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  1. #1
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    new mtb- cut down seatpost?

    I've had my new mtb for several weeks now- I love it, but I've not done more than 10 miles on it yet. I just ride beginner trails so far. I love the way it fits me, but from what I've been reading it's probably a little big. Smaller ones felt too cramped- like my knees were going to hit the handlebars.
    I got a new terry liberator Y saddle for it, but when I put it on, the seat is now too high- I can't touch the ground with either toe without tilting the bike to one side. This is not a good feeling.
    The seat is as low as it can go- the bontrager saddle that came with it is very flat, and the terry is thicker so puts me about an inch or so higher. Is it safe to cut down the seatpost? I hadn't realized it was at it's lowest, it just felt good where it was with the original saddle.
    So, for now, I've got the original saddle back on- it's not bad, and I like how narrow it is so I can move around freely, but it just feels like it won't be so nice on longer rides.
    The seatpost is aluminum or some hollow metal, doesn't look like it would be too hard to cut. Any tips?
    thanks

  2. #2
    JRA. BikEthan's Avatar
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    You mean the frame? No... don't cut down the seat tube. I don't think cutting down the post will help any unless there is an obstruction in the frame keep the seat post from being lowered (like a bottle cage bolt). And FYI when the bike is sized and adjusted properly for your height you would have to lean to one side to touch the ground when you're not riding. I would recommend sliding forward off the front of the saddle when stopped as this usually eases any discomfort.

    Do you have any photos of the bike? And of you on it? Preferably with your legs at 12 and 6.
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  3. #3
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    A pic of the bike with seat at it's lowest setting would help. I can't tell from your description if the seat is basically sitting on the frame. Or it the post is somehow so long it's not bottoming out to the frame and is therefor too high for you.

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    ok, here's a photo. There's room on the seatpost for the reflector, etc- it just won't adjust down any further than this. This photo has the stock bontrager saddle on; the terry sits higher on the rails and raises me up by about an inch. It's a little hard to see because of the rear window of the vehicle, but you can see the rear reflector sticking out just above the dog decal- the reflector is just above where the seatpost goes into the seat tube. so there is quite a bit sticking up, and it feels perfect at this height, with this saddle. With the taller saddle, it feels like it needs to drop maybe and inch.
    I put the terry seat back on it to try riding around a nearby trail tonight, to try to tell if it's something I just have to get used to. I searched some threads on cutting the seatpost, and it seems some people do it to save weight?
    I hope I'm using the correct term- not the bike frame at all, but the adjustable post that the saddle is attached to.
    thanks

  5. #5
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    Hmmm weird, yeah it def should be able to go down quite a bit more. Can you feel it hit anything inside the frame that is stopping it from going down more? If that's the case then yeah you should be able to cut the seatpost down. it's just odd that you can't move it more than that.

  6. #6
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    yeah, there's something stopping it from going down further. Not sure if it's something protruding into the tube or what.
    vickie

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    I guess that'd be my first step, take the seat post out totally and use a flashlight and take a look. As Ethan stated maybe a bottle cage bolt that you can loosen? Hard to tell from this pic where the cage bolts are. Try and figure out what's blocking the post before you take a hacksaw to it. might be as simple as loosening an allen bolt on the frame.

  8. #8
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    You have quite a bit of seatpost showing and an uninterupted seat tube so it is odd that it will not go down further.
    As was suggested, it may be the water bottle bolts but they appear to be well down the seat tube. Another possibility is that the tube is out of round due to deformation when it was being welded, if that is the case go ahead and cut it off, it is just an alloy tube. Note how much distance there is from the minimum insertion line to the end before cutting and measure and mark a new minimum insertion line after it has been cut. You want to make sure you still have enough seat post in the seat tube, the original line will become meaningless once you trim some of the post off.
    Alternatively you could just buy a shorter post, they are not that hard to come by.

