"Qui si parla Campagnolo" <[email hidden]> wrote :
Quoted message said:
ideally, as a rider gets taller, his femur gets longer and there is a need for slacker seattube angles. Just making the seatpost longer doesn't make up for that. Why frames of 1 cm increments also have decreasing seat tube angles as well.
But at a constant (non-90 degree) seat angle, the seat moves back as it is raised. As a 6'2" rider with over 35 years of racing experience, I prefer frames with 73 degree seat angles, as they allow me to keep the saddle clamped about in the middle of the rails. My belief is that large frames tend to have slack seat angles to allow builders to quote longer top tube lengths, even though the length comes not from stretching the front-center, but simply from moving the saddle back.
Some people, including myself, think that torsional and vertical compliance are a bad thing. I prefer that the force I exert on the crank rotates the chain wheel rather than twisting the frame. At 155 lb, the only place I look for compliance is in fork blades thin at the ends with an exaggerated curve.
The difference in compliance will be negligble, but the torsional compliance of the "compact" frame will (all else equal) be less than that of a traditional frame. I'll also point out that virtually all energy that goes into flexing a frame will be returned as useful work as the pedals approach TDC, so there's no significant difference in mechanical efficiency between flexible and stiff frames. I'd wager a large sum you flex frames a lot less than did Sean Kelly on his (very) flexible small-tubed aluminum frames.
"Qui si parla Campagnolo" <[email hidden]> wrote :
Quoted message said:
ideally, as a rider gets taller, his femur gets longer and there is a need for slacker seattube angles. Just making the seatpost longer doesn't make up for that. Why frames of 1 cm increments also have decreasing seat tube angles as well.
But at a constant (non-90 degree) seat angle, the seat moves back as it is raised. As a 6'2" rider with over 35 years of racing experience, I prefer frames with 73 degree seat angles, as they allow me to keep the saddle clamped about in the middle of the rails. My belief is that large frames tend to have slack seat angles to allow builders to quote longer top tube lengths, even though the length comes not from stretching the front-center, but simply from moving the saddle back.
Harry Phinney
i agree. shallow seat angles suck for us larger guys - i like to have my knees well and truly over the pedals and power up accordingly. too laid back and all you can do is be a fred.
Some people, including myself, think that torsional and vertical compliance are a bad thing. I prefer that the force I exert on the crank rotates the chain wheel rather than twisting the frame. At 155 lb, the only place I look for compliance is in fork blades thin at the ends with an exaggerated curve.
The difference in compliance will be negligble, but the torsional compliance of the "compact" frame will (all else equal) be less than that of a traditional frame. I'll also point out that virtually all energy that goes into flexing a frame will be returned as useful work as the pedals approach TDC, so there's no significant difference in mechanical efficiency between flexible and stiff frames. I'd wager a large sum you flex frames a lot less than did Sean Kelly on his (very) flexible small-tubed aluminum frames.
Harry Phinney
the disadvantage of excessive flex is unintended rubbing. as you're saying, there's no hysteresis loop for flexible metal, but if that flexibility allows a brake to contact a rim for example, you're worse off with the flexible frame. and then there's the whole issue of shimmy....
Calling sloping top tubes a "technology" is evidence that the software industry has triumphed and that word no longer has any meaning.
software industry? explain?
as for use of the word, just because something is commonplace and taken for granted, doesn't mean it's not worthy.
The software biz calls every operation or algorithm a "technology." (If your technology plugs and plays with something, it's a "solution."😉 For example, Amazon has a patent on "one-click technology." Leaving aside whether this innovation should be patentable, it's an algorithm somewhere in the front-end of their website that lets you order a book with only one click. That's not "technology," it's just a putting together of various pre-existing algorithms. Something like the TCP/IP protocol or Ethernet (or Amazon's entire warehouse backend) is more like what it takes to rise to the level of "technology."
Getting back to bikes, butted frame tubes, bladder molding carbon, TIG welding, these are technologies. Sloping top tubes are not technology. They are a design element. It doesn't take anything different to make a sloping top-tube frame, you join the tubes the same way. That's not pejorative; they are a sometimes useful and functional design element. But calling something "technology" that isn't serves to make it sound more mystical and sophisticated than it actually is. (This is of course why Amazon calls their one-click thingy "technology," to make it seem like retailing WMD that should be kept out of Barnes & Noble's hands.)
"Qui si parla Campagnolo" <[email hidden]> wrote :
Quoted message said:
ideally, as a rider gets taller, his femur gets longer and there is a need for slacker seattube angles. Just making the seatpost longer doesn't make up for that. Why frames of 1 cm increments also have decreasing seat tube angles as well.
Quoted message said:
But at a constant (non-90 degree) seat angle, the seat moves back as it is raised. As a 6'2" rider with over 35 years of racing experience, I prefer frames with 73 degree seat angles, as they allow me to keep the saddle clamped about in the middle of the rails. My belief is that large frames tend to have slack seat angles to allow builders to quote longer top tube lengths, even though the length comes not from stretching the front-center, but simply from moving the saddle back.
Quoted message said:
Harry Phinney
i agree. shallow seat angles suck for us larger guys - i like to have my knees well and truly over the pedals and power up accordingly. too laid back and all you can do is be a fred.
What also sucks is having a big frame with such a forward seat tube angle that you can't get your saddle far enough back to get you knee over the pedal spindle. There are LOTS of zero setback SPs, few way aft SPs.
