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  1. #1
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    Stem Length - Is their any rule of thumb?

    I'm building up a new 29er and the one part I have not purchased yet is the stem. I plan on temporarily fitting a stems from one of my other bikes, and go from there.

    Is there any better way of determining what stem length or angle or is it all by feel?

  2. #2
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    the rule of thumb is that the stem should be longer than your thumb...

    seriously though, why type of bike (cross country, trail, all-mountain, etc.) and how wide is the handlebar you're using?
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  3. #3
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    Quote Originally Posted by TwoNeener View Post
    the rule of thumb is that the stem should be longer than your thumb...

    seriously though, why type of bike (cross country, trail, all-mountain, etc.) and how wide is the handlebar you're using?
    yep

  4. #4
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    For xc, longer stretched out. For am/ dj, shorter works. What is your height? What size frame are u building?

  5. #5
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    Ask your lbs to lend you a few cheaper ones in different lenght. No rule of thumb.

    I'm 5'5", ride a Tallboy LTc with 35mm stem, 750mm bars. I've never ridden longer than 90mm in the last 15 years.

  6. #6
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    Age can be a factor too, I'm 53 and not too flexible so prefer to sit more upright and less stretched out on my xc bike otherwise my neck and back start hurting on the longer rides.
    Self employed picture framer, selling the odd cycle part/light as a sideline
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  7. #7
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    I thought I would need to go from a 100mm to a 90mm when I went from a 72* HA to a ~69* HA and 660mm bars to 710mm. Turns out it just felt better at 100mm. Not sure what the reason, so yeah, it's pretty much by feel. I bought (3) $15 handlebar stems, tried them all, then took them all back (mostly to prove a point since the shop refused to lend them) and ordered the one I needed (elsewhere).

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  8. #8
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    You're on the right track, try to get a few cheap stems and see what feels best with the bar you chose, then spend the money and buy a nice one in the length you want. As to if there's a rule, not really, but using a shorter stem for more aggressive riding with a wider bar gives you more control and you'll find that on most bikes designed for this and for XC having a bit longer stem and maybe slightly narrower bars stretches you out a bit more for more efficient pedaling and aerodynamics. I used to ride stems in the 110-120mm range and 685mm wide bars, now I've gone to much wider bars 750mm> and use stems anywhere from 65-90mm depending on the bike.
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  9. #9
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    No Rule of thumb, get a stem from another bike, if you dont have get a trainer borrow one (Or have someone hold you up or plan lots of test rides), put bike on trainer, level front wheel, starting tweaking postion.

    This link will help.

    Bike Stem Calculator - Brightspoke

    In general use the calculator to figure out what you need to do and take some real trail ride time under varying condtions to lock it down, trend now adays sees to be shorter stem wider bars.
    XC, Road, XXC, Endurance, Mtn, All-Mtn, Cross, Gravel, just go have fun on 2 wheels!

  10. #10
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    I just built up a new bandersnatch and have been through 4 stems in combination with 3 bars trying to get the cockpit sorted out. Every frame will have its nuances, and every rider will be different, and different types of trails will have different requirements. So start like you're doing with stuff you already have and go from there. A little higher? A little closer? Using cheaper stems til you hit it is good advice too.
    Use it, use it, use it while you still have it.

  11. #11
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    Quote Originally Posted by Epic_Dude View Post
    or is it all by feel?
    What else could it possibly be based on?

    Rules of thumb are pointless.

  12. #12
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    Quote Originally Posted by TwoNeener View Post
    the rule of thumb is that the stem should be longer than your thumb...

    seriously though, why type of bike (cross country, trail, all-mountain, etc.) and how wide is the handlebar you're using?
    XC Riding
    6'-0"
    190 lbs
    680 mm wide bars on order

    I have a XC 26er FS with a 100mm stem (650mm riser bars) I can try, and a XC 69er HT with 110mm stem (660mm riser bars) I can also try. Depending on what I like between those two stems I guess I can decide what I need.

