Frame Sizing again !

"Graham" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

What is the difference between a bike with a 73.25 deg. seat tube and

54.5cm

Quoted message said:

top tube, and a bike with a 74 deg. seat tube and a 54.3 cm top tube ?

Which

Quoted message said:

one has the longer top tube ? I am setting the saddle to pedal position on both bikes the same but
the second bike works out longer to the levers

than

Quoted message said:

the first. Despite both having 11 cm stems ! Can anyone help.

Graham

Well, the one with the longer top-tube has the longer top-tube. I think it depends what you're doing
with the saddle. Assuming both frames have 53cm seatposts (you didn't specify) the top of the seat
post on the
55.25 degree frame will be 0.67cm further behind the bottom bracket than for the 74 degree frame.
The difference at the saddle will be greater. If you're pushing the saddle on the 73.25 degree
frame forward on its rails to correct for this difference you'll end up with a shorter distance
between saddle and bars than on the 74 degree frame. Is this the effect you're seeing?

Michael MacClancy

Graham said:

What is the difference between a bike with a 73.25 deg. seat tube and 54.5cm top tube, and a bike
with a 74 deg. seat tube and a 54.3 cm top tube ? Which one has the longer top tube ? I am setting
the saddle to pedal position on both bikes the same but the second bike works out longer to the
levers than the first. Despite both having 11 cm stems ! Can anyone help.

According to my quick calculations, everything else being equal, on the second bike the distance
from the saddle to the handlebar should be 0.5 centimetres longer. This is because the top tube,
even if it's slightly shorter, connects to the seat tube closer to the bottom bracket horizontally.

This is only true if the saddle is set fore-aft exactly the same amount behind the bottom bracket on
both bikes. If you use the same seat post and saddle, on the bike with a 73.25-degree seat tube the
saddle should be positioned more forward relative to the seat post clamp or it will be farther
behind the bottom bracket, increasing the difference you are experiencing.

Of course, these differences are really small. I don't think calculations like this are very
meaningful because you can't really count on the accuracy of the manufacturer's frame geometry. If
the difference really bugs you, just use a slightly shorther stem on the second bike.

-as

Graham said:

What is the difference between a bike with a 73.25 deg. seat tube and 54.5cm top tube, and a bike
with a 74 deg. seat tube and a 54.3 cm top tube ? Which one has the longer top tube ? I am setting
the saddle to pedal position on both bikes the same but the second bike works out longer to the
levers than the first. Despite both having 11 cm stems ! Can anyone help.

These are very small differences. I'll assume you have the saddle and stem heights adjusted the same
on both bikes and that the cranks are the same length. The distance to the levers could be due to
the handlebar shape and/or where the levers are mounted on the bars.

Making the KOPS measurement to within a couple of mm isn't easy; just moving slightly on the saddle
can make a difference. I wouldn't worry as long as you're setup is within 1 cm on the two bikes. How
much difference are you seeing?

Art Harris

To compare top tube lengths on frames with different seat tube angles, measure from the bottom
bracket forward.

Top_Tube_Length - (COS(Seat_Tube_Angle) * Seat_Tube_Length)
--
David Blackburn

"Graham" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

What is the difference between a bike with a 73.25 deg. seat tube and

54.5cm

Quoted message said:

top tube, and a bike with a 74 deg. seat tube and a 54.3 cm top tube ?

Which

Quoted message said:

one has the longer top tube ? I am setting the saddle to pedal position on both bikes the same but
the second bike works out longer to the levers

than

Quoted message said:

the first. Despite both having 11 cm stems ! Can anyone help.

Graham

graham-<< What is the difference between a bike with a 73.25 deg. seat tube and
54.5cm top tube, and a bike with a 74 deg. seat tube and a 54.3 cm top tube ? << Which one has the
longer top tube ?

The 54.5cm is longer.

<< I am setting the saddle to pedal position on both bikes the same but the second bike works out
longer to the levers than the first.

Saddle to pedal position isn't going to work unless you put your knee in the same place on both
framesets. So, if you knee is proper on the 73.25 degree one, then it needs to slide back on the 74
degree one... .75 of a cm, which increases top tube(effectively) of the second bike . Also, need to
have the seat height the same and also have the headtube angle the same...

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(55)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

"Qui si parla Campagnolo" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

graham-<< What is the difference between a bike with a 73.25 deg. seat

tube and

Quoted message said:

54.5cm top tube, and a bike with a 74 deg. seat tube and a 54.3 cm top tube ? << Which one has the
longer top tube ?

The 54.5cm is longer.

<< I am setting the saddle to pedal position on both bikes the same but the second bike works out
longer to the levers

than

Quoted message said:

the first.

Saddle to pedal position isn't going to work unless you put your knee in

the

Quoted message said:

same place on both framesets. So, if you knee is proper on the 73.25

degree

Quoted message said:

one, then it needs to slide back on the 74 degree one... .75 of a cm,

which

Quoted message said:

increases top tube(effectively) of the second bike . Also, need to have

the

Quoted message said:

seat height the same and also have the headtube angle the same...

