Nice interesting video, thx for making it in english for non italian watchers!❤

Great video Dave 👍 Totally agree on all your points. Thanks for sharing 😊

Fantastic info and so well presented 👍Unfortunately, most don't have a choice and go with the current trend / industry offerings. Also, re: rear stay lengths - it's fascinating how the same stay length can be used across all sizes offered, I'm using Spec Chisel as an example: same 432mm from size small to XL - meaning weight distribution variation @ BB almost 4% depending on the size!

Awesome truth! Thanks for sharing this information with fellow bike lovers.

Very enlightening, And it makes perfect sense when you explain it. Thank you. I learnt a lot 👍

Your doing gods work Dave! ❤ I really liked that you gave us some numbers to look out for. Im asking myself about other factors like stack, bb height etc... i know Aston made a video about his bike going a little into it, but i would love to see one of you two (or maybe even both) give us some tips to find the right geo bike or even to get a custom one build. Thank you alot for sharing your knowledge 🤟👍

Love you and thank you. Finally an intelligent mind within the industry, I hope people appreciate you and your valuable knowledges. I watch all of your videos and inventions. Guys like you make the World a better place to live in it by having true knowledge. Much much appreciated.❤

awesome video, very interesting!!!

This is very educational and crystal clear to understand! Cheers mate! ✌️✌️✌️

Many thanks for this very explanatory video. A master pièce of explanation demonstrating the vast majority of the bike industry looks like a the fashion industry.

Thank You for sharing this magic. Very informative video!

Great video! Thanks for sharing.

always loved a short or direct stem, but never realized the chainstay. Great point

Hi Dave, congrats for the video. I have a 470mm chainstay, 500mm reach, 1320mm wheelbase custom made hardtail bike (I'm 180cm tall), and couldn't agree more with you. In my opinion, the only downsides in comparison with a "traditional" bike are: - more side lean is needed to corner on very twisty, old school trails; therefore, switching between consecutive turns needs a lot of aggression; - the added front wheel loading makes intentionally lifting the front wheel over obstacles quite harder. Now I'm going to experiment with mullet set-up and higher rise handlebars. Happy Christmas holidays!

Longer rear end = more front grip. Makes total sense when explained by a real engineer 👏

Love it

Yo man! Awesome video I see why now you ride banshee bikes. The geometry on their bikes are good. I am 6’1 185cm I ordered a titan in XL I see now the “bigger head tube” “longer chainstay than other bikes and high stack. Higher bb it makes sense! I am glad to have bought this bike I cannot wait to build it up and ride it

Hey Rulezman, geat video, thanks. I'd like to comment on two things. - Moto vs bicycle. I read an article by someone from Mondraker a while ago on why they abandoned the 0 mm stems and why it works on moto. The deal (as far I can remember) was that on moto the whole system is way heavier and more stable and therefore does not rely on the stabilizing effect of the cantilever (stem) while going straight. Therefore even negative stem length works on moto that would destabilize the ride. Mondraker figured out that the optimal effective lever for mtb to provide a good compromise for straight line stability was 1-2 cm I believe. Effective means you need to subtract the backsweep of the handlebar since you would obviously end up with a negative lever with a 0 mm stem and a common mtb handlebar. With more modern bike geometries (shorter fork offset, slacker head angle) this may not be valid any more, as you said. Btw. the so called "Raised Reversed Stem", this crazy high short stem you may have heard of: the idea I believe is that by raising the handlebar you reduce the weight on the handlebar to moto regions. - Chainstay length. I am sure you are aware of it, but for the regular audience: please consider small bike sizes. I am currently on a bike that has a 430 mm chainstay and a 430 mm reach with a 35 mm stem (I'm only 167 cm short). This is great. Nowadays I see bikes that have 450 mm chainstays on all sizes, so you might get a 430 mm reach on small size. This sucks. Difficult to manual, bunny hop or make bike oversteer (very important to me). Just keep the 1:1 ratio between chainstay and reach. So if you have a 520 mm reach on size XL, give it a 520 mm chain stay. Crazy, I know, but it's just science.

