# The perfect stem size for a general trail riding 29er?



## febikes (Jan 28, 2011)

What's your theory about the perfect ratio between top tube length and stem size for a 29er?

On my bike I run a 100mm stem and like the way it feels but some people have recommended a longer frame and a shorter stem. Personally on a 29er for the type of trail riding I do I am concerned about the extra wheel base that would result from the long top tube and short stem configuration. If anything, I might consider running a 110mm stem so I could have a slightly shorter top tube but frankly I am pretty happy at 100mm stem length. Would a slightly longer stem and the resulting slightly shorter wheelbase even be something that I would notice?

It could be that the preference for longer stems results from growing up at as a roadie. On the road I used to run a 120mm stem. I feel we need shorter stems on mountain bikes but honestly I am not really sure about theory. It just seems for me that 100mm stems worked well on stock bikes that I road so when I built my own I stayed with 100mm. 

My thinking is that the more road like your riding is the longer the stem. For serious down hill style bombing a short stem makes sense because it is strong and keeps the front end lighter and more ready to take impacts (i.e. not going over the bars). For general XC the stems seem longer and gravel grinders are basically road bikes.

What are your thoughts? Have you ridden different bikes that are the same in other respects but trade top tube and stem length? ( i.e. keeping the body position and angles the same ).


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## Thylacine (Feb 29, 2004)

I think you answered your own question.

90-110mm is a good range for XC/Enduro, 80-120mm travel bikes.


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## Walt (Jan 23, 2004)

*Design around front center/trail*

Do your design with front center, trail, and the coordinates of the BB, saddle, and grips as the independent variables (ie, choose those things) and then let the TT and stem length be dependent on those. Stems are just for putting the bars where they need to be based on the other attributes of the frame you've designed for.

-Walt


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## TrailMaker (Sep 16, 2007)

Hey;

Generally, I would think you'd want to lay things out so that you could keep the stem on the shorter side of trail bike range (80-110). Having had to use crazy stuff like 135mm x 20-30* rise stems to make up for bikes that did not fit taught me that. They steer kinda weird. Even short bars put you into this strange circular steering motion where the stem is pivoting around an arc with much too large a radius and distance from the steer tube. Like you are steering a huge bus wheel with your hands at 11 & 1 instead of 9 & 3.

For me it's 90 x 10*. From there you g longer or shorter, flip it for lower or add a riser bar if needed. Steers nice too. Important on a 9r.


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## Walt (Jan 23, 2004)

*Why?*

You do not steer a bike with the handlebars! I get so tired of hearing that...

You steer it by leaning, unless you're going <5mph in a parking lot. It's VERY easy to prove this to yourself by just taking a smooth corner (paved or not) at a moderate speed (any bike will work) and actually paying attention to what you're doing with your arms. Seriously, try it. You actually push down/forward (mostly down) with the inside grip. The angle of the bars relative to the bike barely changes.

Stem length should be purely to put the bars where you need them for comfort and/or ability to move your weight around on the bike. All the handling and weight balance needs to be designed into the positions of the wheels, bb, and saddle, and the trail number you want. Period. That can mean a very short stem, or a very long one, but regardless, the stem length is not the variable that is determining how the bike handles.

Note that I'm assuming you're designing a bike from scratch here.

-Walt



TrailMaker said:


> Hey;
> 
> Generally, I would think you'd want to lay things out so that you could keep the stem on the shorter side of trail bike range (80-110). Having had to use crazy stuff like 135mm x 20-30* rise stems to make up for bikes that did not fit taught me that. They steer kinda weird. Even short bars put you into this strange circular steering motion where the stem is pivoting around an arc with much too large a radius and distance from the steer tube. Like you are steering a huge bus wheel with your hands at 11 & 1 instead of 9 & 3.
> 
> For me it's 90 x 10*. From there you g longer or shorter, flip it for lower or add a riser bar if needed. Steers nice too. Important on a 9r.


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## Glide the Clyde (Nov 12, 2009)

Walt said:


> You steer it by leaning, unless you're going <5mph


Walt, I know you know your stuff. I'm assuming a tight, almost track-standing switchback falls into the <5mph category. Does stem length have any effect on how a bike handles in short, slow maneuvers? What about the effect on getting weight forward for steep ups or back for descents?


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## Walt (Jan 23, 2004)

*No*

Assuming everything else (front center, wheelbase, bb height, trail, etc) is the same (and you can, in fact, accomplish this while varying the stem length, though you have to play with the headtube angle, fork offset, and toptube length to do it) the answer is basically no.

