Proper Frame Sizing & Fit per Wrench Science

[Hkek]

I was surprised to learn that I should be riding a 17" frame when I put my body dimensions in into
the MTB fit calculator at:

http://www.wrenchscience.com

My 3 bikes have 19" frames (Gary Fisher and Jamis MTBs). I also have a 17" Trek MTB, but I have
never been comfortable on it. Even on my 19s I have the seat set as far rearward as possible.

Have I learned to ride on the wrong geometry frame? What other good (reputable) web sites exists
that can determine ideal frame size/fit?

 

[Qui Si Parla Ca]

HKEK-<< I was surprised to learn that I should be riding a 17" frame when I put my body dimensions
in into the MTB fit calculator at: >><BR><BR>

These online and over the phone formulas are some place to start only. The onbly way to
get a proper fit is hands on, via a fit person, with you on a fit cycle or you on an
existing bike.

The fallicy of most of these is that don't take into account femur length, the start of any
really good fit. Inseam means little...

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

[Rick Onanian]

On 16 Aug 2003 18:22:55 -0700, HKEK <[email protected]> wrote:
> I was surprised to learn that I should be riding a 17" frame when I put my body dimensions in into
> the MTB fit calculator at: http://www.wrenchscience.com
>
> My 3 bikes have 19" frames (Gary Fisher and Jamis MTBs). I also have a 17" Trek MTB, but I have
> never been comfortable on it. Even on my 19s I have the seat set as far rearward as possible.

The seat set as far rearward as possible is not solely an issue of frame size; combine it with stem,
seat tube angle, and seatpost setback.

You could get a longer stem, and a set-back seatpost, for the bikes where you feel you need to
stretch more.

> Have I learned to ride on the wrong geometry frame? What other good (reputable) web sites exists
> that can determine ideal frame size/fit?

You possibly have. However, what you're comfortable on is, by my definition, the right size frame;
so a 19" is your size, regardless of what a computer says. You're body doesn't lie.

http://www.bsn.com/Cycling/ergobike.html http://www.peterwhitecycles.com/fitting.htm
http://www.sheldonbrown.com/frame-sizing.html

Also look on bike manufacturers' websites for sizing guides. Many, or even most, have some useful
information.
--
Rick Onanian

 

[Hkek]

Femur length? Is there a good way to measure that without an x-ray? Is there some sort of
chart/graph relating frame size to femur length? -- thanks!

[email protected] (Qui si parla Campagnolo) wrote in message
news:<[email protected]>...
> HKEK-<< I was surprised to learn that I should be riding a 17" frame when I put my body dimensions
> in into the MTB fit calculator at: >><BR><BR>
>
> These online and over the phone formulas are some place to start only. The onbly way to get
> a proper fit is hands on, via a fit person, with you on a fit cycle or you on an existing
> bike.
>
> The fallicy of most of these is that don't take into account femur length, the start of any
> really good fit. Inseam means little...
>
>
>
> Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
> (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

[Sheldon Brown]

HKEK wrote:
> Femur length? Is there a good way to measure that without an x-ray?

Measure crotch height standing, and also kneeling. Subtract.

Sheldon "Close Enough" Brown +---------------------------------------------------------+
| There are several good protections against temptation, | but the surest is cowardice. --Mark
| Twain |
+---------------------------------------------------------+ Harris Cyclery, West Newton,
Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts
shipped Worldwide http://captainbike.com http://sheldonbrown.com

 

[Ian Lilly]

Sheldon Brown wrote:

> HKEK wrote:
>
>> Femur length? Is there a good way to measure that without an x-ray?
>
>
> Measure crotch height standing, and also kneeling. Subtract.
>
> Sheldon "Close Enough" Brown +---------------------------------------------------------+
> | There are several good protections against temptation, | but the surest is cowardice. --Mark
> | Twain |
> +---------------------------------------------------------+ Harris Cyclery, West Newton,
> Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts
> shipped Worldwide http://captainbike.com http://sheldonbrown.com
>
Wouldn't that give the lower leg length?

 

[Rick Onanian]

On Wed, 20 Aug 2003 14:27:28 +1000, Ian Lilly <[email protected]> wrote:
>>> Femur length? Is there a good way to measure that without an x-ray?
>> Measure crotch height standing, and also kneeling. Subtract.
>>
>> Sheldon "Close Enough" Brown
>>
> Wouldn't that give the lower leg length?

No, it would subtract lower leg length. Actually, you could use that method to get both, obviously.

I'd say, just guess where the center of the joint is (at knee and butt), and measure. It should be
easy to get sufficient accuracy.

--
Rick Onanian

 

[Jim Adney]

On Wed, 20 Aug 2003 16:10:47 -0400 Rick Onanian <[email protected]> wrote:

>On Wed, 20 Aug 2003 14:27:28 +1000, Ian Lilly <[email protected]> wrote:
>>>> Femur length? Is there a good way to measure that without an x-ray?
>>> Measure crotch height standing, and also kneeling. Subtract.
>>>
>>> Sheldon "Close Enough" Brown
>>>
>> Wouldn't that give the lower leg length?
>
>No, it would subtract lower leg length. Actually, you could use that method to get both, obviously.

No, it subtracts the ~upper leg length (that's what the crotch height kneeling is) leaving just the
lower leg and foot portion. If you go back and subtract that from the crotch height standing you'll
just get back the crotch height kneeling figure, which, by itself is probably a pretty good measure
of femur length.

>I'd say, just guess where the center of the joint is (at knee and butt), and measure. It should be
>easy to get sufficient accuracy.

I agree.

-
-----------------------------------------------
Jim Adney [email protected] Madison, WI 53711 USA
-----------------------------------------------

 

[Tim McNamara]

In article <[email protected]>, [email protected] (Qui si parla
Campagnolo) wrote:

> coolmate-<< Femur length? Is there a good way to measure that without an x-ray?>>
>
> Yes, directly using a straight edge while the person is sitting, indirectly on a fit cycle. Since
> femur length(NOT inseam) determines proper seattube angle and saddle positioning, which affects
> everything else in the fit, a measurment of it is essential.

Ummm, you're still not measuring femur length. If you want to be acurate, femur length should be
measured between the dynamic center of the hip, which is not accessible to external measurement
without some sp[ecialized equipment, and the lower condyle's contact surface with the tibial contact
surface- also not easily measured.

But the point made by Sheldon is quite correct: close enough is close enough. You don't need an
exact measurement of any of the lengths of the various limbs and such. It sounds more scientific and
makes people feel better about spending $5,000 on a bike, even though the simple standover method
can prvide a perfectly comfortable fit for the majority of people.

> Why formulas and on line things are a starting place and are incomplete.

This is certainly something I agree with. For heaven's sake, bike fit is adjustable and bodies are
adaptable. Ever since Lemond published Guimard's measurement ideas in his book, and Hinault
detailing them quite a bit further in his book (and both harking back to the CONI book), we've
thought that just measuring bone length can give us proper fit. It doesn't, and I think Peter's
point in this regard is very well taken. Fit is also affected by intended purpose, strength,
flexibility, etc.