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  1. #1
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    Correct stem length for MTB versus road bike

    I am a road biker and just bought a mountain bike. It is an AM (all mountain) Orbea AM H30 with 140 mm front fork (dual suspension). On road bikes, the correct stem length is determined by sighting down the bar with arms comfortably on the handlebar. The cross section of the stem/bar should obscure the axle of the front wheel. And in general, the handlebar should be lower than the saddle. On a road bike, I usually use a 120 mm stem since I have a long torso.

    I read that on a MTB, the stem should be around 50-90 mm for quicker steering. On my Orbea, the 70 mm stem has a 6 degree rise and the stem is 20 mm short of obscuring the front axle. With my saddle positioned correctly, the bar is 2" above the saddle. So are these distances OK? Or should I get a longer 90 mm stem so the bar obscures the front axle when I am stretched out and pedaling?

    So on MTBs, the handlebar should always be above the saddle so you are riding more upright?

  2. #2
    RAKC Industries
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    Wow literally never heard of that way of fitting a road bike handlebars and my LBS owner used to race road for Trek. Very odd. Handlebars are part of a proper fit of an entire bike set up. Width, height (how many spacers underneath) saddle height and fore/aft positioning.

    You bought a bike that is about as far from anything road related as you can get, only second to long travel enduro and downhill bikes. So it's best to forget everything you know except your saddle height

    You handlebar height can be above, even or below your saddle. Depends on the fit. You change stems based on reach. Bar width plays into this as well. Shorter stem means going wider on the bars, longer means shorter bars. For bar height you remove or add spacers under it.

    Advise, unless you have a dropper post, do not set your saddle height the same as your road bike, you will need the room to move around.

    Truly may be best to get a professional fit done for the mountain bike as they are set up so much different than road bikes. And fit changes greatly depending on the bike and what you ride. If you wanted something more what your accustomed to, an XC bike would have been more closely related to a road bike.

    I've seen many life long road cyclists try out mountain biking and have a lot of problems because they are stuck on their habits from the road. You have to scrap 95% of what your used to as soon as you get on your mountain bike. You dont spend 90% of your time on the seat unless your on smooth beginner trails.

    As I said, forget what you think you know about bike fit, best to get a professional fit done otherwise your going to spend more time typing trying to find solutions to fit and handling problems that have absolutely nothing to do with the bike, than you will riding it.

    Also take at least a couple skills courses to help break the road habits. Save you on first aid supplies and broken bike parts.


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  3. #3
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    It's really personal preference to a large degree. Personally I like my saddle the same height as my bars. I think at least 50% of riders prefer their bars a bit lower than their saddle, but that style leans more to XC and level bar/saddle leans more to "trail."

    Stem length is the product of proper riding position (that is to say proper position determines stem length, not the other way 'round) but ideally you're on the right size frame if a 40-80mm stem allows you to see the hub in front of the bar when you're in the ready stand-by / attack position. If the hub is behind the handlebar, no bueno -- your ETT is too short. If the bar just obscures the hub, you're okay.

    Longer stems tend to mess front end handling up.
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  4. #4
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    Quote Originally Posted by Clevor View Post
    I am a road biker and just bought a mountain bike....

    I read that on a MTB, the stem should be around 50-90 mm for quicker steering. On my Orbea, the 70 mm stem has a 6 degree rise and the stem is 20 mm short of obscuring the front axle. With my saddle positioned correctly, the bar is 2" above the saddle. So are these distances OK? Or should I get a longer 90 mm stem so the bar obscures the front axle when I am stretched out and pedaling?

    So on MTBs, the handlebar should always be above the saddle so you are riding more upright?
    I went through this too. And it's one reason I started out on a small Krampus, and ended up changing out the frameset for a medium Karate Monkey. Basically, stems on mountainbikes tend to be a lot shorter. This article covers it.

    Size matters: why we’re all riding bikes that are too small - MBR
    2018 Surly Karate Monkey 'dingle' speed
    2013 CAADX 105
    2012 Pinarello Quattro
    2002 Zurich LeMond

  5. #5
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    This varies a lot depending on type of mtb, rider preference, and fit. I have not used a stem that long in 5-6 years. If I can not get a good fit with a sub 50mm stem I pass on that frame. I love the DHness of a short stem/wide bar, yet both my bikes with 30 & 35mm stems are amazing climbers. There is a myth that a short stem will hinder climbing but my 30+ years of mtb have shown me that's BS. 70mm ain't short, but isn't so long as to be a big hindrance. You can swap spacers, flip the stem (if it has rise), or last resort get a lower rise bar if you feel the bar is too high. Your shop should help you out with this.
    I got some bad ideas in my head.

