1. The most important thing about buying a new bike is to make sure it fits. The only way you'll know if the bike is right for you is to size up the bike and make sure that the bike's geometry matches your body's geometry. Ask questions and do some research.
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2. If possible, try to find a shop that will let you demo the bike on real dirt. Five minutes in a parking lot won't cut it. You wouldn't buy a car without a real world test drive, and a bike should be no different.
3. Don't belive the hype. Just because your favorite rider or best friend rides a certain bike, that doesn't mean that's the best one for you. Have an open mind and be realistic about your needs and ability.
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  1. #1
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    stem length: Please educate me?

    Can someone give me a synopsis of the effects and benefits of changing stem length? I see that there are MANY different options. I've gathered that a shorter stem length tends to make a more relaxed feel as a longer stem can give a more racey position. What I'm curious about though is how to tell if you have the right length stem for ones peticular body build? What would the use of a too short stem result in? Too long? Thanks in advance!

  2. #2
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    The basic principles of which I'm aware are these:


    • The longer the stem; the slower, more imprecise, and more stable the handling. The shorter the stem; the more agile, more twitchy, and quicker the handling. The reason is not too difficult to understand, if you imagine exaggerated scenarios. Think of having a 24-inch stem. In order to effect a 30-degree turn of your front wheel, you'd be sweeping the handlebar through several inches of of side-to-side motion. If your stem is only half-an-inch long, on the other hand, the arc swept by the mount point of your handlebar on that stem will be only a fraction of an inch long for that same 30-degree turn. Similarly, it's harder for a trail obstacle to deflect your wheel when your stem is longer, because the angular momentum it has to work against (your grip on the handlebar) is being applied at a larger distance from the point where the rotational force is applied (the head tube).



    • A longer stem will also imply a longer "cockpit" (seat-to-handlebar distance), which is considered to be better for racing or climbing, since it's a bit more conducive to applying a larger force on the pedals. I believe this is because it makes leaning forward a little easier and leaning forward allows you to pedal harder. The drawback of this would be that biking for long periods of time in that forward-leaning pose is fatiguing and would not be as comfortable as a more upright posture if you do extra long rides frequently. (The "more relaxed" feel you have in mind might be arising from this posture comfort, rather than in terms of "relaxed steering". The steering will, in fact, become more on-edge and nervous, with a shorter stem--comparatively speaking.) Conversely, with a shorter cockpit, you might be tempted to stand more frequently when the need arises to pedal harder.


    In terms how you should decide on the best stem length for your particular case, the best advice anyone can give you might be "try it and see". Try at least a couple of different stem lengths (or different bikes with different stem lengths). If you feel like constantly having to reach too far in order to hold onto the handlebars or if you're experiencing back pain, it's probably too long. If you're feeling too skittish on technical descents, then it might be a bit too short. And so on... The longer the test rides you can do while you experiment with stem lengths, the clearer will be the impression that you get.
    Looking for local rides? You'll find plenty on my website: Bay Area Mountain Bike Rides.

  3. #3
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    Basically on any bike the position of your butt is determined by the location of the pedals....so your back end is fixed..

    Extending the stem just pulls your upper body forward and down...good for climbing and going fast on the flats....not so good on downhills and especially steep down hills...

    You can't really know whether a shorter stem is going to make the wheel turn faster or slower, unless you have straight bars, cause if your bars sweep back more than your stem is long the whole situation reverses....

    Lastly most stems are angled up so you actually move the bars up a bit and forward when you go to a longer stem.

    So just figure out what is going on on your bike.

  4. #4
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    Quote Originally Posted by jeffscott View Post
    You can't really know whether a shorter stem is going to make the wheel turn faster or slower, unless you have straight bars, cause if your bars sweep back more than your stem is long the whole situation reverses....
    Good point. But, given the same handlebar, the effect of a longer vs. shorter stem would still apply in the same way.
    Looking for local rides? You'll find plenty on my website: Bay Area Mountain Bike Rides.

  5. #5
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    Quote Originally Posted by erginguney View Post
    Good point. But, given the same handlebar, the effect of a longer vs. shorter stem would still apply in the same way.
    Not quite if the bars sweep back say 100 mm and you have a 80 mm stem then your hands are 20 mm behind the pivot...

