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  1. #1
    RoadBikeReview Member
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    How do I determine stem length?

    I know how to determine my seat adjustment, knee over pedal axle. I know how to determine seat height, knee bend 15 degrees or less. I have what I believe is the right frame size according to all the different sites that I've used for determining frame size measurements.

    How do I determine the stem length? Right now when I'm in the drops and look down, the bar cuts across the front hub. Does this mean the stem length is correct? Is stem height important?

    Can I assume because I used many different frame size measurement websites and using these websites measurements, have determined that I have the correct frame size, can I assume the stem length and height is also the right size?

  2. #2
    CRM
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    No right answer.

    There are several guidelines for stem length and rise but ulitmately the answer is that you need what makes you comfortable on your bike. Ride your bike and if you feel cramped, get a longer stem. If you feel too stretched out, get a shorter one. If you need it higher or lower, make the appropriate adjustment. There are some adjustable stems on the market that make these adjustments easy if you're inclined to go that route.

    Everybody has a different "perfect fit." You have to ride a lot to know what your's is.
    No racing, okay? Seriously, we're just going to take it easy this time. . .

  3. #3
    Bike Wing Conspiracy
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    My rule of thumb was always

    to make my back flat when in the drops.

    This has served me well for so long now I would be scared to alter my setup.

    Thats just me though.

  4. #4
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    Works for me too.

    Quote Originally Posted by onespeed
    to make my back flat when in the drops.

    This has served me well for so long now I would be scared to alter my setup.

    Thats just me though.
    The question than becomes whether you lower your shoulders by lowering the bars or putting them further forward. No correct answer or formula that I know of besides trial by ordeal. It has occurred to me that the Look Ergostem would be really handy for fiddling around until you find that sweet spot.
    We have nothing to lube but our chains.

  5. #5
    johnny99
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    This method works as well as any:
    1. sit on your saddle
    2. grab the handlebar hooks (near the brake levers)
    3. bend over so that your forearms are horizontal (parallel to the ground)
    4. your upper arms should be vertical (90 degree angle with your forearms)

    Adjust stem length to create the 90 degree angle. If you can't bend over far enough to make your forearms horizontal, then there is something else wrong with your riding position (e.g., handlebar too low or hips too upright).

  6. #6
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    while you can start with 'rules of thumb', i think every rider has a different biomechanical position that suits him/her to best advantage. stem length/height some say, is judged by (a) a weight distribution of 65% on the rear wheel and 35% on the front wheel, and/or (b) when your front axle is hidden by the bar when in riding in the 'down' position.

    as others have said, i think it's more a trial and modify adjustment until you feel most comfortable. what is best for joe may not be best for bob and etc.
    You're never too old to have a happy childhood

  7. #7
    johnny99
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    Quote Originally Posted by liv2padl
    while you can start with 'rules of thumb', i think every rider has a different biomechanical position that suits him/her to best advantage. stem length/height some say, is judged by (a) a weight distribution of 65% on the rear wheel and 35% on the front wheel, and/or (b) when your front axle is hidden by the bar when in riding in the 'down' position.

    as others have said, i think it's more a trial and modify adjustment until you feel most comfortable. what is best for joe may not be best for bob and etc.
    I think saddle position affects weight distribution a lot more than stem length. Hiding your front axel was kind of hokey back when bike geometries were pretty similar, but much more so now that everyone had oversized handlebars and widely varying handlebar heights.

    "Feeling comfortable" isn't a good metric either since trying different stems is very expensive and time consuming. Also, most people are fairly comfortable under a wide range of conditions.

  8. #8
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    my 2 cents

    Dude getting my stem situation dialed has been the biggest pain of all the stuff to dial in on my bike....and sometimes what feels right changes over time!

    Basically, I recommend doing what I did...getting an adjustable stem, and riding the different settings on it for at least 45 minutes to make sure its a good fit over the long haul...then just try and find the closest stem to your adjustables' setup as you can.

    OR, you can just run the adjustable stem...they are a bit heavy....but not really if it keeps you comfy. You can get 'el cheapo' adjustable stems from most online joints.

