Does Stiffness in the BB REALLY Make a Difference? I am guessing not really....
01-24-16, 05:37 AM
#76
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So, I've weighed in on this discussion many times in the past. I'll just put this here:
Yes, a spring returns energy. If that energy is returned out of phase to the torque pulses from the legs, then that energy is simply stored in oscillation until it is dissipated, likely through the leg muscles working in contradiction to the pedaling force. In the power industry, this is called "reactive power" and is not productive. It is contra-productive though, in that the energy source (legs in this case), must provide both the energy to move the bike plus the reactive energy. If the crank is at constant angular velocity, this energy is just stored in the pedal/bike motion; you supply the reactive energy once, and it just sits there and oscillates with the frame, like filling a bucket. As the cranks see angular accelerations though, this reactive energy "bucket" will be constantly emptied (by going back into your muscles to be dissipated, or raising your body weight, for instance) and require refilling every pedal stroke.
As many here know, there are different modes of pedaling. There is circular pedaling, there is pulsed pedaling, there is standing, there is really tired (or overtorqued) pedaling where your crank velocity slows almost to a stop at the dead spots of the pedal stroke. In circular pedaling, the effects of a soft frame are probably minimal and you simply get a torque lag during any transient. As torque becomes more pulsed and as the angular velocity of the crankset becomes less constant, a soft frame will require a lot of non-productive reactive power, dissipated into your leg muscles as you fight your bike to produce a good pedal spin, or into raising your body weight if you are standing. Of course, for a stiff frame, none of these modes matter, since little reactive power is generated in the first place.
All in all then, a good, stiff frame is better than a noodle, unless you need the shock absorption.
Yes, a spring returns energy. If that energy is returned out of phase to the torque pulses from the legs, then that energy is simply stored in oscillation until it is dissipated, likely through the leg muscles working in contradiction to the pedaling force. In the power industry, this is called "reactive power" and is not productive. It is contra-productive though, in that the energy source (legs in this case), must provide both the energy to move the bike plus the reactive energy. If the crank is at constant angular velocity, this energy is just stored in the pedal/bike motion; you supply the reactive energy once, and it just sits there and oscillates with the frame, like filling a bucket. As the cranks see angular accelerations though, this reactive energy "bucket" will be constantly emptied (by going back into your muscles to be dissipated, or raising your body weight, for instance) and require refilling every pedal stroke.
As many here know, there are different modes of pedaling. There is circular pedaling, there is pulsed pedaling, there is standing, there is really tired (or overtorqued) pedaling where your crank velocity slows almost to a stop at the dead spots of the pedal stroke. In circular pedaling, the effects of a soft frame are probably minimal and you simply get a torque lag during any transient. As torque becomes more pulsed and as the angular velocity of the crankset becomes less constant, a soft frame will require a lot of non-productive reactive power, dissipated into your leg muscles as you fight your bike to produce a good pedal spin, or into raising your body weight if you are standing. Of course, for a stiff frame, none of these modes matter, since little reactive power is generated in the first place.
All in all then, a good, stiff frame is better than a noodle, unless you need the shock absorption.
Whatever happened to the simplicity of Newton's 3rd law, that for every action there is an equal and opposite reaction?
Many years ago I read an article in the major cycling magazine at that time reporting on how some track riders were as fast on their noodly bikes than those on stiffer bikes. Energy is not lost, it is returned was their conclusion. How have things changed since then? Advances in marketing speak because you can't make a flexible bike out of today's "advanced" materials that will not snap so they have to be made stiffer, so now stiff is better because that's what bikes have to be to made from, the lightest materials possible because *lightness*, not power transfer is the true objective in the long run?
If you really want to get a better understanding of how frame stiffness can negatively impact the power transfer and handling of two wheelers, look at the debacle in motorcycle racing when any major manufacturer, none of whom are short on engineering talent, has tried to use the stiffest frame designs be they Al or c/f or even cromoly. They usually go back to more "tuned" frames, and away from the stiffest ones: better power "hook up", and better handling because of the right amount of frame flex, not the absence of it.
01-24-16, 06:45 AM
#77
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So you're points are based on "ifs", therefore I will counter with "what if not?" and we're back to Square 1.
Whatever happened to the simplicity of Newton's 3rd law, that for every action there is an equal and opposite reaction?
Many years ago I read an article in the major cycling magazine at that time reporting on how some track riders were as fast on their noodly bikes than those on stiffer bikes. Energy is not lost, it is returned was their conclusion. How have things changed since then? Advances in marketing speak because you can't make a flexible bike out of today's "advanced" materials that will not snap so they have to be made stiffer, so now stiff is better because that's what bikes have to be to made from, the lightest materials possible because *lightness*, not power transfer is the true objective in the long run?