👍👍👍👍

Complimenti David. questo video mi conforta. io sono 176cm e su una Hightower v3 misura L. tutti mi dicono che avrei dovuto scegliere la M, anche se mi trovo molto bene con la geometria della mia L (arrivo da una Bronson v2 size M, e ho sempre avuto l'impressione che fosse piccolina per me). Ora voglio comunque adottare qualcuna delle modifiche che suggerisci in questo video e in altri (attacco più corto, sella in avanti, settaggio sospensioni). Sono sicuro che può solo migliorare. Grazie

Im currently puzzling with bars that are comfortable for me so I have round 7 different ones at home. I measured them all and one thing I noted is that they very strongly differ in how much they reduce the Reach. E.g the ergotec with 12deg reduced reach by 70mm. The SQlab with 12deg however only 35mm and the FAST flex one sits somewhere in between. All other bars with 6deg (Renthal) or 9deg (Nukeproof) sit in between. Its really mad. I guess that should be added to the equation of correct stem length because with that Ergotec my 40mm Stem is effectively Zero offset - and it feels great :)

I have been saying this since the early 2000s! I currently run 35mm stems, but I would love a 15mm stem. I don't see anywhere I can get one though. As for chainstay length, a shorter chainstay gives a bike more pop for jumping. Longer chainstays make pulling up the front wheel more challenging and because many riders like the catch air a short chainstay makes that a lot easier. Comparing a motocross bikes chainstay to a bicycle is a bit odd considering you have a motor with a bunch of power to get the front end up, something you don't have for a mountain bike. On a bicycle you have to control the pitch of the bike with your arms, legs, and body position. So I am not so sure I agree on your statements about making chainstay lengths longer simply for more equal front real balance during cornering. You do a lot more on a mountain bike that cornering so the frame geometry needs to be well balanced to accommodate all the different situations. So for my height of 5' 7" anyway, a 435 - 440mm chainstay is perfect. As a rider gets taller, the chainstay length should get longer, not just the front of the bike.

I watched the full video, thanks! I agree otherwise, but in my experience 12 degree backsweep handlebar is only good when riding bike from sitting position, but when riding from attack position, 8 degree backsweep (0 degree upsweep) handlebar is better. I've tested both backsweeps on long test periods. In attack position wrists are at more direct angle to the handlebar and upper body muscles are better activated with the 8 degree bar. It´s also easier to ride correct attack position = elbows out. Many pro downhill riders prefer fairly straight bars for this reason (such as Renthals). Also Fabio Wibmer understand this and his signature SQlab 3OX Carbon bar has only 7 degree backsweep. Motocross racers also will usually prefer a lower bar with less sweep, this keeps their body weight further forward, helping with cornering and hard acceleration. I think on a lot of mx motorcycles, handlebar grips are actually located little behind steering axis, not in line with it. Steering felt good with 32mm stem, 42mm fork offset and 8 degree bar combo on my bike, but the bar snapped recently and I had to switch to a spare bar with more backsweep. Now the steering feels way too sensitive and fast due to shorter "cantilever" with the same stem. I haven't even gotten used to it for several days. "Steering ratio" is too high, which means that front tire tends to "oversteering". I must do many steering corrections for one task on slippery surfaces, ruts, etc. Previous setup was very balanced. I use always 800mm width bars and now my grips are still 23mm front of steering axis measured in the middle of the grips. If I would use even shorter stem, wouldn't the steering of the bike become even more twitchy? Fork offset, which is also "cantilever", plays also role here and it´s 42mm on my fork and head angle is of course 63 degrees. I have tested different offsets such as 42mm, 46mm and 51mm. 42mm is the best of those. Chris Porter has experimented with a huge range of fork offsets on his bikes, and he has found that shorter offsets give a calmer handling bike, which tends to go faster when the stopwatch is brought to bear. Following this, Chris has landed on a 30mm offset for his 27,5" bike. Shorter offset also reduces the ‘floppy’ feeling that can occur when tackling tight corners, where the wheel can feel like it wants to tuck under. This is nothing to do with "trail", but simply the fact that a longer offset will put the contact patch further inside of the bike when cornering, causing it to pull to the inside of the turn. Interaction between stem cantilever and fork offset cantilever is actually quite important. Steering ratio is 1:1 when fork offset is zero and handlebar grips are in line with steering axis or if distance from steering axis is equal on both; offset and grips. As Greg Minnaar once said: "You don't want a stem any longer than the offset of your fork." Greg didn’t want a stem length too different to the offset of his fork and I can agree. If I would ride with 15mm stem, I would need also shorter than 42mm offset for the balanced steering ratio. Unfortunately, the offsets of forks on the market are too long for that. Of course bar width (cantilever) is also important factor for steering sensitivity.