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

Thanks for all the replies so quickly, and very useful too ! I should also have said that on the
first bike the head tube angle is 73 deg and on the second 71.7 deg. Both bikes use 3ttt bars
with, according to the 3ttt web site, the same reach and drop. The bikes are both 53 cm c-c but
the first uses a 3ttt Synthesis stem and the second an ITM millennium stem, both 11 cm. I am,
through my own measurements, finding that the first bike is all other things being equal approx.
1cm shorter saddle to levers. In line with what you all have been telling me. I hope you don't
mind me not giving the brand of bikes, but this is to avoid any bias. I find that people have a
lot of pre-conceived ideas when you give them a brand name. But it would be interesting if
anyone could have a guess at the manufacturers of both bikes.

Thanks again

Graham

"Graham" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

"Qui si parla Campagnolo" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

graham-<< What is the difference between a bike with a 73.25 deg. seat

tube and

Quoted message said:

54.5cm top tube, and a bike with a 74 deg. seat tube and a 54.3 cm top tube ? << Which one has
the longer top tube ?

The 54.5cm is longer.

<< I am setting the saddle to pedal position on both bikes the same but the second bike works
out longer to the levers

than

Quoted message said:

the first.

Saddle to pedal position isn't going to work unless you put your knee in

the

Quoted message said:

same place on both framesets. So, if you knee is proper on the 73.25

degree

Quoted message said:

one, then it needs to slide back on the 74 degree one... .75 of a cm,

which

Quoted message said:

increases top tube(effectively) of the second bike . Also, need to have

the

Quoted message said:

seat height the same and also have the headtube angle the same...

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

Thanks for all the replies so quickly, and very useful too ! I should also have said that on
the first bike the head tube angle is 73 deg and on the second 71.7 deg. Both bikes use 3ttt
bars with, according to the 3ttt web site, the same reach and drop. The bikes are both 53 cm
c-c but the first uses a 3ttt Synthesis stem and the second an ITM millennium stem,

both

Quoted message said:

11 cm. I am, through my own measurements, finding that the first bike is all other things being
equal approx. 1cm shorter saddle to levers. In line

with

Quoted message said:

what you all have been telling me. I hope you don't mind me not giving the brand of bikes, but
this is to avoid any bias. I find that people have a

lot

Quoted message said:

of pre-conceived ideas when you give them a brand name. But it would be interesting if anyone
could have a guess at the manufacturers of both

bikes.

Quoted message said:

Thanks again

Graham

Don't know about the first, but the second's a 55cm Colnago, eh? ;-)

General rule of thumb is that for mid-sized bikes, a one degree change in seat tube angle will move
the seat post forward or back about 1cm. As you've noted, a change in headtube angle will also
affect the reach, but the end result will be affected by your bar height relative to your saddle and
the stem's quill angle as well. A slacker head angle than seat angle will reduce the reach as your
bar height increases, and vice-versa. For a given bar height and stem length, reach will increase as
stem quill angle approaches 90 degrees.

We all paid attention in Trig class didn't we? ;-)

SB

"Steve Blankenship" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Graham" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

"Qui si parla Campagnolo" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

graham-<< What is the difference between a bike with a 73.25 deg. seat

tube and

Quoted message said:

54.5cm top tube, and a bike with a 74 deg. seat tube and a 54.3 cm top tube ? << Which one has
the longer top tube ?

The 54.5cm is longer.

<< I am setting the saddle to pedal position on both bikes the same but the second bike works
out longer to the levers

than

Quoted message said:

the first.

Saddle to pedal position isn't going to work unless you put your knee

in

Quoted message said:

Quoted message said:

the

Quoted message said:

same place on both framesets. So, if you knee is proper on the 73.25

degree

Quoted message said:

one, then it needs to slide back on the 74 degree one... .75 of a cm,

which

Quoted message said:

increases top tube(effectively) of the second bike . Also, need to

have

Quoted message said:

Quoted message said:

the

Quoted message said:

seat height the same and also have the headtube angle the same...

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

Thanks for all the replies so quickly, and very useful too ! I

should

Quoted message said:

Quoted message said:

also have said that on the first bike the head tube angle is 73 deg and

on

Quoted message said:

Quoted message said:

the second 71.7 deg. Both bikes use 3ttt bars with, according to the

3ttt

Quoted message said:

Quoted message said:

web site, the same reach and drop. The bikes are both 53 cm c-c but the first uses a 3ttt
Synthesis stem and the second an ITM millennium stem,

both

Quoted message said:

11 cm. I am, through my own measurements, finding that the first bike is

all

Quoted message said:

Quoted message said:

other things being equal approx. 1cm shorter saddle to levers. In line

with

Quoted message said:

what you all have been telling me. I hope you don't mind me not giving

the

Quoted message said:

Quoted message said:

brand of bikes, but this is to avoid any bias. I find that people have a

lot

Quoted message said:

of pre-conceived ideas when you give them a brand name. But it would be interesting if anyone
could have a guess at the manufacturers of both

bikes.

Quoted message said:

Thanks again

Graham

Don't know about the first, but the second's a 55cm Colnago, eh? ;-)

General rule of thumb is that for mid-sized bikes, a one degree change in seat tube angle will
move the seat post forward or back about 1cm. As you've noted, a change in headtube angle will
also affect the reach, but

the

Quoted message said:

end result will be affected by your bar height relative to your saddle and the stem's quill angle
as well. A slacker head angle than seat angle will reduce the reach as your bar height increases,
and vice-versa. For a

given

Quoted message said:

bar height and stem length, reach will increase as stem quill angle approaches 90 degrees.

We all paid attention in Trig class didn't we? ;-)

SB

Well done SB, any takers for the other.

Graham