If you really want to get a better understanding of how frame stiffness can negatively impact the power transfer and handling of two wheelers, look at the debacle in motorcycle racing when any major manufacturer, none of whom are short on engineering talent, has tried to use the stiffest frame designs be they Al or c/f or even cromoly. They usually go back to more "tuned" frames, and away from the stiffest ones: better power "hook up", and better handling because of the right amount of frame flex, not the absence of it.
Whatever happened to the simplicity of Newton's 3rd law, that for every action there is an equal and opposite reaction?
Many years ago I read an article in the major cycling magazine at that time reporting on how some track riders were as fast on their noodly bikes than those on stiffer bikes. Energy is not lost, it is returned was their conclusion. How have things changed since then? Advances in marketing speak because you can't make a flexible bike out of today's "advanced" materials that will not snap so they have to be made stiffer, so now stiff is better because that's what bikes have to be to made from, the lightest materials possible because *lightness*, not power transfer is the true objective in the long run?
If you really want to get a better understanding of how frame stiffness can negatively impact the power transfer and handling of two wheelers, look at the debacle in motorcycle racing when any major manufacturer, none of whom are short on engineering talent, has tried to use the stiffest frame designs be they Al or c/f or even cromoly. They usually go back to more "tuned" frames, and away from the stiffest ones: better power "hook up", and better handling because of the right amount of frame flex, not the absence of it.
As to your other motorcycle analogy in terms of frame tuning...more misinterpretation. You can't or rather shouldn't compare the two. Motorcycles are yes about power transfer but not in energy lost to the frame or the rider but rather transmitted to the ground in terms of lost traction. This is why frame stiffness tuning is desirable...to keep the tire contact on the ground as long as possible under power due to undulating road surfaces. In effect a bike frame like a motorcycle frame is an integral component of a suspension and in the case of motorcycles around a track, suspension rules in terms of speed including fore/aft weight transfer. As it turns out, excepting the wheels and tires, the frame 'is' the suspension on a bicycle.
If you followed the bike industry and what Specialized has done with their latest race bikes you would understand better. Specialized does tune their bikes...in fact extensively thru strain gauge testing between different frame sizes based upon weight demographics within a given model. They worked with McLaren to perform this testing. Overall frame stiffness and force deflection matters. So does BB stiffness. It isn't a difficult calculation to know that if a 2000 watt rider can't appreciably torque a BB under load that it will be fine for a 1500w rider or even an average rider. BB stiffness can be independent of vertical force/deflection. No greater example than the new Madone which has a great ride but is uber stiff laterally...what a racer prefers in a bike.
Last edited by Campag4life; 01-24-16 at 06:55 AM.
01-24-16, 08:01 AM
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You are wrong on so many levels. First Newton's 3rd law is alive and well. You just don't understand it. Energy is conserved in terms of energy in = energy out. It is simply not transferred back to the bike because there is no such thing as a perfectly efficient mechanical system. You brought up motorcycles...whoops. Take a motorcycle engine of 100 brake horsepower at the crankshaft. How many hp do you believe gets actually transferred to the rear wheel where its measured on a bike dynamometer? About 85 horsepower depending on the motorcycle...chain being more efficient than belt. Where does this power go? Gee, I wonder.
As to your other motorcycle analogy in terms of frame tuning...more misinterpretation. You can't or rather shouldn't compare the two. Motorcycles are yes about power transfer but not in energy lost to the frame or the rider but rather transmitted to the ground in terms of lost traction. This is why frame stiffness tuning is desirable...to keep the tire contact on the ground as long as possible under power due to undulating road surfaces. In effect a bike frame like a motorcycle frame is an integral component of a suspension and in the case of motorcycles around a track, suspension rules in terms of speed including fore/aft weight transfer. As it turns out, excepting the wheels and tires, the frame 'is' the suspension on a bicycle.
If you followed the bike industry and what Specialized has done with their latest race bikes you would understand better. Specialized does tune their bikes...in fact extensively thru strain gauge testing between different frame sizes based upon weight demographics within a given model. They worked with McLaren to perform this testing. Overall frame stiffness and force deflection matters. So does BB stiffness. It isn't a difficult calculation to know that if a 2000 watt rider can't appreciably torque a BB under load that it will be fine for a 1500w rider or even an average rider. BB stiffness can be independent of vertical force/deflection. No greater example than the new Madone which has a great ride but is uber stiff laterally...what a racer prefers in a bike.
