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  1. #1
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    Seat Post Height

    I recently bought a GT Karokoram 2.0. Large size. LBS owner is a friend I used to ride BMX with, back when Stu Thompson was the man. I am 6'4", 255 lbs.

    I have never had a bike that really fit me, and I am wondering if I should have gotten the XL size frame. He told me to ride the bike on some trails, to see if I wanted him to get me the XL. First few times on the trails, bike felt big, but riding fireroads yesterday, I ran the seat post within 1/4" of max height. I noticed I am more efficient with my legs, straight, while foot parallel to the ground while sitting. Top tube height is about four fingers below baggage. On trails, this height feels a bit odd. Like I could go OTB at any minute. Getting arse down and behind the seat is a little tough, but doable.

    Is it dangerous to have seat post so close to max height, that it can cause frame damage or should I see about getting the XL size frame? The rest of the bike feels great, as far as reach and weight forward. Thanks in advance for your responses.

  2. #2
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    We are about the same height and weight, although I'm a bit lighter , and I lined up with Stu, Dennis Dain, Harry Leary, Bobby Encinas, Clint Miller. MTBing, I rode a large frame for a while and then an XL and glad I made the change. Sitting for power and efficiency are the norm for MTBing while standing is the norm for BMX. The larger cockpit fits better over time, and it sounds like you are pushing the seat-post and frame to the designers' max limits with the Large already. You will get used to the little more stretched out cock-pit over time.
    Right now my seat post height is 82mm from BB to the top of the seat, which seems to be optimal, but changes with the mood. Give the XL a try. Good Luck.

  3. #3
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    We are about spot on with height and weight. I am currently riding an XXL Lenz Leviathan full susser and a XL Singular Swift hardtail.. I could not imagine riding a Large in anything to be honest.

  4. #4
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    Quote Originally Posted by Locool View Post
    Right now my seat post height is 82mm from BB to the top of the seat, which seems to be optimal, but changes with the mood. Give the XL a try. Good Luck.
    Think you might have missed a '0' there fella!
    As far as seat height goes, if your leg is nearly straight with your heel on the pedal, you are close to a good neutral starting point for XC riding. It feels high to start with but you'll get used to it. I'd probably have you closer to XL myself, so if he can get one for you to try, go for it.

  5. #5
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    Think you might have missed a '0' there fella!

    Fuzzy translation! You're right TooTallUK. 820mm, 82cm and something in inches. I'll catch up with the metrics someday.

  6. #6
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    Being an x-BMX'er, at 6'3" 230, I find myself riding L rather than XL bikes. I still like the ability to throw the bike around unrestrained. The XL frames just don't give me enough clearance for 'da junk.
    That being said, it all depends on what type of riding you are doing. If trail riding is the norm, then the bigger bike may be more comfortable over longer distances. But if you still like doing ledge drops or lining up the neighborhood kids on the street to bunny-hop over them, then the smaller frame may be of more value. lol

    Pick the one that 'feels' right.

  7. #7
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    Quote Originally Posted by Xlr8n View Post
    Being an x-BMX'er, at 6'3" 230, I find myself riding L rather than XL bikes. I still like the ability to throw the bike around unrestrained. The XL frames just don't give me enough clearance for 'da junk.
    That being said, it all depends on what type of riding you are doing. If trail riding is the norm, then the bigger bike may be more comfortable over longer distances. But if you still like doing ledge drops or lining up the neighborhood kids on the street to bunny-hop over them, then the smaller frame may be of more value. lol

    Pick the one that 'feels' right.
    When I was being sized for my Mojo Hd purchase I "should have" bought the XL but I like having a more nimble bike that can be thrown around with ease. Also having the clearance for the junk is essential!!!!!

  8. #8
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    I do believe I will just get a dropper and have the best of both worlds. I won't have to worry so much about the frame cracking. Yes?

  9. #9
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    Re: Seat Post Height

    I don't see how to dropper post will help keep the frame from cracking. It will still need to be raised quite high to give you proper leg extension. Depending on total length of the seatpost you choose, of course. If you are this worried about your frame cracking or the seatpost cracking then it sounds to me like you need to find a longer seatpost or a taller frame. Nothing wrong with a dropper post. But on the surface I don't think that's going to solve your problem.

