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Best way to install a new seatpost while retaining similar height

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Best way to install a new seatpost while retaining similar height

Old 03-06-17, 07:19 PM
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Best way to install a new seatpost while retaining similar height

I'll be replacing my current seatpost with a differently setback seatpost (will be using the same saddle). What is the best way to approximate the height of the current seatpost with the newly installed one? I'd like a good baseline, height-wise, before making other adjustments. I'd love to learn the tips and tricks your experience has taught you.
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Old 03-06-17, 08:34 PM
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I'm not sure how great my tips are, but I take measurements from definable locations on the bike to specific locations on the saddle. Mine are top tube to underneath of saddle at front... center of steerer tube to a point under the back of saddle. I also take a measurement from the center of the crank to the same point at the back of the saddle. You can pick what you want as a reference point. It does make it loads easier with the same saddle.

John

Edit added... If I am trying to duplicate a fit to another bike, I will use the measurement from the center of the handlebar to the back of the seat. This seems to get me close while taking stem length into consideration. If I can't get close, I re-evaluate the stem length and may change it. But I want the center of the crank measurement to be the same if has worked well for me. This is also based on same length of crank arms on both bikes. If different, I'll start doing some math. At that point I'm only looking for close.

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Old 03-06-17, 09:07 PM
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Your butt will want to seek the same position along the saddle. So mark a spot on the saddle's top side and from this measure down to the BB. Install the new post and decide on the new set back you want (even if it's the same as before) and then measure back up to the spot you marked from the BB, adjust post height to match. Andy
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Old 03-06-17, 09:12 PM
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When doing the same,

1/
I measure from the centre line of the BB to the top of the saddle, make sure the tape is directly in line with the seat tube, that gives you the exact height.
2/
The saddle will have rails underneath so you need to measure from any fixed point say the tip of the saddle to the centre line of the stem, this is very important if your new seat post has a set back, then you can slide the saddle to its original position.

Its interesting to note different saddles have different lengths of rails so sometimes you may need to change the saddle to ensure you end up in the correct position or original position.
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Old 03-06-17, 09:13 PM
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I use measuring tape.
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Old 03-06-17, 10:50 PM
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I like the idea of measuring to the top of the saddle and have done it when changing to a different saddle. But I don't like to bend the tape measure around the edges if I am using the same saddle on a different bike. With an identical saddle I use the underneath side since there is very little angling or bending of the tape measure.

I do agree that the top is where you sit so it eliminates differences in saddle rails or thicknesses without having to resort to calculations. And with a new saddle you are just getting it close.

John
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Old 03-06-17, 10:59 PM
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Thanks, all!
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Old 03-07-17, 10:18 AM
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In the Campagnolo professional's tool box, was the special tool number 736, but back then top tubes were all horizontal, and the seat posts were shorter..



I just use a Yard Stick, bottom, Zero end, sits on top of the pedal Spindle..






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Old 03-07-17, 11:32 AM
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If you're just replacing the seat post, a carpenter's square works. Set it to the current height above the top tube, use a piece of masking tape on the top tube to record the forward position of the nose of the saddle, and a bubble level or angle gauge for the saddle angle.

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Old 03-07-17, 12:57 PM
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For height, my rule for my own body proportions is: put my armpit on the saddle where I think my butt goes. The second joint of my middle finger should reach the center of the BB spindle. I might have long arms for my legs, as I believe most people let the tip of the middle finger reach the spindle.

For fore-aft, just measure the distance behind the stem.

For angle, take a picture and approximate it upon reassembly.
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Old 03-07-17, 03:39 PM
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My procedure is identical to that outlined by Bike tinker man
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Old 03-07-17, 06:40 PM
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On my bikes, all saddles get set at 32 inches from center of crank to top of saddle. Then I fine tune by riding.
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Old 03-07-17, 08:39 PM
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Originally Posted by xenologer
I use measuring tape.
Yeah, no need to complicate things. If you are starting with a saddle position that you want to replicate, measure from the BB center to the top of the saddle along the seat tube. Put some painters tape on the top of the saddle and mark off where the center of the seat tube intercepts. Now put on your new seatpost and measure to the right height, and put the mark in the same place. Voila!
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Old 03-07-17, 09:42 PM
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All you need to do is to run a plumb line from the front of the saddle. Measure the length from the top of the saddle to the BB, and from the plumb line to the BB horizontally. Assuming the same crank length the saddle will be in exactly the same position in relationship to the cranks.

Last edited by cny-bikeman; 03-07-17 at 09:48 PM.
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Old 03-09-17, 12:22 AM
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Originally Posted by cny-bikeman
All you need to do is to run a plumb line from the front of the saddle. Measure the length from the top of the saddle to the BB, and from the plumb line to the BB horizontally. Assuming the same crank length the saddle will be in exactly the same position in relationship to the cranks.
Ah, this is my favorite, so far.
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Old 03-09-17, 06:49 AM
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Originally Posted by lyrictenor1
Ah, this is my favorite, so far.
Thanks. I'm realizing now it might be a little easier to reverse it - run the plumb through the BB, then measure to the tip of the saddle.
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