    Not really an answer tou how to find YOUR fit, but a good way to keep from buying tons of diferent stems. PLUS you can use the stem when you switch frames to find new length/ setup on you new ride.

  9. #9
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    you're on the right track...

    A weight distribution of 65/35 is far too little on the front wheel. 60/40 is about the minimum you should shoot for and up to 54/46 won't hurt a thing. Two things have the largest affect on weight distribution, the saddle fore/aft position is number one, followed by torso angle. Stem length changes alone affect the weight distribution very little.

    As for stem length, you can't decide that without also considering the handlebar height. A height difference in the 5-10cm range is common on road bikes. Riders looking for comfort will use less drop and riders wanting a more aerodynamic position will want more. Higher bars will allow most riders to tolerate more stem length.

    My rule is to avoid knee to arm interference when riding in the drop section of the bars, with my fingers in reach of the brakes and my upper back nearly horizontal, or as low as I can tolerate for an extended (mountain) descent or ride on the flats. If you can pedal without knee to arm interference, then the stem is long enough. This length may prove to be too long for some riders, resulting in a arm to torso angle that is too extreme, causing shoulder or neck pain. If you can't tolerate this much length, try one size shorter.

    In general, a short stem is unlikely to have any affect on the "flatness" of your back or cause discomfort. It just forces you to bend your arms more to achieve the same position. If a short stem caused discomfort then riding with your hands on the top section of the bars would be very uncomfortable. On the contrary, it's the most common position for an extended climb.
    Last edited by C-40; 07-27-2006 at 02:26 PM.

  10. #10
    Resident Curmudgeon
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    Quote Originally Posted by johnny99
    This method works as well as any:
    1. sit on your saddle
    2. grab the handlebar hooks (near the brake levers)
    3. bend over so that your forearms are horizontal (parallel to the ground)
    4. your upper arms should be vertical (90 degree angle with your forearms)

    Adjust stem length to create the 90 degree angle. If you can't bend over far enough to make your forearms horizontal, then there is something else wrong with your riding position (e.g., handlebar too low or hips too upright).
    Or you're too damned old & aren't that flexible any more.
    Before you criticize someone walk a mile in their shoes. That way when you criticize them you'll be a mile away & you'll have their shoes.

  11. #11
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    worthless...

    Quote Originally Posted by johnny99
    This method works as well as any:
    1. sit on your saddle
    2. grab the handlebar hooks (near the brake levers)
    3. bend over so that your forearms are horizontal (parallel to the ground)
    4. your upper arms should be vertical (90 degree angle with your forearms)

    Adjust stem length to create the 90 degree angle. If you can't bend over far enough to make your forearms horizontal, then there is something else wrong with your riding position (e.g., handlebar too low or hips too upright).
    This process seems worthless to me. If you have the bars set very low, like 7-10cm below the saddle, your nose might be an inch or so above the bars by the time you get the forearms horizontal. Few people would ride in this position for any length of time. I've got my bars 9cm below the saddle. If my forearms are horizontal, I'm in a ridiculously low position and I've got a huge interference between my knees and arms while pedaling, even with a very normal 110mm stem on a 51cm frame. This does not mean my bars are set too low. On the contrary, my bar height produces a comfortable position while riding with my hands on the brake hoods. This is a far more critical position to get correct, since most riders spend a great deal of time in this position. Stem/bar height has a significant afect on stem length. You have to get the height in the ballpark first, then go about fine tuning.

    Setting the forearms horizontal might be applicable to a touring bike set up with the bars extremely high, with virtually no saddle to handlebar height difference.

    Take a look at a pro riders, using 10cm of drop (or more). When they ride aggressively on the flats, with the upper back horizontal, there is almost no bend in the arm at all and there is clearance between the arm and knee. About the only time the arms get a significant bend is when they deliberately bring their nose down close to the bar when descending, and that's only done after reaching a speed when pedaling is of no value (45-50mph).
    Last edited by C-40; 07-28-2006 at 05:41 AM.