There is probably some very small difference (the longer the stem, the farther the grips have to move to accomplish the same change in angle of the front wheel - think of a 100-foot long stem as a thought experiment) that you could detect if you made the stem VERY long or VERY short and compared head to head. But it's not going to be something you could detect if you're talking about 90mm vs. 110mm or something.

Edit: Also, just to clarify, moving your weight around on the bike depends on where the wheels are, and where you are. That's all. If the bars are so far away, or so close, that you can't get your weight where you want it, that's obviously bad, but once again - you need to pick appropriate locations for the wheels and BB, then put the bars where you want them to go - the stem length is going to be driven by the other variables.

-Walt



Malibu412 said:


> Walt, I know you know your stuff. I'm assuming a tight, almost track-standing switchback falls into the <5mph category. Does stem length have any effect on how a bike handles in short, slow maneuvers? What about the effect on getting weight forward for steep ups or back for descents?


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## Blaster1200 (Feb 20, 2004)

Another thing to consider when talking stem length is bar width. Wider bars will automatically pull your upper torso forward to reach outward to the bars. So a short stem with wide bars may put your head/shoulders/torso in the same position as a long stem with narrow bars. 

For me, I generally tend to design around a 70 mm stem and 710+ mm bars. I use this setup for aggressive trail riding and plenty of XC, but with a focus on the aggressive riding.


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## TrailMaker (Sep 16, 2007)

Walt said:


> You do not steer a bike with the handlebars! I get so tired of hearing that...
> 
> You steer it by leaning, unless you're going <5mph in a parking lot. It's VERY easy to prove this to yourself by just taking a smooth corner (paved or not) at a moderate speed (any bike will work) and actually paying attention to what you're doing with your arms. Seriously, try it. You actually push down/forward (mostly down) with the inside grip. The angle of the bars relative to the bike barely changes.


Nah...

Not buying it. I hear the same sort of hair splitting from guys trying to describe how to steer a car. "You pull down with your inside hand, nut push up with the other." Meh... whatever. I happen to do both, to some varying split percentage, just like on a bike. Sure it's the rapid negative acceleration - and the usual inelastic impact with something hard - at the end that kills you, but it is still part of the fall. Steering the bars is part of the turn.

There are so many ways to change the direction of a bike that it renders this a distinction without a real difference. By whatever means necessary. Using the handlebars is one way to steer a bike, and you can make it go either left or right by steering in the same direction, depending on how you do it. Think on THAT one for a while. :skep: (cuing the crickets)

Let's just compromise and say that the handlebars are the main way of controlling the direction of travel, in essence.

The joy of a bike built to fit is that the stem length does NOT need to be used to cover up fit or handling deficiencies, and a fairly wide range of lengths will not ruin a well fitting machine. That's why we are all here... eh? Yet, you can radically alter the way ANY bike feels by going to one extreme or the other with a stem. I know relative bupkis about frame building because I've not built one, yet, but trust me, I've played more games trying to make little toy bikes like you "average people" ride work for me than you can shake a carbon bar at. If I've got a bike that I can even CONSIDER using an 80-90mm stem on, it must be at least close to fitting me... sort of. Thank GOD for the 29" wheel!

But we do digress....... If you want stable fast rolling at speed feel, go "long" wheelbase, which likely = shorter stem. If you need ground clearance, tight twisty quick steer agile, go "short" WB and choose a stem that fits the rider. Of course, short or long are different for each size rider, so bracket your rider accordingly. Make that all work within a 70-100 stem length and you will not be building freak. Perhaps it's time you built a long TT/short stem bike for yourself as a test piece, hmmmm? Just think of what a luxury that ability really is!!


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## Walt (Jan 23, 2004)

*Go try it.*

Go out in the parking lot and try it. You're not steering with the bars. In fact, you're mostly fighting to keep the bars straight as you lean. Anyone can tell immediately that this is the case. It's not like the steering wheel in a car in any way at all.

If you *really* don't believe me, try pulling back hard on the inside grip as you enter a corner - you can post from the ER and let us know how it went.

Your original question was about what stem length is "ideal". The answer is the stem that puts the bars where you need them, once you've designed the rest of the bike to steer and handle how you want it to. Stems have almost nothing to do with how a bike steers in that context. Changing out stems on an existing frame will obviously radically change the position of the rider, weighting of the wheels, and handling. But that was not the question.

-Walt



TrailMaker said:


> Nah...
> 
> Not buying it.