Wow explained in a way everyone can understand. I'm 1.98 m tall with long legs. Very happy reach is rising, but rear chains stays only a few milimeters and stack even getting shorter. Also the shrinking seat tube lengths in biggest size(very often 46cm ore less) is a concern for tall riders. To be able to use a 18mm stem I need a reach of well over 55cm. Not found yet. Fisrt time I noticed what a long chainstay and wheelbase mean was on, our tandem with 485 mm chainstays. We can climb the sky. Only disadvatge : turning circle.

the chainstay length is quite interesting as it is more fun to have it shorter for nimble and fun rides. pop manuals from time to time and get out of corners quick.

Love the content with actual math and physics to prove the point. Have you and can you create a chart with your evidence based approach on what are good reach and CS length numbers for different rider heights. That would be great.

Good video. Geometron has always kept the chainstays in proportion to the front centres.

Very interesting video. I think the only bike manufacturer with modern geometry today is Nicolai bikes.

I have thought that short rear centres for all sizes has been wrong for some time. On my own Chameleon hardtail I extended the drops all the way to 435. No negative to my riding. I’m 164 tall too. Been on short 31mm stems too. Again, works well for me. The myth of a long front or long stem to put weight on the front wheel for climbing is so obviously wrong as you eloquently describe. No one pushes down on a bike while climbing steep bits. We pull back on the bar on steeps. And I know steeps. I live and ride in Whistler .

My second DH Bike was an YT tues vor 15 years. While i have No Money i buy it in Large but i am only 1.70. than i Put the on Off stem from the Mondraker on it. All Guys laught but that was the Best.

Vorsprung has talk about ratio between front and rear axel/bottom braket Lee mackormack has a sizing rider area distance Some chooce their bike with a hypothenuse of stack and reach

So is there a front center to rear center ratio you like. My bike at static has a 1.8 ratio and it corners quite well, but I think it could corner even better

Fantastic video thanks! A big difference between motos and bikes is the rider is an essential handling piece as the system center of gravity can be changed much more than a motorbike. How do you view the effects your ideal setup would have on jumping via 1: build ramp and 2: bunny hopping? 1 a moto can do but 2 is unique to bicycles.

You're obviously a talented engineer by solving these issues. But if the mountain bike engineers do the same today what will the bike companies sell you tomorrow?

I just started riding a mountain bike, coming from motorcycles. I find it infuriating that sub 20mm or even a 0 offset aren't regularly available. It may be that I'm new to a mountain bike, but the cantilever steering feels like such a garbage. I'm 5'10" on a large 18-inch frame 29er. Maybe that's my problem, but all the strange feelings are coming from the odd steering, in my opinion.

Congrats on the the reall y well made video. The point that that never makes it into the discussion is the dynamic change in cs length and it's effects. A Banshee legend for example has a really long static cs but shortens a lot as it moves into it's travel. So being tall (196 cm) i sometimes wonder if the static cs length is the real info i should be looking for?

Mondraker is playing a lot with these ideas

Crashing into an obstacle (the crash shown at 15:30 ) is less of an issue for 'cantilever' stems as pushing on the bars with both hands will want to straighten the bars. More so than with a zero offset stem. Regarding the torque applied to the steerer tube by the 'cantilever' stem (even the one shown in the video, never mind what's actually being run on modern bikes en masse), it's peanuts compared to what the fork is doing to the bearings, steerer tube and headtube.

Another thing people don't realize is how much reach you lose with riser bars. I typically lose 5 cm from the frame reach once I get bars that meet my "real stack" preference. I need bikes with 530-540mm frame reach typically.

