Fit Questions

hi, is there an easy way to determine proper stem length (assuming you
already have the correct size frame)? maybe an approximate angle your
elbows should be bent when on the hoods/drops?

also, is there an easy way to determine proper seat fore/aft position
on the rails? maybe a certain length behind the bb, or is it just
based on feel? thanks!

wrote in message
ups.com...
hi, is there an easy way to determine proper stem length (assuming you
already have the correct size frame)? maybe an approximate angle your
elbows should be bent when on the hoods/drops?

also, is there an easy way to determine proper seat fore/aft position
on the rails? maybe a certain length behind the bb, or is it just
based on feel? thanks!


A quick guide to stem length. when holding the drops the bars should
approximately obscure the centre of the front hub, this is normally a fairly
decent starting position. as for seat fore and aft whatever comfortable
should do it, a combination of both the previous should sort you out but I
try and keep the seat fairly central then sort out the stem length.

cheers
Jon_H

wrote:
hi, is there an easy way to determine proper stem length (assuming you
already have the correct size frame)? maybe an approximate angle your
elbows should be bent when on the hoods/drops?

also, is there an easy way to determine proper seat fore/aft position
on the rails? maybe a certain length behind the bb, or is it just
based on feel? thanks!


I think that both are based on feel & comfort. Since those 2 factors are
so related, I think it makes the most sense to set your "effective seat
tube angle" with the saddle fore/aft position, then get a stem that's a
comfortable height & reach. General rule is the flatter you want your
back, the steeper your seat tube angle needs to be. Back angle is
strictly a matter of personal preference (not to mention flexibility).

Peter Cole wrote:
wrote:
hi, is there an easy way to determine proper stem length (assuming you
already have the correct size frame)? maybe an approximate angle your
elbows should be bent when on the hoods/drops?

also, is there an easy way to determine proper seat fore/aft position
on the rails? maybe a certain length behind the bb, or is it just
based on feel? thanks!


I think that both are based on feel & comfort. Since those 2 factors are
so related, I think it makes the most sense to set your "effective seat
tube angle" with the saddle fore/aft position, then get a stem that's a
comfortable height & reach. General rule is the flatter you want your
back, the steeper your seat tube angle needs to be.

Just the opposite, as the ST gets steeper, and the position of the
saddle in reference to the seatpost stays the same, the rider will get
closer to the hbars, making them more upright BUT KOPS, a small and
variable 'constant' will indirectly measure femur length and also
determine 'best' seatube angle. After finding this and height of the
saddle, then the top tube, stem lengths can be determined along with
Hbar width..these depending on the rider's needs, desires, flexibility,
etc.

Back angle is
strictly a matter of personal preference (not to mention flexibility).

Qui si parla Campagnolo wrote:
Peter Cole wrote:

wrote:

hi, is there an easy way to determine proper stem length (assuming you
already have the correct size frame)? maybe an approximate angle your
elbows should be bent when on the hoods/drops?

also, is there an easy way to determine proper seat fore/aft position
on the rails? maybe a certain length behind the bb, or is it just
based on feel? thanks!


I think that both are based on feel & comfort. Since those 2 factors are
so related, I think it makes the most sense to set your "effective seat
tube angle" with the saddle fore/aft position, then get a stem that's a
comfortable height & reach. General rule is the flatter you want your
back, the steeper your seat tube angle needs to be.


Just the opposite, as the ST gets steeper, and the position of the
saddle in reference to the seatpost stays the same, the rider will get
closer to the hbars, making them more upright BUT KOPS, a small and
variable 'constant' will indirectly measure femur length and also
determine 'best' seatube angle. After finding this and height of the
saddle, then the top tube, stem lengths can be determined along with
Hbar width..these depending on the rider's needs, desires, flexibility,
etc.

Both Keith Bontrager and Gary Klein disagree with the use of KOPS and
present some pretty reasonable arguments:

http://www.sheldonbrown.com/kops.html
http://web.archive.org/web/19980201073043/www.kleinbikes.com/Technology/Myth/Knee_Over.html

Bontrager seems to concentrate on climbing (seated and standing)
positions, while Klein is more about just locating rider CG to BB
distance (independent of KOPS) for comfortable seated riding.

I tend to favor the Klein approach, locating my CG first with the saddle
position (given that I can't change my seat tube angle), then setting
bar height and reach with the stem choice to get the right cockpit
length and bar height. It's been somewhat of a moving target though as
over the years I've wanted to get my back flatter which closes up my
hips too much (thighs hit ribs), so I've been forced to a more forward
saddle position and longer reach stems. I find that spending a few hours
total on the trainer spread out over a few days is the only way to get
things really dialed in.

On Tue, 10 Jan 2006 11:41:53 -0500, Peter Cole wrote:

Qui si parla Campagnolo wrote:
Peter Cole wrote:

wrote:

hi, is there an easy way to determine proper stem length (assuming you
already have the correct size frame)? maybe an approximate angle your
elbows should be bent when on the hoods/drops?

also, is there an easy way to determine proper seat fore/aft position
on the rails? maybe a certain length behind the bb, or is it just
based on feel? thanks!


