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  1. #1
    mik
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    Curved/swept back seat posts...

    What (if any) are the advantages or disadvantages or pros & cons of a curved or swept back seat post?
    I'm considering one because I'm putting a much shorter stem on to replace a 120mm stock one, so then thinking to compensate the distance from seat to bars with a swept back post

  2. #2
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    Couple of reasons

    As you described, setback seatposts can be used to stretch out the cockpit a bit. They also bring your weight further back over the rear wheel, which is helpful on downhill stretches.

    Bob
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  3. #3
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    Hold the phone.

    ONLY use a setback post to place your weight over the cranks properly. IT is not a good idea to use a setback to stretch out the cockpit.
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  4. #4
    "Mr. Britannica"
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    Quote Originally Posted by damion
    ONLY use a setback post to place your weight over the cranks properly. IT is not a good idea to use a setback to stretch out the cockpit.
    Yeah, the cynic will say that they are used to fit a frame that is too small.

  5. #5
    Don't be a sheep
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    Quote Originally Posted by roadiegonebad
    Yeah, the cynic will say that they are used to fit a frame that is too small.
    Actually setback WAS the standard and all frames were designed around them, non-setback is a recent invention from the MTB industry to get people forward for climbing steep pitches. Whatever it takes to get your saddle where you like it.
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  6. #6
    "Mr. Britannica"
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    Quote Originally Posted by Rivet
    Actually setback WAS the standard and all frames were designed around them, non-setback is a recent invention from the MTB industry to get people forward for climbing steep pitches. Whatever it takes to get your saddle where you like it.

    I agree. When he wrote "curved or swept back" I was thinking if the radically bent ones, not the standard 1-2cm set back.

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    Setback posts arent necessarily for those with poor-fitting frames. Some freaks of nature like myself have really short legs and longer torsos. The tradeoff for me seems to be adequate standover height vs. a cramped cockpit.

    Im running a Thomson setback with an old-school 120mm stem on my all-mtn, and it works great. I believe the Easton posts offer more setback via the clamp design (as opposed to the shaped mast of the Thomson)

  8. #8
    RTM
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    Damion makes a good point. A layback seat post will open up the cockpit but you will change the angle of your lower leg. Watch the line from knee to pedal axle. A touch forward is good for climbing, a touch back is good for descents. You can use the seat to fine tune for the type of riding you do. A layback seatpost may actually push you too far back. A few degrees won't be a big deal if you do a lot of up and down and move around in the saddle alot. However, if you do a lot of long XC climbs a forced rearward angle will eventually hurt you physically and in climbing ability.
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  9. #9
    "Mr. Britannica"
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    Quote Originally Posted by Reposado Man
    Setback posts arent necessarily for those with poor-fitting frames. Some freaks of nature like myself have really short legs and longer torsos. The tradeoff for me seems to be adequate standover height vs. a cramped cockpit.

    Im running a Thomson setback with an old-school 120mm stem on my all-mtn, and it works great. I believe the Easton posts offer more setback via the clamp design (as opposed to the shaped mast of the Thomson)

    You- and other "freaks of nature"- are the perfect examples... and the perfect candidates for custom frames. Don't confuse what I said about curved/swept back with (nominal) set back.

  10. #10
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    If I was still riding rigid steel, I'd be all over it.

    Rare is the FS frame that comes in a full complement of sizes, even rarer is the custom option (for shlubs on a budget)

  11. #11
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    Try it, it's all personal preference.

    Quote Originally Posted by mik
    What (if any) are the advantages or disadvantages or pros & cons of a curved or swept back seat post?
    I'm considering one because I'm putting a much shorter stem on to replace a 120mm stock one, so then thinking to compensate the distance from seat to bars with a swept back post
    If you are talking about a setback post in general, go ahead and try it. A setback post of an inch is still within pretty normal specs for almost any bike. In fact, I have found I never like how far over the cranks I am with a straight post. It's good for climbing and xc, but I don't like it for technical riding and steep downhill stuff. It is perfectly OK to do what you are thinking and you may even prefer it.

    Now if you are thinking about a post that uses a curve in the post itself to acheive that setback (as opposed to a setback at the clamp) I would guess that it would be stronger, but I would make sure it can be dropped enough for your style of riding.

  12. #12
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    You should always use the post required to get your saddle in the right position in relation to the BB spindle. There is no correct kind of seatpost for this. There are many factors like your body proportions, the effective seat tube angle on the frame and so on. Most of the posts in the market are actually setback posts and its what most people typically need. Most mountain bikers opt to be with the knee just slightly behind the pedal axle (using the KOPS method as reference) to generate more power so its more common to use setback posts. Besides the Thomson, straight posts are actually rather rare. Actually I think the reason many people mistakenly even consider straight posts is because of the popularity of the Thomson. I see a lot of riders running the straight version when its obvious they should have bought the setback model. A setback post should never be used to stretch out a cockpit. Thats a sure sign of a wrong sized frame.

