New version V8. Biomechanical & sizing & fitting spreadsheet

A light bike doesn't replace good fitness.

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beatnik
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by beatnik

Thx fellows ;)
Biomechanical spreadsheet. Sizing&Fitting.

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

Super_fast
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by Super_fast

For my strange body this sheet doesn't work out. I have quite long legs (90.5 cm inseam, 1m88) and a short torso and short arms (48,5 cm).

My road bike has a 565 toptube with a 130 mm stem. It shouldn't be longer because then I coudn't grab my brakes anymore :wink: The last season I had a Ridley Excalibur, the frame has a long headtube so I mounted my stem without spacers. The drop between sadle and bars was something like 15 cm. Most people can deliver less power when their hip angle becomes smaller, but strangely it works almost the opposite way for me. I compare quite well to the Schleck brothers when it comes to bike fitting. :wink:

The Excel sheet want to put me on a 55 cm toptube with a woman's stem :lol: (10 cm). These are more the measurements of my cx. When I ride my CX I can for example see my fronthub before my bars when I ride with my hands on the hoods. On my roadbikes I see the fronthub below my handlebar with my hands on the hoods.

by Weenie


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Ant
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by Ant

Super_fast I found a similar thing. I think Beatnik's sheet works well for a lot of people but breaks down at the odd ends. This is no different to any other system though from what I can see.

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beatnik
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by beatnik

I ride a 9 cm stem and i´m not a woman, in my mtb i ride a 7.5. I´m 88 inseam, and 50 armlength and 1.87 tall. And i have short arms. But if you actually are 48.5, you have very short arms.

Nevertheless, a 13 cm stem means a wrong fitted bike. The perfect fit is considered with a 10 cm stem. And that´s all. Your saddle handlebar drop is huge, because your frameset size is wrong, and in fact it can´t be right with "standard framesets".

I ride a 58, with a 58.5 toptube. You must do the same. A 56 is small, and you would need an stem with very positive angle. Bigger frameset and shorter stem, the bike is uglier for sure.

That´s my point of view, but as usual, people use to fit their bikes according to their eyes. I can´t do anything about it. If you consider a 10 cm stem a "women´s stem", what can i say?.
Last edited by beatnik on Sat Dec 20, 2008 1:56 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

And the same can be told for Ant, i have spent a lot of time with him, but again he felt the bike twitchy and ugly with shorter stem, i can´t do anything about it. He rides a wrong size also, and is difficult to fit it well. Buying another one is not always posible, and fitting a wrong size oblies to put "non pro looking" stems or seatpost, if you prefer that your bike looks better, it´s your choice.

And please don´t say it´s another standard fit, i have spent a lot of time and money and pain riding "wrong sized bikes", because my inseam corresponds with a 56 ;)
Biomechanical spreadsheet. Sizing&Fitting.

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

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beatnik
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by beatnik

Just one thing more, your top tube measure is your best t.tube for a 10 cm stem and perfect fit. But nowadays bikes have std. geometries, and we can´t change them.

If you would buy a "custom frameset" these would be the measures you must order.

And my "best stem" calculation is an aproach as i told before. But actually you will find that your best stem is more or less +-1 cm, depending on your seatpost, ttube "real length" and saddle length.

If you feel better with your fit, it´s your choice, but perhaps you must measure your body or your bike again. Best regards
Biomechanical spreadsheet. Sizing&Fitting.

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

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Tapeworm
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by Tapeworm

beatnik wrote:...Nevertheless, a 13 cm stem means a wrong fitted bike. The perfect fit is considered with a 10 cm stem. And that´s all. Your saddle handlebar drop is huge, because your frameset size is wrong, and in fact it can´t be right with "standard framesets"...


I am curious as to how you come to this conclusion.

Why is 100mm stem perfect?

This is the point where I tend to disagree with you Beat.

Professionals are not the best place to look, however, I am sure you will find quite a few 130mm stems running around.

I believe the best size frame, stem, drop, set back etc is the one where the person is comfortable, addresses postural issues (if any), produces the most power, facilitates good handling and optimises aerodynamics (if applicable). If this necessitates a 150mm stem and a 50cm frame for someone who is 190 cms tall, then so be it. This may result in a setup and position that is wrong by conventional means.

Unless you have some solid data or studies to show me otherwise then I will maintain my belief that positioning requires a holistic outlook not a formulae.

That being said, if I were fitting someone to a bike, I would use something like your spreadsheet to start with. However I would not be concerned should the end result be far, far from this.

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Ant
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by Ant

beatnik wrote:And the same can be told for Ant, i have spent a lot of time with him, but again he felt the bike twitchy and ugly with shorter stem, i can´t do anything about it. He rides a wrong size also, and is difficult to fit it well. Buying another one is not always posible, and fitting a wrong size oblies to put "non pro looking" stems or seatpost, if you prefer that your bike looks better, it´s your choice.