  12. #12
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    Having your eye in line w/ the bar & hub is all about theoretically best steering stability. But you can get used to variations & do well. The sshorter the wheelbase & shorter the stem the tighter the steering & quicker responsiveness. Like on a race car center of balance is important. Are you wanting a Cadillac or Ferrari?

  13. #13
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    ????

    Quote Originally Posted by venus
    Having your eye in line w/ the bar & hub is all about theoretically best steering stability. But you can get used to variations & do well. The sshorter the wheelbase & shorter the stem the tighter the steering & quicker responsiveness. Like on a race car center of balance is important. Are you wanting a Cadillac or Ferrari?
    Having the eye in line with the bar and hub is a meaningless coincidence that has no relationship to "steering stability". You could create the same line with a long TT and very short stem or a short TT and a long stem. Depending on the head tube angle and fork offset (which dictate steering trail) either bike could be made to be very stable or very unstable. Steering stability is a combination of front-center, wheelbase and steering trail.

    A change in stem length from 80-120mm only changes the length of the steering arm about 15%, so it takes a large change to make a significant difference.

  14. #14
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    Quote Originally Posted by C-40
    Having the eye in line with the bar and hub is a meaningless coincidence that has no relationship to "steering stability". You could create the same line with a long TT and very short stem or a short TT and a long stem. Depending on the head tube angle and fork offset (which dictate steering trail) either bike could be made to be very stable or very unstable. Steering stability is a combination of front-center, wheelbase and steering trail.
    I thought I said something like that. If you get the rake right & correctly inline w/ your arm angle w/ center of weight, steering feels "natural".

  15. #15
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    Quote Originally Posted by C-40
    Having the eye in line with the bar and hub is a meaningless coincidence that has no relationship to "steering stability". You could create the same line with a long TT and very short stem or a short TT and a long stem. Depending on the head tube angle and fork offset (which dictate steering trail) either bike could be made to be very stable or very unstable. Steering stability is a combination of front-center, wheelbase and steering trail.
    I thought I said something like that. If you have the fork proberly in line w/ your arm angle w/ center of weight, steering feels "natural".

  16. #16
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    simple thoughts to help guide you. You need to be comfortable on the hoods. Your elbow should be bent when in a comfortable back angle. You know your too long when you extend(or shrug a little) your shoulder to reach the hoods. You are probably too short if from the side your elbow is under your shoulder as opposed to even or slightly foward of it.
    It was good enough for Eddy

  17. #17
    Lemur-ing
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    Another stem question guys:

    I just got a new Trek Madone SSL 5.9 and when I used a 100mm strem length, it felt that I had to reach a little too far but on a 90mm, it felt perfect, wit perhaps a little more room to stretch out(not very sure though) I'm just wondering whether it is normal to have a stretched out feel on a road bike or whether what I'm feeling on the 90mm stem is the 'normal' feel. I also understand that using a 100 or 110mm stem is deemed 'best' in terms of handling and all. What about a 90mm stem? Your takes on this guys? Thanks.

  18. #18
    kytyree
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    I think if a 90mm makes you more comfortable then that is way more important than any effect a 10-20mm change might have on steering.

    And about being stretched out or more upright, again this is a very personal thing and many factors go into it. Just look at pictures of how stretched out Eddy Merkcx was he rode very long and low (reflected in the long top tubes of his bikes now) then compare his position to the relatively upright position of Miguel Indurain.

  19. #19
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    Quote Originally Posted by kytyree
    I think if a 90mm makes you more comfortable then that is way more important than any effect a 10-20mm change might have on steering.

    And about being stretched out or more upright, again this is a very personal thing and many factors go into it. Just look at pictures of how stretched out Eddy Merkcx was he rode very long and low (reflected in the long top tubes of his bikes now) then compare his position to the relatively upright position of Miguel Indurain.
    Funny you should talk about a stretched look vs more upright. I was watching an american stage race on OLN this weekend and it seems to me that the riders look more stretched in general than the european pros. Their arms seem to be more out in front of them. Hmmm... Maybe the excesss stretch drops their watts and explains why they're slow compared to european pros.
    It was good enough for Eddy

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