  9. #9
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    Thanks for the replies. I will explore with a flashlight tonight when I get home and see if there's a simple protrusion down there. I'll look into shorter seatposts as well, just something about cutting on a new bike.. even if it's just a greasy seatpost.

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    Quote Originally Posted by fastdogs View Post
    Thanks for the replies. I will explore with a flashlight tonight when I get home and see if there's a simple protrusion down there. I'll look into shorter seatposts as well, just something about cutting on a new bike.. even if it's just a greasy seatpost.
    I'd personally just cut off an inch before buying a new post. won't hurt anything.

  11. #11
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    Obviously, you don't want to cut the seat tube (a.k.a. frame). It is, however, perfectly acceptable to cut the seat post shorter. I had to do this on my last mountain bike. I cut the tube shorter with a hack saw, then filed the edges with a 2nd-cut file, followed by a smooth file. As long as you've got 2-3" of seat post inside the seat tube, you should be fine.

  12. #12
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    I know this is going to sound strange, but you aren't suppose to be able to touch the ground with your feet unless you lean off to one side. When I stop, I have to slide off the seat and place a foot down. I don't even come close to touching the ground when seated on the saddle. It's just something you need to deal with. It takes some getting used to but it sounds like the seat height is probably OK, dropping it down further would make the seat too low and cause all sorts of problems.

    I'm not a mechanic but no way I would cut a seat post. If you make a mistake and nick the metal, you can cause a stress crack or fatigue. Just too dangerous.

    Have you thought about fitting the bike to see if everything is set up correctly? That way you know for sure what is going on.

    BTW what is your height and what is the size of the bike? For instance, I am 5'8" and ride a medium (17") MTBike. Some bikes work betetr for me than others. I am much more comfortable on a cross-country bike than say an all mountain bike because of the reach.
    Last edited by Pamestique; 08-05-08 at 03:04 PM.
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  13. #13
    Senior Member Bill Kapaun's Avatar
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    Quote Originally Posted by BCIpam View Post
    I know this is going to sound strange, but you aren't suppose to be able to touch the ground with your feet unless you lean off to one side. When I stop, I have to slide off the seat and place a foot down. I don't even come close to touching the ground when seated on the saddle. It's just something you need to deal with. It takes some getting used to but it sounds like the seat height is probably OK, dropping it down further would make the seat too low and cause all sorts of problems....
    +1
    IF your seat is too low, you can't exert proper leverage with your legs AND PUT EXCESSIVE STRAIN ON YOUR KNEES!
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  14. #14
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    Quote Originally Posted by BCIpam View Post
    I know this is going to sound strange, but you aren't suppose to be able to touch the ground with your feet unless you lean off to one side. When I stop, I have to slide off the seat and place a foot down. I don't even come close to touching the ground when seated on the saddle. It's just something you need to deal with. It takes some getting used to but it sounds like the seat height is probably OK, dropping it down further would make the seat too low and cause all sorts of problems.

    I'm not a mechanic but no way I would cut a seat post. If you make a mistake and nick the metal, you can cause a stress crack or fatigue. Just too dangerous.

    Have you thought about fitting the bike to see if everything is set up correctly? That way you know for sure what is going on.

    BTW what is your height and what is the size of the bike? For instance, I am 5'8" and ride a medium (17") MTBike. Some bikes work betetr for me than others. I am much more comfortable on a cross-country bike than say an all mountain bike because of the reach.

    This comment on bike fit is 100% correct - most people cannot touch the ground while on the seat. The most important consideration when riding is that your leg is (almost) fully extended when your pedal is furthest from the seat. And since you don't want your pedal hitting the ground while you ride, you cannot, on most upright bikes, easily touch the ground while seated. Slide forward off the saddle and put your foot down when you stop.

    However, if you find you have to reach with your foot while riding, or you can feel your hips rocking, then there is absoluely nothing wrong with cutting an inch or two off the bottom of your post. You can use a hacksaw or a pipe-cutter, and you should use a file to remove all burrs and irregularites off the new end of the post when you are done. Just make sure, as someone said above, that you still have post left in the frame equal to the amount that used to be your minimum insertion (usually ~4", but you should measure to be sure.