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## HomeGrownSS (Jan 18, 2006)

TrailMaker said:


> Nah...
> 
> Not buying it. I hear the same sort of hair splitting from guys trying to describe how to steer a car. "You pull down with your inside hand, nut push up with the other." Meh... whatever. I happen to do both, to some varying split percentage, just like on a bike. Sure it's the rapid negative acceleration - and the usual inelastic impact with something hard - at the end that kills you, but it is still part of the fall. Steering the bars is part of the turn.
> 
> ...


ugh. this is debated ad infinitum in motorcycle circles and forums.


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## febikes (Jan 28, 2011)

Thanks for the feedback from everyone. I think some people may have missed the original question so I am going to simplify.

My personal frame is as follows:









Someone asked me why I built the frame around a 100mm rather then an 80mm stem. This person felt that handling would be better with an 80mm stem. My feeling is that the 100mm stem likely helps the bike handle quickly.

With an 80mm stem I would need the wheelbase to be 20mm longer to give me the same body position. Would you agree? Does a longer front center and shorter stem result in noticeably slower handling if you keep everything else exactly the same? Would the extra 20mm of front center make the front end noticeably harder to lift?

I love the why my bike rides and as such this is mostly a theoretical discussion.


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## TrailMaker (Sep 16, 2007)

HomeGrownSS said:


> ugh. this is debated ad infinitum in motorcycle circles and forums.


Indeed;

Same on driving forums, hence my comments regarding "by whatever means necessary" and "distinction without a difference." Basically, WHO CARES about such minutia? Suffice it to say that you can't lean to make a car change direction, and the dynamic situation is very different in many ways (not all), but the steering motions are virtually identical. Oddly enough, I do have a friend who weighs around 400lbs who's car will steer in one direction unless he has it aligned to compensate, but... he would be rather an exception.

The difference in 20mm will make the bike somewhat more stable at high speed, somewhat harder to get a round a tight turn, somewhat more likely to hang on a log in some cases, potentially somewhat harder to loft the front, in theory, but will all of that be noticeable? Possibly, if one is on the margin in either direction of what is "perfect," but likely not to the complete detriment to the bike's usefulness. Minutia.

Make it 10mm and call it a bike.


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## Walt (Jan 23, 2004)

*20mm is huge!*

20mm in front center/wheelbase is a massive difference that almost everyone will notice immediately, even if you keep all the other fit and geometry variables the same. That's easily the difference between _full frame sizes_ on many mass-produced bikes!

Honestly, if you really think that this kind of "minutia" isn't interesting, I'm not sure why you are participating in this discussion or this forum. Most people here are VERY interested in the fine details of frame geometry and construction - otherwise we'd all be happily riding Treks, right? If you're building a bike from scratch, why not make the fit and handling as perfect (admittedly an impossible goal, and totally subjective for each rider) as possible?

Fe - to answer your question, the longer the front center, the more "stable" and slower the bike will steer, all other things being equal. Lifting the front end is *mostly* determined by where the rider is located relative to the rear axle, but you will be moving some stuff forward that has mass (wheel, fork) and hence you'll need a tiny bit more effort to lift those items off the ground. I would guess it's not noticeable in your particular hypothetical.

-Walt



TrailMaker said:


> Indeed;
> 
> Same on driving forums, hence my comments regarding "by whatever means necessary" and "distinction without a difference." Basically, WHO CARES about such minutia? Suffice it to say that you can't lean to make a car change direction, and the dynamic situation is very different in many ways (not all), but the steering motions are virtually identical. Oddly enough, I do have a friend who weighs around 400lbs who's car will steer in one direction unless he has it aligned to compensate, but... he would be rather an exception.
> 
> ...


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## TrailMaker (Sep 16, 2007)

Walt said:


> 20mm in front center/wheelbase is a massive difference that almost everyone will notice immediately, even if you keep all the other fit and geometry variables the same. That's easily the difference between _full frame sizes_ on many mass-produced bikes!
> 
> Honestly, if you really think that this kind of "minutia" isn't interesting, I'm not sure why you are participating in this discussion or this forum. Most people here are VERY interested in the fine details of frame geometry and construction - otherwise we'd all be happily riding Treks, right? If you're building a bike from scratch, why not make the fit and handling as perfect (admittedly an impossible goal, and totally subjective for each rider) as possible? -Walt


Pishhh...

You're talking to someone that has never had a TT length within 2" of what it needed to be on an off-the-rack bike, so maybe I'm used to adapting and overcoming. Going over the bars a lot too as a result, but that's life. 20mm? Pocket fuzz. Besides, *you're taking my comments out of context*.

