What's Your Seatpost Height?- Mtbr.com
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  1. #1
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    What's Your Seatpost Height?

    FYI: this isn't an inquiry regarding proper seatpost height. Since it's already a proven fact that SS riders like to set their bikes up differently than the rest of our two-wheeled brethren , let's just forget convention and discuss what you set yours at and why.

    I run my SS post about 1.5"-2" lower than my geared MTBs. I do this for a number of reasons:

    1. I use 180mm cranks and feel more comfortable on the downstroke while seated.

    2. Most of my climbing is while standing.

    3. During strenuous seated climbs, I get more leverage on the pedals by shifting my seat-bones (ischial tuberosities) behind the seat and pulling the h-bars back to my hips.

    4. I don't have to drop the seat post during the rocky DH sections.

    What do you do?
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  2. #2
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    Same height as my gearie. When I am in the saddle it does not matter if it is the SS, the BigShot or the Coiler, I want the same leg extension. Still just a bike.

    Note on your #1: Saddle height has to take crank length into account. Change the crank length and you have to change the saddle position to maintain the same relative height.
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  3. #3
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    Quote Originally Posted by shiggy
    Same height as my gearie. When I am in the saddle it does not matter if it is the SS, the BigShot or the Coiler, I want the same leg extension. Still just a bike.
    .
    Exactly.

    If I did 40 miles on the SS w/ the saddle 1.5" lower, i wouldn't be able to walk the next day.

    Nope...all heights the same. Drop when neccessary.

  4. #4
    TR
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    Same height centre of BB to top of saddle on both my gearie and my SS 29'er.

  5. #5
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    Agree with everyone else, doesn't matter if road, HT, FS or SS. All measure the same from seat to pedal (different crank lengths)

  6. #6
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    Quote Originally Posted by skinl19
    Agree with everyone else, doesn't matter if road, HT, FS or SS. All measure the same from seat to pedal (different crank lengths)
    Yup. Actually I measure from the top of the seat straight down to the center of the BB, then I can figure exactly, in an instant, depending upon crank length. I need 27" with 175mm cranks. So my seat is about 5mm lower on my SS with 180mm cranks. And a tad higher on my road bike with 172.5mm cranks. Knowing this I can quickly set up a new, demo or rental bike that I may ride. I don't think crank length matters as much as just making sure your bike and seat hight are set up best for you, whatever you ride. I have 170mm cranks on my DH bike, but that's an exception because I rarely ride seated or climb on it, so the seat is usually dropped to where I can best contact it and "steer with my legs". Handy and cuts fatigue when riding down resorts and leaning into high speed curves. But I can raise it the correct climbing height if I leasurely want to ride it up a mountain pass, which I do some summers. I mark all my posts on bikes with a QR clamp so I can put them back up without guessing or looking at grease or dirt marks after dropping them for any reason. Most are Thomsons, so for example,I tape around the marking spot leaving a small sliver and lightly sand that spot with a folded peice of (wet) sandpaper. It only makes a visual marking in the black anodizing, no mark in the post itself. Obviously this won't work on a silver post.

    Cheers,

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  7. #7
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    Same here

    I always use the same measure. Center BB to seat level. If i even snudege a few MM i notice the difference. If a seat post doesn't have marks for height a just put a little scratch on it so if i take it off for whatever it goes back in the same spot.I don't even lower it for DH, it feels akward to me. I used a bike fit calculator a few years ago and still have all the measurements printed in my tool box. The only thing i have changed over the years has been to go with a shorter stem reach(not related? sorry)
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  8. #8
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    Same on all of my bikes as well - all of which have 175mm cranks. For some stupid reason I always feel the need to try to raise the seat just a little. I bumped up my seat about 1/4 inch before a 40-mile road ride the other day and my calves hurt for 3 days. In 6 months or so I'll forget and do the same thing and probably get the same result.

  9. #9
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    Wow, I must say I'm a bit surprised. I thought for sure at least someone would respond who had found that the seatpost height on an SS doesn't have to follow the same rule as a geared bike.

    First let me say I also went through a bike-fit session a few years back and always set my height, fore and aft position and nose tilt in the exact same position on my geared bikes. Except of course my freeride and urban bikes.

