As with most people you get the math correct, but your tactics model is incorrect.

Most of bicycle racing is simply putting time in. It is only the rare periods - such as grades greater than 8%, that decide a bike race.

If the winning tactic is to attack on the 8% grade, then that is where you need the advantage. And light wheels provide that advantage.

I am not saying that light wheels are better on an 8% grade. There may be tactics that negate the tactic of attacking on the 8% grade. One such tactic might be to keep the speed up so everyone needs the benefit of aero wheels to stay with the leaders. Another tactic might be to let the guy with light wheels sit off the front and cook. The pack will catch him - if they want to.

The current level of analysis is not up to answering the questions.

If you are so convinced of this, show us the numbers to prove it.

So Alejandro Valverde was never a contender, either early on in this Tour de France or thoughout the last Veulta d'Espagne?


Such is their propaganda. Is it backed up in reality for every aspect? Sometimes I wonder.

Not quite, due to the non-linearity of aerodynamics, you do go a wee bit faster on a flat road if wheel inertia is increased and your pedal power is pulsing. However the effect is extremely small, should be ignored, and would require increasing wheel inertia without increasing mass.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Yes you are absolutely correct.

In both cases the effects are small enough they should never probably never be considered. They may be interesting to discuss theoretically though, or if all else where completely equal.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

An aero wheel is generally faster than a light wheel even on an 8% grade for pro tour riders.

For cat 5s it is about dead even. So if you are a cat 5 in colorado, pick the light wheel for the big climbs.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Nothing in your statement contridicts anything in my statement so I fail to see where the not quite comes from. Are saying flat out that with heavier wheels yiu can sometimes get more energy out of the system than you put in? Aside from that the power pulsing has to be a pretty specific frequency and amplitude and "would require increasing wheel inertia without increasing mass." Basically makes it impossible anyways. If it was possible we'd just keep increasing wheel mass until we get to ride 60 mph and win the Tour easily. Heck with super weight weenies parts you could build a bike with 5 pound steel rims on each wheel and still make the UCI minimum. That should be quite an improvement over the wheels the Pros use.

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Styrrell

Which wheels are you talking about. Froome used an roughly 500 gram rear wheel on the back which likely had about the aero drag of a ZIPP 202. His normal wheel is a Shimano which is going to be probably 300 grams heavier and more aero but Froome climbs fast and its a rear wheel so the aero benefit is cut by 30% or so and the yaw for him is still pretty low. I doubt the actual difference in speed for his case was very much at all up the climb, for either choice.

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Styrrell

I'm saying it isn't a zero sum game, because you go faster.

The pulsing does not have to be a specific frequency.

The current Eddy M hour record was broken with extremely heavy wheels to take advantage of this effect, if he was increasing wheel weight to hit the uci minimum that would make sense. It might even make sense to add mass above it, given the CRR is so low on a velodrome.

The advantage of the increased inertia only applies when going a near constant speed with oscillations. It would be lost the minute you attacked or had to surge. So given how small the effect is, I don't think it would ever be a net advantage to weight weenie everything and run super heavy wheels.

Maybe for a time trial though! Unless the starting acceleration penalty overwhelms the advantage.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

 Rule of thumb here? Are you saying they should all be riding 808s, or is 30mm enough?



quote jackmott]An aero wheel is generally faster than a light wheel even on an 8% grade for pro tour riders.

For cat 5s it is about dead even. So if you are a cat 5 in colorado, pick the light wheel for the big climbs.

[/quote]

The increase in speed during one pedal stroke is so small I can't see how heavier wheels would make a significant difference. I suspect Eddy used them to increase inertial load which feels better and allowed him to put out more power. Similar to the reason many riders have trouble putting out the same power when riding on a low inertia trainer.

On the wheel inertia going up an 8% hill, I happen to have an old inertia noodling spreadsheet model lying around to provide some numbers.

Assuming:
1. Equivalent weight bikes (i.e. UCI minimum so lighter wheels require more ballast)
2. Light wheel of 500g with all weight located in rim
3. Heavy wheel of 900g
4 Starting speed of 20kph (~390w for Chris Froome) on an 8% hill
5 Attack with 700w for 30s reaching 32kph

It takes 13J to spin up the lighter wheel from 20 to 32kph and 24J to spin up the heavier wheel. Thus the penalty for using the heavier wheels during this acceleration is 11J spread over 30 seconds or a whopping .35W for 30S. This is not surprising as it doesn't take much effort to spin a wheel up to any speed on a bike stand.

I think any aero benefit would outweigh .35W.

It's funny...we keep doing the math on this and yet nobody believes it...and major cycling review publications insist on using wheel inertia as a major ranking point when doing wheel reviews.

Madness :-/

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http://bikeblather.blogspot.com/

That's what I was looking for. Thanks.

It doesn't make a significant difference. I said that from the beginning.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I'm officially in the market for some 1080s

I'm still waiting for "An old guy" to show the maths to the contrary...

I thought you were implying Eddy went faster because the heavier wheels were smoothing speed variations from his pedal stroke.

Eddy didn't really have heavy wheels but the current record holder did. although he also tested positive 2x, just not during the record attempt.

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Styrrell

To quote an old boss of mine, "I don't need math to tell me what I already KNOW!"

(BTW, this was in regards to something he was provably wrong about) ;-)

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http://bikeblather.blogspot.com/

I do not think the math is the problem. It is more the willingness to adapt.
It is interesting that in F1 racing the engineers can take the data and cross reference with the drivers experience. Many times the driver's perception is not accurate. One of the few who was close to matching the data was Schumacher.

In cycling I think we are dealing with a lot of the same. What feels correct is not necessary the fastest. Really light wheels feels great, but that is an emotion not speed.

The Olympic champion in cross country skiing Thomas Alsgaard brought the favorite pair of skies to a test for the manufacture Madshus. This was the pair he had had some amazing races on. After he tested that pair against the new pair he said, "I cannot believe I was happy with my old pair." The old pair was good for its time, but crappy compare to the new skis.

I'm starting to think we should institute a Math and Physics quiz that everyone on ST has to pass before they're allowed to argue about aero/weight/related topics.

I tend to be all for letting ignorant people be ignorant. It gives me an advantage :)

Hi Halvard,

Grat story, thanks. I just want to quote this part:

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Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

cdw did so:


cdw wrote:
The modeling shows that you need an 8 percent grade for "light wheels" to outperform "aero wheels." Now, they certainly hit those grades on occasion, but for the other hundred miles of riding the aero wheels have been outperforming light.

Harrass him for the numbers if you want them.

That seems like a broad conclusion. What do you base that on?