I didn't say that geo does not matter, and did not term it minutia for everyone. It is to me, but I'm not everyone. I think there are just as many other factors that are at least as important. I've been battling TT length -vs WB -vs Trail for some time. I'd like my TT a certain length, but correcting the trail and staying within my chosen wheelbase has shortened my TT every time I tweak something. I'll have to compromise a little. Build your bike as perfect as possible. That's why we are all here, eh?* How you get the bike turned is the real minutia to me*. I really don't care how people do it, but to say that everyone does it the same is certainly folly. Lean into the turn, yank the bars, bunny hop, grab a tree, drop your left nut out of your shorts... I don't really care.

I'm dealing stem length here, and its effect on handling. So is the OP, if indirectly. Look below. 50 -vs 100mm stem, turned 10*, everything else the same. Here are the numbers. Decide for yourselves if it makes a difference, and if it matters to you. I can tell you from experience, it does.

Length DOES matter.


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## Thylacine (Feb 29, 2004)

Sorry Walt, while I agree most of the steering on a bike is done with leaning, I can't go so far as to say stem length and bar length/sweep doesn't matter.

In the same breath I can't argue that most of a bikes' shock absorption happens in your arms and legs and therefore suspension offroad is unnecessary.

Have I mentioned recently how much I hate BikeCAD?

Febikes, theres a few things that jump out at me here.

1. Firstly, 30mm of handlebar drop? How old are you, 70? My initial thoughts are your bars are too high.

2. Do you really need a 320mm BB height?

3. How did you arrive at a 74 degree STA? I see no indication of saddle setback.


ps: Trailmaster, I think you forgot your meds. You're contradicting yourself and I think I spot a bit of froth in the corner of your mouth. Go clean yourself up and come back.


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## febikes (Jan 28, 2011)

Thylacine said:


> Sorry Walt, while I agree most of the steering on a bike is done with leaning, I can't go so far as to say stem length and bar length/sweep doesn't matter.


The faster you are going the more the bike is driven by leaning but at slow rock crawling speeds and climbing on a MTB you don't lean into turns. At slow speeds the big benefit of getting the correct stem length is to distribute weight across the bike in a way that feels balanced.



Thylacine said:


> Have I mentioned recently how much I hate BikeCAD?


BikeCAD is just plain awesome! I have a 3D parametric cad system but frankly for working on bikes BikeCAD is much nicer and worth the money.



Thylacine said:


> 1. Firstly, 30mm of handlebar drop? How old are you, 70? My initial thoughts are your bars are too high.


The bike pictured is a singlespeed. Yesterday I road about 70 miles on it and next weekend I have a six hour race planned. I am 40 but after racing bikes since I was 14 years old some parts of my body feel 20 while other parts feel 80. For east coast off road this position feels good to me and is actually lower bars then many fairly fast people in my area ride.



Thylacine said:


> 2. Do you really need a 320mm BB height?


East coast trails are more technical with logs down and such. I really like the way a higher BB works for my area plus I pedal with very knees in and as such the higher then normal BB and lower then normal TT gets the top tube out of the path of my knees. On most stock bikes my knees would brush the top tube in my natural stroke. (or you could say unnatural stroke).



Thylacine said:


> 3. How did you arrive at a 74 degree STA? I see no indication of saddle setback.


Once again this is driven by my personal position. My seat post has 16mm built in setback (see drawing). The position puts me in exactly the same position relative to the BB as my 26er with a Thomson zero post. I am running a 80mm fork on the 29er and using these angles opens up the the possibility of later running a 100mm fork and going to a zero offset post.


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## Walt (Jan 23, 2004)

*Didn't mean to upset you*

First, please don't take anything personally. This is a fun debate.

I agree completely that the grip has to travel further as the stem gets longer, in order to achieve the same deflection of the front wheel. Can I assume that you would go further and argue that since the grip has to move farther, the longer-stem bike will steer less quickly and react less quickly to rider inputs?

If that's the case, would you conclude that 2 bikes with the same reach to bars (say, your 50mm stem vs 100mm stem) but correspondingly different front-centers (taking a number out of a hat here, let's say 650mm for the 50mm stem and 600mm for the 100mm stem, keeping HTA/offset/trail the same) would differ significantly in their handling, in that the shorter-stem, longer front center bike would be considerably *quicker* handling?

Edit: Here's a quick picture of what I'm talking about. Note the rider's *inside* arm is straightening, while his *outside* arm is pulling to help keep the wheel from turning in too far.

