Fore/aft measurement after seat change question

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mosa
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Joined: Sun Apr 03, 2011 09:08 am

Fore/aft measurement after seat change question

Postby mosa » Sun Mar 10, 2013 20:44 pm

After recently having a bike fit I have decided to try another saddle due to comfort. My question is do I have to buy the same length seat ? Or do I just measure the front of the seat to my fore position? (75mm) or do I adjust / compensate to allow for length difference if any. Going to try a fizik aliante from my prologo zero
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TrekVet
Posts: 108
Joined: Sun Nov 06, 2005 17:08 pm

Re: Fore/aft measurement after seat change question

Postby TrekVet » Sun Mar 10, 2013 21:30 pm

Haven't tried it, but you could try this: Sit on bike-fit saddle with hands on bars and get a friend/passer by to drop a plumb line from your butt to chainstay [sets fore and aft], and mark with sellotape with paper on it. Take posture photo with mobile phone. Then measure from top of saddle to BB axle (in-line with seat tube), and note [sets height]. Fit new saddle, assume same posture, and set saddle to same readings. Or words to that effect.
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keef66
Posts: 8712
Joined: Tue Apr 29, 2008 09:46 am

Re: Fore/aft measurement after seat change question

Postby keef66 » Mon Mar 11, 2013 12:36 pm

Tis a tricky one, because the shape of the saddle determines where you tend to sit on it.

Saddle height is a straightforward measurement from the top of the saddle, in line with the seat tube, to the centre of the BB.

Saddle fore / aft; best to get someone with a plumb line and ruler to measure the position of your knee relative to the pedal spindle with the cranks horizontal. Do both sides.

Swap saddles, get the height the same, then sit on the bike and with your attractive assistant's help, try and get the knee to pedal spindle set up as it was before.


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