    If you increase the stem to 100mm then the hand are at the pivot so the bars are fastest...

    If you then increase the stem to 120mm then the hands move the bars slower again.....

    So it can swing both ways.

  6. #6
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    Fair enough. I guess I should have qualified my explanation by adding "for common mountain bike handlebar shapes". I wouldn't call the scenario you're describing (handlebar sweep back equivalent to or greater than stem length) "typical" exactly.
    Looking for local rides? You'll find plenty on my website: Bay Area Mountain Bike Rides.

  7. #7
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    If longer rides don't murder your hands, wrists, arms, shoulders, neck or back, you're at least close enough with your stem length.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  8. #8
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    Quote Originally Posted by erginguney View Post
    Fair enough. I guess I should have qualified my explanation by adding "for common mountain bike handlebar shapes". I wouldn't call the scenario you're describing (handlebar sweep back equivalent to or greater than stem length) "typical" exactly.
    The effect is more common on downhill bikes with very short stems, and more swept bars.

  9. #9
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    Thanks for all the input guys. This is exactly what I was looking for. FWIW I have a XC setup and am basically looking for the best base setup. Long rides don't "murder" my hands, but I have noticed that I seem to put more pressure on the palms of my hands closer to my wrists when I ride. I always try to make it a point to keep my wrists in line w/ my arms and hands. Its noticeable, but again certainly not painful.

  10. #10
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    One thing you can try is to make a conscious effort to bend at the elbows...This will help keep the support in your torso and off your hands.

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  11. #11
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    Quote Originally Posted by flynbryan19 View Post
    Thanks for all the input guys. This is exactly what I was looking for. FWIW I have a XC setup and am basically looking for the best base setup. Long rides don't "murder" my hands, but I have noticed that I seem to put more pressure on the palms of my hands closer to my wrists when I ride. I always try to make it a point to keep my wrists in line w/ my arms and hands. Its noticeable, but again certainly not painful.
    Oops, I didn't see this.

    Try moving your stem up and down in the spacer stack and see if that makes a difference. WIthout seeing you on the bike, nobody can fit you over the internet. But you can end up with too much pressure from either too high or too low a handlebar position.

    The great Sheldon Brown covered fit extremely well on his page, especially when it comes to correcting discomforts.

    Bicycling and Pain

    I seem to be good enough at turning a deaf ear to my body that I often won't notice something that seems relatively small until it's heinously bad. I don't know how long your rides are, but I can almost guarantee that if they're sufficiently long, any little discomfort will get pretty bad.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  12. #12
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    Some good points made.
    More degree of rise on a stem of the same length will also shorten it's length from the pivot point, shorten your reach/cockpit, speed up steering, and put you more upright (less weight on hands), while raising your stem with spacers will not speed steering but will put you more upright. Also, the wider the bars are, the slower the steering, and the more the bars are wider than your shoulders, the lower your riding position will be.

    Have also noticed that when I change to a bigger taller tire in front because that seems to be what I like lately, that that'll also change saddle/hand weight, while the cockpit and reach remain the same.
    Round and round we go

  13. #13
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    Quote Originally Posted by AndrwSwitch View Post
    Oops, I didn't see this.

    Try moving your stem up and down in the spacer stack and see if that makes a difference. WIthout seeing you on the bike, nobody can fit you over the internet. But you can end up with too much pressure from either too high or too low a handlebar position.

    The great Sheldon Brown covered fit extremely well on his page, especially when it comes to correcting discomforts.

    Bicycling and Pain

    I seem to be good enough at turning a deaf ear to my body that I often won't notice something that seems relatively small until it's heinously bad. I don't know how long your rides are, but I can almost guarantee that if they're sufficiently long, any little discomfort will get pretty bad.
    Thanks. I'll check out the link. I lowered my stem by shuffling the spacers and it seems to feel better, but I haven't got out for an extended run yet. As for the ride time... Its usually between 2-3hrs.

  14. #14
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    Sorry to resurrect a dead thread like this, but I got here through a google search and thought I would add a personal experience when it comes to stems.. IF YOU ARE A NEW RIDER, AND ARE LOOKING FOR STEM INFORMATION, READ THIS STORY.

    If you are just getting into mountain biking, choose your stem length carefully, because what you initially train with could train with could acclimate your body to a specific length of this, or size of that..

