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Thread: Stem Length

  1. #1
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    Stem Length

    I've been a roadie since '81 and I've been riding mountain bikes since '06. My first mountain bike was a well-worn(out) Trek Mountain Track 800, admittedly not a trail shredder but it got me hooked, that had a somewhat long stem. Since then I've acquired a 29er and a 27.5er and another vintage ('98 Marin) 26er. Obviously both the 29er and the 27.5er have short stems, I've got 50's on both, and wide bars (780 on both) but when I bought the Marin it had a 50mm stem that, as far as I can tell, is original and somewhat narrow (maybe 640mm) bars. From what I've read most early 26er's had 100-120mm stems so I'm not sure why the Marin had such a short stem. I've rebuilt a '99 RM Hammer Race for my son-in-law that had a 120mm stem. My question is why did the early 26er's have such long stems? Was it due to the more XC oriented trails from that period? I ride more techy trails than XC trails and the '98 Marin now has a 45mm stem and 740mm bars and it handles far better than the long stemmed 26er's I've ridden. I've also installed a 50mm stem and 780mm bar on my son-in-law's RM and he says it handles much better than before even while climbing. The shorter stem moves his weight back yet the wider bars lower his torso and ditto that for me. I've still got the Trek, rebuilt now as a SS and it too has a quill stem adapter combining a 60mm stem with 720mm bars.
    So, again, what was the reason for long stems back in the day? Trails? Geometry? And am I as well as my son-in-law 26er oddities for modifying (bastardizing) our beloved 26er's?

  2. #2
    Sneaker man
    Reputation: mik_git's Avatar
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    Feb 2004
    narrow bars = longer stem, shorter frame reach = longer stems. And 640 isn't a narrow bar, normal back in the 90's was like 580 or less (and take off some width for bar ends.

    Do you know what brand the bar and stem on the marin were as 50 and 640 seems quite wide for 98, which of course doesn't mean it's not OEM

    My 90's bike has a 120 stem with 660 bars, my mid 00 bike has a 135 stem and 660 risers, my new 650b bike came with 80 stem and 700 bars, but now has 100mm stem and 720 bars. I just go with what feels good, bought a pile of stems last year to try stuff out with, and thats what I settled on.
    All the gear and no idea.

  3. #3
    mtbr member
    Reputation: justwan naride's Avatar
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    Oct 2008
    MTB's from that era were heavily influenced from road bikes AFAIK, hence the short steep geo, long stems and narrow bars.

    From personal experience there's a limit to how short you can go on a bike not designed for it before handling is negatively affected. 120mm is obviously too long, 60-80mm is a good range for a 26" with a steep head angle. You fit wider bars to gain back stability and effective reach, but even with 800mm bars a 40-50mm stem would be too short for a traditional XC bike. Twitchy handling and lack of weight/traction on the front wheel are the main drawbacks I've found from my experiments with different stem lengths and bar widths.

  4. #4
    Trail Ninja
    Reputation: Varaxis's Avatar
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    Mar 2010
    Riders ran what they felt was the best compromise at that time, heavily influenced by what the top/fastest riders were on. Didn't help that organizers made race courses where roadie athletes would excel. They generally said that the races were won on the climbs, so that's where they focused. Some of the hills were legit steep, and they'd waste less energy if the bike kept the front wheel on the ground and pointed straight more naturally.

    Long stems offer more potential for leverage from than wide bars. 10mm of stem is equal to 20mm of bar width. They can be made lightweight, yet still strong and stiff, thanks to tubular construction. In comparison, stems 50mm and shorter typically were made like bored out blocks of metal, very heavy for their size. Lightweight trustworthy handlebars didn't come in very wide widths, and there was weight saving from combining a long stem with a compact frame, narrower bars, and shorter cable housing. Suspension forks weren't very good back in that era, but the bikes equipped with good forks didn't come with long stems, so staying looser on the bike helped make up for control, and narrower bars offered more arm "suspension travel".