"Qui si parla Campagnolo" <[email hidden]> wrote : > ideally, as a rider gets taller, his femur gets longer and there is a > need for slacker seattube angles. Just making the seatpost longer > doesn't make up for that. Why frames of 1 cm increments also have > decreasing seat tube angles as well. But at a constant (non-90 degree) seat angle, the seat moves back as it is raised. As a 6'2" rider with over 35 years of racing experience, I prefer frames with 73 degree seat angles, as they allow me to keep the saddle clamped about in the middle of the rails. My belief is that large frames tend to have slack seat angles to allow builders to quote longer top tube lengths, even though the length comes not from stretching the front-center, but simply from moving the saddle back. Harry Phinney
i agree. shallow seat angles suck for us larger guys - i like to have my knees well and truly over the pedals and power up accordingly. too laid back and all you can do is be a fred.
What also sucks is having a big frame with such a forward seat tube angle that you can't get your saddle far enough back to get you knee over the pedal spindle. There are LOTS of zero setback SPs, few way aft SPs.
well, as the rider and tester of many large frames, my experience is that i've never experienced a problem with the seat being too far forward with a normal setback post, only too far back due to the frame angle. even a 75 degree track frame is fine. 72 degree "road" frame is awful.
Harry Phinney wrote: > "Qui si parla Campagnolo" <[email hidden]> wrote : >> ideally, as a rider gets taller, his femur gets longer and there is a >> need for slacker seattube angles. Just making the seatpost longer >> doesn't make up for that. Why frames of 1 cm increments also have >> decreasing seat tube angles as well. > But at a constant (non-90 degree) seat angle, the seat moves back as it is > raised. As a 6'2" rider with over 35 years of racing experience, I prefer > frames with 73 degree seat angles, as they allow me to keep the saddle > clamped about in the middle of the rails. My belief is that large frames > tend to have slack seat angles to allow builders to quote longer top tube > lengths, even though the length comes not from stretching the front-center, > but simply from moving the saddle back. > Harry Phinney i agree. shallow seat angles suck for us larger guys - i like to have my knees well and truly over the pedals and power up accordingly. too laid back and all you can do is be a fred.
Quoted message said:
What also sucks is having a big frame with such a forward seat tube angle that you can't get your saddle far enough back to get you knee over the pedal spindle. There are LOTS of zero setback SPs, few way aft SPs.
well, as the rider and tester of many large frames, my experience is that i've never experienced a problem with the seat being too far forward with a normal setback post, only too far back due to the frame angle. even a 75 degree track frame is fine. 72 degree "road" frame is awful.
The I think you are one of those who has shortish femurs for your height, perhaps leg length predominately in your lower leg or a long torso. Merckx/DeRosa type geometry, IMO, suits taller riders, with seat tube angles in the 72 degree range for 60cm-ish frames. 72.5 for a 58cm. Colnago, on the other hand, don't with steep seatutbe by comparison and short top tubes. 'A 75 degree track frame' being fine I think explains a lot.
Other than handlebar height, which has changed since I took that picture, those bikes fit similarly. I actually have more standover clearance on the upper bike. As you can see, the geometry of the lower frame is a bit extreme to accomodate the tall front end and still provide semi-reasonable standover.
The bike rides well and feels plenty stiff. It's plenty heavy, but the wheels and fork account for far more of that than the seatpost. The only drawbacks I've noticed as a result of the steeply sloping top tube are that the bike looks a bit odd, can only carry one water bottle, and sits awkwardly on the kind of car rack that cradles the top tube.
On Apr 10, 7:38 pm, "Harry Phinney" <[email hidden]>
Quoted message said:
"Michael Press" <[email hidden]> wrote
Quoted message said:
Some people, including myself, think that torsional and vertical compliance are a bad thing. I prefer that the force I exert on the crank rotates the chain wheel rather than twisting the frame. At 155 lb, the only place I look for compliance is in fork blades thin at the ends with an exaggerated curve.
The difference in compliance will be negligble, but the torsional compliance of the "compact" frame will (all else equal) be less than that of a traditional frame. I'll also point out that virtually all energy that goes into flexing a frame will be returned as useful work as the pedals approach TDC, so there's no significant difference in mechanical efficiency between flexible and stiff frames. I'd wager a large sum you flex frames a lot less than did Sean Kelly on his (very) flexible small-tubed aluminum frames.
If the statement that the energy is returned useful work is 100% correct, then the smoothing of the power delivery curve is in fact beneficial.
Some people, including myself, think that torsional and vertical compliance are a bad thing. I prefer that the force I exert on the crank rotates the chain wheel rather than twisting the frame. At 155 lb, the only place I look for compliance is in fork blades thin at the ends with an exaggerated curve.
The difference in compliance will be negligble, but the torsional compliance of the "compact" frame will (all else equal) be less than that of a traditional frame. I'll also point out that virtually all energy that goes into flexing a frame will be returned as useful work as the pedals approach TDC, so there's no significant difference in mechanical efficiency between flexible and stiff frames. I'd wager a large sum you flex frames a lot less than did Sean Kelly on his (very) flexible small-tubed aluminum frames.
I never believed that the energy of elastic flex in the frame will be transmitted into turning the rear wheel. The system is too complicated for that to be accepted on the face of it. It would take a meticulous laboratory study of the greatest exactitude to persuade me that frame flex energy is not mostly lost.