    I think one of the local bike shops also have loaner stems I may be able to borrow.

  13. #13
    Root Master
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    Quote Originally Posted by Epic_Dude View Post
    XC Riding

    I have a XC 26er FS with a 100mm stem (650mm riser bars) I can try, and a XC 69er HT with 110mm stem (660mm riser bars) I can also try. Depending on what I like between those two stems I guess I can decide what I need.

    I think one of the local bike shops also have loaner stems I may be able to borrow.
    Sounds like a good place to start. The reach on the new bike is what will really dictate things. I think folks on XC race bikes like to be a little more stretched out anyway.
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  14. #14
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    If you can, cancel that 680mm bar and order up at least a 720mm wide one. At your height I think you'd appreciate the extra width and if you don't like it you can always cut it down, you CANNOT add to a too short bar.

    Quote Originally Posted by Epic_Dude View Post
    XC Riding
    6'-0"
    190 lbs
    680 mm wide bars on order

    I have a XC 26er FS with a 100mm stem (650mm riser bars) I can try, and a XC 69er HT with 110mm stem (660mm riser bars) I can also try. Depending on what I like between those two stems I guess I can decide what I need.

    I think one of the local bike shops also have loaner stems I may be able to borrow.
    One day your life will flash before your eyes, will it be worth watching??
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  15. #15
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    Try a few. I would think for XC a 90mm or 100mm would work fine. I recently rented a Turner Sultan in Moab and it had a stump for a stem and I hated it.

  16. #16
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    Quote Originally Posted by Epic_Dude View Post
    I'm building up a new 29er and the one part I have not purchased yet is the stem. I plan on temporarily fitting a stems from one of my other bikes, and go from there.

    Is there any better way of determining what stem length or angle or is it all by feel?
    Once you get your new 29"er assembled, use a stem from one of your other bikes to help figure out what you need. First, dial in your seat height and fore/aft positioning of the saddle to get your legs/knees where you prefer in relation to the cranks. There's probably more a rule of thumb for that portion of the fit in terms of how much knee bend you have at the bottom of your pedal stroke and not being too far in front of the pedal knee relationship or too far behind that.

    Once that is set up, then you can see what length of stem and how much rise or negative rise you need from the stem. As others have said, it is nice to have 3 or 4 different types of stems (length and rise options) to try out to see how close you can get to one that fits the best and provides the best bike handling. 10mm length difference can make quite a welcome change in fit and handling, so having them in increments of 5 or 10mm would be my suggestion. Typically, you could borrow some from an LBS to take home and try out (or bring your bike to the LBS and do it there).

    And even then, it might take quite a few rides to actually figure out what you prefer. Not to mention, your preferences may change throughout a riding season as you get in good riding shape. So owning a few different stems is never a bad thing as you can easily swap them out, flip them positive/negative, add/remove spacers, etc... .

    I have seen this photo and description of a sort of "rule of thumb" for fit, but it doesn't work for me at my height as my bar preference is much more forward than what this photo suggests...

    handlebar-height

    Although this photo shows what happens to "weight on the head" with our posture while standing, a similar thing happens to us on the bike if we get our body too out of position and if we are too stretched out, the extra "weight on the head" can really create some neck and back pain.

    Weight on the head...

    Hence, spending the trial and error process of getting the balance points correct (feet, saddle, bars) is well worth the experimental process - even if that involves some extra $$$ for various stems, spacers, bars. As others have mentioned, width of bars/sweep of bars/rise of bars will all contribute to determine what length of stem and how much rise it has (or doesn't have).

    Best of luck. We've all been through it.

  17. #17
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    I built up a larger 29er than my previous 26er...longer top tube + wider bars = shorter stem. Went from 95mm to 50mm, although it took a few steps... 95mm / 70mm / 50mm

  18. #18
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    Stem Length - Is their any rule of thumb?

