Do they know what they talking about?

There are a lot things that influence what a rider feels on the bike, and many of those things have nothing to do with the performance they think they're feeling/seeing. Given that, I take wheel reviews with a grain of salt and discount them completely when they say things like, "The wheels make the bike accelerate like a rocket", "The wheels want to climb without me even pedaling", or "I gained 5mph in my average speed with my new wheels!" Yes, there are other things to consider about wheel performance besides how someone perceives they accelerate, things like durability, handling in wind, trueness, handling in general, ride qualities, and so on. The science says that acceleration differences between wheels of different weight are smaller than people would think, and that's using models that use a moment of inertia expression for wheels that produces relatively large differences in wheel acceleration as a function of weight. Using actual wheel moments of inertia makes the acceleration differences even less.

Ask Chris Froome if he knows what he is talking about. The dude accelerates.

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What little Columbians on Movistar climb on...ask Quintana about accelerations.

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Ask Riblon. Double Alpe du Huez stage winner on his Fulcrum low mass wheels that accelerate better than aero wheels.

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Polka dot outfits and lightweight wheels...who'lda thunk it?

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When acceleration matters those that really know the score go for reduced mass.
Queue the moment formulas...in Three...Two...One...

Aero for the flatter stuff and TT's, of course.

i broke the last two light rear wheels that i had in a fairly short mileage, so two facts i already knew but that i can now almost prove: 1) excess body weight (in my case a lot) takes their toll on your bike 2) bomb proof wheels ( 36 spokes, a bit wider rim & tyre) make you go slower (a couple of minutes slower for a course that i use very often)

There is a major issue with the "acceleration" argument, which is the speeds which most of us accelerate at in bike races. We feel the difference when going from 0 to 15mph, but in a race it is often going from 23 to 30 mph. Sure if you are on a mountain lower profile wheels may make a difference, but it is all down to the speed and affect of weight vs affect of aerodynamics. Cavendish races on 808's because they accelerate faster than lightweight wheels at the speeds he is going in a sprint.

Part of it is mental too, for pro's if they think the wheels are faster they are, because at the speeds the are going most calculators will show that a basic aero wheel is about even with a low profile ultralight wheel (202s or 303s vs featherlight stuff)

Quoted post said:

Originally Posted by joroshiba [IMG]/img/forum/go_quote.gif[/IMG]...Part of it is mental too, for pro's if they think the wheels are faster they are, because at the speeds the are going most calculators will show that a basic aero wheel is about even with a low profile ultralight wheel (202s or 303s vs featherlight stuff)

I'd say a very big part of it is mental and perhaps more for amateurs than pro's.

People are convinced that rotating mass and MOI is super important and in most cases it just isn't. Don't forget that you have to accelerate your own body and bike mass in a linear way as well as the MOI of the rotating wheel. Do the math on kinetic energy changes of even a lightweight 60 kg of rider plus bike and then how little a percentage a couple of hundred grams of rim weight and its associated MOI is of that total change in kinetic energy. And that's not even getting into potential aero benefits of higher MOI but more aero wheelsets. Some pretty good examples over at: http://www.analyticcycling.com/ check out the discussion, examples, and calculators under the Wheels & Aero & Weight tab. Sure MOI is real but it's not as significant as many riders think.

-Dave

Read Mark McM's analysis over at Weight Weenies. In his analysis, the wheels are modeled such that they would yield more extreme differences in acceleration and velocity than real wheels (i.e. they're model as if all of their mass is in an infinitely thin hoop with the same diameter as a bicycle wheel). To make the results stand out more, he does the calculations for three different wheel set weights (0kg, 5kg, and 10kg) on two different climbs (one with a 3% slope, the other with a 10% slope). The acceleration in his model shows up as a result of power being applied sinusoidally, and you can see it in the velocity variation he reports. All the simulations are done at the same power output (250W). The end result is that velocity doesn't fluctuate much between the wheels and climbs, meaning the resulting accelerations don't vary much between the wheels and climbs. Again, I'll emphasize that if the wheels were modeled more accurately--i.e. they used the actual measured moment of inertia of the wheels--the differences you'd see would be smaller. You have to be careful when you use what racers do as an explanation of something. In racing, competitors will do virtually anything to gain any edge whatsoever, even if what they do produces a negligible edge or merely a psychological edge. A psychological edge can be a huge factor in performance. What pro racers do doesn't necessarily demonstrate any physical reality. For that, you need science and math, and as Neil deGrasse Tyson said, "The good thing about science is that it's true whether or not you believe in it."

