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PostPosted: Sat Nov 11, 2017 1:19 am 
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I would argue that those stiffness improvements are inconsequential for performance regardless of power output.* They won't affect efficiency. But stiffer components feel nicer and more responsive than flexy ones, generally speaking, and some people really like that.

I've been engaged with the technical side of this for so long that I have a hard time guessing how non-technical people understand these things (as you may have noticed ;) ) So I have a serious question: when non-boffins buy a new frame that's advertised as, say, 12% stiffer than their old frame, do a plurality of them expect to be faster because of that stiffness?

I'm not asking to make fun of anyone who has that expectation...it's not a crazy idea. I legitimately can't fathom whether they might think that. Or is it more like, "well, it's stiffer, so it might be a little faster when I'm really sprinting hard"? Either one is reasonable.


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* Pros aren't gods; they're just faster than the rest of us. Their requirements aren't wildly different from those of amateurs. Pros don't even necessarily make more power than amateurs. Nairo Quintana weighs about 58 kilos and generates around 6.5 watts per kilo at FTP. That's a sustained 380 watts. Meanwhile, a 2-meter-tall 110-kilo cat IV may make 3.5 watts per kilo for 385 watts sustained. Similarly, a sprinting cat IV generates about 15 watts/kilo, while Andrei Greipel probably puts out more like 25 watts/kilo when sprinting. In other words, regardless of weight, pros make less than twice the power of amateurs. They ride way more miles and in arguably rougher conditions, but it's not like Andrei Greipel could bend a Shimano 105 crank with his legs.

By way of comparison, my Subaru BRZ, a sportscar, makes 200 HP/149 KW and weighs 2750 lbs/1250 kilos. An F1 car makes about 900 HP/675 KW and weighs about 1650 lbs/750 kilos. My BRZ therefore makes 120 watts/kilo (on a good day) and the F1 car makes 900 watts/kilo, for a power-to-weight ratio nearly eight times that of my Subaru. I'd only need to boost my car's output to 333 HP if I wanted to make it faster in the same way that Andre Greipel is faster than your average Cat IV. People do that all the time with BRZs; it only costs about $5000. If I could somehow make myself sprint like Greipel, it would be a bargain at ten times the price!


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Posted: Sat Nov 11, 2017 1:19 am 


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PostPosted: Sat Nov 11, 2017 1:58 am 
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I still don't understand what's so misunderstood by the OP. Is this really about how pros ride less-than-ideal kit or why fans of the sport love dumping loads of cash on kit despite knowing it won't make them as fit as their idols?

Richie Porte is 5'8 and has a threshold of around 400w. We ride the same frame, therefore it's certainly way more than good enough for my sorry ass. Likewise, Wiggins did 472w over 52 minutes at the London Olympic time trial while using SpeedPlay, therefore the power transfer efficiency you get from them is without a doubt more than good enough for me and is not what's holding me back. See? The argument is both easy and logical. You can buy whatever piece of kit you like for whatever reason you want. If someone justifies their use of whatever equipment while citing pros that are better than any of us, it's fair game. If anything, it shows how ridiculous the person critiquing this argument is being, because they can chase whatever boutique, high-performance piece of kit that is "better than what the pro's use" but at the end of the day, the gap between pro-used equipment and whatever high-end equipment still won't make up for the lack of comparable fitness.

If you prefer X equipment because of whatever performance benefit you think it has over pro-used Y, go for it. But maybe don't shit on someone using Y because it's absolutely more than good enough for them.

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Last edited by bilwit on Sat Nov 11, 2017 3:43 am, edited 1 time in total.

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PostPosted: Sat Nov 11, 2017 2:23 am 
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The way I understand it, the OP was annoyed when others used "the pros ride it" as a trump card for debates about equipment when he'd rather have a thoughtful discussion.

I'm sort of sympathetic. Pros are very conservative and not as technically savvy as some assume, so I think it's a little silly to hold them up as technical exemplars. But I don't care what anyone else rides or why they ride it. I usually race crits, and I want my competition to ride light, shallow wheels with lots of drag and super-stiff, 35mm-diameter round-section bars with lots of frontal area. It only helps me (infinitesimally)*.