-Walt



TrailMaker said:


> Pishhh...
> I'm dealing stem length here, and its effect on handling. So is the OP, if indirectly. Look below. 50 -vs 100mm stem, turned 10*, everything else the same. Here are the numbers. Decide for yourselves if it makes a difference, and if it matters to you. I can tell you from experience, it does.
> 
> Length DOES matter.


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## 99sf (Nov 30, 2011)

I think thats more an issue of just trying to keep himself upright. One way to settle this would be for one of you frame builders to fab up a frame with a fixed front wheel. Might be fun to play around with


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## smdubovsky (Apr 27, 2007)

HomeGrownSS said:


> ugh. this is debated ad infinitum in motorcycle circles and forums.





99sf said:


> One way to settle this would be for one of you frame builders to fab up a frame with ...


Agreed debated "ad infinitum" but only one side is right Its been done:

Superbike School :: No B.S. Machine

Now with a bicycle, while the rider weight is a MUCH higher percentage of the total weight it doesnt change the underlying physics. Yes you can influence it some with your body weight. More on a bike than a motorcycle. But you steer by turning the wheel in the opposite direction not leaning. Game over. Go home. Nothing else to see here.

The stem/front center discussion part of this thread is good though.


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## Walt (Jan 23, 2004)

*Interesting*

So why can I ride all sorts of terrain, even *relatively* tight turns, without even having my hands on the bars? I mean, I'm not a trick rider or ready to join the circus, but it's dead easy to ride around town, or even on smooth singletrack with pretty decent radius turns, without touching the bars once. Of course if it's bumpy, that doesn't work since I get bounced off the bike, but not because I can't make the turns.

Obviously I agree about the countersteering. You're obviously not trying to pull the wheel into the direction of the turn.

-Walt



smdubovsky said:


> Agreed debated "ad infinitum" but only one side is right Its been done:
> 
> Superbike School :: No B.S. Machine
> 
> ...


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## motorbykemike (Oct 9, 2011)

Walt said:


> So why can I ride all sorts of terrain, even *relatively* tight turns, without even having my hands on the bars? I mean, I'm not a trick rider or ready to join the circus, but it's dead easy to ride around town, or even on smooth singletrack with pretty decent radius turns, without touching the bars once. Of course if it's bumpy, that doesn't work since I get bounced off the bike, but not because I can't make the turns.
> 
> Obviously I agree about the countersteering. You're obviously not trying to pull the wheel into the direction of the turn.
> 
> -Walt


because a bicycle is super light w/ very little gyroscopic weight compared to a motorcyclye , what you are doing is subconsiously / instinctively "flicking" the chassis w/ your hips to countersteer or "pushing down" w/ your hips in the direction of the turn for a slower entry/reponse from machine , still countersteering but very slowly . because of it's lighter weight , esp gyroscopic weight , it responds much more than a m/c

think about the path of the front end upon shifting your hip over to the left and continuing to push down w/ said hips . the caster , which is what trail gives you , will make the tire turn to the right as it really wants to stay vertical/have the most caster and the closest thing it can find is to go right , or straight actually but the machine is starting to go left and as a result the headstock is no longer vertical so..... the tire goes to the right , seeking the most caster available .

as far as motorcycles i am not 100% in agreement w/ mr. codes black and white / right and wrong / my way or the highway deduction w/ the "no b.s." series of bikes . a freind and i built a similar rig after seeing this years ago and hearing all the hype from our students .
yes you can turn the bike w/ body steer/weight , weighting the pegs , and doing the "hip jerk" , not very effectively or quicky but it turns and it turns as a result of countersteering . pushing down/pulliing up on the bars was the least effective , we agreed that this was a result of leverage afforded .

you can also turn a bicycle/motorcycle by pulling on the inside bar w/ no countersteer input but the chassis and tire are not very happy doing this and can unload the front , it also requires a substantial amount of force to do so which should be telling the rider he/she is probably doing something wrong . the machine will also try to stay vertical as it wants to react to what should have been a countersteer to "get into" then follow up w/ "maintain" but as you continue to pull on the inside bar it pushes / looses the front / as it tries to throw rider over the top or highside but the rider forces the issue into a front end crash .

and we hang off or stay vertical over the bike mid corner to adjust the cg/traction as needed


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## Feldybikes (Feb 17, 2004)

You're both right. Steering in the opposite direction and leaning amount to the same thing. On a bike with reasonably "normal" geometry, if you turn the front wheel to the right, it will lean to the left. Think about a bike falling over by itself, the front wheel always points up, never down. (I guess I use the term "always" a little bit loosely here, but I think the point is clear)


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## Walt (Jan 23, 2004)

*Right*

I agree with everything you just said - as I said, you *can* steer the bike without any direct input at the handlebars. That's all I meant. Of course you're countersteering. And yes, if you're pulling/pushing hard at all on the bars, you're doing something wrong.

