Need help with fitment

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I've looked at www.bikefitting.com (http://www.bikefitting.com) and Colorado cyclist to figure out my frame size. I also went into a store and had a Trek dealer fit me. I have a 83cm inseam and stand 5'9.5" I came out as a 56 on the Trek. I want to buy a Look which is either L (55) or M (53).

When using the above calculators with my 83cm inseam I should have a C-C size frame of 54 cm and C-T of 55.6 cm.

When I look at the Look geometry they have a real C-C and a virtual C-C.

For example, for the L frame: real C-C = 50.5cm and virtual = 55.7

Q1: Is the L frame too big for me?

Q2: This is puzzling, the C-T (Actual) measurement is 55cm but the C-C (virtual) is 55.7!! Can the C-T actual really be smaller than the C-C virtual?

Thanks
Azzy

I've looked at www.bikefitting.com (http://www.bikefitting.com) and Colorado cyclist to figure out my frame size. I also went into a store and had a Trek dealer fit me. I have a 83cm inseam and stand 5'9.5" I came out as a 56 on the Trek. I want to buy a Look which is either L (55) or M (53).

When using the above calculators with my 83cm inseam I should have a C-C size frame of 54 cm and C-T of 55.6 cm.

When I look at the Look geometry they have a real C-C and a virtual C-C.

For example, for the L frame: real C-C = 50.5cm and virtual = 55.7

Q1: Is the L frame too big for me?

Q2: This is puzzling, the C-T (Actual) measurement is 55cm but the C-C (virtual) is 55.7!! Can the C-T actual really be smaller than the C-C virtual?

Thanks
Azzy
I would not pay too much attention to the seat tube dim. The top tube length is more important.
regarding your question: the actual is shorter because is measured along the actual seat tube length; the virtual dimension is measured along an imaginary line that would extend the seat tube until it meets the virtual top tube (if the frame has a sloping top tube geometry)
check a site like:
http://www.competitivecyclist.com/za/CCY?PAGE=FIT_CALCULATOR_INTRO
where you get a top tube dimension based on your upper body and arm length reach and the "position" you want achieve.
I am 5-10 and could ride a 56, 57, 58 and 59 cm frames depending on how i want to ride. The bigger frames minimize the saddle to handlebar drop while the smaller frames get you in a more "aero" position with a higher saddle to handlebar drop. The distance from BB to saddle will remain more or less the same in any of the sizes I'd ride since its based on my leg length (crotch dim)