# Frame geometery

Discussion in 'Cycling Equipment' started by Colin Marshall, Aug 17, 2004.

1. ### Colin Marshall Guest

Hi,

I have a frame with a 72 seat angle 57.5 top tube and 55(c-c) seat tube with
a 120 stem.

It has been suggested that a 73 seat tube with a 56.5 top tube and a 120
stem is exactly the same.

My maths is not that good, are the equivalent?

Thanks

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2. ### Qui si parla Campagnolo Guest

cpm-<< I have a frame with a 72 seat angle 57.5 top tube and 55(c-c) seat tube
with
a 120 stem.

It has been suggested that a 73 seat tube with a 56.5 top tube and a 120
stem is exactly the same. >><BR><BR>
<< My maths is not that good, are the equivalent? >><BR><BR>

Essentially. General rule of thumb is as you change the seattube angle by one
degree, and moving your saddle forward or aft ro accomodate this to retain
KOPS, you move it 1cm.

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

3. ### Bruce Frech Guest

the setback of the toptube and seattube intersection is cos(angle) times
seattube length. So the difference between a 72 and a 73 seat angle for a
55 C-C seattube is:

55cm * (cos(72) - cos(73)) = 0.924 cm, which is close enough to one

Bruce

"Colin Marshall" <[email protected]> wrote in message
news:[email protected]
> Hi,
>
> I have a frame with a 72 seat angle 57.5 top tube and 55(c-c) seat tube

with
> a 120 stem.
>
> It has been suggested that a 73 seat tube with a 56.5 top tube and a 120
> stem is exactly the same.
>
> My maths is not that good, are the equivalent?
>
> Thanks
>
>
>