My original point was (to vaguely get back on topic) that designing around trail and front center is the way to go, letting stem length vary within some reasonable range (80-120mm or so?) to get the reach where you want it, and that the length of the stem (at least in the "normal" range) has a minescule effect on the steering of the bike compared to those two other variables.

-Walt



motorbykemike said:


> because a bicycle is super light w/ very little gyroscopic weight compared to a motorcyclye , what you are doing is subconsiously / instinctively "flicking" the chassis w/ your hips to countersteer or "pushing down" w/ your hips in the direction of the turn for a slower entry/reponse from machine , still countersteering but very slowly . because of it's lighter weight , esp , gyroscopic weight , it responds much more than a m/c
> 
> think about the path of the front end upon shifting your hip over to the left and continuing to push down w/ said hips . the caster , which is what trail gives you , will make the tire turn to the right as it really wants to stay vertical/have the most caster and the closest thing it can find is to go right , or straight actually but the machine is starting to go left and as a result the headstock is no longer vertical so..... the tire goes to the right , seeking the most caster available .
> 
> ...


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## motorbykemike (Oct 9, 2011)

Walt said:


> I agree with everything you just said - as I said, you *can* steer the bike without any direct input at the handlebars. That's all I meant. Of course you're countersteering. And yes, if you're pulling/pushing hard at all on the bars, you're doing something wrong.
> 
> My original point was (to vaguely get back on topic) that designing around trail and front center is the way to go, letting stem length vary within some reasonable range (80-120mm or so?) to get the reach where you want it, and that the length of the stem (at least in the "normal" range) has a minescule effect on the steering of the bike compared to those two other variables.
> 
> -Walt


so that being said , everyone on the planet that has ever ridden a bicycle w/ no hands has proved mr. code wrong .

wow , epic threadjack so back on topic

i agree w/ your statements but i have to add that the stem length may change the feel (the tiller feel i call it) but the actual steering would not make be dramaticly different .

i have been playing w/ stem length on one of my bikes to the tune of 50mm and the biggest difference is the weighting .


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## ade ward (Jun 23, 2009)

So at speed it doesn't matter how you incite the lean , once lent over the bike acts like a rolling cone ,

I originally came from a motorbike background running the ohlins suspension race service back in the late 80's and you could tell riders who knew about counter steering as they went from upright and braking to fully lent over and back on the gas, very quickly whereas others spent more time tipping it in,and getting the bike settled before starting to feed the throttle ,

So you can ride a bike no handed, but once you start to get into a fast bit of single track getting a bike to change direction quickly involves countersteering works for me ,

Anyway back to the original question I have designed my 29er to have a very short chainstay 407-427 an effective TT of 609 a seat angle of 71.5 and I fun a 60 or 70 stem depending if I am running ragley carnegie bars or j bars All this works or me makes. Very nimble 29 er


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## TrailMaker (Sep 16, 2007)

20mm means nothing?

Yeh, of course that was dumb. Don't equate saying dumb things or not backing down with getting mad. Not so. Everything matters or we would all be riding off the shelf Treks. Seems like I heard that somewhere.  Saying that makes about as much sense as saying the stem doesn't change handling, really... eh? Touche! The truth is that we are all learning (me more than most), for if that ceases, we should, by rights, be dead.

*Febikes *is building a bike for where I ride too. You simply do not want the tiller effect that someone else mentioned. It just doesn't work. you need quick steering, or at the very least highly manageable. I'm surprised he has been with 100mm that long, altough it is only 10 more than I have found I like. Ground clearance too, so I would not necessarily call 320 BB/H excessive, especially if the wheelbase gets long, and extra especially if it were a dual suspension 29er.

If it were me, I would investigate putting that 20mm in the TT so I might be able to take it out of the stem. As long as the WB does not get too long, this might be beneficial to a 29r, especially if a longer bar were being used for leverage. And, there are few things as luxurious as the ability to tune for a nice roomy cockpit! Of course there are a lot of other parameters to consider, and it might not work up against other needs/wishes, but it definitely food for thought.


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## Walt (Jan 23, 2004)

*Let me clarify*

I thought this was pretty clear from my previous comments, but maybe not.