As to your other motorcycle analogy in terms of frame tuning...more misinterpretation. You can't or rather shouldn't compare the two. Motorcycles are yes about power transfer but not in energy lost to the frame or the rider but rather transmitted to the ground in terms of lost traction. This is why frame stiffness tuning is desirable...to keep the tire contact on the ground as long as possible under power due to undulating road surfaces. In effect a bike frame like a motorcycle frame is an integral component of a suspension and in the case of motorcycles around a track, suspension rules in terms of speed including fore/aft weight transfer. As it turns out, excepting the wheels and tires, the frame 'is' the suspension on a bicycle.
If you followed the bike industry and what Specialized has done with their latest race bikes you would understand better. Specialized does tune their bikes...in fact extensively thru strain gauge testing between different frame sizes based upon weight demographics within a given model. They worked with McLaren to perform this testing. Overall frame stiffness and force deflection matters. So does BB stiffness. It isn't a difficult calculation to know that if a 2000 watt rider can't appreciably torque a BB under load that it will be fine for a 1500w rider or even an average rider. BB stiffness can be independent of vertical force/deflection. No greater example than the new Madone which has a great ride but is uber stiff laterally...what a racer prefers in a bike.
Some times power is better transmitted with some flexing...we agree. Oh, and the motorcycle analogy...... is bang on.
deal with it.
01-24-16, 08:06 AM
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It would be nice if there were data proving that there is an efficiency gain. I like the discussions about springs and reactive power and so on, but without some modelling and math to quantify, or some data, I assume the effect of BB stiffness on efficiency is either only important to racers or so small as to be not important to anyone at all.
OTOH, I'm happy to accept that many like the feel much better. However, I would however need measurements from a standardized test to show me there is a difference in actual acceleration between two real frames as a result of flex.
In this industry, too much is claimed, too little is proven.
OTOH, I'm happy to accept that many like the feel much better. However, I would however need measurements from a standardized test to show me there is a difference in actual acceleration between two real frames as a result of flex.
In this industry, too much is claimed, too little is proven.
01-24-16, 08:22 AM
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hahah...so, a stiffer frame is not a better/faster frame, isn't that what you just said? If you're going to accuse me of being wrong at so many levels, you shouldn't agree with my premise that stiffness is not always better. Some times power is better transmitted with some flexing...we agree.
Oh, and the motorcycle analogy...... is bang on. deal with it.
Some times power is better transmitted with some flexing...we agree. Oh, and the motorcycle analogy...... is bang on.
deal with it. Stiffness isn't monolithic through a frameset. Not even close. Rear seat stays are whimpy compared to chainstays...chainstays are whimpy compared to a top tube and top tubes are much softer in flexing compared to down tube. BB bracket stiffness can be independent of afore mentioned. So its possible to have an uber stiff BB with a compliant ride. But, no you conflate all of it. Your motorcycle analogy is a joke and I called you out on it because a bike's ability to transfer energy to the driving wheels can be independent of a bikes ability to handle or provide good ride quality. Stiffness can be decoupled from the vertical plane to the horizontal plane is the point.
01-24-16, 08:33 AM
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It would be nice if there were data proving that there is an efficiency gain. I like the discussions about springs and reactive power and so on, but without some modelling and math to quantify, or some data, I assume the effect of BB stiffness on efficiency is either only important to racers or so small as to be not important to anyone at all.
OTOH, I'm happy to accept that many like the feel much better. However, I would however need measurements from a standardized test to show me there is a difference in actual acceleration between two real frames as a result of flex.
In this industry, too much is claimed, too little is proven.
OTOH, I'm happy to accept that many like the feel much better. However, I would however need measurements from a standardized test to show me there is a difference in actual acceleration between two real frames as a result of flex.
In this industry, too much is claimed, too little is proven.
Stiffness is amount of deflection per unit force. So a stiff bike to the girl mentioned can be a rag to the weight lifter. So there isn't common ground among bike riders in terms of energy transfer relative to BB stiffness.
I come from a world of engineering and computer modeling. Where are theories devised? Through computer simulation if dynamic modeling is even possible. Where is reality tested? On the road. All the members here that question the truth about a stiff BB not being more efficient, I have to laugh. Anybody actually believe that Specialized who cashes in on their TdF victories doesn't tweak carbon layup...or in the case of the redesigned Al Allez just grew the BB to the size of a grapefruit..and not evaluate this at the track in A to B testing among their competitive riders against the clock? Really? All those victories and profit at stake?
Theories are manifold. The truth is born out of physical testing in the real world. If top racing bikes were faster with a whippy BB, they would be made weak and flexible and not uber stiff. The stop watch doesn't lie. Dynamic computer modeling is a facsimile of boundary conditions and assumptions. Mathematics can be wrongly modeled. Reality is the truth. Stiffer BB's have more efficient energy transfer which translates to better bike performance and speed.
