Bike fit: saddle-to-bar drop and seat tube angle?

mike anderson wrote:

After reading up about ’length of top tube’ at RBT archives on Google,
I stumbled on this message:
-----------------------------------------
For my money, there are only 2 important dimensions: toptube length and
seattube angle. If you get those right, you can tweak everything else.
No fit kit can tell you what your ideal saddle to bar drop (or rise)
should be, that's all personal preference, ditto for bar width. Knowing
your desired saddle to bar drop, you can avoid buying a frame that
would require awkward stems or risers to get the bar height you want. A
wrong toptube length is a disaster. You can fudge around it by sizing
stem reach & saddle position, but that screws up weight distribution
and steering response. Seattube angle sets the angle of the hips for a
given bar drop. Generally, if you want your bars really low, you want a
steep seattube angle or else you'll be too closed at the hip. The only
dimension the fit kit needs to really help you with is toptube length,
that, and your personal preference for bar height determine almost
everything else.
---------------------------------------------------

Can somebody tell me what the preferred seat tube angle would be for a
saddle-to-bar drop of: 0cm (yes I like to have the saddle and handle
bar leveled)?

Seat tube angle doesn't determine where the saddle ends up... only the
RANGE of fore/aft positioning possible. Most bikes have "average
enough" seat tube angles that you can get the proper position by
choosing the right seat post (with or without setback), and then
adjusting the saddle accordingly.

The seat tube angle DOES affect the "cockpit length" relative to the
listed top tube length. Since the saddle's position is determined by
the rider's position on the bike, it will be in the same place
regardless of seat tube angle. If the bike has a steeper seat tube,
that places the saddle further behind the top tube/seat tube junction,
effectively lengthening the cockpit. If the seat tube is shallower,
the opposite is true.

Neither condition really affects the ability to get the bars up as
high as you need them, however. You just need to be sure that the top
tube horizontal component plus the stem's reach add up to the "cockpit
length" you need.

To get some info on how a stem's rise and length affect the horizontal
and vertical positioning of the bars, check out my infamous stem chart
at: http://www.habcycles.com/fitting.html

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

"mike anderson" wrote in message
news:2005110201511816807%seeunderneath@mypostcom.. .
After reading up about 'length of top tube' at RBT archives on Google,
I stumbled on this message:
-----------------------------------------
For my money, there are only 2 important dimensions: toptube length and
seattube angle. If you get those right, you can tweak everything else.
No fit kit can tell you what your ideal saddle to bar drop (or rise)
should be, that's all personal preference, ditto for bar width. Knowing
your desired saddle to bar drop, you can avoid buying a frame that
would require awkward stems or risers to get the bar height you want. A
wrong toptube length is a disaster. You can fudge around it by sizing
stem reach & saddle position, but that screws up weight distribution
and steering response. Seattube angle sets the angle of the hips for a
given bar drop. Generally, if you want your bars really low, you want a
steep seattube angle or else you'll be too closed at the hip. The only
dimension the fit kit needs to really help you with is toptube length,
that, and your personal preference for bar height determine almost
everything else.
---------------------------------------------------

Can somebody tell me what the preferred seat tube angle would be for a
saddle-to-bar drop of: 0cm (yes I like to have the saddle and handle
bar leveled)?

Thanks
mike anderson

email: sbREMOVE46©bigREMOVEfoot.com

remove REMOVE

It sounds to me that you, depending on your size, would be more comfortable
on a bike with a slack seat tube angle (71-73deg).. Great for climbing, long
distance riding, and good stability in wet/ icy conditions. triatheletes
tend toward a steeper 75+ deg angle, which typically has them forward,
hunkered down over aerobars.
Your size might mitigate the seat tube able preference in that if you are
short in height, the seat tube angle might need to be a bit steeper;
vice-versa if you happen to be tall.

Laz

After reading up about ’length of top tube’ at RBT archives on Google,
I stumbled on this message:
-----------------------------------------
For my money, there are only 2 important dimensions: toptube length and
seattube angle. If you get those right, you can tweak everything else.
No fit kit can tell you what your ideal saddle to bar drop (or rise)
should be, that's all personal preference, ditto for bar width. Knowing
your desired saddle to bar drop, you can avoid buying a frame that
would require awkward stems or risers to get the bar height you want. A
wrong toptube length is a disaster. You can fudge around it by sizing
stem reach & saddle position, but that screws up weight distribution
and steering response. Seattube angle sets the angle of the hips for a
given bar drop. Generally, if you want your bars really low, you want a
steep seattube angle or else you'll be too closed at the hip. The only
dimension the fit kit needs to really help you with is toptube length,
that, and your personal preference for bar height determine almost
everything else.
---------------------------------------------------

Can somebody tell me what the preferred seat tube angle would be for a
saddle-to-bar drop of: 0cm (yes I like to have the saddle and handle
bar leveled)?