What I meant was that 20mm of front center is way more important than 20mm of stem length, so if you're making the choice that febikes is making between 650 front center/100 stem and 670 front center/80 stem, the shorter front center/longer stem is probably the way to go for what he wants (a little quicker steering). The longer stem will require more arm/hand/grip movement, but it's almost insignificant in the larger context of the wheel positioning relative to the rider.

I *think* this is also what you recommended to him:


> If you need ground clearance, tight twisty quick steer agile, go "short" WB and choose a stem that fits the rider.


So I'm confused as to why you are making the stem-length-drives-steering argument - if a shorter stem makes the bike steer quicker (less arm/hand/grip movement required to turn the bars) then he should go with the 80mm stem/670 front center, right? Or, heck, 20mm stem, 730mm front center... Am I not understanding you?

-Walt



TrailMaker said:


> 20mm means nothing?
> 
> Yeh, of course that was dumb. Everything matters or we would all be riding off the shelf Treks. Seems like I heard that somewhere.  Saying that makes about as much sense as saying the stem doesn't change handling, really... eh? Touche!
> Febikes is building a bike for where I ride too. You simply do not want the tiller effect that someone else mentioned. It just doesn't work.


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## Thylacine (Feb 29, 2004)

febikes said:


> BikeCAD is just plain awesome! I have a 3D parametric cad system but frankly for working on bikes BikeCAD is much nicer and worth the money.


I use Illustrator with CADTools, which is better again.



febikes said:


> The bike pictured is a singlespeed. Yesterday I road about 70 miles on it and next weekend I have a six hour race planned. I am 40 but after racing bikes since I was 14 years old some parts of my body feel 20 while other parts feel 80. For east coast off road this position feels good to me and is actually lower bars then many fairly fast people in my area ride.


I still don't like it. 



febikes said:


> East coast trails are more technical with logs down and such. I really like the way a higher BB works for my area plus I pedal with very knees in and as such the higher then normal BB and lower then normal TT gets the top tube out of the path of my knees. On most stock bikes my knees would brush the top tube in my natural stroke. (or you could say unnatural stroke).


You honestly think that +/- 6mm of BB height would stop you brushing your legs on the top tube?



febikes said:


> Once again this is driven by my personal position. My seat post has 16mm built in setback (see drawing). The position puts me in exactly the same position relative to the BB as my 26er with a Thomson zero post. I am running a 80mm fork on the 29er and using these angles opens up the the possibility of later running a 100mm fork and going to a zero offset post.


Well if you're confident your position on the 26er is right....


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## TrailMaker (Sep 16, 2007)

Oh Damn...

Don't you have any frames to build? I hit the wrong key before I finished with that last feeble attempt, let alone fixed it. To be perfectly honest, I am not completely sure what you mean by front/center. I would go longer with the frame and shorter on the stem. This would seem to me to give the option for a nice long cockpit, but also the option for quicker 29r steering. Yes?

I have a feeling this is turning out to be one of those dumb situations where we both agreed all along. If my ignorance facilitated that, well... I still don't care how people steer their bikes.


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## Walt (Jan 23, 2004)

*What?*

I'm going to stop now, because I no longer have any idea what you're trying to say here. Your earlier post ("If you want stable fast rolling at speed feel, go "long" wheelbase, which likely = shorter stem. If you need ground clearance, tight twisty quick steer agile, go "short" WB and choose a stem that fits the rider") says the *opposite* of what you're saying now.

FYI, front center is the distance from the BB to the front axle. It's a very useful number for comparing frames to each other and figuring out how they'll ride.

Fe, sorry for the massive hijack. I'm the worst moderator ever!

-Walt



TrailMaker said:


> Oh Damn...
> 
> Don't you have any frames to build? I hit the wrong key before I finished with that last feeble attempt, let alone fixed it. To be perfectly honest, I am not completely sure what you mean by front/center. I would go longer with the frame and shorter on the stem. This would seem to me to give the option for a nice long cockpit, but also the option for quicker 29r steering. Yes?
> 
> I have a feeling this is turning out to be one of those dumb situations where we both agreed all along. If my ignorance facilitated that, well... I still don't care how people steer their bikes.


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## smoothsam (Mar 27, 2011)

Walt, Try this, weld a fork to a frame and hit the trails, then tell us how it goes.