Last edited by Campag4life; 01-24-16 at 08:37 AM.
01-24-16, 08:53 AM
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You conflate is your problem. You find false analogies that don't apply.
Stiffness isn't monolithic through a frameset. Not even close. Rear seat stays are whimpy compared to chainstays...chainstays are whimpy compared to a top tube and top tubes are much softer in flexing compared to down tube. BB bracket stiffness can be independent of afore mentioned. So its possible to have an uber stiff BB with a compliant ride. But, no you conflate all of it. Your motorcycle analogy is a joke and I called you out on it because a bike's ability to transfer energy to the driving wheels can be independent of a bikes ability to handle or provide good ride quality. Stiffness can be decoupled from the vertical plane to the horizontal plane is the point.
Stiffness isn't monolithic through a frameset. Not even close. Rear seat stays are whimpy compared to chainstays...chainstays are whimpy compared to a top tube and top tubes are much softer in flexing compared to down tube. BB bracket stiffness can be independent of afore mentioned. So its possible to have an uber stiff BB with a compliant ride. But, no you conflate all of it. Your motorcycle analogy is a joke and I called you out on it because a bike's ability to transfer energy to the driving wheels can be independent of a bikes ability to handle or provide good ride quality. Stiffness can be decoupled from the vertical plane to the horizontal plane is the point.
Power transmission and handling differences based on the stiffness of the frame are linked, motorcycle or bicycle. No false analogies. Nobody stated stiffness is monolithic. Forks and swing arms and frames and even engines at times are all tuned differently, for handling and power transmission, no different than a bicycle. Power losses in a MC are similar to a bicycle, i.e. bearings and cranks and cogs and chains and gears etc. Do you have some links showing dyno charts for bicycles, one with a very stiff frame/BB and one with out showing better power to the wheel from the same amount of power? (none of this power meter stuff either please)
01-24-16, 09:32 AM
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Anybody actually believe that Specialized who cashes in on their TdF victories doesn't tweak carbon layup...or in the case of the redesigned Al Allez just grew the BB to the size of a grapefruit..and not evaluate this at the track in A to B testing among their competitive riders against the clock? Really? All those victories and profit at stake?
It is all hypothetical at this point. All I know is it feels better to some people. That could be the sole reason a manufacturer adopts it. Or there could be a real gain. I don't know that either.
And yes, I'm sure there is no result that is broadly applicable. But that doesn't stop the manufacturer from proving increased efficiency under some scenario with a realistic weight rider. This is why test engineers exist.
01-24-16, 10:06 AM
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So, what you are saying is that maybe there is performance data, but it isn't made public. Why?
It is all hypothetical at this point. All I know is it feels better to some people. That could be the sole reason a manufacturer adopts it. Or there could be a real gain. I don't know that either.
And yes, I'm sure there is no result that is broadly applicable. But that doesn't stop the manufacturer from proving increased efficiency under some scenario with a realistic weight rider. This is why test engineers exist.
It is all hypothetical at this point. All I know is it feels better to some people. That could be the sole reason a manufacturer adopts it. Or there could be a real gain. I don't know that either.
And yes, I'm sure there is no result that is broadly applicable. But that doesn't stop the manufacturer from proving increased efficiency under some scenario with a realistic weight rider. This is why test engineers exist.
After you publish force/deflection for automotive chassis stiffness, then post to me the correlation between hp efficiency and tire adhesion....or....how chassis stiffness manifests higher lateral acceleration on a skid pad at the track? Where is that data?
Also, in spite of taking Specialized word for it, post Specialized strain gauge data that shows equivalency now between their smallest and biggest frames for their best selling race bike. I want to see that data as well. Then you can tell me what force/deflection locations correlate best to handling equivalency and why.
Get back to me ok?
3. Specialized Tarmac: Rider-First Engineered | Specialized model year 2015 bikes: Tarmac and Diverge
01-24-16, 10:46 AM
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Preferences Vary
As a counterpoint, some people prefer some give:
01-24-16, 10:58 AM
#86
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High dimensional systems + people's tastes = How many angels can fit on the head of a pin?
01-24-16, 02:13 PM
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Tell you what, you show me where Porsche publishes force/deflection or torque/angle for their chassis stiffness...or Chevrolet for their Corvette or any top mfr that produces a sports car and then we can talk why there isn't any published data from bicycle manufactures for BB stiffness.
After you publish force/deflection for automotive chassis stiffness, then post to me the correlation between hp efficiency and tire adhesion....or....how chassis stiffness manifests higher lateral acceleration on a skid pad at the track? Where is that data?