But if you complain about someone else's equipment to the point where they need to "rebut" your complaints, that's a little ridiculous. Maybe the OP can weigh in and clarify what he meant.



*They say lotteries are a tax on people who are bad at math. Similarly, you could say that bike racers who are bad at physics have to pedal a little harder than everyone else. I knew one guy who declined to buy a power meter and instead bought PowerCranks (the left and right crankarms freewheeled individually, forcing you to keep your legs in sync yourself. It was really hard to do and didn't make you any faster). He was a friend of mine, and I didn't want my friend to waste his money; I advised him to get a power meter. But he was convinced, partially (IIRC) because some pro swore by those cranks. At that point, what can you do?


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PostPosted: Sat Nov 11, 2017 8:55 am 
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Bilwit, youngs_modulus is right about the point of the OP. Its not to suggest that the PRA is illogical, rather, it just doesn't ad value to the determination of 'what it's like' to use a piece of equipment. As such, its moot and defeats the purpose of asking 'what it's like' questions on forums such as this.

youngs_modulus you've made a fantastic contributions to this thread, thanks!

To answer your question about manufacturers reports about metric changes in quantities like stiffness, I do not assume that such 'improvements' yield greater speeds for the user. Rather, I may be more inclined to believe that the new model will feel nicer than the preceding one. That kind of assumption seems to make sense, particularly with carbon bikes e.g. they've gotten lighter and more comfortable over the last 15 years all whilst maintaining/improving the feeling of 'stiffness/responsiveness' whatever that may be. I guess overtime manufacturers have become more adept at converging of high levels of difficult to combine properties within the same frameset (weight, stiffness, comfort, aero) e.g. my XR4 feels fairly stiff but it possesses a level of comfort that is absent in any other racer I've tried all whilst being bullshit-aero and not grossly overweight.

Also kudos on the 'pros arent gods' argument. It helps put things in a clearer light.

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PostPosted: Sat Nov 11, 2017 8:50 pm 
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youngs_modulus wrote:
You're close about the power loss, but there's more to it.

Power is absolutely lost through strain; it's just a very small amount. Laminar composites dissipate more power than steel or aluminum...they damp better, and damping is energy dissipation. Things that don't spring back as fast as they're deformed are said to exhibit hysteresis. Tires have a lot of hysteresis, relatively speaking, which is why some tires have much less rolling resistance than others. (N.B.: tires are also laminar composites).

Even if deformations are perfectly elastic, it's not clear that the energy absorbed in bending is all returned as useful work. This is a hard thing to test, and there's been a fair amount of debate about it. For example, cranks deform torsionally quite a bit at the 3:00 position. The crank "unwinds" as you go through the rest of your pedal stroke, but there's no obvious way for that unwinding to be converted to forward motion.

Finally, no, you can't "optimize" power delivery on a bike via tuned flex (AKA driving at resonance). Think about it: you just said that no power was lost to flex, and then you wondered whether you could gain efficiency with tuned flex. If you weren't losing any energy to flex to begin with, how can you get anything back with tuned flex?

I'm not trying to come down too hard on you here: you're right that energy losses to deformation aren't worth worrying about because they're so low. Also, other sports equipment like tennis rackets and golf clubs do deliver more energy via tuned flex. (Notice a theme here? It has to do with impulse...) These are reasonable questions to ask. I've done a fair amount of work on this question, so I'm skipping right to the answer (insofar as we have one).

Finally, what you're suggesting about resonance is essentially the same idea as Jan Heine's "planing" concept, which (in Heine's case) is straight-up cargo cult science*. People who like Heine tend to accept the "planing" idea as true, or at least plausible, which it isn't. As a federally licensed boffin, I feel obligated to explain this. ;)




*Just today, I ran across a post on Heine's web site wherein he makes it clear that he has no idea how vectors work. That would be fine, except his post is primarily a rumination on how vectors work. This was pointed out to him in the comments, but he still didn't get it.