And please don´t say it´s another standard fit, i have spent a lot of time and money and pain riding "wrong sized bikes", because my inseam corresponds with a 56 ;)


I rode a 90m stem for a long time and when I changed to the 110mm it jsut felt better. I also have more saddle to bar drop and again this took pressure off my lower back. It's not like I didn't try your system and I certainly never said it was bad.

Super_fast
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by Super_fast

@Beatnik, I like your idea very much, but with only inseam and armlength it isn't possible to calculate the right size in all circumstances. I tried to have some positive criticism, a free calculator for bike fitting would be ideal for everyone that doesn't know their size. I get every multiple questions when it comes to picking a size for a new bike.

I consider a 120 mm stem to be the standard for most roadbikes, only in small sizes the most optimal stem length is probably shorter. When you look in de pro peleton the smallest stems are 120 mm, most riders ride with 120-140 mm stems. Comparing to pro riders isn't a good idea when you're advising a recreational rider that only does a few hours in the weekend. But for someone who's competitive it isn't a bad idea.

When I would lower the height difference between my saddle and handlebars to only 9 cm I would change in a windscreen :lol: When you'd like to see them I could post some pictures of me on the bike. When you see them you'd probably say thay it looks cramped, but that's because of my upper back that is... can't find the right word in English (it is too round). But I am comfortable on the bike and I can get the power in my legs to the pedals. I haven't had problems with my shoulders, neck or back, even after 7 hours training or in the 8e day of a stage race.

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Amadeus
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by Amadeus

Just popping in to the discussion again.

There is said a lot about fitting already in this forum.

I just say that if you are able to find 3 people with exactly the same body measurements it will be most likely that the 3 will find a good starting point from the spread-sheet Beatnik provided. But this said I am 100% sure that after riding for some time/km and readjusting to their personal preferences the 3 will end up in different bike fit.

Body measurement is not all.
How supple is the body of the rider?
And other aspects are also of influence.

@super_fast

For your info: if your overall length is 188cm 90,5 inseam is within normal range and certainly not short! Your arms are short that is a fact.

NOTE: You have to take in account that due to my racing history I like small frames (for most of us 1cm + won’t matter at all).


Looking at your sizes and inseam I would recommend a frame in size 59cm (58,8 cm) c/c in classic geometry and classic tubing. That would be a frame in 60-60,5 c/t.

In modern/actual sizes with OS tubing that would translate in to a frame size 56 or 56,5 c/c which results also in 60-60,5 c/t.

For frame size the above mentioned seat tube measurements are old day style in measurement in c/c. Today it is easier to use c/t. This is due to variation in OS tubing. (but always translate to virtually classic frame measurements so you have to ad 3 up to 6 cm to a sloping frame depending on how much the top tube slopes).

Top tube is always measured in c/c.

Frames in this size have different top tube lengths.
-And the top tube length may be even more important then the seat tube length.
-Today with sloping geometry ruling, it is useful to look at head tube length and top tube length.

For instance:
- a Cervélo R3 in size 56 c/c (= approximately 60cm c/t) has a 73 degree seat tube angle and a top tube length of 56,5
- a Trek Madone 6.9 in size 60 c/t (M) has a 72,8 degree seat tube angle and top tube length of 58,6
- a Pinarello in 56,0 cm c/c (=approximately 60cm c/t) has a 73 degree seat tube angle and a top tube length of 56,5
- a Colnago Extreme Power traditional in 58 (=approximately 59,5-60cm c/t because Colnago measures height till seat-post clamp and not to top!) has a 72,83 degree seat tube angle and a top tube length of 56,5
- a GIOS in size 56 cm c/c (= approximately 60cm c/t) has a 74 degree seat tube angle and a top tube length of 56,0
We can conclude that most brands are using a standard geometry, no matter what they tell you. But you see Trek and GIOS are different Trek has a long top tube and GIOS a Short one, due to the steeper seat tube (the latter is a good thing for longer riders).

Due to these findings I believe your frame-size is O.K. if you use longer cranks (but like I already wrote I like small frames. So a bit taller frame is an option like Beatnik suggested).

Due to the fact that you have short arms the 13cm stem you mention is strange to me. I believe it should be shorter (but that is based on just this marginal info).

The drop of 15cm is a racers drop but could be O.K.. What you write about your power in relation to your hip angle is correct from Biomechanical views.

I can’t give you an exact advice because there is too much information missing.

Just some questions:
Do you use a seat post with or without set-back?
How much is your set-back?

If I have to judge from the data you provided I would say use a 10 or 11 stem … but I can’t be sure. Give some more info?