    Does anybody else think a 50 or 70mm stem would pull CoG backwards from the neutral center that frame builders plan for when they design a frame? I generally want to stick with a 90-120mm stem on my bikes... I have a 90mm 10 degree up stem on my 29er (Titus with 24.75" ETT, a 100mm 5 degree down stem on my other 29er (Cannondale with 24.3" ETT) , and a 120mm 12 degree up stem on my flat bar commuter/buddy bike .... All of them put the center of the handlebar about 22-5/8" to 22-3/4 " from my saddle tip, which feels about right for me. I ride a little lower on my race 29er .... But not much lower. And even higher on the easy-breezy commuter. I've been trying wider bars but have settled on 27" ie ~680mm.

  19. #19
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    Quote Originally Posted by Scott In MD View Post
    Does anybody else think a 50 or 70mm stem would pull CoG backwards from the neutral center that frame builders plan for when they design a frame? I generally want to stick with a 90-120mm stem on my bikes... I have a 90mm 10 degree up stem on my 29er (Titus with 24.75" ETT, a 100mm 5 degree down stem on my other 29er (Cannondale with 24.3" ETT) , and a 120mm 12 degree up stem on my flat bar commuter/buddy bike .... All of them put the center of the handlebar about 22-5/8" to 22-3/4 " from my saddle tip, which feels about right for me. I ride a little lower on my race 29er .... But not much lower. And even higher on the easy-breezy commuter. I've been trying wider bars but have settled on 27" ie ~680mm.
    I'm in between sizes so I play with things a bit. Generally the set up that feels best for me wins... I would hate my bike if forced to the exact parameters of the original design intentions. For that matter I would probably dislike all bikes.

  20. #20
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    I have found that a shorter stem, with wider bars handles far better. When I got away from trying to get a road bike type fit on my mountain bike like it seems everyone wants to put you on and set up my bike for the best handling, I became way better on the steep descents and on the technical climbs where I like to ride. Optimal handling for me meant a 70mm or shorter stem and wide bars. That shorter stem and wider bar upgrade is the best thing I did for making the bike better handling and improving my riding, especially fast or technical downhills.

    This is a good read on the topic:BetterRide Mountain Bike Skills Tips
    Last edited by Haymarket; 04-24-2013 at 06:21 AM.

  21. #21
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    Re: Stem Length - Is their any rule of thumb?

    Buy a cheap short stem and see how it feels. Thats all there is to it. This was i did and only regret is why didnt i switched sooner. I rock a 50mm stem now and 30inch bar.

    Sent from my S3 using Tapatalk 2

  22. #22
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    Rules of thumb are pointless.[/QUOTE]

    So 20 replies and thousands look at this question, and you poop on him/her for asking the question? I'd say it is a good question JeffS. Don't folks make a lot of $$ setting folks up with stems, bars, seatposts, etc. based on some common ideas?

    I've asked myself the same question many times - where should my bars be? Regardlesss what feels good to me at this moment, I'd rather be riding what years of experience and knowledge says is correct. I tend to adapt to whatever I ride, so if someone with more experience could tell me what is approximately right, I will probably adapt and be better for it.

    In the end, the tone of your response, as well as the advise, is a bit rude and perhaps not very helpful.

  23. #23
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    Re: Stem Length - Is their any rule of thumb?

    Yep get 1 that goes all the way from the steerer tube to the handle bars.

    Any shorter & you will have problems.

  24. #24
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    I would start on your most comfortable saddle position then decide from there what stem length match your preferred riding position.
    When trails gets tougher, Just stand up and deliver.

  25. #25
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    What I find works for me and can spend hours in the saddle without the body complaining is to have my setup so when pedaling at my average cadence on a flat track I can lift my hands off the grips and not have to adjust my body weight forward or backward on the bike to keep my cadence and balance
    Self employed picture framer, selling the odd cycle part/light as a sideline
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