Thanks
mike anderson

email: sbREMOVE46©bigREMOVEfoot.com

remove REMOVE

"Laz" wrote in message
...

snip

Your size might mitigate the seat tube able preference in that if you are
short in height, the seat tube angle might need to be a bit steeper;
vice-versa if you happen to be tall.

Laz


Why do shorter riders need steeper seat angles?

Peter

"vesel" wrote in message
...

"Laz" wrote in message
...

snip

Your size might mitigate the seat tube able preference in that if you
are
short in height, the seat tube angle might need to be a bit steeper;
vice-versa if you happen to be tall.

Laz


Why do shorter riders need steeper seat angles?

Peter


I think that leg length is the given reason, you must remember that crank
length is fairly consistent at 170mm for most road bikes.

Laz

"Laz" wrote in message
.. .

"vesel" wrote in message
...

"Laz" wrote in message
...

snip

Your size might mitigate the seat tube able preference in that if you
are
short in height, the seat tube angle might need to be a bit steeper;
vice-versa if you happen to be tall.

Laz


Why do shorter riders need steeper seat angles?

Peter


I think that leg length is the given reason, you must remember that crank
length is fairly consistent at 170mm for most road bikes.

Laz


I keep hearing leg length is the reason but it doesn't make sense to me. Leg
length is generally in proportion to height. I am a short arse because I
have short legs and a short body. So proportionally I am the same as a
taller person. So why not the same seat angle.


Peter

Dans le message de ,
vesel a réfléchi, et puis a déclaré :
"Laz" wrote in message
.. .

"vesel" wrote in message
...

"Laz" wrote in message
...

snip

Your size might mitigate the seat tube able preference in that if
you are short in height, the seat tube angle might need to be a
bit steeper; vice-versa if you happen to be tall.

Laz


Why do shorter riders need steeper seat angles?

Peter


I think that leg length is the given reason, you must remember that
crank length is fairly consistent at 170mm for most road bikes.

Laz


I keep hearing leg length is the reason but it doesn't make sense to
me. Leg length is generally in proportion to height. I am a short
arse because I have short legs and a short body. So proportionally I
am the same as a taller person. So why not the same seat angle.


Kind of simple, really. You need to have clearance for the rear wheel, and
there are limits of useful variations for the bottom bracket height and
chainstay lengths.

Using 650 wheels allows for more play with the seat-tube angle.
--
Bonne route !

Sandy
Verneuil-sur-Seine FR

vesel wrote:
"Laz" wrote in message
...

snip

Your size might mitigate the seat tube able preference in that if you are
short in height, the seat tube angle might need to be a bit steeper;
vice-versa if you happen to be tall.

Laz


Why do shorter riders need steeper seat angles?

Peter

Because they generally have shorter femurs and altho not a hard
constand, knee over pedal spndle is a great place to start.

If the femur is short and the seat tube is slack, not able to get the
KOPS, even with a no setback seat post and the saddle all the way
forward.

"Qui si parla Campagnolo" wrote in message
oups.com...

vesel wrote:
"Laz" wrote in message
...

snip

Your size might mitigate the seat tube able preference in that if you
are
short in height, the seat tube angle might need to be a bit steeper;
vice-versa if you happen to be tall.

Laz


Why do shorter riders need steeper seat angles?

Peter

Because they generally have shorter femurs and altho not a hard
constand, knee over pedal spndle is a great place to start.

If the femur is short and the seat tube is slack, not able to get the
KOPS, even with a no setback seat post and the saddle all the way
forward.


Ok I can accept my femur may be shorter, but so is my lower leg, trunk
length arm length etc.
So overall all measurements are shorter.
That being the case then the seat tube angle should be similar, just top
tube length on standover height should change.

Peter

vesel wrote:

Ok I can accept my femur may be shorter, but so is my lower leg, trunk
length arm length etc.
So overall all measurements are shorter.
That being the case then the seat tube angle should be similar, just top
tube length on standover height should change.

KOPS is knee over pedal spindle with the crank horizontal. If you
follow that philosophy, *and* you use standard sized cranks
(170-175mm), then you will be positioned farther forward (steeper seat
angle) if you are short, and farther back if you are tall. Everything
about your body may be proportional, but the cranks aren't.

KOPS is really just an approximation that generally works out to a
balanced position for most people... meaning that with a level seat and
a normal pedalling stroke they will not tend to slide forward or back.