I'll try.

Push straight down on the wheel axle. The rim deflects at the ground, the spoke tension there decreases. If the spoke is thick and inflexible, the tension will drop substantially. If the spoke is thin and flexible, the tension will not drop nearly as much.

Fatigue-prone materials like aluminum last longer when their cyclic stress amplitudes (difference between max and min stress) are smaller, so the thin spokes maintain a higher tension and make a more durable wheel.

A thinner spoke stretches more for a given tension.

I'll make a crassly over the top example.

Let's say a 2mm spoke stretches 1mm with a tension of 100kgf. If the wheel is loaded so much that the rim moves 1mm towards the hub, some spokes are going to go completely slack.

If a 1.8mm spoke stretches 2mm with a tension of 100kgf, when the wheel is loaded enough to move the rim 1mm towards the hub you'll still have 1mm to go before the spokes go slack.

I don't know how much spokes stretch. I picked easy to use numbers. But that's the basic principle of it.

This is exactly what I expected from this thread.


https://cimg9.ibsrv.net/gimg/bikefor...225eb0c7a3.png

Got it. Thanks!

First paragraph also (I think) indirectly explains why DB spokes are preferable: the spoke can flex more, and can flex more along its center section rather than concentrating the stress at the j-bend.

Zipp did a calculation on the power required for a full bore acceleration on 2 sets of wheels (see page 7 - Inertia):-

https://www.sram.com/globalassets/pu...explained2.pdf

Summary:-

For a 20% lighter wheel with 23% less rotational inertia, the difference in power due to the reduction in wheel mass was 3.5W and the difference in power due to rotational inertia was 0.6W. The total power required was 1076W of which the wheel mass contributed 38W total (3.5%). The total rotational inertia component was 9W (0.8%)

Remember this is for maximal sprint acceleration, when rotational inertia is at its most significant.

So I say it's a myth to say "an ounce off the wheels is worth a pound off the frame". It would be far more accurate to say "an ounce off the wheels is worth an ounce off the frame"

What are you talking about with regard to "energy requirements"? If you're referring to steady-state, riding in a straight line, and once you get it up to speed, then sure. It takes a minimal amount of increased power to keep a bike moving with heavy wheels as it does with lighter wheels.

But if you accelerate or decelerate, turn or lean the bike, of course there are going to be differences. The heavier the flywheel the greater the inertia and the gyroscopic effect of the wheels. Basic physics have never been "proven ridiculous" and anyone that has ever actually swapped heavy wheels for light wheels on the same bike will confirm that it's a huge difference in acceleration, braking, and handling.

I think the 1.85x is reasonable when calculating wheel inertial forces during acceleration, but as per Zipp's calculation in post 65 above, it's worth next to nothing in terms of real world power. I would say it shrinks to the wheel mass being worth exactly the same as any other mass on the bike. Given that the power requirement due to rotational inertia is less than 1% of total power required to accelerate, we are talking about small fractions of a percent when reducing wheel mass and only then when actually accelerating. Unless we hit the brakes we also recover the energy from accelerating the wheels when decelerating.

#1 The romanticism around batch produced lugged steel frames of the 70’s and 80’s especially if they were Italian. That somehow one of the thousands of Colnagos made in a certain year somehow ride better than a Bianchi, Cinelli, Pinnarelo, Raleigh, Schwinn, Masi etc. That these bikes were rare and hand built by a craftsman and this somehow impacted the performance of the bicycle is nothing but a illogical connection with a persons past. These bikes when perfectly restored are wonderful wall art but for day to day riding when compared to current tech they have not aged well.


#2 That these forums represent the sport of cycling or typical cyclist. This traditional Bike Forum has existed for decades and began when the typical internet connection was dialup. Younger participants in the sport have moved on leaving a older less progressive demographic. You would think 50% of riders still use tubulars when you look at these forums yet when participating in any mass start event its probably less than 1%.

Right, so what do you think about Zipp's calculation of inertial forces in post 65 above? The physics doesn't lie. When you swap heavy wheels for light wheels on the same bike, what you actually feel is the simple static reduction in mass, not rotational inertia. Gyroscopic effects being important are another myth too. We can debate that one if you like?