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## febikes (Jan 28, 2011)

TrailMaker said:


> *Febikes *is building a bike for where I ride too. You simply do not want the tiller effect that someone else mentioned. It just doesn't work. you need quick steering, or at the very least highly manageable. I'm surprised he has been with 100mm that long, altough it is only 10 more than I have found I like. Ground clearance too, so I would not necessarily call 320 BB/H excessive, especially if the wheelbase gets long, and extra especially if it were a dual suspension 29er.
> 
> If it were me, I would investigate putting that 20mm in the TT so I might be able to take it out of the stem. As long as the WB does not get too long, this might be beneficial to a 29r, especially if a longer bar were being used for leverage. And, there are few things as luxurious as the ability to tune for a nice roomy cockpit! Of course there are a lot of other parameters to consider, and it might not work up against other needs/wishes, but it definitely food for thought.


Putting 20mm into the TT would also require 20mm in the wheel base and I think overall the bike would be less suited for the trails I ride.

Sure the 320mm BB might be what some consider high for a hard tail. I prefer to be a inch higher then others so I can look down on them. The higher BB gives the bike more tight twisty trail ability. Since it is a single speed the bike is not really focused on high speed big mountain descending. Two wheel drifting on gravel corners is not what this bike is about. The higher BB gives the bike better handling in rock gardens log crossing and twisty washed out bandit trails.


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## TrailMaker (Sep 16, 2007)

Sorry, then;

Didn't really mean to wad your whities. Contradictory, ya say... Really. Does not a long wheelbase lend itself to high speed stability? Does not a short one lend itself to nimble handling? Don't we all want both? Don't we want everything? We want great BB height for rolling over boulders but we want a low BB height for low CG stability. We want a slack HT for bombing downhills, but we want a steep one for quick steering response. We want a relaxed rear bias for floating the front over technical terrain, but we want front bias offering solid front weight for climbing. Is not the perfect bike nothing more than a carefully chosen compromise between all these disparate traits? Bikes are nothing more than contradictions reconciled.

I would always opt for a roomy cockpit, because I like being (and staying) behind the handlebars as much as possible. If the cockpit is long enough, I might have to use that "shorter" stem to get my reach, eh? For me you can always throw in a 2.5 riser bar as well. This long TT brings with it a longer wheelbase. Yet, I know it will be harder to get that moose around a tight switchback, so I'd look to keep the HT angle at or beyond 70 somewhere, trail well within reason (3.5-ish), and as short a stem as possible (80-90). While a long bar takes a bit more wingspan & time to row, it gives better leverage and keeps things in check, so I'd add that too. And yes I do completely agree that I would want a layout that relegated the choice of stem to being purely a decision based on ergonomics. I fail to see where any of the above does not make sense, so enlighten me, please.

As I recall, the OP wondered if less in his front end would mess up his bike. He also mentioned traditionally using a 100mm stem, but perhaps opting for more to compensate. I thought that PLUS 20mm would be the way to go, as he had been advised elsewhere, and then he might like to SHORTEN the stem a tad, to 80 or so. Isn't that what I said? He mentioned classic East Coast rock crawling, and high bottom brackets and stability. There's the inherent contradiction again; not in what I'M saying, but what making these choices REQUIRES US TO JUSTIFY. I don't see where anything I said does not lend itself to his questions. I know what he wants, because I ride what he rides, and I think I offered that, not based on my vast frame building experience, but in riding what he rides and struggling for years to find the right equipment for me to do that.

As for hijacks, I was not the one with the gun to the pilots head... Hmmm... I wonder if he leans into the turns?


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## Walt (Jan 23, 2004)

*Um, ok...*

Where did I say that the front wheel should be fixed?

-Walt



smoothsam said:


> Walt, Try this, weld a fork to a frame and hit the trails, then tell us how it goes.


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## febikes (Jan 28, 2011)

*Beast of the East*

We got a bit off topic and BB height became an interesting sub topic. In any case, for east coast riding I think the formula is shorter front center, shorter wheelbase, and a higher BB. This is not really a new approach and IMHO the formula still works.

The 1995 Cannondale "Beast of the East" model shipped with a 330mm bottom bracket height and a rigid fork. The beast was a little bit unusual but it was very good in technical stuff. I am doing 29er wheels and have a suspension fork but I still think the trails I ride today deserve a high bottom bracket.

The beast is in the middle of the kataloge.
http://www.mtb-kataloge.de/Bikekataloge/PDF/Cannondale/1995.pdf

My geometry drives me to us a slightly longer stems and shorter front center. Like everything it comes down to personal taste more then where you live. There may not really be any "perfect stem size".


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## Yogii (Jun 5, 2008)

I can steer my Waltworks with my knees. Just drop my inside knee and around I go. Front-center is the most important(and most overlooked) geo question there is. I used to think that trail figure, mechanical or otherwise, was...


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