    Just curious: those of you who said you'd pay the price the next day if you had your seat an inch lower- Why? What's going to hurt more? Your knees aren't experiencing any greater stress if they aren't reaching near-full extension. The only difference in the quadriceps is you utilize more of the vastus medialis during the last 15 degrees of knee extension. Your upper body position shouldn't be compromised with an inch or two lower saddle. I don't understand what price you'd pay.

    For those of you who are remotely interested in my reasoning, here's my half-baked logic that's worked for me.
    I don't have the lungs to grind up a mountain for 45 minutes while standing. When I take it to the saddle, my quads can only take so much before the lactic acid accumulation takes its toll. Once I am tapped out with standing and sitting intervals, I look for more power while trying not to blow the pressure cooker.

    Normally most of the power stroke occurs from about 2 o'clock to 6 o'clock position on the crankarms. In the early part of the stroke range, the gluteal muscles and quads are the "primary movers". In the latter stage of the power stroke range, the glutes lose their mechanical advantage which forces the quads to become the primary mover.

    If I shift my IT's behind the back edge of the saddle, I can generate more power on the pedals from the 12 o'clock to 4 o'clock position by pushing more forward than downward. In order to prevent my knees from over extending, I have to lower my seat about 1.5".

    In relation to my upper body angle, the glutes start the movement in a greater "prestretch" and are at a greater mechanical advantage than the conventional position. As a result, I benefit from the gluteal muscles working with the quads throughout the full stroke range. Considering the glutes are a much larger and stronger muscle group than the quads, I am able to climb longer without my head popping off.

    Of course this is in my own humble opinion. And if you don't buy it, you all can toss-off...
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  10. #10
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    Hmmm...these responses are very interesting. I must be backward then from the consensus. My ss has cranks that are 170mm (5mm shorter than my FS bikes) and I tend to feel better running the seat almost an inch higher than on the other bikes. Wonder why that is?

  11. #11
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    Bottom line is do what works for you.

    If (and when) I try climbing as you describe in #3 I flip over backwards.

    After 6+ years of riding mostly SS I tend to ride all of my bikes, including the Coiler DL, like a SS. Still just a bike.
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  12. #12
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    Quote Originally Posted by shiggy
    Bottom line is do what works for you.

    If (and when) I try climbing as you describe in #3 I flip over backwards.

    After 6+ years of riding mostly SS I tend to ride all of my bikes, including the Coiler DL, like a SS. Still just a bike.
    Shiggy, of course we all know what the "bottom line" is. Heck, that's why I ended with "Of course this is in my own humble opinion". I only posted the topic to stimulate thoughtful conversation in an attempt to get others to think outside of the office cubicle. It seems that when someone plays the "do what works for you" card, they've decided the board has had enough of the topic. AGAIN, this is only my perception of things...

    I cracked up picturing you flipping over backwards like a turtle on his shell. That must be one mother of a steep hill!

    It's a crying shame. You have all of these other bikes and they only get ridden like another singlespeed. Poor things are just waiting to be seen as they really are.
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  13. #13
    JMH
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    Here you go...

    Same height on all bikes for me (road, ATB, SS) >>>EXCEPT<<< my TT saddle position, which I always ran 1cm higher and 3cm forward of all my other saddles.

    There you go, I guess I don't all run all my saddles the same.

    JMH

    Quote Originally Posted by Upchuck
    Shiggy, of course we all know what the "bottom line" is. Heck, that's why I ended with "Of course this is in my own humble opinion". I only posted the topic to stimulate thoughtful conversation in an attempt to get others to think outside of the office cubicle. It seems that when someone plays the "do what works for you" card, they've decided the board has had enough of the topic. AGAIN, this is only my perception of things...

    I cracked up picturing you flipping over backwards like a turtle on his shell. That must be one mother of a steep hill!

    It's a crying shame. You have all of these other bikes and they only get ridden like another singlespeed. Poor things are just waiting to be seen as they really are.

  14. #14
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    Just curious: those of you who said you'd pay the price the next day if you had your seat an inch lower- Why? What's going to hurt more?
    Try riding a bmx around all day (seated) and get back to us. I know its an extreme, but singlespeeders have bad knees already, right?
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  15. #15
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    Quote Originally Posted by spuddy
    Try riding a bmx around all day (seated) and get back to us. I know its an extreme, but singlespeeders have bad knees already, right?
    Uh, no. Singlespeeders don't all have bad knees. I don't. None of the ones I ride with have bad knees. I'd say if you already have bad knees, SS might not be the thing for you. But I wouldn't necessarily say SS will create a problem that doesn't exist.