Guys that earn their living while pissing themselves on a bike and that have their pick of every component in the service course garage generally choose the stuff that gets them their next paycheck.

If Hewlett-Packard calculators were turning the pedals the winners would all be on Zipp 808's "smoothing out their pedal strokes". But, they're not.

Want to know, qualitatively, how much effort it takes to accelerate a rotating wheel?

Put your bike on the trainer without any resistance and pedal. Going from 0 to ridiculous is requires trivial effort. Multiply trivial x 2 for the effect of both wheels.

Better yet, do 100 jumps from 10 MPH to 20 MPH with a pair of climbing wheels and repeat it on Zipp 404's.

Get back with me as to which pair of wheels you want to use to do a third set with resistance this time.

maydog said:

Want to know, qualitatively, how much effort it takes to accelerate a rotating wheel? Put your bike on the trainer without any resistance and pedal. Going from 0 to ridiculous is requires trivial effort. Multiply trivial x 2 for the effect of both wheels.

+1.

Quoted post said:

Originally Posted by CAMPYBOB [IMG]/img/forum/go_quote.gif[/IMG]

Better yet, do 100 jumps from 10 MPH to 20 MPH with a pair of climbing wheels and repeat it on Zipp 404's.

Get back with me as to which pair of wheels you want to use to do a third set with resistance this time.

Ya know the science on that is very clear and the 404s win out every time.

But I know you don't believe in science. So let's make it simpler. How many sets of climbing wheels do you see during high level track racing where repeated accelerations are the name of the game? Which type of wheel does a national level points racer roll? How about a pro track sprinter that has to accelerate from slow speeds and sometimes a complete standstill on the track, what's Sir Chris Hoy or Theo Bos running in competition? WIth elite track racers it's usually something like this:

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You could also ask why Jens Voigt, Cancellara, Cav and others actually do ride and win races on something like Zipp 808s. Your assertion that pro riders don't ride deep wheels is pretty dated, sure many still opt for weight over aero properties on the big mountain stages in part because they have to descend on those wheels as well and in part because they believe what they believe. Josh over at Zipp has written some interesting things about discussions with folks like Contador and others and how they can do the tests, look at the results but still stick with what they 'know' to be true and in the end you go with what the pro wants whether or not it makes sense. But realistically there are an awful lot of deep wheelsets rolling in the pro peloton on most days.

Maybe these guys didn't get the memo:

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But I'm sure you'll cut and paste me into submission as when it comes to image surfing to 'prove' a point I openly admit my skills are not on par with yours Campy.

Cheers and roll what you will but just not liking the physics doesn't make it go away. You do realize this is the same physics that is used to design jet airliners and modern fuel efficient cars. I'm thankful the engineers working on those projects don't trust their instincts and mythologies over science. There that should give you even more fuel for a psychotic tirade and internet clip fest.

That should keep you busy for a while and out of trouble, happy to help 😉

-Dave

"How many sets of climbing wheels do you see during high level track racing where repeated accelerations are the name of the game?"

Please quote the number of accelerations per miss & out v. a Tour stage over three Cat. 3 climbs, a Cat. 4 climb and and hors cat. finish. Please quote the speeds achieved during a kilo, match sprint, miss & out, keirin, etc. v. climbing the Alpe...twice. The track ain't the Pyrenees or Dolomites.

"How about a pro track sprinter that has to accelerate from slow speeds and sometimes a complete standstill on the track,"

Please quote the number of accelerations and terminal velocities of a match sprint v. 40 minutes of climbing. One v. ??? 70+ KPH v. ??? Please quote the advantage in watts launching a dive off the rail gives over driving an attack straight up a 10% grade.

"Your assertion that pro riders don't ride deep wheels is pretty dated..."

Woah, woah, WOAH! there Tonto! Just where did I say riders don't ride deep wheels? Learn to read. I actually said, "Aero for the flatter stuff and TT's, of course.". Very first post. Very last line. Next time I'll put it in 36-point Arial font if you think it will help. I'll also be certain to add "various & sundry track racing disciplines" to that qualifier, next time around.

"I'm thankful the engineers working on those projects don't trust their instincts and mythologies over science."

33 years in aerospace engineering and 42 seasons of cycling. I'll continue to trust my "instincts".

"There that should give you even more fuel for a psychotic tirade and internet clip fest."

Sucks to see the winners on low pro wheels? Why does that stymie the physics and 'science'? It's like...an alternate universe where the Newtonian Laws are all backwards 'n stuff.