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.
mtn. biking 101
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.
Results 1 to 7 of 7
  1. #1
    mtbr member
    Reputation: xxbrittonxx's Avatar
    Join Date
    Sep 2009
    Posts
    73

    Stem length question...

    I'm trying to figure out what the differences are between stem length. I know a lot of it is personal preference, but why are DH stems short and while XC stems tend to be long? Is there more/less control attributed to either vs strength? Anyone want to enlighten me on this? Thanks, guys.

  2. #2
    Fat-tired Roadie
    Reputation: AndrwSwitch's Avatar
    Join Date
    Nov 2007
    Posts
    14,293
    One could make a DH stem adequately strong with less material by sticking with shorter lengths, but I think it's more about control. Other things being equal, a shorter stem makes it easier to get weight off the front wheel. It also reduces a bike's tendency to nosedive under braking, or on an abrupt transition from a jump or steep section. Sometimes it's desirable to have more weight on the front wheel, but that's really not difficult on the way down.

    Cross country riders spend more time climbing than descending, on most trail networks. A good XC setup facilitates climbing too, and it can feel awkward to try to weight the front wheel or climb out of the saddle with too short a reach. Too short a reach also murders the rider's back. Too long a reach does too, and stem length and height is used to fine-tune this. Honestly, I'm not sure if there'd be a negative consequence to a long frame with a short stem. My instinct is that it would be twitchy. Certainly that's what happens with too short a stem on a road bike. DH bikes have very slack head tubes and most DH riders use very wide bars, so a short stem wouldn't make such a bike twitchy to the degree that it would screw up the handling on something with a steeper head tube and narrower bars.

    So, I guess what it comes down to is that for neutral handling on a bike with a fairly steep head angle and relatively narrow handlebars, a longer stem is necessary. For getting weight off the front wheel, a short stem is helpful. Reach is important too, but it's also effected by bike size.

    A trend recently is for XC and AM riders to use short stems and wide handlebars too. Fisher bikes historically have run a little long, and used a shorter stem and slightly differently-dimensioned fork. So you can see there's a few ways of thinking.

    Are you trying to choose a stem for your bike?
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  3. #3
    mtbr member
    Reputation: xxbrittonxx's Avatar
    Join Date
    Sep 2009
    Posts
    73
    Damn, couldn't have asked for a better explanation. Thank you!

    Well, I'm reatively new to the sport. Only been riding for a little over a year now, and not with experienced riders. And since I've been upgrading my bike, as well as my wifes, it's become one of the questions in the back of my head as I look at parts to upgrade.

    My bike originally had a 90mm 5* rise along with a 1 1/2" riser bar. I ride mostly XC/single track so I switched to 100mm 6* with a flat XC bar. I went with a farther reach because I always felt a little high along with being a little top heavy in the turns. I live in Flagstaff, AZ and all the trails are snow covered or muddy so I've only been able to ride around the neighborhood to test, but I have to say that it does feel different. But I wont know if it's good or bad till I hit the trail this weekend in Phoenix.

  4. #4
    Fat-tired Roadie
    Reputation: AndrwSwitch's Avatar
    Join Date
    Nov 2007
    Posts
    14,293
    That's a pretty big transition. It'll be interesting to see how it works for you - you'll probably know inside of a half hour or so of riding. You can also experiment with flipping the 90mm stem (or the 100mm one) for negative rise, and with position in the spacer stack. Flipping the stem makes a surprisingly big difference. You may need to adjust your fork a little - you're likely to have more weight on your front wheel.

    I actually was trying a longer stem myself today, and decided I didn't like it. Too much for me - all my weight got dumped on my hands and my back started to hurt. Lame. I liked the uphill handling, though.

    Good luck, and let us know how it turns out.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  5. #5
    usually cranky
    Reputation: b-kul's Avatar
    Join Date
    Sep 2009
    Posts
    10,020
    mainly its about weight distribution. if you are a dh racer do you want each wheel to be weighted about evenly or do you want a strong bias towards your front wheel?

  6. #6
    mtbr member
    Reputation: lew242's Avatar
    Join Date
    Aug 2008
    Posts
    527
    Look at any motorcycle and any DH mountain bike and you'll notice the bars range between 700mm-800mm in width, and the equivalent stem length is 30-50mm. This is for high speed control, specifically to initiate turn in. XC stems are specifically longer at 75mm-150mm, the idea being to keep the front end of the bike down when climbing, although these days many XC riders who also ride more aggressive disciplines like AM, FR, DJ and DH prefer around 70-90mm stems even for XC use, when they do this they often choose a bar around 600mm-700mm.

    In short if you had a traditional XC bar around 500mm-600mm, you wouldn't want to go shorter than about a 90mm stem, as it would make the bike too twitchy or flighty. Same thing if you had a bar around 700mm, you wouldn't want a stem over 70mm, as you end up with handling that was too slow.

    Although there is an element of personal preference, human anatomy and frame size variations that make a difference.

    My opinion is that narrow bars 500mm-580mm are only for aerodynamic reasons or to do bar spin tricks, and have no place on a bike that might ride technically demanding terrain.

  7. #7
    mtbr member
    Reputation: Jeff in Bend's Avatar
    Join Date
    Jun 2010
    Posts
    423
    This has been an overly discussed topic, here are a few threads.

    just went to 50mm stem and...
    Stem Length
    Proper stem length
    In praise of wide low bars and a short stem

Posting Permissions

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