P.S.
To give you an indication (not to compare because you can’t compare different people)
My sizes are:
190cm long
My inseam is 93,5.
I ride two 58 c/c GIOS frames (62 cm c/t).
Top tube is 57 (nice short!)
Stem is 12cm
Drop is 13,5 cm (when I loose some more kg it will also be 15cm again)
Crank length is 180cm
My bike is Italian so it is Nervosa and of course has Anorexia I like them thin!
GIOS "New" Carbon Ultra 2006 Campa Record+Special parts.
GIOS "New" A90 2008 Campa Record+Special parts. My winter and vacation bike.

Burning Dogma
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Joined: Sat Oct 04, 2008 5:14 pm
Location: Portugal

by Burning Dogma

Hi guys,

I'm 1.82m, 84.5cm inseam and 48.7cm elbow-middle finger distance (hope those are well measured). My bike is a 57 (56.5 top tube) and i'm running a 90mm stem (83mm recommended by the sheet). This sheet recommends 8cm setback and 75.2cm saddle height and that's how my bike is fitted. But since I bought my bike and even after fitting it according to this sheet, I feel neck pain after about 2, 2.30h in the saddle. My bike came with a 110mm stem and after some months I changed it to a 90mm. It felt a little better, but I still feel neck pain. Should I run a little bit less setback, like 7.5cm?

Thanks

Super_fast
Posts: 341
Joined: Tue Nov 01, 2005 9:36 am

by Super_fast

Some pictures, so everyone can judge me :wink:

Image

On a steep (10% avarage, but it's Holland so after 1k you're on the top):
Image

Image

And the last corner in the same race (the only one I won this season)
Image

The bikes are Ridley Excalibur in size M (toptube 565 mm, headtube 175), no spacers, 130 mm stem, oval seatpost (28 mm set-back). When I look at the pictures my postion doesn't seem to be so strange. I like to sit a bit stretched on my roadbike.

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Amadeus
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Location: Leiden, NETHERLANDS

by Amadeus

Looks O.K. to me.

Like I said I like small frames my-self.

Pretty stretched but if you are comfortable with this fit it is O.K.

You could also ride a size bigger and a shorter stem. It wouldn't make difference.
My bike is Italian so it is Nervosa and of course has Anorexia I like them thin!
GIOS "New" Carbon Ultra 2006 Campa Record+Special parts.
GIOS "New" A90 2008 Campa Record+Special parts. My winter and vacation bike.

Rezne
Posts: 33
Joined: Mon Jul 07, 2008 3:54 pm
Location: the Netherlands

by Rezne

I find that the spreadsheet puts me in a shorter position, compared to my current position (about 4 cm).
I ride a CR1, size L (Toptube 56 cm, heatube 17 cm) with a 120 mm stem. The spreadsheet 'tells' me to get a 85 mm stem.

I'm 1m 85 with 94 cm inseam. Fairly long legs. Like Super Fast i have quite a big drop: 16 cm

My new bike will be a different brand. One sizer larger: with a 58 cm toptube and a 18 cm headtube. We'll see how that works out.

Next monday i'll be fitted on my bike by an expert. I'll let you know what the result is. I'm curious to know the difference between my current position, the spreadsheet position and the new position.
Let the legs do the talking

by Weenie


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beatnik
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by beatnik

Tapeworm wrote:
beatnik wrote:...Nevertheless, a 13 cm stem means a wrong fitted bike. The perfect fit is considered with a 10 cm stem. And that´s all. Your saddle handlebar drop is huge, because your frameset size is wrong, and in fact it can´t be right with "standard framesets"...


I am curious as to how you come to this conclusion.

Why is 100mm stem perfect?

This is the point where I tend to disagree with you Beat.

Professionals are not the best place to look, however, I am sure you will find quite a few 130mm stems running around.

I believe the best size frame, stem, drop, set back etc is the one where the person is comfortable, addresses postural issues (if any), produces the most power, facilitates good handling and optimises aerodynamics (if applicable). If this necessitates a 150mm stem and a 50cm frame for someone who is 190 cms tall, then so be it. This may result in a setup and position that is wrong by conventional means.

Unless you have some solid data or studies to show me otherwise then I will maintain my belief that positioning requires a holistic outlook not a formulae.

That being said, if I were fitting someone to a bike, I would use something like your spreadsheet to start with. However I would not be concerned should the end result be far, far from this.



13 cm stem means a bad fitted bike, that´s all. Well at least the bike frameset is not made for you, that´s what i ment.

Nevertheless, i think you must measure your body better, Superfast has quite normal arms, and not very short.

My spreadsheet is a guide, i have another version considering "back flexibility", but again is not worthy, you can find your best fit according to the sheet, and just "give your touch" to finish. Same can be told for Ant, his body measures must be reviewed.

The one who has neck pain, perhaps you must try another handlebar, yours seems to be wider than you need.
Biomechanical spreadsheet. Sizing&Fitting.

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

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