    As far as the BMX analogy, you're right. It is a reach to compare riding a BMX bike all day to lowering ones saddle 1". That's like comparing riding a wheelie to riding a unicycle: it's done on one wheel, so it must be the same, huh?
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  16. #16
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    Quote Originally Posted by shiggy
    Same height as my gearie. When I am in the saddle it does not matter if it is the SS, the BigShot or the Coiler, I want the same leg extension. Still just a bike.

    Note on your #1: Saddle height has to take crank length into account. Change the crank length and you have to change the saddle position to maintain the same relative height.
    true dat

  17. #17
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    Quote Originally Posted by Upchuck
    Uh, no. Singlespeeders don't all have bad knees. I don't. None of the ones I ride with have bad knees. I'd say if you already have bad knees, SS might not be the thing for you. But I wouldn't necessarily say SS will create a problem that doesn't exist.
    Sorry, it was a joke

    Quote Originally Posted by Upchuck
    As far as the BMX analogy, you're right. It is a reach to compare riding a BMX bike all day to lowering ones saddle 1". That's like comparing riding a wheelie to riding a unicycle: it's done on one wheel, so it must be the same, huh?
    For me, a too-low seat (anything lower than 10 or 15mm than i usually have) results in sore knees after 15 or so minutes in the hills. My BMX saddle is a full 10 inches too low, but, alas . I dont necessarily think SS-seatheight should differ to geared bikes either, only if the cranks are different lengths.

    Do you have problems (pains) when you run your seat lower than usual? I'm also wondering why longer cranks on your SS makes you run your seat lower than usual, care to elaborate? I don't mean to sound like a nong by asking, im truly interested.
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  18. #18
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    same same

    both my geared hardtail and singlespeed rigid have the exact same distance from pedal spindle to top of seat.

    same thing with my geared and fixed roadies.
    Last edited by mtnpat; 01-12-2006 at 06:54 AM. Reason: jus cuz

  19. #19
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    Over simplified problem...

    Quote Originally Posted by spuddy
    For me, a too-low seat (anything lower than 10 or 15mm than i usually have) results in sore knees after 15 or so minutes in the hills.
    5mm too low is very noticable to someone acclimated to riding, 15mm is totally obvious and would be uncomfortable as you won't get your full leg extension. When I head to the, uh, hills, I make sure my seat is already up to the right height. On a mountain bike which is (should be!) designed around geometry for a properly located saddle possition at full leg extension (slight bend in knee, just how much is another topic...), this matters. BMX bikes and urban/dirt jump bikes usually are not designed to put the seat in the correct possition for seated climbing anyway, whether that's too low or too far forward or backward, those bikes are not designed foremost with any seated climbing in mind... my Cannondale Chase dirt jumper had a seat tube so short you couldn't raise the seat high enough with a 350mm post, and my Evil Imperial has such a laid-back seat angle that the seat is too far back for a proper seated climbing possition, even with barely enough post with a 410mm post. I mention all this because when you start talking how high you have your BMX saddle, a lot of this is a moot point. I have a Mosh BMX saddle on my Evil, and it is about the most uncomfortable seat to climb on because it wasn't designed for it. BMX saddles don't have the propper sit bone support for seated climbing and this matters about as much has riding with your seat at the right height. I raced BMX for seven years. Those bikes are not designed to be ridden seated, much less seated climbing.

    Quote Originally Posted by spuddy
    My BMX saddle is a full 10 inches too low, but, alas .
    10" too low for what? Dirt jumping? (I'm assuming you have that saddle on a mountain bike of some type here or this is a moot point). I had no luck riding my dirt jumper type bikes as trail bikes, there is not much of a comparison here if your bike is not designed for seated climbing. My Chase wasn't bad with a seatpost that was longer than the frame's seat tube and with a setback head on the post to put it back in closer to the right possition to get the correct fit in correlation to where the bottom bracket and seat were in relation to each other, but it was a dirt jumper, not a cross country bike meant for a lot of climbing.

