm rise bars. (Nukeproof Giga 29 445 chainstays) What made me go back was the wheelbase was just less agile and fun, despite it being a fast bike. Shocking how different it was to the 475 reach frames I've had.
I'm doing an XCM race for fun on a borrowed XL Ibis Exie (520 reach!! but does have 60mm rise bars) and am very interested in how it will handle given the terrain. (old backcountry singletrack)
I'm in the same boat if it helps. Other than rotating the model in CAD and measuring the angles I haven't found a good way to go around it...
That should work. But you'd need the points to do it. Not a problem if you're designing bars, a problem if you're just buying them. Intuitively I think it should work without the points (as per your 90 degree test), but maybe it breaks down for the intermediate angles if you have varying setback?
Checking off a model might make sense here...
When mondraker first did it....15 years ago? They specifically sized up and went much longer in the front centre at the same time. I think the main goal was to ride longer bikes without changing the cockpit length, but eventually people realised you could just go with a longer bike anyway and keep a normal stem
I just saw the formula at the top, why couldn't the stack be negative? XC stem-bar combos are close to that, maybe some bars too.
.'It will feel different because your cockpit is longer,'
That's the whole point. The rest of the stuff about hands not turning anymore with regard to stem length is irrelevant.
Anyone who has ridden a bike knows the feeling of a 35mm compared to a 70mm. It's just down to what is comfy for you and what works on your bike. Some bikes that you need a bit more over front wheel so maybe 50mm , it'll help on tricky climbs, some bikes your fine 35mm. I have a flat bar commuter that came with an 80mm I just put a 40mm on it and it feels so much better and faster. I wouldn't want to do 70 miles on it but that's not the point. It's what works for you not your internet feed.
I am not entirely sure anymore. I made this sheet a long time ago. But I believe it was because of the quadrants in trigonometry.
Stems with negative length or rise, or handlebars having negative stack, head angles being more than 90° and combinations of all those theoretical possibilites, even some values keyed in as "0", would sometimes calculate unexectedly or noinsense stuff with these formulas. You would have to make many more "IFs" into those excel formulas formulas to have any possible combinaitons you'd key in there be calculated correctly. some of them are considered and will calculate correctly.
But I think at some point I just gave up to make it work for everything that is theoretically possible, but which is not relevant for what this tool was meant for. Formulating long formulas in excel is really messing your brain (at least it does with mine).
That's why I focused on making the toll work within reasonable limits and those limits were that bars had to have a non-negative stack.
@Primoz It won't work with how most bars are currently measured (rise, backsweep, upsweep). Because those dimensions do not define the goemetry of a handlebar. I will not go down that rabbit hole agaion and explain why
But if you have stack and reach and the sweep angles, then it will actually work, I think.
I think @CascadeComponents gave me the bump I needed.
From the side view:
I already have the side view:
The end point of the handlebar is at x= -35mm and y = +65mm from the center of the bar in neutral position.
With the handlebar trim calculator that I already have in the tool, I can get the coordinates of another point on the straight portion of the bar.
So, in the example below there is a point on the straight portion that is 25mm inwards (at 750mm handlebar width) at x = -31.1 and y = 62.4
And for both points I can also get the rotated coordrinates using the cockpilt calculator. So I know the x and y deltas bewteen those two and I also know that the distance between those two points is 25mm. Connecting these points and projecting this line on two orthogonal planes X-Z and Y-Z I can make two triangles and calulcate each sweep angle. I think.
When I got some time, I will try around a bit.
Obviously I didn't mean calculating from the rise, when I said two points I meant what you're talking about, the two points defining the straight part of the bar.
I think you can also calculate the new backsweep and upsweep directly from the originals and roll using the formulas:
new backsweep = atan(cos(roll).tan(backsweep) + sin(roll).tan(upsweep))
new upsweep = atan(cos(roll).tan(upsweep) - sin(roll).tan(backsweep))
This assumes the roll is positive when the bars are rolled backwards and that the original upsweep and backsweep values are defined at zero roll.