Also, in spite of taking Specialized word for it, post Specialized strain gauge data that shows equivalency now between their smallest and biggest frames for their best selling race bike. I want to see that data as well. Then you can tell me what force/deflection locations correlate best to handling equivalency and why.
Get back to me ok?
3. Specialized Tarmac: Rider-First Engineered | Specialized model year 2015 bikes: Tarmac and Diverge
After you publish force/deflection for automotive chassis stiffness, then post to me the correlation between hp efficiency and tire adhesion....or....how chassis stiffness manifests higher lateral acceleration on a skid pad at the track? Where is that data?
Also, in spite of taking Specialized word for it, post Specialized strain gauge data that shows equivalency now between their smallest and biggest frames for their best selling race bike. I want to see that data as well. Then you can tell me what force/deflection locations correlate best to handling equivalency and why.
Get back to me ok?
3. Specialized Tarmac: Rider-First Engineered | Specialized model year 2015 bikes: Tarmac and Diverge
Well, I think we are going to have to disagree on this.
I think the reality is that the contribution of BB stiffness to performance is a very complicated piece of physics and physiology. For example, human tendons tend to function as springs that absorb and return energy. Does that play into how the energy that is put into the elastic frame flex is returned? Also, when the BB is returning from flexing in one direction, is the energy that is presumably being "returned" going to the rider's leg that is rising, or interacting with the leg that is extending and applying power, or both? And what effect does this have, if any? This complexity is what makes me doubt that the matter is a simple as saying a stiffer BB will provide more efficient energy transfer. There is too much going on to conclude that without some kind of data.
And no, I don't personally want detailed data about structural flexing or whatever, just performance outcomes. I wonder if one could simply use the difference between crank and rear hub power to measure whether there is a difference between different bottom brackets on the same bike models. And then there would be something to accept.
As for whether one should expect data from companies, well, that's up to them. But plenty of companies provide performance data (even Porsche) and we see it in some of the more interesting bike wheel manufacturers for aerodynamics.
Last edited by Igualmente; 01-24-16 at 04:14 PM. Reason: grammar.
01-24-16, 03:30 PM
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The tri geeks have been trying to quantify this for years. If they can't, it's either non-existent or so small as to be meaningless.
01-24-16, 03:53 PM
#89
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Yea... So, there are, like, three "ifs" in my post, and they are all referring to situational conditionals. I do not need to guess about physics nor do I resort to arguments by analogy.
Obviously, the frame dynamics of motorcycles are extremely different, seeing as they do not suffer from torque pulses like a bicycle. Their frame dynamics are all about bike handling. Different problem altogether. Here, the bicycle weighs 1/10th of the cyclist, the engine is very high torque, low speed, and it delivers torque in 3-pulses-per-second basis, rather than the 100's of pulses per second that a motorcycle engine sees. Finally, while handling does come into play with bicycles, particularly off-road, it is a secondary concern to power transfer, mostly because most of the handling problems are soaked up by the much larger diameter wheels of bicycles (as opposed to motorcycles).
So, maybe engage the discussion at the level of dynamics rather than resorting to half thought out analogies.
Obviously, the frame dynamics of motorcycles are extremely different, seeing as they do not suffer from torque pulses like a bicycle. Their frame dynamics are all about bike handling. Different problem altogether. Here, the bicycle weighs 1/10th of the cyclist, the engine is very high torque, low speed, and it delivers torque in 3-pulses-per-second basis, rather than the 100's of pulses per second that a motorcycle engine sees. Finally, while handling does come into play with bicycles, particularly off-road, it is a secondary concern to power transfer, mostly because most of the handling problems are soaked up by the much larger diameter wheels of bicycles (as opposed to motorcycles).
So, maybe engage the discussion at the level of dynamics rather than resorting to half thought out analogies.
__________________
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"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Last edited by Brian Ratliff; 01-24-16 at 04:00 PM.
01-24-16, 04:09 PM
#90
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They tell themselves this to justify spending $8k on the latest frame that trades stiffness (and weight) for the latest in aero design. It is all situational though. in a triathlon, yea, aero wins out (their peak power is still in the three digits). For a sprinter, stiffness is more important than aero (peak power is >1500 Watts; >2kW is routine for a track sprinter). For a climber, weight is more important than either.