  13. #13
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    Never said it was a good idea

    Quote Originally Posted by damion
    ONLY use a setback post to place your weight over the cranks properly. IT is not a good idea to use a setback to stretch out the cockpit.
    But it has been done, and I don't know that anyone's been crippled as a result

    I agree 100 % that correct frame size is the right way to go, but the setback can compensate when the circumstance calls for it, IMHO.
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    ok, so question:
    I'm getting a large cannondale prophet 600 and it feels too cramped in the cockpit to me--like the handlebars are too close and i'm too upright.
    I'm between 6'2 and 6'3, 210lbs. The XL frame is too big for me, but it's stretched out a bit better. should I just get a longer stem?

  15. #15
    RTM
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    Quote Originally Posted by chris_nor_cal
    ok, so question:
    I'm getting a large cannondale prophet 600 and it feels too cramped in the cockpit to me--like the handlebars are too close and i'm too upright.
    I'm between 6'2 and 6'3, 210lbs. The XL frame is too big for me, but it's stretched out a bit better. should I just get a longer stem?
    it all depends on that all-important imaginary line from your knee to your forward pedal axle when the pedals are in the horizontal position. at 6'3" with a straight seatpost I'd bet you are tall enough that your knee hangs over the pedal, in which case a layback seatpost would be perfect. of course, once that knee angle is right either with a straight or layback post you're done there and the stem is your best bet.
    "The bitterness of poor quality remains long after the sweetness of a low price is forgotten." - Benjamin Franklin

  16. #16
    Bicyclochondriac.
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    Quote Originally Posted by RTM
    it all depends on that all-important imaginary line from your knee to your forward pedal axle when the pedals are in the horizontal position. at 6'3" with a straight seatpost I'd bet you are tall enough that your knee hangs over the pedal, in which case a layback seatpost would be perfect. of course, once that knee angle is right either with a straight or layback post you're done there and the stem is your best bet.
    I think "imaginary" is the key word. I remember learning the rule of thumb you are speaking of, but I wonder how much it still applies. Over the past few years frame geometries (as well as rider position) have gone through some real changes. Handlebars are often much higher and wider than a few years ago. I think cockpits are generally shorter as well. There is a big difference between a racing/xc setup and an all mountain/trail setup.

    I have my road bike set up excactly as you suggest with regard to seat/knee/pedal placement, and my earlier mountain bikes were close, but as my bikes have become more all mountain in build and riding style, that seat has kept moving back relative to the pedals. I recently built a SS and I notice I do like the seat more forward, but not like the road bike.

    I guess my point here is that I think that rule of thumb is a good one to keep in mind, especially in road bike and racing/xc setups, but there are good reasons to consider deviating from it for other setups(besides getting a small frame to fit).

    I'm no expert in this field, I just know what works for me. I have so-so knees and seat placement is pretty key for the comfort of my knees, and I have found that moving it back is OK as long as I keep the seat height correct. Of course if there is some physiological reason to keep the seat where you suggest, (such as it generally being harmful to deviate from this) then don' tlisten to me. However, I have never heard of recumbant bikes being harmful.

  17. #17
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    This has been beaten to death, but here's my take: There is only one advantage to using a straight or setback seatpost. Proper placement of your saddle in relation to your pedal stroke (which involves your knees) is the most important thing. Like someone said, most frames are designed around a seatpost with setback. I agree.

    I ran a straight Thomson on my 2 mtn bikes for years (they were originally spec'd with setback posts; one was my first mtb, the other was a custom build; same company, size frame, and frame geometry). Never felt comforatble b/c I always wanted to move my butt further back. A year or two ago, I bought a Thomson setback (they just started making them in 26.8) and now riding has been much more comfortable. It's like everything had fallen into place...YRMV.

    The shorter stem will give you a more upright riding position. If you're comfortable with your current saddle position, I'd say leave it and try out the new stem before making any drastic changes.
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  18. #18
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    RTM, thanks. that explained it.

  19. #19
    mik
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    Cool, thanx for all the feedback people!, some bloody good points; I didn't even really think of how it could change the setup re saddle-to-pedal posi etc, defenately gonna take that into account, I think as 'beeristasty' (and hell yeah it is!!) mentioned; I'll do the stem thing, see how that goes, then if I reckn it'll be more comfy (not that comfort is tooo important) I'll go the post swap. While I'm on it (no pun intended): is there any recomendations to good posts? And how 'swept back' are they? Also, are the shortest stems out there?
    I've got a Mongoose Teocali btw...

  20. #20
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    Quote Originally Posted by kapusta
    I think "imaginary" is the key word. I remember learning the rule of thumb you are speaking of, but I wonder how much it still applies. Over the past few years frame geometries (as well as rider position) have gone through some real changes. Handlebars are often much higher and wider than a few years ago. I think cockpits are generally shorter as well. There is a big difference between a racing/xc setup and an all mountain/trail setup.
    Thats why I mentioned that the imaginary KOPS line is just a reference point. Its not the correct point. Commonly mountain bikers tend to run the saddle so the knee is behind that line by maybe an inch or so. It allows for more power and maching down harder. Thats why its common for setback seatposts to actually be the more standard. With most saddle rails it's nearly impossible to slide them back far enough on a straight post to get that positioning.

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