    To prevent the frame from cracking over time you need to have the seat post inserted far enough into the frame that the lever action won't cause metal fatigue. Typically this would be below the junction of your top tube in seat tube and and below any gusset that might be there. Preferably several inches lower than that. To keep your seat post from cracking you need to run no more than the maximum extension that's noted on the seatpost.

  10. #10
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    Yes, I have 1/4" until I get to my max seat post mark. I have always ridden bikes that were too small for me. Since getting this bike, it feels big to me, compared. If that makes sense? My only concern was seat post tube. My LBS owner/friend, said he has no problem getting the other frame, but noticed I would be stretched a little more than I am used to. I took a ride on a different brand XL, and I see his point. 3 position dropper seems more versatile to me. High position uphills, Next position flats, lowered, downhills, for getting weight back.

  11. #11
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    Quote Originally Posted by Bdabike View Post
    Yes, I have 1/4" until I get to my max seat post mark. I have always ridden bikes that were too small for me. Since getting this bike, it feels big to me, compared. If that makes sense? My only concern was seat post tube. My LBS owner/friend, said he has no problem getting the other frame, but noticed I would be stretched a little more than I am used to. I took a ride on a different brand XL, and I see his point. 3 position dropper seems more versatile to me. High position uphills, Next position flats, lowered, downhills, for getting weight back.
    I'm not sure we are on the same page re: the dropper post.

    Yes, a dropper post is more versitile for riding a mtb but using one does in any way change the fact that you run a lot of exposed seatpost when in the 'high' position. It sounds like you may be on the cusp of not enough insertion into the frame as well but I can't really tell from what you have stated so far. And more to this point re: the dropper post, when you 'drop' the post it does not insert into the seat tube further, that position is fixed and determined by how high you need to run it with the post fully extended to achieve proper pedaling position (high position as you called it). For example: If you only have 2'' of dropper post down into the seat tube then that will not change when you drop the post 5'', it will still be only inserted 2''.

    There are two things to to concern yourself with in your situation.
    1) Seat post insertion length INTO the seat tube.
    2) Seat post maximum extension - the "max" line scribed on the seatpost itself.

    The 2nd is easy, it's marked right on most seat posts. The 1st not quite as obvious as I don't think many frames have a sight-hole on the back of the seatpost to visually check minimum insertion...and I don't think many manufactures list min insertion in their specs. So.....the rule of thumb is to insert the seatpost AT LEAST as far as needed to bring it below the seat tube and top tube junction...again preferably lower and if is gusseted to below the gusset to be safe.

    If you don't meet both requirements the leverage action you impose on both the massively exposed seat post OR the frame itself can be tremendous and metal fatigue (Al frame, right) is sure to happen far quicker than a properly fitted post.

    Sorry for the long winded reply, I just keep thinking you are under the impression a dropper post will help. What you may need is a longer post.....dropper or not.

    How long is your post? That's a good question to begin with. Find out and go e-net shopping for a longer one and see what you come up with.

  12. #12
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    Couple more things...

    1) If you are new to mtb'ing then yes, a mtb feels quite big and awkward at first. This feeling goes away.
    2) You say you are worried about being stretched out on an XL frame. If you have a long stem (100mm is long these days) then a larger bike with a much shorter stem is an option. There's a little more than that to bike fitting but it's not rocket science....like with a a road bike apparently. MTBing is much more dynaminc than road riding. You are standing, sitting, getting behind the seat, flicking the rear end around corners....sizing is much more of a preference than a science on a mtb, that's all I'm saying.

  13. #13
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    I understand what you are saying. At my highest position I have 4 1/2" of seat post still in tube. It extends 3 1/4" below top tube junction. I have another 1/4" of seat post to pull out before I reach the post max mark. Hope this makes it a little clearer. So, do you think that is in the safe zone?

    I do not think the dropper is going to give me any more height to the seat.

  14. #14
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    Re: Seat Post Height

    Quote Originally Posted by Bdabike View Post
    I understand what you are saying. At my highest position I have 4 1/2" of seat post still in tube. It extends 3 1/4" below top tube junction. I have another 1/4" of seat post to pull out before I reach the post max mark. Hope this makes it a little clearer. So, do you think that is in the safe zone?

    I do not think the dropper is going to give me any more height to the seat.
    If you're not quite at the maximum extension line point of your seat post then I think you're safe. I'm no expert. And at that extension it certainly causes more leverage on your seat post then if you had it inserted much further. But the line is there for a reason so I think you're okay.