__________________
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
01-24-16, 06:40 PM
#91
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Head to head test: stiff versus noodley bike
For the last 2 days I’ve done a stiff vs. noodley bike smackdown. A team-level carbon bike (stiff) vs. a 30-year-old Vitus 979 (noodle). I’m not mentioning the name of the carbon bike, because I don’t want this companies rapacious lawyers parachuting into my back yard with Kevlar vests and night-vision goggles. They’ve come after small-fry for less. But I can assure you that the carbon bike is a 2013 Tour-level, 16 pound uber-bike, the only downgrade being I was on clinchers. Of course, pros ride tubulars.
On Saturday I rode a 50-mile loop with the carbon bike. Today I rode the Vitus on exactly same route. Same clothing, same breakfast, same tire size and tire pressures. Almost identical frame dimensions and bar/saddle position.
Yesterday I felt pretty beat up. Hands, wrists and shoulders. Had to cancel my usual post-ride tennis match.
Today, I feel much better today after riding the Vitus. Got to play tennis.
I have to admit that the Vitus was likely slower. It is at least 3 pounds heavier. And on the flats, I could hear the 36-spoke wheels churning air.
But the clear evidence that the Vitus is slower, for the first time ever, I was passed by a woman cyclist. It was on the flats, she sat on my tail for a minute, she cheerily said hello, and then just powered by me. Hmmm.
But the upside: the Vitus was kitted out with 1994-vintage Campy Record shifters and drivetrain. Amazing stuff. Faster, cleaner and smoother shifting than on the carbon bike.
On Saturday I rode a 50-mile loop with the carbon bike. Today I rode the Vitus on exactly same route. Same clothing, same breakfast, same tire size and tire pressures. Almost identical frame dimensions and bar/saddle position.
Yesterday I felt pretty beat up. Hands, wrists and shoulders. Had to cancel my usual post-ride tennis match.
Today, I feel much better today after riding the Vitus. Got to play tennis.
I have to admit that the Vitus was likely slower. It is at least 3 pounds heavier. And on the flats, I could hear the 36-spoke wheels churning air.
But the clear evidence that the Vitus is slower, for the first time ever, I was passed by a woman cyclist. It was on the flats, she sat on my tail for a minute, she cheerily said hello, and then just powered by me. Hmmm.
But the upside: the Vitus was kitted out with 1994-vintage Campy Record shifters and drivetrain. Amazing stuff. Faster, cleaner and smoother shifting than on the carbon bike.
01-24-16, 06:50 PM
#92
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I knew it all along, it IS about the bike.
And you let a woman pass you, mercy! Turn in your man card and destroy the Vitus.
And you let a woman pass you, mercy! Turn in your man card and destroy the Vitus.
01-25-16, 03:50 AM
#94
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For the last 2 days I’ve done a stiff vs. noodley bike smackdown. A team-level carbon bike (stiff) vs. a 30-year-old Vitus 979 (noodle). I’m not mentioning the name of the carbon bike, because I don’t want this companies rapacious lawyers parachuting into my back yard with Kevlar vests and night-vision goggles. They’ve come after small-fry for less. But I can assure you that the carbon bike is a 2013 Tour-level, 16 pound uber-bike, the only downgrade being I was on clinchers. Of course, pros ride tubulars.
On Saturday I rode a 50-mile loop with the carbon bike. Today I rode the Vitus on exactly same route. Same clothing, same breakfast, same tire size and tire pressures. Almost identical frame dimensions and bar/saddle position.
Yesterday I felt pretty beat up. Hands, wrists and shoulders. Had to cancel my usual post-ride tennis match.
Today, I feel much better today after riding the Vitus. Got to play tennis.
I have to admit that the Vitus was likely slower. It is at least 3 pounds heavier. And on the flats, I could hear the 36-spoke wheels churning air.
But the clear evidence that the Vitus is slower, for the first time ever, I was passed by a woman cyclist. It was on the flats, she sat on my tail for a minute, she cheerily said hello, and then just powered by me. Hmmm.
But the upside: the Vitus was kitted out with 1994-vintage Campy Record shifters and drivetrain. Amazing stuff. Faster, cleaner and smoother shifting than on the carbon bike.
On Saturday I rode a 50-mile loop with the carbon bike. Today I rode the Vitus on exactly same route. Same clothing, same breakfast, same tire size and tire pressures. Almost identical frame dimensions and bar/saddle position.
Yesterday I felt pretty beat up. Hands, wrists and shoulders. Had to cancel my usual post-ride tennis match.
Today, I feel much better today after riding the Vitus. Got to play tennis.
I have to admit that the Vitus was likely slower. It is at least 3 pounds heavier. And on the flats, I could hear the 36-spoke wheels churning air.
But the clear evidence that the Vitus is slower, for the first time ever, I was passed by a woman cyclist. It was on the flats, she sat on my tail for a minute, she cheerily said hello, and then just powered by me. Hmmm.