The xl giga 290 isn't terribly long, 1290mm wheelbase. It was around a 1.89 ratio. So pretty much a traditional f/r balance. Not what you want if you're "sizing up". They feel longer than they are simply because you're stretched out over the bikes polar moment of inertia, as opposed to being more central to it.
I had both an xl 290 and also the 297 with 435mm chainstays. You had to ride that 297 like the front end was a bloody unicycle. My wife has one too in size small, and it facilitates a much better ratio and riding position for her. the 435mm stays are actually appropriate in that smaller size.
My current mondraker crafty e-bike is a pretty good candidate for a 0 offset stem. It's a 1320mm wheelbase with a 490mm reach and 465mm stays. It came with a 30mm stem, a 0 wouldn't be a massive leap I don't think.
What is the general consensus of where to have your grips in relation to the steering axis - for an "all-mountain" rig?
Personally I feel slightly behind to be balanced and safer for avoiding otb's.
Where is your 1.89 ratio from?
Where do your grips go, I hope you’re talking about rotation 🤣??
Longer reaches work best with longer chainstays, Makes the bike more balanced and thus easier to turn. My Nicolai G1 has a 1349mm wheelbase with 510mm reach and 474mm chainstays with a mullet setup. It turns and corners great. I think even longer chainstays would make it even better. Currently run it with a 20mm stem and 60mm risers. I'm "only" 180cm or 5'11".
Longer reach works better with higher ratios (shorter chainstays/long front centers).
The g1 does not have a long chainstay for it's wheelbase. It is around a 1.84 ratio. Most forbidden's are 1.8, regardless of size.
This is either a language issue, or you're high as hell 😛
I think you have it the other way around... Long reach and short chainstays will make it impossible to weight the front wheel.
I think so as well haha. When I bought the G1 in 2020 I had the chainstays at 442mm. Front end grip on flat corners was not great.
Then went up to 453mm, 462mm and now 474mm chainstays. Bike is so much better now!
I think this thread confirms that there is absolutely not a consensus on where to have your grips in relation to the steering axis.
I would argue that long stem lengths can be thought of as analogous to positive rake on skateboard trucks, which generally results in inherent instability and quicker turning.
That analogy is reasonable until you consider that mountain bikes don’t only operate on flat ground. We are frequently going down steep hills and weighting the bars from back to front, which changes the rake effect to negative, resulting in greater stability.
Bicycle steering and stability is insanely complex. There is a lot going on and I don’t pretend to be an expert.
IMO we are arguing over very minor changes when you talk about 32mm vs 50mm stem length. Run whatever makes the bike fit you best and you’ll probably go faster.
Ramble over. LMK what you think.
Ride the same bike with 40 and 80mm long stems and tell me which one turns quicker.
You don't need the two points that define the beginning and end of the straight portion of the bar.
Any two points sitting on that straight portion (no matter where) are enough.
One of the is the reach and stack point (X1/Y1) (the tip of the handlebar) as defined in our geometry. Another reference point one can be calculated (with more than enough accuracy) using the given backsweep and upsweep and a length of your chice on that stright portion angles going from that tip point. That new point would be (X2/Y2) that is also on that straight portion.
Then calculate the new coordinates of those points after rotation, using geometric transformation around the handlebar center by the angle you intend to rotate the handlebar.
You would get the rotated points (X1'/Y1') and (X2'/Y2')
Then take the △X and △Y deltas of these two and calculate the new angles for backweep and upsweep.
Actually quite simple, I just needed to concentrate a lot as this all messes with my brain if you spend too much time with excel and formulas.
I also noticed that using coordinate transformation is much better than going through Pythagoras (what I used before), as you don't need to worry about rotating out of the quandrant.
Thanks to @CascadeComponents tipp, I was now able to include the handlebar rotation into the tool and also allow negative stack and reach.
