Eric F 

In my early road racing days (late-'90s), I was on a long mountain ride with some friends. One of whom was rolling his new set of Mavic Cosmic Carbone wheels. I don't know the exact specs, but they were 50+mm deep, and probably weighed more than 2000g. He weighed about 10lbs less than me, and we were on similar steel-framed bikes. My wheels were typical 32H shallow aluminum rims. That was the first day I witnessed the advantages of aero wheels. On long coasting downhills, despite being heavier than my friend, I could not match his speed with our bodies in similar positions on the bike. It was vivid.

These are the same wheels I commented about earlier in this thread in regards to the "flywheel effect" sensation.

rsbob 

Any sane person with an advanced degree in engineering, physics or math would stay the h away from this forum.

tomato coupe

As part of my plea bargain (for dooring cyclists), I have to perform community service, which requires that I post a certain number of times per month on biking forums.

Fredo76

Is my statement just preceding incorrect or worded wrong? I thought 2x during acceleration was right in the model. I thought that right there was the 'basic physics' involved WRT rotating weight at the radius.

As far as actual results, if the measurements are capable of recording small real-time changes in the rotational speed of the wheels, and the data indeed shows such changes, I would call those accelerations, and say they matter. Can we measure "wow and flutter" for a bicycle wheel? I would suppose that it's possible.

But, I'm only a computer scientist...

What do the observations show?

terrymorse 

I got the degrees, but I don't think I'm nuts.

I prefer to call myself "colorful".

Eric F 

I request a second opinion.

rsbob 

They never do. Insane by degrees? But colorful works too.

Eric F 

As mentioned by TC previously, additional weight of a heavier wheel isn't all located at the outermost part of the wheel. A heavier axle would not be affected by any rotational effects. A heavier hub would be less affected than the rim.

I'm just a dumb contractor, though.

urbanknight

That's the speed I climb at thanks to a lot of extra weight around my mid section. Now I'm going to shave 2lb off my wheels to compensate.

rydabent

Bikes with disc brakes can have rims that are lighter more aero and stronger.

tomato coupe

3 swings, 3 misses, you're out.

PeteHski

Yes you can very roughly approximate to double the mass during acceleration. But that is if 100% of the wheel mass is at the outer diameter. Obviously it will be somewhat less in practice.

While that may sound significant, the accelerations are very small and insignificant in all but full bore acceleration from a standstill. Even then the rate of acceleration is maybe 0.1 to 0.2g for only a few seconds and we are talking about accelerating only a few hundred extra grams on modern aero wheels.

Data from a head unit is typically recorded at 1 sec intervals and show virtually zero acceleration during a steady state climb. Changes of speed with gradient and power variations are usually happening at a snails pace. If you fitted an accelerometer on the bike it would just flatline on a climb. So 2M x zero = zero

Also, as repeated many times, unless you are actually using your brakes, the work done in accelerating the mass will be recovered during deceleration. So any cyclical micro-accelerations will be smoothed out over the pedal stroke. To even see them you would need to log speed at 0.1 sec intervals or faster. But that’s a total waste of time when those accelerations are almost infinitely small.

I worked in F1 as a race engineer for a decade and even in that extreme case rotational inertia of wheels is not a very significant factor in the vehicle model. It’s an order of magnitude below the effect of the static mass. It can easily be modelled and often is for completeness.

In summary you can treat the wheel mass just like any other mass on the bike and rider for the purpose of calculating your speed on a climb. Obviously lighter is better, but as the pros have figured out, aero gains can often offset the weight penalty depending on rider speed and gradient.

PeteHski

Maybe that’s why I tear my hair out on BF alternative physics discussions!

tomato coupe

Quick back-of-the-enveolpe calculation: an extra 100 g located just inside the rim will cost you less than a watt if you're climbing at 60 RPM, and you accelerate from 5 mph up to 10 mph every pedal stroke.

PeteHski

Yeah and my second to second speed variation on a climb is typically 0-0.1 kph. Virtually nothing as far as changes in wheel rotational energy are concerned.

Maelochs

You make it sound so reasonable.

But don't get complacent because ... there is surely a flaw in there.

There must be---because it makes sense to me. When it comes to math and physics, if I think i get it, it isn't what it is .....