    I rode an incredibly durable 2004 Blast for my first MB. It was great. I rode single track black trails with guys who had been doing it for years and never, ever fell. The ONE time I did fall it was on a flat grassy ride and there was a hole that disconnected my from my bike, it was not on a single-track. The Blast was a 21, which is large for me at 6', but at 240+ lbs (10% BF) at the time it actually seemed to fit. But that year bike came with an incredibly long stem. As long as a stem as I've seen. I haven't measured it, but I would guess 120mm. The bike fit worked fine for me. I did not know anything else and I just learned to put weight forward and go. As a fitness buff, I had no trouble with rocks, roots, and terrain that was supposed to be for high level riders. Not trying to brag, but other than a ingrained wuss fear of serious down-hill adrenaline stuff I saw some guys doing, I was actually a natural at tough single track/climbing trails.


    So basically I got pretty good on my big 21' bike with a super long stem. I saw the guys who were faster than me riding smaller bikes and ripping them around. I wasn't rich, so I decided to get a 2009 19' Rockhopper pro for my second bike and minor upgrade. This bike had a significantly shorter natural top bar (top tube), and a no length stem. I felt it whipping back and forth in the p-lot when I bought it, and it felt like it handled great. It seemed "small" for a 19', but I thought I would get used to it. So first time I went out I ran into a serious rider who decided that we should ride together. I was familiar with the area, and it was pretty tough stuff so I thought I would show him around. Well besides my pedals hitting a dozen rocks which almost threw me a bunch of times, I went over the handle bars three times. One time over a ridge and down about 6 feet. I had never, not once, hit a rock/root/anything in FIVE (5) years of riding and gone over the handle bars. I was embarrassed, and I was sad. I wanted so bad to explain that there was a problem with the bike and not me, but that would not have been completely true. My body was completely and totally accustomed to weight forward riding where I simply could not go over the handle bars. I was 100% acclimatized to the long top tube/super-long stem combo. This was 4 years ago, I haven't rode hard single track the same since. I just fell into a routine of commuting and mild trail riding since that terrible experience. I haven't climbed the mini mountain I used to all the time, and that has taken away from my fun in life. I tried to re-train myself on the new bike, and let the Blast go actually taking parts off it etc..

    I put a longer Raceface stem on my RH Pro. but maybe 80 MM and it wasn't enough to make me feel like I would not go over the handlebars again. Despite my sad story, I still have AND like that bike. I have it down to about 24 lbs (I only have a back brake on it lol) and I commute and ride it for 2,000 miles a season at least. My 2009 RH Pro is not a bad bike. But the moral of this story is "Be careful what size and stem you really learn to ride on, because that could be the size and stem you body completely acclimates to that you will need forever."

    This post is not bashing short stems. They handle better etc. But it IS telling you to be careful what you ride hard on when you are getting into the sport.

  15. #15
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    Read up a bit on front-center distance before you blame the stem.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

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    Thanks. I did. I see that 45% of your weight on the front tire, and 55% on the back is "normal." Pretty sure I got used to putting 50% on my front and not noticing any ill-effects because of the long top tube/long stem combo. I felt like I was going over the handle bars constantly when I changed bikes. I'm going to get a Carve next week and put a 100mm stem on it the dang thing and try to get back to riding single track. As for my my derailed thread about the other bike I was going to buy a few weeks back, I just got a refund. It should be noted that I am a long torso guy, so when my weight leans forward, it really leans forward. Thanks for the recommendation.

  17. #17
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    45/55 is widely cited for road bikes. My suspicion is that there's a greater rear bias for mountain bikes. A shorter stem, other things equal, tends to move a rider back on the bike. So it does have some effect on weight distribution. For me, at least, my riding position is actually not very malleable. If I don't have the right weight distribution to begin with, changing stem size will hurt my back more than help my bike's stability. This is why I think getting the size right is so important - it's really the only opportunity to choose front-center distance on a bike.

    I'm glad you're getting a new bike soon. I bet your experiences help you get the most out of test riding and really nail your size. I won't be surprised if 100mm is the right stem length for you on that bike, but I also won't be surprised if it's not. Just try to keep an open mind.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  18. #18
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    Its tough to say. If you look at some of the world cup XC riders...they have massive saddle to bar drops with long stems...and they are riding some crazy steep terrain with drop offs.

