Road Cycling - Bicycle Geometry

I love my current frame, a Steelman SR525 - and figured that if i ever bought another (when i bought another) frame i'd buy something different for different ride character. But i've been recently thinking not about material, but geometry and how that effects a ride's character.

I went on-line and compared popular models. i checked the Seven site, the Steelman site, Lightspeed site and for the ultimate in comparison (for its reputed relaxed angles) the Lemond site.

Since i ride a 57cm frame size i compared based on that size.

Seven, Steelman and LeMond all have 'standard' frames with a top tube measure of 57.5cm and Seven & LeMond offer 73.5cm Head Angles with Steelman at 74cm. all 3 have chainstay lengths of 41-41.5cm.

The Lightspeed's have a whole cm shorter top tube length (56.5cm) only a 73 degree head tube angle, a much shorter chainstay measure (39.3cm)

Everyone says that the Lemond is relaxed and greg used to get all his power from this type of geometry - because the saddle is further behind the bottom bracket and you can use your power muscles to stoke. But I find many bikes with this same geometry.

So I guess my question is: what is the measure of your machine and does anyone have any feedback on the differences or comments on the spec's of differing geometries.

How could someone buy a Lightspeed for many $$$$ and then 'customize it' for more $$$$$ by changing the top tube length (which would then change all the other angles on the bike) and expect the same ride feel as the one they rode/tested?!

and finally, could these geometries be changed by sliding the saddle up or back a cm... to simulate another geometry?!

These days, frame geomerty is less important than it used to be, now that seatposts are available in a wide variety of laybacks.
I use my saddle far forward on a post with an inline clamp. In olden days I would have had a custom bike with a very steep seat-tube. Must be my strange legs.

A variety of frame geometries mean you can pick and chose the one which suits your setup best.

When comparing top tubes, you have to note how much of the TT is infront and behind the BB. I mark the TT (with tape) using a plumbline, then measure back and forward.

I still like the fairly traditional Italian racing geometry of my 1982 Bianchi (99cm wheelbase, 73-74 degrees, etc.), as it provides me with a good all-round compromise among comfort, control, responsiveness, maneuverability, and stability. In contrast, the very long fork rake of my 1973 Peugeot UO-8 gave it what I considered to be overly slow steering response.

These days, frame geomerty is less important than it used to be, now that seatposts are available in a wide variety of laybacks.

Walter, I don't completely agree with you on that because sliding the saddle forward/rearward to simulate different seat tube angles also changes the effective top-tube length with consequences that can be good or bad depending on the situation.

Your physiology requires a steep seat tube angle which can be simulated by sliding the saddle forward. This also shortens the reach which probably makes your bike more comfortable. I am not that lucky...

I have long femurs and a long torso, both of which require a slack 72 degree seat tube angle. Standard bikes have a 73 degree seat tube angle but I can simulate 72 by sliding the saddle way back. The problem is, that lengthens the reach which then requires a super-short stem to compensate. That, in turn has negative affects on the steering and handling.