A BBSHD ! I got no probs large chain stay ! Hard to even lift the front wheel on a hill ! Large frame full suspension ! 730 handlebars !

This is super interesting, thanks for making this video. I do have a couple of questions though. How would someone go about finding what reach they should theoretically be riding? Are there any measurements we can take to help get us in a ball park? And I know you and Paul are big fans of the moto style suspension that's much stiffer and damped than what we are probably conventionally used to riding. Does this style of geometry require this style of suspension setup to work well? Cheers for the video anyway, It's really got me thinking.

Where should I go to learn more on how wide I should keep my bars at?

Ciao, innanzitutto complimenti per il canale 💪🏻💪🏻 riusciresti a fare questo video in italiano o con i sottotitoli in italiano?? Non tutti sono anglofoni 😅 Grazie

Correct in theory. And might work nicely. But the bike will be very long (front to rear) for this to work (assuming you want the same reach). Dont know how agile it will feel on twisty trails and going over obstacles in lower speed...

I wonder about your opinion on the stabilizing effect of a longer stem; I think 30-50mm is not uncommon stem length that's been seen around EWS and many casual riders, myself included. The issue with super short stems and narrower bars, say 760, is that the steering can become twitchy - front wheel gets deflected easier by the obstacles the front wheel hits. This can be mitigated by slightly increasing the stem length. So a longer wheelbase will not neccessarily aid in controlling wheel flop.

Sounds amazing! would you like to do a podcast video for the Israeli audience as well? Plus, can you touch base on the logic for XC based bikes and not only DH/Enduro ones?

I use 12 degree backsweep 40mm rise with a 40mm stem . Effective stem length is now arroumd 0 . / frame is long xl honzo 510mm reach

How about fork offset? I can buy 37mm, 42mm, 44mm or 46mm offset fork for my 27.5" enduro bike. You are correct about the 15-18mm stem lenght because the grip is going to be centered with the steerer tube and I totally agree with your view, long stems are terrible. But how about fork offset? How can I choose the correct fork offset if my handlebar is centered with the steerer tube and what effect does it have if use "shorter" or "longer" offset?

eBikes now a day have involuntarily grow the CS just to fit the motor, just by concidence, 0 credits to them xD Bikes are finally getting to MX geometry. Better in every way BUT the only gripe is that on long bikes is harder to pick up the front, wich in a moto is no problem since you do it by trhotle.

I really like this presentation. I have a hard time with long CS unless I have a motor propelling the rear wheel and can change turn radius with throttle. On a MTB, long CS just opens up the needed turn radius for a given turn, and/or requires you to square the turn w/o throttle, or do a nose pivot to bring the rear wheel around. The grip is incredible, yes. But the maneuverability suffers for me.

Brilliant!

Complimenti per le spiegazioni chiarissime. Una domanda: tu Dici che preferisci le taglie XL ma in realtà la maggior parte delle case usa le stesse proporzioni per tutte le taglie. Quindi prendendo una taglia più grande si andrebbe a peggiorare la posizione del Cg. Mi pare che ad oggi qualche casa propone chain stay “ tailored” per ogni taglia. Si potrebbe avere quindi un miglioramento. Dimmi se il mio ragionamento è giusto e cosa ne pensi. Grazie mille!

Hi Dave, congrats for the content, but you just made me wonder a question. Why not make a stem and bar with each 0 offset instead of doing additions and teakeaways with values? Wouldn't that generate even less stress since there is no force's arm?

Great explanations! Where can I find a bike frame with suitable geo for a guy 184 cm tall?

about chainstay length, I noticed many bike brands just increase the reach as you go to larger sizes, while keeping chainstay the same. That means the problem of weighing the front end only gets worse with larger sizes, so going for 1-2 sizes up doesn't mean more modern geometry. Or am I wrong somewhere?

Do you have a recommended optimal range for chainstay to wheelbase ratio? Quick point of reference: Banshee Prime large 450/1250 is a .36 ratio.