You are in the “Blonds have more fun” category of logic here.

Not really on handling though. I notice a difference in steering between a 5.4kg wheelset / tire combo and a 2kg wheelset / tire combo. But I don't notice a difference between 2.5kg and 2kg.

1. Electrolytes other than sodium require replenishment during exercise.

2. Exercise-related cramping is due to dehydration/electrolyte depletion.

3. By the time you're thirsty it's too late.

4. Caffeine is dehydrating.

Sure. "Steering" and "handling" are related (maybe the same thing), and it's no surprise you can tell the difference. Naturally there is a threshold where the difference is marginal, as you discovered with your second example.

I'm fairly certain that any of the people saying that rotational weight is no different than static weight, have never build a second set of lightweight wheels for their existing bike, and actually hit the road to experience the difference. It can be like night and day. Upgrading your wheels is one of the biggest improvements you can make to a bike.

If that blond is riding a bicycle with high-quality lightweight wheels then yes, they absolutely will have more fun riding their bike compared to the heavy, sluggish wheels that they had when they were a brunette.

A change-up...

Truth: I just get on and ride.

But good thread.

I completely agree with the statements:

"In addition to this efficiency gain, many discerning cyclists will sense a qualitative improvement in a
wheel that is 20% lighter and has 23% lower moment of inertia compared to its predecessor."

"Additional benefits of lowering wheel inertia include improved braking capability."

"In addition to efficiency gains, lower inertia contributes to a perceived improvement in ride quality."

As you might know, inertia is responsible for the gyroscopic effect of a wheel, so lower mass at the circumference = lower inertia = less gyroscopic effect of the wheels. And on a bicycle, lower is better with regard to all of those things.

But, they have to be meaningfully lower for them to be ... meaningful.

Good point. They can also be used for medium-length distances on flat terrain.

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It is also possible to do this with a full suspension mountain bike, as long as the frame is carbon and you have a coil shock.

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Steel has carbon in it.

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They are for me, which is all that really matters. If they aren't more comfortable for you, it might be worth getting a bike fit.

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Said no one, ever. Unless they have AVID juicies.

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Fact: Cycling is a seasonal activity that is dependent on the weather.

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Riding up a 50% incline is.

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Only if you can't count above 2000.

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Passing gas when you pass another rider means you are a Canadian single-speeder.

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They are definitely useless on a hydraulic disc brake system. Unless it is AVID Juicy. In which case a back up rim brake is a great idea.

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Relax. The pavement will be fine.

Do you take the same approach to posting nonsense on BikeForums?

Myth: The greatest comeback in cycling history is Lance Armstrong's comeback from cancer.
Truth: The greatest comeback in cycling history is Greg LeMond's 1989 TdF time trial.

Of course, it's silly to suggest romanticism is a myth. You have to be an experienced rider to feel the differences. No one ever said that. Newer bikes are of course technically superior. However, as stated most eloquently in Cyclist magazine, "for most people, bike riding is not a matter of numbers alone. They ride because they enjoy it on many levels, including an aesthetic one, a pleasure in riding a bike they like to look at...Nothing illustrates that better than the continuing appeal of the limited-production steel Italian bike. The operative word here is style, and Italian bikes, like most things Italian, have it by the bucketful" (emphasis added).

It's sort of hard to apply the term "bellissime" to modern black plastic bikes.

And yes, many of them are rare. And the top-end frames, like the Super Corsa, were indeed hand built and in limited quantities, often by a single craftsman (by which I mean the actual brazing--not the mundane tasks like mitering or painting). Which is why there isn't a "Show me your Cinelli" thread, and why I've refrained from starting one. A thread three posts long wouldn't be very compelling.

Sounds like this alleged "myth" is just a bunch of sour grapes from someone who can't appreciate the style and romance of fine, rare, hand-made Italian steel bikes. Which is fine. As I've said here many times, not everyone can understand everything.

My touring bike is a pig of a ride. It's heavy, slow, cumbersome, handles like a freight train ( good thing for a touring bike) and all the other adjectives denoting slowness.

My (all)road bike is quick, nimble, fast, quick steering and fun to ride. Accelerates quickly and all that.

the wheelset weights are almost the same. But the road bike is several kilograms lighter as it doesn't have racks, fenders, a frame mounted pump, has vastly faster tires, lighter components and all that.

