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We bought a second hand bike just like in the picture but it's to big for my daughter so I tried lowering the seat but the post is hitting the frame and it looks like the previous owner had the same problem. So I was wondering what the three holes are used for where the suspension shock bolts to. I was hoping that I could change the shock position and it will higher the frame.
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The top one would indeed raise the frame a little, but thats hardy solving your issue. What you want is a hacksaw to trim the bottom off the seatpost.
... Also those two part seat posts you can sometimes reverse the clamp so that it sits right up inside the saddle which drops the saddle height by a couple of cms.