But the upside: the Vitus was kitted out with 1994-vintage Campy Record shifters and drivetrain. Amazing stuff. Faster, cleaner and smoother shifting than on the carbon bike.
First, something is wrong with your fit or your unnamed carbon bike if you ride 50 miles on it and you feel beat up enough to cancel your tennis game. Carbon bikes as you know aren't created alike...nor are contemporary Al bikes which are leaps and bounds better than they used to be not only in ride but yes, in power transmission with their monster BB's aka new Allez.
Here is an article about the new 2016 Allez where they made the BB much stouter rivaling that of the Tarmac. Note comments by the tester.
First Ride: 2016 Specialized Allez Sprint | Bicycling
You feeling beat up has little to do with the speed difference. Perhaps you feel this is too big a price and I agree that feeling beat up after 50 miles, I would sell the bike. Consider buying a fast carbon bike with uber stiff BB that is more vertically compliant. Pick one. The world is changing. The Tarmac SL3 was a brick in vertical compliance compared to the new SL5. The SL5 is much more laterally stiff for better power transfer. There is much conflation in this thread about the two planes of stiffness. They can be decoupled which is the true advancement in technology of carbon AND latest AL bikes. If you like a lot of bar drop, consider a Tarmac. If you like to keep up with A groups in comfort, choose a Roubaix like I ride. I can't budge the BB on that bike and it is easily as fast as any uber slammed race bike. I ride with guys on Dogmas, TCR's, Cervelo S series, you name it...some ride massive bar drop...I give up nothing in speed to those guys.
But the premise of your post has been the contention all along, a bike with a stiff BB is faster than one without. That is the point of discussion here. Obviously, you do not bolster your case with your post.
The only thing you say is that your Vitus is a slower bike and you got more beat up on carbon bike.So if there is a take away, its, by all means sell your carbon bike. Ridiculous for you to feel beat up on it after 50 miles. I ride with guys who ride 80 miles a day on their carbon bikes. Then they will do a double century. So something is wrong with your bike fit, your fitness, your carbon bike or all of them. Consider even changing your riding position even tho it works for your French Vitus.
Replace your carbon frameset with one that is uber stiff laterally for efficient power transfer but is vertically compliant. The new Tarmac is a magic carpet ride for those that prefer an aggressive position. The Tarmac is as fast as a scalded dog and yet has a very compliant ride and in fact the choice of champion riders versus an Aero bike on climbing stages because of its efficiency.
Carbon like modern Al bikes are not the same. If the bouncy French Vitus...before they even went to ovalized tubing to try and take some of the deflection out...if this was the preferred formula for speed, then the whole industry would be making bikes like the Vitus...a trampoline on 2 wheels. But they don't for all the reasons discussed. I have owned steel bikes with same bouncy ride and whimpy BB where I could make the bike rattle out of the saddle. It used to be, having a stiff BB for power transfer meant a bike had to ride like a cattle truck. Not any more. Modern bikes can have a very stiff BB and yet be vertically compliant. I mentioned the Madone which has an actual pivot at the seat tube/top tube juncture. Power transfer and ride quality doesn't have to be mutually exclusive.
Good luck
PS: how fast was the girl riding? you mean you couldn't hold her wheel, really? If a girl is fast enough to past me, normally the view is good enough to draft behind
Last edited by Campag4life; 01-25-16 at 04:02 AM.
01-25-16, 03:56 AM
#95
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like a bunch of fat blokes at a pub arguing whether a naturally-aspirated 12-cylinder awd car is a more effective tool for going fast on the nurburgring than is a turbocharged 6-cylinder rwd car.
meanwhile none than lap their local tracks in a miata without spinning out.
meanwhile none than lap their local tracks in a miata without spinning out.
01-25-16, 04:12 AM
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like a bunch of fat blokes at a pub arguing whether a naturally-aspirated 12-cylinder awd car is a more effective tool for going fast on the nurburgring than is a turbocharged 6-cylinder rwd car.
meanwhile none than lap their local tracks in a miata without spinning out.
meanwhile none than lap their local tracks in a miata without spinning out.
01-25-16, 04:21 AM
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Basically the guy in the video is comparing a straight section Ti bike to a lugged straight section carbon bike aka 20 year old tech. This comparison denigrates the true advance of carbon and even Al which is differential sectional modulus throughout the bike for modern framesets. In fact, Al has proven that shape matters more than material and why Al has made so much of a comeback on the heels of determining how to mold carbon to make it create a laterally stiff bike with great ride and handling characteristics.