I think that both are based on feel & comfort. Since those 2 factors are
so related, I think it makes the most sense to set your "effective seat
tube angle" with the saddle fore/aft position, then get a stem that's a
comfortable height & reach. General rule is the flatter you want your
back, the steeper your seat tube angle needs to be.


Just the opposite, as the ST gets steeper, and the position of the
saddle in reference to the seatpost stays the same, the rider will get
closer to the hbars, making them more upright BUT KOPS, a small and
variable 'constant' will indirectly measure femur length and also
determine 'best' seatube angle. After finding this and height of the
saddle, then the top tube, stem lengths can be determined along with
Hbar width..these depending on the rider's needs, desires, flexibility,
etc.

Both Keith Bontrager and Gary Klein disagree with the use of KOPS and
present some pretty reasonable arguments:

http://www.sheldonbrown.com/kops.html
http://web.archive.org/web/19980201073043/www.kleinbikes.com/Technology/Myth/Knee_Over.html

Bontrager seems to concentrate on climbing (seated and standing)
positions, while Klein is more about just locating rider CG to BB
distance (independent of KOPS) for comfortable seated riding.

I tend to favor the Klein approach, locating my CG first with the saddle
position (given that I can't change my seat tube angle), then setting
bar height and reach with the stem choice to get the right cockpit
length and bar height. It's been somewhat of a moving target though as
over the years I've wanted to get my back flatter which closes up my
hips too much (thighs hit ribs), so I've been forced to a more forward
saddle position and longer reach stems. I find that spending a few hours
total on the trainer spread out over a few days is the only way to get
things really dialed in.

How about having the stem and bars set so that in sprint position from drops and
climb from tops the shoulder, hand and tire contact patch are all in line for
smoothness. The saddle is set to allow one to pivot on a foot at bottom of the
crank circle into standing moving your CG in an arc without effort and this
coincidently leaves me balanced on the bike in normal seated pedalling with my
butt back for motoring along or up on the rivet as well as doing a rough ground
hover.

That's the theory I'm working from on my new cross bike anyway and it's fitting
like I've ridden it all my life. Now maybe I'm thinking Cross and that's why all
the variations on standing and transitioning to and from and all the varied
seated positions seem so important to me. Maybe someone who rides less busy
would have different criteria. Still this is all stuff we all do on a bike.

Anyhow, there's an awful lot of ways of looking at this problem. The amazing
thing is that there's thousands of theories and most of them work. Of course
there's riders of all shapes and sizes to make 'em work - any doubt look at the
podium from the last Olympic road race.

Ron

RonSonic wrote:
...
That's the theory I'm working from on my new cross bike anyway and it's fitting
like I've ridden it all my life. Now maybe I'm thinking Cross and that's why all
the variations on standing and transitioning to and from and all the varied
seated positions seem so important to me. Maybe someone who rides less busy
would have different criteria. Still this is all stuff we all do on a bike....

Who is we, upright man?

--
Tom Sherman - Fox River Valley Pedant

On 10 Jan 2006 20:26:34 -0800, "Johnny Sunset" wrote:


RonSonic wrote:
...
That's the theory I'm working from on my new cross bike anyway and it's fitting
like I've ridden it all my life. Now maybe I'm thinking Cross and that's why all
the variations on standing and transitioning to and from and all the varied
seated positions seem so important to me. Maybe someone who rides less busy
would have different criteria. Still this is all stuff we all do on a bike....

Who is we, upright man?

"We" is the people who can ride in the woods get off the pavement and go ride
single-track.

Ron

Peter Cole wrote:

etc.

Both Keith Bontrager and Gary Klein disagree with the use of KOPS and
present some pretty reasonable arguments:


Place to start only and a small 'c' constant. Yu have to start
somewhere and KOPS, when used in that vein, is a great place to start
and also in general, a way to prevent injury while making the best
amount of power. CG is nice but almost impossible to find.

Per RonSonic:
The saddle is set to allow one to pivot on a foot at bottom of the
crank circle into standing moving your CG in an arc without effort and this
coincidently leaves me balanced on the bike in normal seated pedalling with my
butt back for motoring along or up on the rivet as well as doing a rough ground
hover.

That's the theory I'm working from on my new cross bike anyway and it's fitting
like I've ridden it all my life.

Before getting a Seven Duo to fit my statistical outlier of a body, I went
through three off-the-shelf frames and two customs which were set up any way I
could to feel comfortable.

Seven, of course, told me to go pound sand when I offered my supposedly helpful
suggestions on what frame dimensions to use.

Lucky for me...

The thing about the Duo that hit me first and hardest was that I could go from
sitting on the saddle to just touching the saddle to completely out of the
saddle with no apparent change in the bike's balance - a totally smooth
transition. Might sound trivial, but I think it's a big part of why this bike
rides so much better than own abortive attempts to make a bike work for me.
--
PeteCresswell