    Also, if your seat is at the absolute maximum height that you can ride comfortably, you will generally want it slightly lower (maybe an inch or two lower than optimum road pedalling height) for riding rough trails - a lower seat allows you to move the bike around independantly of your body to better handle tight trails.

    Remember - if you cut the seatpost and you take off too much, you were planning on buying a new one anyway!

  15. #15
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    The posts about seat height are applying a rule that applies to some styles of biking as a general rule, that is more than a little dangerous.
    Would you expect a BMX rider to have their seat up so that they had to lean over to get a toe down, or a mountain biker that rides a downhill bike in the bike parks or maybe someone that uses their bike for dirt jumping??? Of course not is the correct answer.

    The OP indicated "I can't touch the ground with either toe without tilting the bike to one side." Not being able to touch your toe, not foot, "toe", down without tilting to the side at the lowest saddle position is no way to have a mountain bike set up. Certainly you would want to have the seat post range be broad enough to set up a position where your leg was almost straight at the lowest point in the crank cycle but you also want to be able to slam the seat to the bottom when you are faced with a long steep descent covered in roots and rocks. The OP is barely able to get a toe down at the "lowest" setting, this is not something he/she should get used to.

  16. #16
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    Quote Originally Posted by andymac View Post
    The posts about seat height are applying a rule that applies to some styles of biking as a general rule, that is more than a little dangerous.
    Would you expect a BMX rider to have their seat up so that they had to lean over to get a toe down, or a mountain biker that rides a downhill bike in the bike parks or maybe someone that uses their bike for dirt jumping??? Of course not is the correct answer.

    The OP indicated "I can't touch the ground with either toe without tilting the bike to one side." Not being able to touch your toe, not foot, "toe", down without tilting to the side at the lowest saddle position is no way to have a mountain bike set up. Certainly you would want to have the seat post range be broad enough to set up a position where your leg was almost straight at the lowest point in the crank cycle but you also want to be able to slam the seat to the bottom when you are faced with a long steep descent covered in roots and rocks. The OP is barely able to get a toe down at the "lowest" setting, this is not something he/she should get used to.
    I agree that there needs to be more room for adjustment, but on a lot of new bikes, suspesion jacks the bike up by several inches - what would have been a setup able to put a toe on the ground on a rigid bike is now a setup that you have to slide forward off the saddle to touch the ground. Of course, there needs to be adjustment for difficult terrain, but more hurt their knees riding a bike with the saddle 5" too low than get hurt because they have their saddle too high.

    However, it is impossible to say exactly what is going on in this case because we do not exactly how the OP fits on the bike in question!

    FWIW, I think the seatpost should definitely be cut.

  17. #17
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    Most current mountain bikes, the pictured one included, have a sloping top tube so the standover height is actually lower than many of the rigid bikes from the past. What tends to make the seat very high on this style of bike is that they have been designed to have a high bottom bracket height to provide ample ground clearance. Full suspension bikes used to be "jacked up" as you suggest but most of those early designs have gone by the wayside, many full suspension are now quite low.


    Regardless, you need to be able to slam the seat when the riding you are doing calls for it.

  18. #18
    Senior Member deraltekluge's Avatar
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    So, what's stopping you from lowering the seat? It kinda looks to me like it's the reflector and the bag. Throw away the reflector if you don't ride in the dark. I don't see any lights on the bike, so it wouldn't be legal or safe to ride in the dark, anyway.

