User Tag List

Results 1 to 16 of 16

Thread: why are MTB stems so short?

  1. #1
    Join Date
    Mar 2013
    Posts
    335
    Post Thanks / Like
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)

    Default why are MTB stems so short?

    I have some theories. What do you think?

    popular ideas include:
    • steering dynamics
    • weight distribution over the front axle
    • fitting
    Jonathan - Austin, TX

  2. #2
    Join Date
    Aug 2010
    Location
    Ashland, OR
    Posts
    364
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Because when riding down steep angles and drops your weight distribution feels correct.
    XC bikes generally have longer stems.
     

  3. #3
    Join Date
    Jul 2008
    Location
    SF Bay Area
    Posts
    2,114
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    the moment you take a 8-10" bike off a big drop it all makes sense.
     

  4. #4
    Join Date
    Aug 2011
    Location
    DURHAM, North Cackalacky
    Posts
    1,845
    Post Thanks / Like
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    I am an idiot so take with salt, though one impression I have is that short stems maintain the same reach on a bike that has a much longer front center. While chainstays remain short and wheelbases try to remain in the ballpark, slack head tubes and long TTs stretch out the part of the bike the rider "experiences" and the stem compensates to maintain normalcy.
     

  5. #5
    Join Date
    Oct 2008
    Location
    Kingman, AZ
    Posts
    4,408
    Post Thanks / Like
    Mentioned
    4 Post(s)
    Tagged
    1 Thread(s)

    Default Re: why are MTB stems so short?

    Quote Originally Posted by zambenini View Post
    I am an idiot so take with salt, though one impression I have is that short stems maintain the same reach on a bike that has a much longer front center. While chainstays remain short and wheelbases try to remain in the ballpark, slack head tubes and long TTs stretch out the part of the bike the rider "experiences" and the stem compensates to maintain normalcy.
    That's what I thought too. Back in the day, mountain bikes were just glorified touring bikes without the slack head tube angles that came later. We made them handle better on single track with longer stems and stupid narrow bars (because that's what Tomac did). My Coconino hardtail has a 70mm stem, my Raleigh Chill had a 150mm Tioga stem.
    Weight Doper

  6. #6
    Join Date
    Jun 2009
    Location
    Aix-en-Provence
    Posts
    10,918
    Post Thanks / Like
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    It's to cope with a revolutionary geometry change. A revolution happens every other year or so.
     

  7. #7
    Join Date
    Apr 2011
    Posts
    1,001
    Post Thanks / Like
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Quote Originally Posted by mack_turtle View Post
    I have some theories. What do you think?

    popular ideas include:
    • steering dynamics
    • weight distribution over the front axle
    • fitting
    i ran a 120 stem on a ti hardtail with pretty steep headtube (vs. "modern" geometry)...i went over my bars with regularity

    doesnt happen anymore with a short stem and slack front end
     

  8. #8
    Join Date
    Mar 2013
    Posts
    335
    Post Thanks / Like
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Quote Originally Posted by funcrusher View Post
    i ran a 120 stem on a ti hardtail with pretty steep headtube (vs. "modern" geometry)...i went over my bars with regularity

    doesnt happen anymore with a short stem and slack front end
    is it the head tube angle, the reach, or the front-center that changed? or all three? if one were to build a bike with a relatively slack HTA but a short reach, would the rider still want a short stem? would a bike with a long reach and a relatively steep HTA then need a longer stem?

    just trying to open discussion to narrow down what the real issue is. I am not trying to prove anything, just curious about what is fact and what is pseudo-science.
    Jonathan - Austin, TX

  9. #9
    Join Date
    Aug 2010
    Location
    bend
    Posts
    1,498
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Quote Originally Posted by mack_turtle View Post
    is it the head tube angle, the reach, or the front-center that changed? or all three? if one were to build a bike with a relatively slack HTA but a short reach, would the rider still want a short stem? would a bike with a long reach and a relatively steep HTA then need a longer stem?

    just trying to open discussion to narrow down what the real issue is. I am not trying to prove anything, just curious about what is fact and what is pseudo-science.
    Likely similar total reach to old stretched xc positions, but now the tt is longer.
    I've become a fan I think as long as things aren't crazy slack. I ride my xl mtb w/ a 50mm stem (493 reach) and my 58cm gravel bike (406 reach) has a 100/110mm I think. Definitely different setup than older bikes I've had.
     

  10. #10
    Join Date
    Apr 2011
    Posts
    1,001
    Post Thanks / Like
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Quote Originally Posted by mack_turtle View Post
    is it the head tube angle, the reach, or the front-center that changed? or all three? if one were to build a bike with a relatively slack HTA but a short reach, would the rider still want a short stem? would a bike with a long reach and a relatively steep HTA then need a longer stem?

    just trying to open discussion to narrow down what the real issue is. I am not trying to prove anything, just curious about what is fact and what is pseudo-science.
    everything changed..."modern" geo is long/slack...so shorter stem to compensate...definitely stabler on descents