  6. #6
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    Correct stem length for MTB versus road bike

    It should also be noted that stem length should really only be used as a fit mechanism within a narrow range because the length of a stem significantly impacts handling. I wouldnt want to run a 30mm stem with a 70 head angle or a 90mm stem with a 65 head angle. Generally speaking the slacker the bike the slower the handling all else being equal so shortening the stem length will speed up the handling a bit. Similarly increasing bar width will slow down handling so shortening the stem will help again. This is of course assuming you want that effect. Height will also change handling but I think theres a bigger range there. Id suggest fitting that parameter based on comfort first then consider how it rides. For example; if I found that I had a hard time keeping the front of my bike calm on steep climbing I might try lowering it.


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  7. #7
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    OP - that is some really old-school road bike fit technique... like judging frame size by standover height.

    The whole bar, stem, spacer height - is about finding your individual, optimal, balanced position. Comfortable riding position, offering the most control of your bike. Easy to shift weight to the front end for climbs and turns, and just as easy to unweight the front to lift the wheel up. - If you struggle at doing either, then your set up needs adjusting.

  8. #8
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    OP - Longer and lower stems can help a bit with steep climbs, shorter less dropped stems can help with steep descents, but in a relatively narrow range, nobody is running long stems like they used too.

    I'd suggest, since you come from a road background, starting with bars level with saddle and adjusting from there. Most Enduro riders, the fast ones, seems to be running level or a bit lower. In general, the taller you are the more drop you have....

  9. #9
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    Quote Originally Posted by RAKC Ind View Post
    Wow literally never heard of that way of fitting a road bike handlebars ...
    Pretty standard back in the day. Along with other rules of thumb got most riders in a decent position on the bike.
    Do the math.

  10. #10
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    Rack Ind, I think you are right about the AM bike; it has a tall fork, and the Orbea frame is quite massive and big-boned. A XC hardtail might be better suited to my purposes (more on that below). Actually, I used to mountain bike back in 1995 for a couple of years before I got into road riding. The reason I bought this bike now is I was poor at the time and used to ride a cheap Mongoose hardtail. Magura hydraulic brakes were around (and $$$), but discs hadn't debuted. I couldn't afford dual suspension and always wanted to own a bike with Fox shocks. Stan had just debuted the tubeless tire setup. 1x11 or 2x11 drivetrains did not exist. This Orbea I bought has everything (especially the 2x11 since I prefer triple cranks), except a carbon fiber frame. But I got road bikes with that. Also I don't ride 40-50 miles on the road anymore as it's too dangerous where I live.

    Anyway, I will pretty much leave the Orbea alone. I am not a big guy (5'8") and I don't know where Orbea gets their sizing. My MEDIUM frame is supposed to be for 5'3" to 5'9" but the frame is a bit on the large size since I have a short inseam. I had to cut the seatpost and drop the saddle down so it will be maybe an inch below the handlebar. Standover height is barely sufficient but OK. I mainly will be using the Orbea for climbing on roads (to keep fit). It rains a lot where I live and it's a safer ride bombing back down than my road bike with the skinny tires. I can also use the Orbea for sidewalk riding around town (should have no trouble hopping curbs - heh).

    Since I will be doing a lot of climbing a slightly bigger bike is better and if I do hit the trail, at least I won't be prone to going over the bars. So I'll keep the 'short' OEM stem and maybe flop it to drop the handlebar a bit. The bike seems to be dialed in pretty right from the factory for it's purpose since it has wide handlebars, but I do have long arms for my height. So all I'll do is get a drop nose WTB saddle to help remounting the bike at stoplights.

  11. #11
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    You gotta throw out all your preconceptions about bike fit, none of it apply to modern mountain biking.

    A 70mm stem is a huge long stem. For your size, and that bike, its probably too long. I have the same bike, and I have a 50mm stem. Im also the same height. You have to completely ignore where the bars are related to the saddle. Set the saddle where it needs to be, and adjust the bar height until its comfortable.

    Dont worry, you're good. Thats a GREAT bike that does everything fantastic, and you're dead center perfect to fit on that size frame. Dont try to make it fit like your road bike, you'll end up miserable and the bike will ride terrible.

  12. #12
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    I just changed from a medium Knolly Endorphin to a Large. The only geometry change is a 27mm increasingly in reach and I moved my saddle forward 7mm to take advantage of the extra room and steepen my effective STA. I went from a 50 to 35mm stem so I am 5mm more stretched while seated. The change has been very positive both going down and up. Climbing is easier because the saddle is more forward. It's not a drastic change, but is noticeable. Cornering seems just as good, which is to say amazing. I started 30 years ago on 120 and 135mm stems and went shorter and shorter over the years.
    I got some bad ideas in my head.

  13. #13
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    If you're watching your front axle too much, you will crash> Meaningless detail on modern bikes. The precept of this was dead when I started racing road back in the 1970's. Amazed to see it still alive now. Junk information. The bike world has changed. Same goes for the old knee/pedal 3 o'clock thing.

    Eric
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