You now just have to pay attention to the mathematic signs. Typical Handlebars have a negative reach and positive stack and positive back- and upsweep.
If you typed positive reach, the bar end would be in front of the stem center.
If you typed a negative stack, the bar ends would be below the stem center.
Thanks to everyone for the input.
Pretty cool! I am thinking of putting this up on our website. Just need to figure out how.
I do not think you can generally break it down to what and why something turns "quicker" when you only swap stems.
That very much depends on your general body positoning before the swap, too.
In my opinion (and my experience with dozens of bikes changed my opinion over time) stems should be first and foremost be used for achieving a proper pedaling position on your bike (as long as this is a bike that you do pedal and not just ride standing).
That means, get the proper cockpit length for whatever feels comfortable when you are pedaling (that's what you typically do for hours, flat and uphill).
If you pedal a lot, the seated position is much more important than the standing position or steering feel.
40mm stem length can make a very big difference whether your bike feels good or shitty for pedaling.
It simply does not make sense to install a 80mm stem if my overall reach and stack is already long enough for my liking.
At the same time, I can not just install a 15mm stem, if my cockpit length with a 40mm stem is already proper short and I still want to pedal my bike.
I simply won't be able to sit nicely.
When standing, however, I can shift front and rear loading and adapt my body position much more. The stem length stilly plays a role, but not that big one.
The small differences in steering feel is something I can very quickly adapt to.
But in all my bikes, I could not simply install a 10mm or 15mm stem, just to have the settering axis go through the grips of my hands. I would totally compromise on comfort just for a small difference in steering feel that I never have to bother about.
For the new upsweep and backsweep formulas I posted above I essentially did the same process but instead of using points on the bar I calculated a vector in the same direction as the bar using the upsweep and backsweep angles, so (-tan(backsweep), tan(upsweep), 1) and then rotated that about the z axis and calculated the new angles by projecting the rotated vector onto the xz and yz planes. This will give the same result as using the points but can also be used for bars where manufacturers don't give enough information to calculate actual points but do give the sweep angles.
I understand. You can use that to calculate the rotated back- and upsweeps based on original back- and upsweeps only.
But I had to do this calculation anyway, because I added a separate calculation that gives information about reach and stack values for a trimmed bar, e.g. if you trim your bar from 800 to 760.
The additonal trim calculator gives you trimmed reach and trimmed stack and also rotated trimmed reach and trimmed stack.
You could then key in those values from the lower trim calculator into the upper cockpit calculator to see how a trimmed bar will affect these figures.
I think we can all agree that this is for real nerds, but it is fun to play with and give a general understanding what happens when you change one parameter.
For example, most people would most likely not expect that only switching to a higher stack handlebar (other specs identical), would change the effective stem length, while maintaining the overall reach.
And the other way around, switching to a flat bar would shorten the effective stem length greatly, which reach still remains unaffected.
The drawing already shows that the effective stem length will grow with higher stack bar:
I would not mind sharing this file, but the problem is that I can not protect/hide the file and the calculations.
As soon as you import an excel file into google docs, the hidden and protected formulas will be unhidden und unprotected.
If I hide/protect them in google sheets, the same will happens the other way around:
If you export it as excel file, everything will be visible.
Anyone know how to get this file protected?
I was of the exact same opinion, optimise for going up as it takes the longest and consumes the most energy, then I started optimizing my position for descending performance and a new world opened.
I think it depends on how adaptable you are on the down, if you are the type of rider that can get over the front wheel, a lot of different positions will work for you going down. If you have some mental brakes, it's better to optimise for going down as there are also a few different positions for going up that will still work. A more upright position won't suddenly be unrideable.
@Sacki That’s is crazy about a higher rise bar! This seems like it could be translated into a web page calculator with some guided AI coding (it’s insanely good at web stuff now). The web app could be tested alongside the spreadsheet to make sure it’s correct, and not expose the calculations. Open to help if you want. (I am not an engineer, but a designer building things in code now)
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