    and no trade-off because steep seat angle helps for climbing
     

  11. #11
    Join Date
    Aug 2011
    Location
    DURHAM, North Cackalacky
    Posts
    1,845
    Post Thanks / Like
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    It's the classic try before you buy scenario based on your local trail needs. As for me, I did not find with modern bikes that there was "no penalty" when climbing. The length of the front center made it feel very long ... like piloting a Cadillac, so if you ride twisty, classic trails, and technical, rooty climbs, buyer beware. Railing series of berms downhill ... sure, sign me up for the Cadillac, but that's not my area. I tried two modern bikes, one modernish, a two or three year old Trek FS, and the other a 2020 Santa Cruz Tallboy, which is much more "modern". Though I'm a likely hardtail customer til I'm older or ride gnarlier stuff, I thought I'd see what the fuss was about. Couldn't handle the wheel flop or wandering front end on the TB when trying to get up climbs, though back end traction was really impressive. The steep, steep seat angles have you sitting in the middle of the bike - you don't seem to do as much body English or sliding your weight back, it seems mostly about getting low. As for me, I wound up sticking with what I know, as I felt like I was still learning and enjoying classic "get your weight back"/"keep your front end low to aid front-end traction", etc. type techniques and didn't want or need to depart from that for the time being. So, I stuck with a hardtail with old school XC geo, but all the trails I ride are XC oriented - tight, twisty singletrack, rooty, old school singletrack climbs, gently undulating terrain, etc. I went with a low BB, 90mm stem, and thus configured, the 71.5 head angle still feels marvelous both uphill and down. That's road bike geo to contemporary riders, but it has all the precision and snap I like from the front end while climbing. It's been fine downhill - I, for one, quit going over the bars when I switched from 26" to a 29er, though I'd be willing to try maybe a 70 HA. YMMV, horses for courses, etc.

    Let us know what you try.
     

  12. #12
    Join Date
    Jun 2013
    Location
    Portland, ME
    Posts
    98
    Post Thanks / Like
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Stability and leverage.

    Short stem + wide bars = bumps and objects don't knock you off line, you don't endo anymore, handlebars don't flop over sideways once turned, and you have the power to hold the bars still no matter how rough the terrain. Same reason BMX does it, but they don't need a hold a comfortable pedaling position for hours so the rest of the geometry doesn't have to follow.

    Really really strong pro riders can even do narrow-ish bars and short stems and not have to deal with width challenges, but only because their upper bodies and cores are so strong that they don't need as much leverage help.
     

  13. #13
    Join Date
    Jun 2008
    Location
    Asheville, NC
    Posts
    3,441
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Quote Originally Posted by zambenini View Post
    It's the classic try before you buy scenario based on your local trail needs. As for me, I did not find with modern bikes that there was "no penalty" when climbing. The length of the front center made it feel very long ... like piloting a Cadillac, so if you ride twisty, classic trails, and technical, rooty climbs, buyer beware. Railing series of berms downhill ... sure, sign me up for the Cadillac, but that's not my area. I tried two modern bikes, one modernish, a two or three year old Trek FS, and the other a 2020 Santa Cruz Tallboy, which is much more "modern". Though I'm a likely hardtail customer til I'm older or ride gnarlier stuff, I thought I'd see what the fuss was about. Couldn't handle the wheel flop or wandering front end on the TB when trying to get up climbs, though back end traction was really impressive. The steep, steep seat angles have you sitting in the middle of the bike - you don't seem to do as much body English or sliding your weight back, it seems mostly about getting low. As for me, I wound up sticking with what I know, as I felt like I was still learning and enjoying classic "get your weight back"/"keep your front end low to aid front-end traction", etc. type techniques and didn't want or need to depart from that for the time being. So, I stuck with a hardtail with old school XC geo, but all the trails I ride are XC oriented - tight, twisty singletrack, rooty, old school singletrack climbs, gently undulating terrain, etc. I went with a low BB, 90mm stem, and thus configured, the 71.5 head angle still feels marvelous both uphill and down. That's road bike geo to contemporary riders, but it has all the precision and snap I like from the front end while climbing. It's been fine downhill - I, for one, quit going over the bars when I switched from 26" to a 29er, though I'd be willing to try maybe a 70 HA. YMMV, horses for courses, etc.

    Let us know what you try.
    You need to borrow my Chameleon. Think it's a 67.3HA/50mm stem. Its flat enough here that old school still works fine but in the steep (WNC) and the new stuff comes into its own. As per my other thread my next bike will land between 66 and 67 HA trying to balance our local flat terrain with trips back home to AVL.
     

  14. #14
    Join Date
    Aug 2011
    Location
    DURHAM, North Cackalacky
    Posts
    1,845
    Post Thanks / Like
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Quote Originally Posted by Jason Musgrave View Post
    You need to borrow my Chameleon. Think it's a 67.3HA/50mm stem. Its flat enough here that old school still works fine but in the steep (WNC) and the new stuff comes into its own. As per my other thread my next bike will land between 66 and 67 HA trying to balance our local flat terrain with trips back home to AVL.
    That I do! Let's make this happen soon. I also suspect that I might be curious about a larger bike, kind of like that one time I rode your road bike and did not mind the longer reach whatsoever.
     

  15. #15
    Join Date
    Jun 2008
    Location
    Sonoma County, Calif.
    Posts
    49
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Also handlebar width. At 780 or 800mm, there’s a ton of reach just being generated by the bars. You have to shorten the stem, quite a bit, to compensate for that as well.

    Cheers
     

  16. #16
    Join Date
    Mar 2009
    Location
    Meriden CT
    Posts
    1,321
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default Re: why are MTB stems so short?

    Quote Originally Posted by Lionel View Post
    It's to cope with a revolutionary geometry change. A revolution happens every other year or so.
    How about adding a sarcastic "tongue in cheek" emoji with that?!

Similar Threads

  1. Road bikes with extremely short stems?
    By frenk in forum General Discussion
    Replies: 7
    Last Post: 08-10-2011, 10:13 AM
  2. My list is very short
    By Disturbed in forum General Discussion
    Replies: 10
    Last Post: 02-10-2010, 12:31 AM
  3. JP's Short TT
    By ssjimbo in forum General Discussion
    Replies: 13
    Last Post: 01-04-2010, 11:25 PM

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •