Tech Talk - dimensions help?

[Slipstream1988]

If you don't mind...I was hoping someone could help me understand something about my geometry versus frame geometry.

Me:
TT length: 59 cm
Stem length: 11 cm
Seat Tube length (center-to-top)65 or 66cm
Seat Tube length (center-to-center)61 cm
Seat Tube angle: 73
Crank arm length 175
Seat height from BB: 81.5 cm

Now I've been looking at many frames (stock) and it's really difficult to find a bike with a center-to-top size of 65-66cm.

How much would a shorter center-to-top length effect my pedaling efficiency as long as my seat height makes it to 81.5 cm??

Or...what would it effect in my overall position?? Would it cause me to use more energy than I should be using?

I have to keep in mind....I need a "zero" angle seat post (ie - it can't curve back).

I am left with the impression by the person who fit me that it's best to go with the "ideal" frame to one's dimensions.

Stock frames can't be perfect....so where are the "fudge factors" I can work with and not sacrifice my position on the bike???

[John M]

If you don't mind...I was hoping someone could help me understand something about my geometry versus frame geometry.

Me:
TT length: 59 cm
Stem length: 11 cm
Seat Tube length (center-to-top)65 or 66cm
Seat Tube length (center-to-center)61 cm
Seat Tube angle: 73
Crank arm length 175
Seat height from BB: 81.5 cm

Now I've been looking at many frames (stock) and it's really difficult to find a bike with a center-to-top size of 65-66cm.

How much would a shorter center-to-top length effect my pedaling efficiency as long as my seat height makes it to 81.5 cm??

Or...what would it effect in my overall position?? Would it cause me to use more energy than I should be using?

I have to keep in mind....I need a "zero" angle seat post (ie - it can't curve back).

I am left with the impression by the person who fit me that it's best to go with the "ideal" frame to one's dimensions.

Stock frames can't be perfect....so where are the "fudge factors" I can work with and not sacrifice my position on the bike???

Seat tube length is pretty much irrelevant. Top tube length (or effective topt tube length) is the key dimension. You can compensate for seat tube with seatpost height (i.e. compact geometry and standard geometry framesets could have vastly different seat-tube lengths but the same effective top tube length. Center-to-top is even more irrelevant as this incorporates tubing diameter and seat lug/clamp construction which don't affect frame fit. Center-to-center is the way to make comparisons between frame size. Changes in center-to-top will have little effect on the bike fit if the top tube length is the same.

The main parameters that you can adjust to get the bike to fit your body are stem length and rise, saddle height, saddle fore-to-aft, crank arm length, and cleat mounting on your shoes.

Fittings based on formulas are only a starting point and should be adjusted to reflect your individual riding style, flexibility, comfort level, and previous fit issues.

You should easily be able to find a stock frame to close to the geometry suggested to you if you ignore the seat tube measurements and focus on the others.

[Slipstream1988]

Thank you very much, John.

I truly appreciate the information.:)