    The closer the bar width was to your shoulder width, the more arm "travel" you got. It let you get behind your saddle pretty far, despite the long stem. The bike was also more flickable side-to-side. To one rider, that may be a pro, but to others it could be a con. There's no spring in your arm, like a true suspension would have. You only have damping in your arm, and you have to improve that damping through improving upper body strength, and refine how much is needed per obstacle from riding. Which would you choose: build up upper body strength and rely on strong arm damping or gamble with spaghetti arms and springy suspension? Seems like the former calm and controlled look is trying to be emulated in modern times, but one needs upper body strength to pull it off in reality. Spaghetti arms, springy suspension, bouncy tires, side-to-side flickability, and twitchiness from extra leverage combine to make for a wild ride.

    Wider bars add lateral stability for your core, and bike, to help tame some of that wild ride. In cases where you need to pull up the front by throwing your hips back, there's less arm travel to go through when you have wider bars. With less arm travel, you limit your low speed rock rolling ability and ability to get behind the saddle for steeps. Due to these limitations, you are sort of forced to adopt a style of plowing straight and fast, popping and hucking rocks instead of rolling them, and recklessly rely on your equipment on steeps. One can argue that this is a "superior" style since it's faster and simpler, but that old school riding style has its own unique brand of fun; some are re-experiencing this kind of fun with modern CX/gravel bikes, or retro style bikes.

    Short wheelbases are less stable at high speeds than longer wheelbases. A compact frame, small wheels, and short fork A2C length resulted in a short wheelbase. A few trends, such as Genesis geometry, attempted to incrementally increase the wheelbase without changing fit or steering feel: increase front center (longer reach and slacker HA), shorten stem, and increase the fork offset. They marketed it as the best of both worlds, stability at speed, yet steering that wasn't too slow or floppy. Some are pushing stable geo even harder, to make a bike that's even easier to ride at higher speeds (ex. Transition SBG). You might see that they went with a short stem and wide bar on SBG bikes, but that's not the reason for the performance. It's the increased front center and wheelbase, steepened STA, and decreased fork offset (which strengthens the auto-centering effect of the front wheel at speed), that makes the bike easier to ride a higher speeds. The riding style that a wide bar forces you into just naturally suits the higher speeds.

    While stems can offer increased leverage, a significant amount of that leverage can be negated by wide bars with significant backsweep. There's some bars that have 12d backsweep, while others have 20d or more. The 20d versions offset the loss of stem length, by extending itself forward first. Leverage is the length measured from the steerer tube straight to the grips. It's not about getting more or less leverage, as if either is better; it's more about making things easier for you. If you significantly decrease leverage and ride the same trail as you did with the prior setup, you might find yourself going wide off of the trail on corners. Increase leverage and you'll be going inside and overcorrecting (and overcorrecting the overcorrection). That all said, gaining leverage is preferred over losing leverage.

    If you simply shorten a stem without doing anything else, you more accurately transfer weight load from your back to your saddle, due to a more upright position. With the decreased leverage, you also have less weight on the front for traction purposes and increase rearward bias, making it difficult to keep the front wheel down when climbing steeps in a low gear. If you went from a 100-120mm stem with 640mm bar to 50mm stem with 780mm bar, you increased leverage by a bit and decreased your arm travel a lot. Upright positions tend to compromise endurance, power, and efficiency, since your legs get less mechanical advantage with less pelvic tilt. Having more pressure on the seat will make your butt "sore" sooner. With less arm travel, you're more likely to lock up into a tense position, and if your upper body isn't strong enough, you're likely to have less control than if you rode loose (spaghetti arms).

    In short, those sweeping changes you made came with consequences. You're probably looking to upgrade the suspension now, since the wide bars took away your arm travel. You probably have switched from slow speed rock rolling to higher speed rock plowing, and find it to be a demanding challenge that simply rewards you with faster lap times, rather than a challenge that offers fulfillment.

    It sounds kind of silly to build a bike around stem length, rather than the frame and geo and rider dimensions (stuff that can't be conveniently changed). Everything has pros and cons. Try to look at the bike as a system and try get a compromise that allows the rider to become one with it. Consider the bike's area of expertise, the rider's area of expertise, and the terrain, and the many ways to engage the challenge. I question the act of trying to normalize everything to fit some pigeonholed perspective--I encourage you to look for synergy, to draw out brilliance unique to that setup.
    Last edited by Varaxis; 01-30-2018 at 02:05 PM.
    We're all on the same ship, and it's sinking.