    Road bike frames are real short (with steep head tube angles) compared to a MTB. My 54cm (medium) road bike looks tiny next to my medium MTB. On a road bike...well...you're riding on the road. There are no rocks, roots, drops. So you can have that more forward weight distribution.
    Cervelo S2
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  19. #19
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    the riding position and bike setup of professional racers is irrelevant to most recreational riders, especially "beginners." it might also be irrelevant to a 11 month-old thread.

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    Quote Originally Posted by mack_turtle View Post
    the riding position and bike setup of professional racers is irrelevant to most recreational riders, especially "beginners." it might also be irrelevant to a 11 month-old thread.
    who cares how old the thread is,it is good info. it will be forever in cyber space ,so what !!

  21. #21
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    Re: stem length: Please educate me?

    Quote Originally Posted by mack_turtle View Post
    the riding position and bike setup of professional racers is irrelevant to most recreational riders, especially "beginners." it might also be irrelevant to a 11 month-old thread.
    Sorry I must have missed it. But what has changed in the bike frame design since 11 months ago, that makes new comments in this thread irrelevant?
    What works for me may not work for you. What's best for you depends on many factors. We are different from each other.

  22. #22
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    Cool-blue Rhythm

    The simple set up for new riders:

    Get on your bike and ride,,,

    Look down at your front axle,

    If Its behind your bars you need a shorter stem,

    If the axle is visible in front of your bars you need a longer stem.

    Going shorter often needs a wider bar and more stem rise...

    DON'T go nutzoid,,,, Think baby steps.....

    Got a 90 mm stem go to a 75, NOT a 50, your a new rider remember !!

    The bike's geometry will change dramatically if you chop stem length by 40 to 50%

    Got a 7 degree rise, going from a 90 mm to a 75,,, try a 15 degree rise...
    The above changes dictate a bar change provided your not a small person..

    From a 90mm stem to a 70 or a 75 mm stem then 26"/660 mm handlebar
    should become a 28 or 29"/700/711 mm bar...

    Expert riders go radical,,,,,
    1st and second year barnstormers need small changes...

    Wider bars will open your lungs up a little, you will breathe better,,,

    Wider bars smack trees more often, you know, them crazy rodeo style get offs XD

  23. #23
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    Old thread or not it is a good one to keep alive...lol..

    I have gone from a rigid with a long stem and a seat that was way higher than the bars and it never stopped me from riding almost any trail to a bike with 140mm travel fork 60mm stem and 20mm riser bar. Trends change and so do the way we look at how a bike works but at the end of the day it is about being comfortable and confident in the bike. My current set up did take a few minor changes to the one above with a swap to a 90mm stem with a little more rise and a bar with a 30mm rise. The reason for the change? Injury has forced me to change my riding position so I have had to adapt how I ride a little too... I pay very little attention to trends which change and the comment about seeing what pro riders use being pointless.. I agree and disagree too, they set up the bike which is the best for them so there is no point copying their set up but if you see what they ride and think about it, they ignore what others ride and go their own way to make it work for them. Yes make small changes to get to know what works for you but you may still find it ends up a dramatic change from standard. Find what works for you.

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    I'm 6'4" so the vertical height of my 21.5" frame fit me great. Most of my height is in my legs though so I found the stock 100mm stem made me feel too stretched out reaching for the cockpit over my top tube. I picked up a 40mm stem first for REALLY cheap just to see what the other extreme would feel like. I knew pretty much right away that 40mm felt too weird. There was too much tire in front of the stem. I decided to get a 60mm stem to try next. I figured I'd get much wider bars than the stock 680mm ones and just cut them down if I found them too wide to match my stem. So far I've been loving the 60mm stem and 740mm bar combo. Riding single track, the front end is far easier to lift up to get over obstacles and my elbows are more bent in my default position. With the original stem my elbows we're very close to locked. It's improved my ride significantly.

  25. #25
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    Going from a longish stem (100mm) to a short stem (50mm) changed my life. It was like going from my old jeep minus power steering and brakes to a new BMW race machine. It took a few rides to get used to the "twitchiness," then it was nothing but joy and effortless bunny hops. Wider bars are next on the shopping list. I will also say that it helped with pain I had in my back and shoulders on longer rides.

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