  19. #19
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    what's keeping the seatpost from going down further is the water bottle bolt- I removed it but there's still a protrusion inside the seat tube. I'll probably ride it this week with the seat "too high" to see how it goes.
    My bike is a 17.5 (medium). I am 5' 7". I rode the size down but it felt like I was too close to the handlebars, this one felt just right. The bike shops were kinda casual about fit- they'd start me with a small frame but if the larger one felt better they were ok with that. I have had advice that if I were to get into some really technical stuff I'd probably want the smaller frame for maneuverability, but for now I'm having a ball on the easy stuff- roots and rocks and things like that. Since I don't have that much standover (only about 1") I'm sure that's right, but this is the size that felt good. With the terry seat on I cannot touch a toe to the ground at all, I have to let the bike fall to the side to touch. Sitting on it in the kitchen (holding on to the counter), with my legs straight down and pointing my toes hard, my toes are still about an inch of the floor.
    So, it looks like I'll be cutting the seat post- thanks for all the insight, my main worry was that I'd make something unsafe if I cut it. But there will still be plenty of post in the seat tube if I cut 2" off, and it will give me some leeway for adjusting the seat, regardless of what saddle I go with.
    Thanks to all the people who took the time to respond- I learned a lot about bike fit etc!
    vickie

  20. #20
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    Quote Originally Posted by andymac View Post
    The OP indicated "I can't touch the ground with either toe without tilting the bike to one side." Not being able to touch your toe, not foot, "toe", down without tilting to the side at the lowest saddle position is no way to have a mountain bike set up.
    IMHO this is absolutly incorrect. I have mountain biked since the late 80's and proper seat positions almost always means you cannot touch the ground with even a toe unless the bike is tilted. In order to stand you must get off the seat. Having a couple of inches of clearance from the top tube for you crotch when you stand over the bike is a must, but on no bike but cruzer or bmx should you be able to sit on the seat and be flat footed.
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  21. #21
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    fastdogs, if you were able to sit in the saddle, with a foot on the ground, while sitting straight up, your pedals would be hitting all sorts of stuff while riding. Mountain bikes need plenty of clearance, so yes, the proper thing is to not be able to stand with a foot on the ground without leaning over.

    1" of clearance when standing over the tube sounds really, really close. That amount was typical of old-school road bikes with straight top tubes. Mountain bikes generally give a lot more because of the sloping top tube and longer seatposts.

    The frame may feel good now, but all the evidence I'm hearing is it is probably too small. Keep riding it, of course, but you may be limiting your riding ability with a wrong sized frame.

  22. #22
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    you may have to trim some off of the end of the seatpost then if there is a peice for the bottle bracket hitting it ... just don't trim to much ... i would only remove about 1" at the most.

  23. #23
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    A lot of mountain bike seat posts are quite long, 300mm plus. I think you should just go ahead and cut some of it with a hacksaw. Then use a file to smooth out the cut edge.

  24. #24
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    Quote Originally Posted by fastdogs View Post
    what's keeping the seatpost from going down further is the water bottle bolt- I removed it but there's still a protrusion inside the seat tube. I'll probably ride it this week with the seat "too high" to see how it goes.
    Yes, the water bottle bolt screws into a water bottle boss. The boss protrudes into the tube because it needs to have enough threads to hold the bolts that attach the water bottle cage. Bosses aren't typically that thick, but they're thick enough that they won't let the seat tube past.

    If I were you, I wouldn't hesitate to cut 2" off the bottom of your seat post. I think I lopped 4" off the bottom of the 300mm seat post I bought for the custom-built MTB fame that I welded up last year. So far, I haven't had any problems. Just make sure that there's at least 3-4" of seat post below the seat post clamp.

  25. #25
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    ok, you guys who advised me to just deal with it, I am riding with the terry saddle and the seat "too high", and it's not feeling that bad. I was riding an easy trail tonight but had to put a foot down when my front tire fell into a runoff trench and didn't have any problems getting my foot down.
    Tomorrow I'll take it on a bike path for about 10 miles to see how it feels (saddle height AND saddle), then friday I'll take it to the bike shop I got it from to see what they think (they do a lot of mtb). I will still cut the seatpost down, so I've got some options. I sometimes roadwork the dogs on a springer on the bike, and I'll want the seat a bit lower for that.
    Anyway, you can say told you so now, because it actually feels better and better with the seat this high!
    thanks
    vickie

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