The article existed to sell the new Zipp wheels, so of course they are going to appeal to the subjective improvements. 20% lighter, 23% lower moment of inertia. Sounds awesome right up until you actually look at the cold hard numbers I took from their graph. Numbers that they didn't actually display in the article because 0.6W saving from that 23% reduction in rotational inertia on a 1000W sprint doesn't sound quite so impressive. 20% lighter is slightly better at 3.5W, but hardly a big deal in the big picture of accelerating 85kg in a full power sprint.

Let's not get into gyroscopic effects, because that is just going to throw up even more mythical nonsense.

When, exactly, is a bicycle “up to speed”? People like to quote Newton’s First Law: ”A body remains… in motion at a constant speed”…but forget a crucial part of it…”unless acted upon by a force.”. Corners, hills, just pushing several thousand cubic feet of air out of the way all add up to a constantly changing speed requiring constant acceleration. We are never up to speed.

A strong rim makes for a strong wheel.

A bike stands on its spokes.

Using strong spokes is a sign of poor wheel building skills.

Considering there are over 20 of them listed right now on eBay and there are numerous other resellers which have them in stock you should start that thread you would get greater participation than you think.

You could be right though about not being experienced enough or romantically attached to old lugged bikes. Perhaps because I grew up around these bikes and was fortunate enough to own many of the bikes people currently are reminiscing about. Raleigh Professional, Raleigh 753 Team Issue, Masi GC, Teledyne Titan, 3rensho, Custom Marinoni SLX (Still own that one) and then transitioned to carbon. They were very special in their day but not missed at all once sold. Kept the Marinoni because it was built for me and I was measured by Giuseppe, it is perfectly restored and wall art. What’s the point in riding it when I have much better riding bikes available.

I did a lot of touring on my '83 Trek 720. That was an all-out touring bike, complete with nice, sturdy, but heavy wheels. I rode on those wheels even when I wasn't touring, because that was the only bike I had and the only set of wheels.

Then I had my LBS build me a set of high-end lightweight wheels, with Campy hubs, the lightest rims I could find, and very lightweight 1" tires. What a difference! It still wasn't a racing bike (because of the geometry and long wheelbase it still rode like a Cadillac) but it was certainly a lot sportier. Acceleration was quicker, stopping distance was shorter, and it was actually fun to ride on curvy roads. After that I only put the heavy and slow touring wheels back on when I was going on a fully-loaded tour.

I wrote a specific answer to a specific question, and stand by my 1.85x estimate for that limited purpose, In the second paragraph, I clearly stated that this was specific to inertial considerations only, and tried to offer some big picture perspective. So, while it may mean little in the big picture, wheel weight is still roughly equal to 1.85x frame weight.

Gyroscopic effects are mythical nonsense, eh? I'm tempted to make a wisecrack about whether or not you were home schooled, but I'll simply invite you to fire up your Google machine.

Or if your a hardcore science-denier, go take the front wheel off your bike, hold it by the axle with one hand on each side, and have someone give it a good spin. Then try to move the wheel from side to side, as though you're steering it with your hands. Feel that resistance to changes in direction? That's the gyroscopic action of the wheels, and you can feel it with your own two hands. What do you think happens to that resistance, as you either add or subtract weight from the outer edge?

Here's what's meaningful with regard to rotational vs static weight. If bicycle gremlins went into your garage in the middle of the night and added a one-pound weight to the inside of your seat tube, you'd get on the bike the next day and would probably not notice a thing.

But if those same gremlins came in the middle of the night and installed 250g rim strips on both wheels, you'd immediately notice the difference. You'd probably start checking the air in the tires or looking for some other reason that your bike suddenly seems so sluggish. That's true even though once you got it up to speed and were riding in a straight line, it wouldn't be much different than the day before. You'd notice it in acceleration, braking, and handling. Suddenly your bike wouldn't be as fun to ride, and that's the most meaningful thing of all.

Rate of change of speed (acceleration) on a bicycle is relatively small. Therefore inertial forces are pretty minimal. It's not an F1 car with 80 kg of wheel mass accelerating at 2G and braking at 5G.