The level of detail and careful thoughtful analysis that I have seen here from you and Rick is what I was hoping to see in the "Does stiffness matter" thread a few months ago. I didn't expect to see it popping up again here but, bravo.


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PostPosted: Sat Nov 11, 2017 9:53 pm 
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My only anecdote to this fabulous thread is to confirm the notion that pro's are not especially technically savvy. I've had the opportunity to work for the service course of a U.S. Women's team and they just want their bikes to "go". I suppose a sexist slant can be brought to this in that "male pro's are more technical, therefore my experience is moot", but I have a feeling...........


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PostPosted: Sun Nov 12, 2017 8:59 am 
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Pros may or may not be "technically savvy" (some of them are too savvy btw) but there is a whole team around them with managers, coaches, engineers, physicians, technical advisors, sponsors etc.
Thinking that all these persons are not that "techically savvy" either is a naif thought, at least...

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PostPosted: Thu Nov 16, 2017 5:33 am 
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Speaking of flexy bikes
bottom of the page.
Quote:
Standing in place of a conventional down tube is a high-strength steel leaf spring. According to Alter Cycles, the leaf spring stores and releases energy while riding, supposedly harnessing more of your pedaling force into forward motion. In addition, the spring lets wheelbase change in response to bumps for a smoother ride. If this sounds familiar, it perhaps should since the folks behind it are the same people who ran Slingshot Bicycles back in the day. This latest design follows the same principle, but allows for more movement. We’re considering bringing this preproduction prototype in for a first-hand evaluation.

https://cyclingtips.com/2017/11/photo-g ... art-three/
Image

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PostPosted: Thu Nov 16, 2017 10:36 pm 
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silvalis wrote:
Speaking of flexy bikes
If this sounds familiar, it perhaps should since the folks behind it are the same people who ran Slingshot Bicycles back in the day.

I used to race criteriums with a guy who was sponsored by Slingshot. Furthermore, he would show up at the criterium with the MOUNTAIN BIKE version of their cable frame design, with just smooth road tires substituted for the knobbies. He was a just-sub-elite class rider (don't know specific details) but I know he would always beat me.

Maybe that is when I started realizing that the bike doesn't really make much difference one way or another. ;)


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PostPosted: Fri Nov 17, 2017 7:56 pm 
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kgt wrote:
Pros may or may not be "technically savvy" (some of them are too savvy btw) but there is a whole team around them with managers, coaches, engineers, physicians, technical advisors, sponsors etc.
Thinking that all these persons are not that "techically savvy" either is a naif thought, at least...


Exactly, SPONSORS. TEAMS. People who have made products that have to survive x number of cycles in a rig and feel good to y number of people. You always say aero is marketing but you can't see that this is the biggest marketing exercise of them all?

RIDE WHAT THE PROS RIDE. That's marketing.

You forget that there is one thing that trumps the entire team of managers, coaches, engineers, physicians, technical advisors, sponsors, etc. If the pro doesn't want to ride it, he won't. There are many in the peloton where nothing will change what they felt and biases established when they were growing up in U18 and U23 racing.


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PostPosted: Sat Nov 18, 2017 6:39 am 
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I personally like the fact that we can have the same material (or almost the same) than the Pros! :beerchug:
In some other sports you just cannot get the same material (car racing, motorcycle racing, etc...)

Then it is up to you to buy/use it or not BUT at least we have this possibility :thumbup:


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PostPosted: Sun Nov 19, 2017 12:26 am 
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kgt wrote:
there is a whole team around [pros] with managers, coaches, engineers, physicians, technical advisors, sponsors etc.
Thinking that all these persons are not that "techically savvy" either is a naif thought, at least...