How does backsweep effect steering foces/input? You mentioned 9-12 degrees is ideal. Why isn't 12 degrees more popular? It seems like 8 is pretty common.

it all nice to be said and showed with pictures but is there are really telemetry prof for extremely lite hands? when i moved to longer frame it becomes easier to load front by hands, 15-20 kg is not much for trained hands also you don`t really pull bunny hops on motocross bike (without using engine) so short chainstays here to stay for playfulness of bike

This (your) stem brings the handlebar higher up. Does this mean I'll need a handlebar with less rise?

Question. If a longer chainstay increases the ratio of chainstay to front center, wouldn't a shorter front end also accomplish the same thing and thus help with climbing? (of course coupled with a steep seat angle, and assuming the bike is still the right size for someone) Always appreciate your content.

Nice discussion! I am intrigued by the short single crown stem you showed in the video. Will this be available for purchase in the future?

In an ideal world wouldn't you want to create a situation where your hands are lined up with the fork axle to prevent over/under steering? And therefore have a shorter stem combined with a shorter fork offset too?

Great video! Who makes or where do you get a 15-20 mm stem these days?

what about with long or short chainstai on downhill bike? what is better and why? you forget that on the video

Where could someone from the u US get stems like this? I don’t see them on your website.

So I dont understand why my Nicolai G1 felt horrible with a 30mm stem and abolsuty perfect with a 45mm stem? I'm confused

my yellow bike feels sad now :D

You mention back and up sweep? how about bar rise? what do you recommend/ride?

First question: And what about handling tight corners? I am 189cm tall with +12cm ape index. If I put 500mm chainstay and 600mm reach with 78° STA and 64° HTA I would get around 1450mm wheelbase. Second question: If you pair 15mm stem with 63° HTA wouldn't it be too nervous? Third question: If I take 820mm 13😢° backsweep handlebar and it starts curving at 2/5 so it leaves me 3/5 ((410x(3/5))/90°)x13°=35. That means my 35mm stem will put that handlebar in alligment with fork. Is't that true?

You’ve sold me on a 32mm stem for my bike, just wanted to ask why people say a shorter stem results in understeer in correlation to fork offset, and how it really affects steering performance? Thanks in advance!!

where to buy your stem? hope you can ship worldwide.

So the only time a super short stem applies to climbing is if a bike has freakishly long chain stays?

Traditional cantilever stem causes ackermann angle effect to the hands ?

Is it possibile that a 485 R 1260 WB ( L size starling murmur ) works for a 173 rider with this stem?

Where can we buy the stems? Your websites seems to have 2020 and 2021 references and the price list site gives a 404

What do you think about trek slash geo?

Sottotitoli in italiano 👍🏻

So, what is your geometry with custom stem?

Hi Dave, good video. Do you intend to do a more in depth video presenting more complicated mechanics? The general idea is there and your message and assumptions seems sound but I personally would appreciate at least one level deeper - especially for thesis' like the lack of effect (or significance) of forces through the arms/hands or your statement that zero length stem does not cause bending forces to the fork. Also how do you come the right geometry figures? what is the connection to human biomechanics ( or putting it more simply - why not 600mm chain stay?) do you have a white paper that you could share of your calculations? I would certainly enjoy reading.

Cosa ne pensi del nuovo carro specialized??

How do I determine correct reach for my height? I'm 176cm on S3 spec enduro, 40 mm stem

Thanks for a great video with clear explanations! What are your thoughts on RAD (Rider Area Distance) measurement for bike sizing? I've seen a couple of videos where it's claimed to be a good measurement to properly size your bike (e.g. kzfaq.info/get/bejne/qK6RmrWg2663iac.html, kzfaq.info/get/bejne/idSImJWD0t6vog.html), but it seems to lean you towards slightly smaller sizes, where you recommendations seem to lean towards larger sizes. Grazie! 🙏

Per usare una pipa corta come la tua ci vogliono forcelle con 22mm di Offset, come si fa nelle moto da cross e enduro

Kirk Pacenti believes you. P DENT.

how much for this stem in 35mm and 1 1/8" ?

Non so perché fai tutto in inglese, in ogni caso davanti alla fisica le spiegazioni diventano subito inconfutabili 👍

Are you still selling stems?