    Since I just realized I'm posting in the clyde forum (lol) let me add this. We are not all created equal. A 150lb rider riding a the max extension point of his seat post will undoubtedly induce less leverage on the post than a 250lb guy. So while I think your 'safe'...might it fail at some point running it that high???/ Maybe, who knows. I still suggest shopping for a post that will extend further into the frame...I mean, why not right? Then you can get further away from the max extension line if nothing else.
    Last edited by eatdrinkride; 03-12-2013 at 09:19 PM.

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    Agree with the several posts above^^^ Rather than relying on the insertion line, just make sure whatever post you run inserts into the seat tube and passes at least completely through the top tub junction and/or any gussets at that joint.
    In the old days, as long as you had the seatpost inserted past the 'minimum line', you were gold, but there are some newer frames on the market today in which the seat tube extends past the top tube to a much greater extent which makes the seat post insertion line not as reliable.

    If you need a bit more seat height, get a longer post which will have more usable length past the Top tube junction. Pretty straight forward.

    I certainly would not base picking a frame size on how high my seat post is set. Personally I base it on: 1) top tube clearance, and 2) desired reach to the bars. So if you want to follow the latest trend and run a shorter stem for more relaxed control, go with a longer top tube frame (i.e. larger size).

    If you are happy with the straddle height of your current frame but want a bit more cockpit room, try using a laidback seat post such as a Thomson.

    Lots of options available to finding the perfect layout for your body size and riding style.

  16. #16
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    Re: Seat Post Height

    Quote Originally Posted by Xlr8n View Post
    Agree with the several posts above^^^ Rather than relying on the insertion line, just make sure whatever post you run inserts into the seat tube and passes at least completely through the top tub junction and/or any gussets at that joint.
    In the old days, as long as you had the seatpost inserted past the 'minimum line', you were gold, but there are some newer frames on the market today in which the seat tube extends past the top tube to a much greater extent which makes the seat post insertion line not as reliable.
    e.
    Not to beat a dead horse but just to be quite clear. The line on the seatpost has absolutely nothing to do with keeping the frames safe. It is simply there to make sure that you don't over leverage the seat post itself. Whether or not that also provides a enough insertion in into the frame itself is another question, the only way to know is to look or measure.

  17. #17
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    Quote Originally Posted by eatdrinkride View Post
    Not to beat a dead horse but just to be quite clear. The line on the seatpost has absolutely nothing to do with keeping the frames safe. It is simply there to make sure that you don't over leverage the seat post itself. Whether or not that also provides a enough insertion in into the frame itself is another question, the only way to know is to look or measure.
    Correct. I'd never recommend riding with a seatpost mounted above the minimum insertion line, and surely hope I didn't imply as such in my post to this thread, if that is how you read it. I'm stating that inserting to the line on the post alone is sometimes not enough depending on the individual frame construction.

  18. #18
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    You should also consider, that the seatpost min insertion line is for average riders, wich is usually below Clyde weight. Check if there is a weight limit for your post. Thomson for example has no limit on the elite. Ritchey on the other hand states: "The saddles and seatposts are designed to carry a maximum rider's weight of 110 kilos (242 lbs)- luggage eg backpack included."
    So even if you don't raise it above the min insertion line, you might already ride it outside of it's specification. So it might be a good idea to lower the post way beyond the min. insertion line.

    Personally I think as a clyde it's a good idea not to go a size smaller, for that exact reason. Some manufacturers also strenghten the material (wall thickness) on the larger frames.

    Cheers
    Dan

  19. #19
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    I still say pick the size that feels good to you and don't sweat the seatpost. I'm about 230 and have put the beat-down on an '98 F2000 Cannondale since it was new and now a restored '97 Schwinn Homegrown, both in Large 19" size. In all my mountain biking I've never had a seat post fail, but that being said, I'm usually not heavy on the saddle during crunch time. I guess it all depends on your riding experience and style. Shoot, I still fool around on old 20" and 26" BMX bikes with no issues, although those thin Cr-Mo laid back BMX posts will bend if you sneeze at them.

    Actually, until finding this forum, I never even pondered myself to be a 'Clydesdale' as I sure don't feel like one when riding...You guys are making me feel big.

  20. #20
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    Same here, but there are people who break stuff all the time, even if they are lighter.

    Interestingly GT doesen't feel to worried about bigger riders, since i couldn't find any weight restrictions on their site or manual.

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