  5. #5
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    May 2016
    Older bikes also had short top tubes/long stems where as newer bikes have long top tubes/short stems amongst other things mentioned above. Just geometry evolving.

  6. #6
    Hardtail Steel Forever
    Reputation: jestep's Avatar
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    Jul 2004
    For the most part I've converted all my older bikes to 60 - 80mm stems. At least by the mid 90's, the top tubes were already fairly long. Moving the stem back with some slightly wider bars is a much more comfortable riding position and it's worlds better on descents.

    If you want to test different combos out uno and some other stems can be found for cheap on ebay. They're high quality and very light for the price.
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  7. #7
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    Thanks for the input guys. I failed to mention, and judging by some of your input I probably should have, but I'm 6'-2", 225# and my S-I-L is 6'-0" and 170#. My old Trek as well as the '98 Marin are rigid and his RM has a 80mm Bomber fork. Neither of us ride XC trails very often other than the occasional gravel road/logging trail. Most of my local trails are slow, techy single track and I pick my lines on the Marin more carefully and ride it slower than my more capable suspended bikes. With our height naturally we have longer arms and torsos, so moving off the back of the saddle on drops or descents isn't causing us to become too outstretched. Again, even on longer rides we both find the short stem/wide bar combo on these 2 26ers to be more favorable than long/narrow, and since the Marin had a short stem and narrow (for me) bar when purchased, this set-up is more capable than as-purchased. As far as steep climbs, both bikes have a 1x set-up with 32t chainrings, so no super-low granny gears causing front wheel lift on climbs. Maybe it's just the terrain we ride but we're both happy with this set-up and see no need to return to older, traditional long/narrow combos. Again, thanks for the input.

  8. #8
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    Reputation: targnik's Avatar
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    On modern bikes w/ more balanced geo, stem & bars are there as a personal preference i.e. getting what works for you.

    IMO if a bike feels more comfortable with a 100mm+ stem, then it's geo is a bit archaic.

    Modern mountain bikes, 40mm to 60mm stems shouldn't affect handling too much. Should help dial in fit ^^

    'We'll all make it to the top... Some of us, might not make it to the bottom'
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  9. #9
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    Couldn't agree more with Varaxis. Back in the day, it was a about riding and getting through raw trials, both up and down: needing shorter wheelbases and higher BBs to actually ride through the wilderness (like a Jeep). The trend now is to sell bikes that work on "groomed trails" or downhill trials that either have the rough stuff removed or you only encounter it on the way down... Essentially turning mountain biking in to skiing. It all depends on what you want to do and your skill level.
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  10. #10
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    Since this is resurrected....
    I think the real reason was that they were just off road adaptations of roadie designs.
    We've learned, since then.

  11. #11
    Reputation: ninjichor's Avatar
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    Didn't get to read the entirety of the long posts, but they got me to think of how fork offset affects the actual wheel position, not unlike how stem length affects handlebar/grip position when turned. It puts your position more on the inside of the turn...

    Now to figure out if that's a good thing or not, or how much is the sweet spot. I think through trial and error, I ended using stem lengths similar to offset length.

  12. #12
    kk2 is offline
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    My SC Blur Large has 100mm stem with 685mm wide bars. I am 6ft tall and have pretty narrow shoulders. The bike feels fine. Personally I find that anything wider thatn 720 is way too much for me.

  13. #13
    Music & Bikes
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    My take on this is that the need for wider bars came with heavier wheels (700 and 650)
    The heavier the wheel , the more leverage needed.
    Try a narrow bar on a Fatbike , you'll get it.

    Short stems & wide bars will gave a similar position as longer stem & narrower bars.

    I bought a couple of recent bikes and the first thing I did to both was to cut the bars and add a longer stem to compensate the position.
    Trees around here have a tendency to grow close together .....
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