01-25-16, 05:21 AM
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With all this talk about frame stiffnees and so many people swearing by its benefits, I am very curious as to why the engineer filled major manufacturers do not put a specific stiffness rating on their stock frames?
If it is so important and quantifiable why not devise a method to rate it?
If it is so important and quantifiable why not devise a method to rate it?
01-25-16, 05:52 AM
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With all this talk about frame stiffnees and so many people swearing by its benefits, I am very curious as to why the engineer filled major manufacturers do not put a specific stiffness rating on their stock frames?
If it is so important and quantifiable why not devise a method to rate it?
If it is so important and quantifiable why not devise a method to rate it?
As discussed, stiffness throughout a frameset is not a monolith. Not even close. A BB in isolation...its stiffness based upon moment of inertial is meaningless without taking into account stiffness of adjoining frame sections, each tuned to a particular target for force/deflection. These adjoining frame sections contribute to any aggragate stiffness in torsion of a given frame. In fact, the latter is the predicate of wider BB shells available on Trek and Cervelo's top race frames. This increases down tube and chain stay connection for greater BB stiffness and power transfer.
In summary, there are many reasons why mfr's don't publish these values.
I ride with a friend who used to race for Trek. He is a monster of a guy...massively strong... the strongest bike rider I know in terms of physical strength. He is currently 235 and is all muscle...a weight lifter now. His racing weight was still a very large 195. He told me he used to choose his preference of Trek frame based upon bottom bracket stiffness because he could bend a frame so easily.
He isn't like the average rider or me even tho on a 20 mile ride I can keep up with him with him away from his racing form. No question he would benefit from a stiffer BB than me. He rides a Dogma FWIW which is Pina's stiffest race bike.
Last edited by Campag4life; 01-25-16 at 06:00 AM.
01-25-16, 06:40 AM
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With respect, you wouldn't ask if you understood what was written. You are in fact the guy that would misconstrue any published stiffness numbers. Further not to single you out because you are the majority who would ask such a question...mfr's posting their respective stiffness numbers as marketing fodder...this would easily be used against a particular brand or model. In fact, this 'liar's poker' is precisely why manufacturers don't post gram weight for framesets.
As discussed, stiffness throughout a frameset is not a monolith. Not even close. A BB in isolation...its stiffness based upon moment of inertial is meaningless without taking into account stiffness of adjoining frame sections, each tuned to a particular target for force/deflection. These adjoining frame sections contribute to any aggragate stiffness in torsion of a given frame. In fact, the latter is the predicate of wider BB shells available on Trek and Cervelo's top race frames. This increases down tube and chain stay connection for greater BB stiffness and power transfer.
In summary, there are many reasons why mfr's don't publish these values.
I ride with a friend who used to race for Trek. He is a monster of a guy...massively strong... the strongest bike rider I know in terms of physical strength. He is currently 235 and is all muscle...a weight lifter now. His racing weight was still a very large 195. He told me he used to choose his preference of Trek frame based upon bottom bracket stiffness because he could bend a frame so easily.
He isn't like the average rider or me even tho on a 20 mile ride I can keep up with him with him away from his racing form. No question he would benefit from a stiffer BB than me. He rides a Dogma FWIW which is Pina's stiffest race bike.
As discussed, stiffness throughout a frameset is not a monolith. Not even close. A BB in isolation...its stiffness based upon moment of inertial is meaningless without taking into account stiffness of adjoining frame sections, each tuned to a particular target for force/deflection. These adjoining frame sections contribute to any aggragate stiffness in torsion of a given frame. In fact, the latter is the predicate of wider BB shells available on Trek and Cervelo's top race frames. This increases down tube and chain stay connection for greater BB stiffness and power transfer.
In summary, there are many reasons why mfr's don't publish these values.
I ride with a friend who used to race for Trek. He is a monster of a guy...massively strong... the strongest bike rider I know in terms of physical strength. He is currently 235 and is all muscle...a weight lifter now. His racing weight was still a very large 195. He told me he used to choose his preference of Trek frame based upon bottom bracket stiffness because he could bend a frame so easily.
He isn't like the average rider or me even tho on a 20 mile ride I can keep up with him with him away from his racing form. No question he would benefit from a stiffer BB than me. He rides a Dogma FWIW which is Pina's stiffest race bike.
People buying these products are expected to understand this even without ridiculous analogies about massively strong buddies.
What's your point again?
Because you used the phrase 'in summary' yet did not summarize anything.
If each manufacturer cannot account for the stiffness in their own frames based upon the sum of the parts I seriously have to wonder how quantifiable it actually is.
It is very marketable though lol. Since you brought up marketing fodder.
Last edited by bakes1; 01-25-16 at 06:45 AM.