New version V8. Biomechanical & sizing & fitting spreadsheet

A light bike doesn't replace good fitness.

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Ypsylon
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by Ypsylon

Given that beatnik is a fitting guy I'd assume that when he says that someone changes his seatpost it's to change the fit, not the color or weight or whatever.

If you keep your saddle position the same you obviously won't change your stem. But if you change your straight seatpost for one with setback to give you a different position you have to change your stem.

So you're not actually disagreeing with him, the way I see.
"Nothing compares to the simple pleasures of a bike ride," said John F. Kennedy, a man who had the pleasure of Marilyn Monroe.

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beatnik
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by beatnik

foz wrote:beatnik, I just found this thread, and after putting in my measurements, the results are all within 0.5cm of my current setup, so following your chart, I guess I'm pretty well set up already.
One thing that isn't clear from your chart though, is that on the first picture (of the litesped MTB), the saddle set back from the BB is at 8.6cm, with a comment that it's a very important measurement (which is true).
Later on, the stem length calculation is given for different setback seatposts. This is where I have to disagree with your chart - the stem length should always be the same, because the saddle position is fixed for a particular rider.
It is wrong to say that if I change my seatpost to one with different offset, then I should change my stem length to compensate. If I change my seatpost, it will clamp the saddle rails in another position, but the saddle position relative to BB will not change, so stem length will be the same.

foz


Sure, i´ve told before, stem calculation is an aproach, based in your frameset size and your seatpost (is not very accurate). You must always fit the orange lines, and that´s all, you can fit your bike with another seatpost or stem, but as an aproach it works great.

And yep 0.5 cm is almost a perfect fit, congrats :lol:
Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

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beatnik
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Joined: Thu Aug 03, 2006 6:38 pm

by beatnik

Ypsylon wrote:Given that beatnik is a fitting guy I'd assume that when he says that someone changes his seatpost it's to change the fit, not the color or weight or whatever.

If you keep your saddle position the same you obviously won't change your stem. But if you change your straight seatpost for one with setback to give you a different position you have to change your stem.

So you're not actually disagreeing with him, the way I see.


Exactly, if you read carefully i say "Saddle in the center of its rails", because it´s only an aproach.

But you are clever people, the correct order is this one

1st: Saddle-Bottom bracket seatback (you can measure it with a door, put the center of bb and measure your saddle nose setback) + Saddle height

2nd. Saddle nose -handlebar axis

3rd.- Saddle handlebar height (measure your saddle-floor height and your handlebar-floor height and substract)


With 2nd and 3rd point you can check the length of your perfect stem and its angle, how much you need to cut your fork or how many spacers you will need.

It´s not easy, but be patient and make little changes from the "perfect fit" if you don´t feel completely well (we are not Symmetrics )
Last edited by beatnik on Fri Jan 23, 2009 10:38 am, edited 3 times in total.
Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

foz
Posts: 151
Joined: Mon Sep 08, 2008 3:37 pm

by foz

OK, I think I understand what you're saying now. But isn't it better to base the stem length on the saddle position and not the seatpost? What I thought the chart was saying was that for any bicycle I could use an offset seatpost and shorter stem, or zero offset seatpost and longer stem, in each case clamping the saddle in the centre of the rails, but these two combinations obviously give very different riding positions.

I read in your first post that you're in Spain - where are you exactly? I'm in Valencia.

thanks, foz

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beatnik
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by beatnik

foz wrote:OK, I think I understand what you're saying now. But isn't it better to base the stem length on the saddle position and not the seatpost? What I thought the chart was saying was that for any bicycle I could use an offset seatpost and shorter stem, or zero offset seatpost and longer stem, in each case clamping the saddle in the centre of the rails, but these two combinations obviously give very different riding positions.

I read in your first post that you're in Spain - where are you exactly? I'm in Valencia.

thanks, foz


Sure i´m going to Valencia tomorrow for my ACL surgery :lol: I´m not kidding. I live in Alicante.

Saddle rails length is not always the same.
Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

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beatnik
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Joined: Thu Aug 03, 2006 6:38 pm

by beatnik

V8 including your flexibility (Microsoft Excel needed)

Install Winrar

http://www.rarlab.com/rar/wrar380.exe

And double-click in the part 01. That´s all.
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Last edited by beatnik on Fri Jan 23, 2009 12:17 pm, edited 1 time in total.
Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

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beatnik
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by beatnik

p2
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Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

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beatnik
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by beatnik

p3
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Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

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beatnik
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by beatnik

p4
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beatnik
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by beatnik

p5
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Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

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beatnik
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by beatnik

p6
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[The extension zip has been deactivated and can no longer be displayed.]

Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

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beatnik
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by beatnik

p7
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[The extension zip has been deactivated and can no longer be displayed.]

Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

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beatnik
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by beatnik

Same procedure than the previous version. Install winrar and double-click in the first part.

Regards.
Biomechanical spreadsheet. Sizing&Fitting.

http://weightweenies.starbike.com/forum ... 8e319d185b

dee
Posts: 333
Joined: Sun Dec 28, 2008 11:42 pm

by dee

What kind of Winrar?

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cryoplasm
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Joined: Wed Feb 20, 2008 11:20 pm

by cryoplasm

Why the distribution in such fashion? Put it in one composite ZIP or RAR file.

:?

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