So .... this is the miraculous once-in-a-lifetime when I get it .... or this thread is destined to keep shambling along like a headless zombie.

PeteHski

Friends do say I’m quite good at explaining this kind of thing. Working in motorsport engineering for several decades has probably honed that skill. I’ve also developed a really good sense of what parameters matter and don’t matter in vehicle performance. Whether that vehicle is a bicycle or F1 car.

But I won’t get complacent, because I’m sure someone will disagree and come up with some exaggerated anecdote in an attempt to derail it again. What you have to question is their qualifications and engineering knowledge.

Personally I try to only argue about things I’m at least 99% certain of. If I’m uncertain I will say so and listen carefully to anyone who appears to know something I don’t. But I note on BF there is no shortage of people willing to argue stubbornly with little or no knowledge or experience of the subject matter. So threads like this always end up a confusing mess to anyone trying to learn with an open mind - like yourself. But I think you’ve sussed this one out.

Atlas Shrugged

It appears another fable of cycling's past slowly gets beaten down through facts and logic. A freshly recalled mussing from the times of Coppi, Anquetil or Merckx will soon arrive on the forums to entertain us for a while. From the magic of frame builders whose names end with a vowel, superiority of tubulars to more modern myths such as the mysterious vibration absorbing qualities of titanium there will be BF to entertain us.

Maelochs

My bike is faster because it "planes" ......

PeteHski

They are certainly entertaining. We get the same thing in motorsport too. I give you Carroll Smith’s infamous book “Tune to win”. Alternative physics from the 1970s guaranteed to have any University engineering lecturer face palming on every page!

Then you get F1 fans writing in telling us how we are all doing it wrong. No qualifications, no experience, yet very confident in their assertions. One of our engineers used to run a monthly forum where we would review such letters just in case there was a hidden gem of knowledge. I don’t recall ever finding one, but it was definitely great entertainment 😂. I bet football managers get thousands of these too.

Jrasero

I have the previous HUNT Aero Light Disc Wheelset but these are 28mm and 1469g and I love these wheels. I have them on my Litespeed Cherohala City and there amazing for the price. No they are not as responsive and nor light as a carbon wheel but for $500 these have been rock solid

Also $500 more or less to drop 1.5lbs is actually a relative great deal. 1.5lbs off a bike especially rotational weight is huge. I know there some, "just loose weight" bros but 1.5lbs again on a wheelset is massive

Jrasero

Sure but unless OP wants to go used which IMO is a compromise to begin with what light, deep, carbon aero wheels are out there for $500? The Hunts IMO are a perfect blend of weight and performance especially when you factor is price point. IMO in order to get a "decent" set of deep wheels a bare min they would need to spend $900+

surak

Yup, my point is $500 wheels are not worth buying. Save the money toward an upgrade that will make an actual difference. The Hunts are a compromise at that price point just like any other wheels.

Jrasero

Compromise? Listen again at $500 you will have to make grander compromises. I think OP didn't really give much info on their use case besides they ride on flats and thus people assumed deep aero wheels. I personally have the older version of the Hunts on a hybrid/gravel bike and love them for an around town bike but I could see these as a decent set for climbing or training on a budget. Yeah their bets bet is just spending $400 more since hunt sells 45, 50, 65 aero wheels for sub $1K but if they have a hard budget of $500 and don't want or need that aero benefit then I am not getting how these are a waste

Maelochs

The OP has a hard budget of $500, so maybe we should be suggesting the best wheel for a rider on mostly flatland for $500?

Anyone who wants to donate the extra $400 .... go right ahead.

Recall though, that it could be that it would be a year or several of riding his OEM boat-anchors before he could upgrade.

Not sure what the crazy folk (i.e. the ones with math/physics/engineering degrees) think, but with the aero he will still be dropping some weight, and gaining that ultra-important (some claim) aero benefit.

Personally I'd jump on the lighter wheels ... because I am about as aerodynamic as a house. I also weigh about as much as a house, so in either case .... Marginal Gains.

If the OP wants aero, let's all just tell him aero is proven better by the dense and difficult-to-decipher posts of the Colorful Crowd, and he can rest easy with what he always wanted.