It's not that simple; I read somewhere that Armstrong used a Specialized Trispoke when other wheels would have been faster; the person telling him to skip the trispoke was some guy named Steve Hed. (It's my understanding that the Trispoke was only marginally slower than the alternative, however).

justkeepedaling wrote:
Exactly, SPONSORS. TEAMS. People who have made products that have to survive x number of cycles in a rig and feel good to y number of people. You always say aero is marketing but you can't see that this is the biggest marketing exercise of them all?

RIDE WHAT THE PROS RIDE. That's marketing.


I'd say this is a little reductive too. There's a saying in horse racing and motorsports: "racing improves the breed." Some sponsors really do use their pro riders to make better products. Others treat sponsorship as a pure marketing exercise.

Some people treat "marketing" as a four-letter word, as though any company that engages in it is somehow dishonest. I don't agree with that...all companies try to show their products in the best possible light. That's their job. Ours as consumers is to educate ourselves so we can choose what we like without being swayed by specious claims.

justkeepedaling wrote:
If the pro doesn't want to ride it, he won't.

This is true only for superstars. Sponsors have a right to expect their teams to use the provided equipment. The vast majority of the peloton rides what their sponsor provides.

justkeepedaling wrote:
There are many in the peloton where nothing will change what they felt and biases established when they were growing up in U18 and U23 racing.


This I agree with wholeheartedly. Pros tend to be very conservative, but for good reason: they can't afford to throw away any victory due to equipment failure. Combine that with soigneurs and mechanics who are deeply bound to tradition and directeurs sportif who are mostly former pros and you have a culture that's constitutionally averse to change.

Back in the '90s, I worked for a bicycle trade magazine. We'd occasionally hear rumors that we couldn't pursue or write about because they were just hearsay and not especially relevant to the bike industry. One of the rumors I heard was that one reason (among others) that Greg LeMond was despised by some members of the European cycling establishment was that he was not sufficiently respectful of tradition. I mean, they got really mad because he played golf and ate ice cream.

LeMond was among the first pros to use both aero bars and clipless pedals. He was on Calfee carbon frames when many pros were still riding steel bikes. LeMond's technical sophistication made him an outlier among the pros, and it certainly didn't help his popularity. The sport is not quite so hidebound now, but it's not exactly open to new ideas, either.


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PostPosted: Sun Nov 19, 2017 12:31 am 
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wheelbuilder wrote:
My only anecdote to this fabulous thread is to confirm the notion that pro's are not especially technically savvy. I've had the opportunity to work for the service course of a U.S. Women's team and they just want their bikes to "go". I suppose a sexist slant can be brought to this in that "male pro's are more technical, therefore my experience is moot", but I have a feeling...........


I wouldn't say that's sexist; there are plenty of male pros who feel the same way. A friend of mine turns wrenches for a prominent (male) pro cyclocross racer. My friend occasionally suggests moderate changes to equipment or setup, but the pro won't hear of it. He knows what worked before, and sees almost any change to that as threatening. The guy's not dumb or anything...he just isn't interested in technical things and wants to keep his setup constant. It's a point of view I find completely alien, but it's a legitimate one.


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PostPosted: Sun Nov 19, 2017 12:38 am 
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TheKaiser wrote:
The level of detail and careful thoughtful analysis that I have seen here from you and Rick is what I was hoping to see in the "Does stiffness matter" thread a few months ago. I didn't expect to see it popping up again here but, bravo.

Oh, man! I saw that thread and really wanted to participate, but I had a ton going on in my life at the time and just couldn't.

Thanks for saying nice things about what Rick and I posted. I enjoy debating these things, especially with someone (like Rick) who knows his stuff. But those debates are just about angels-on-the-head-of-a-pin unless they help other people learn about this stuff. When I was in college, I learned a lot from Jobst Brandt's posts on rec.bicycles.tech. I'm no Jobst, but I'm glad at least a few people find these threads illuminating.


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Posted: Sun Nov 19, 2017 12:38 am 


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PostPosted: Sun Nov 19, 2017 1:26 am 
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i place more stock in what experienced ex-pros chose when they are no longer beholden to a team or a manufacturer. when they are making personal decisions based on their own years of experience using their own funds its a bit more honest.

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