    Quote Originally Posted by spuddy
    I dont necessarily think SS-seatheight should differ to geared bikes either, only if the cranks are different lengths.
    Well I agree with you here, as do I think most of us.

    Quote Originally Posted by spuddy
    Do you have problems (pains) when you run your seat lower than usual?
    I think it's more of a it is a less effective and less comfortable for climbing issue where I wouldn't run my seat lower than usual anyway, there would be no reason for riding a bike that's not set up right when it could be. The only pain I have when I can't have my seat the right height is not in my knees, it's more of a pain in the @ss from picking and riding the wrong type of bike seated.

    Quote Originally Posted by spuddy
    I'm also wondering why longer cranks on your SS makes you run your seat lower than usual, care to elaborate? I don't mean to sound like a nong by asking, im truly interested.
    Well, it's already been answered here and just above you almost answered it again yourself, but it's still a good question for those that may not be aware that once you find the proper seat hight for yourself for proper leg extension, your pedal and top of your seat should always be the same distance measurement when the pedal on that side is in its furthest possition away from the seat (down). So... if you put 5mm longer (lower) cranks on your bike, you would lower your seat 5mm to keep that distance the same.

    This is assuming you ride enough to stay in about the same relative bike shape. Some people have an argument that during "bike season" (what's that?, I ride all year...), you should have your seat a bit higher, or at the correct possition for proper leg extension while in good physical riding condition as opposed to where you may lower it to if otherwise, but I think if studying that argument or opinion, 5mm of seat hight adjustment may not mean much to that in-less-than-riding-shape rider anyway.

    BTW, I raced BMX on 180mm cranks, and the height of my seat in relation never crossed my mind, I never sat on that seat anyway unless I was waiting in line behind the gate for my moto to be called.

    Cheers,

    Dave
    Last edited by mtbdirteater; 01-12-2006 at 07:34 AM. Reason: blah, blah, blah...
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  20. #20
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    Your knees aren't experiencing any greater stress if they aren't reaching near-full extension. The only difference in the quadriceps is you utilize more of the vastus medialis during the last 15 degrees of knee extension.
    Well, my knees don't agree. With the seat too low, the pedal force is applied at a greater knee angle, thus increasing the shearing forces on the knee joint. The same thing happens when you move your seat all the way to the front, or when you use very long cranks ("very long" = depending on your inseam).

    Of course, some peoples knees don't seem to care, but mine definitely do. It's not the muscles that hurt after the ride, it's the knee joint itself.


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  21. #21
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    Quote Originally Posted by lelebebbel
    With the seat too low, the pedal force is applied at a greater knee angle, thus increasing the shearing forces on the knee joint. The same thing happens when you move your seat all the way to the front, or when you use very long cranks ("very long" = depending on your inseam).
    I’m sure your knees, as well as many others, don’t like pedaling with the seat too low. I know that I don’t especially like to pedal very far with my urban trials bike or DH ride. But I attribute that to an extremely low seat compared to what I’m used to; at least 4”-6” lower.

    Applying a force at a slightly greater knee angle, at least the angles that will occur with a 1.5” lower seat, will not in itself create greater knee strain. In this case, it’s dependent upon where your knee is located in relation to the pedal spindle.

    Here’s why: factoring in the seat tube angle, if you lower your seat, your riding position is more anterior. It’s kind of like shortening the effective toptube length. The lower the seat, the further forward you move. This places the tibial tuberosity (the knot below the kneecap) anterior to the pedal spindle when the crankarms are in the 3 o’clock position. The result is what causes greater knee strain.

    If you’re familiar with performing squats or lunges with weights, you’ll find shear force is related to the fore-aft position of the patellar ligament attachment (just below the patella at the tibial tuberosity) in relation to the linear path of force applied. If you perform squats with a board under your heels, you get more knee strain than if you are flat footed. This is because the knee moves anterior to the ball of the foot resulting in shear forces: the femur translating over the tibia.

    First off, I’m only talking about a 1.5” height difference. That roughly translates to moving your seat anterior by only 3/8” with a 72-degree seat tube (I checked). Secondly, what I obviously should have mentioned was that I have accounted for the anterior movement and have moved my seat back on the post for optimal knee/pedal alignment. And voila, no knee strain. Don’t knock it till you try it…

    YMMV
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