PeteHski

It is quite surprising given the way it feels when riding. It’s just that the rotating weight doesn’t translate into a significant performance advantage, other than the slight reduction in total mass when climbing.

I made a simple spreadsheet to calculate the power required to accelerate a bike, including wheel rotational mass, and even a full-on sprint only requires a handful of extra Watts during the brief acceleration phase.

But if you like the feeling of lighter wheels then it’s all good for the head. Just don’t expect to be significantly faster!

ScottCommutes

People don't always appreciate all the different energy storage "systems" on a bike

1. The whole bike plus rider has considerable mass and therefore inertia when moving forward - more weight equals more inertia and should roll farther
2. The front and rear wheels generally operate together and gather rotational inertia as they are spun up. More weight and faster revs here mean the bike will glide farther due to the stored energy. The wheels act as flywheels. More mass near the rims especially means more rotational inertia. Also some unrelated gyroscopic effects as the wheels are spun up.
3. The riders legs, pedals, and cranks operate together, also with rotational inertia when they are moving. Legs are heavy.
4. The chain and gears - minor, but still a store of energy when moving
5. The rider's body itself has obviously several complex biological energy storage systems.
6. Obviously, elevation is stored energy as well. You can trade speed for elevation and vice versa.

Performance on a bike is related to all of these energy storage systems gaining and losing energy at the same time.

SoSmellyAir

No way. An AI bot would comprehend basic trigonometry.

Bike Forums - View Single Post - Retired and want to get back into cycling in my 60s.

3alarmer

.
...OMG the great wheel rim/ "rotating weight doesn't matter any more" debate is again resurrected. I'll pass. I have my one year chip on this topic, and I don't want to go back to attending 12 step meetings.

Fredo76

Why don't you just blow a little harder?

Shame on you!



Drafting is how sprinters win road races. Competitors who think that's unfair tend to have more slow-twitch muscle fibers, and maybe should switch to time trials, hmm? The rest know that it's just one of the glorious aspects of the sport - the fact that either body type can win. The endurance riders have to drop the sprinters, or tire them enough so that their last sprint, the one that counts, falls short. How is that done? By attacking again and again and again. The sprinter who wants to win will either join, or help to close the gap. Less motivated or less capable sprinters may just stay in the pack drafting and hoping things go their way eventually, but sprinters who want to win must close gaps made by others who attack. At first, this may not be difficult, since sprinters have a good enough jump to easily catch a wheel unless surprised. But being forced to do it again and again takes its toll. And doing it with heavier wheels is physically more difficult. Anyone who says otherwise may as well be a flat-earther.

Dave Mayer is actually right about this, and the pack of people making fun can get kind of creepy, but that’s par for the course at BF.

Are there any members besides RChung that actually perform measured experiments to test hypothesis, i.e. 'do science'? I don't mean plug in numbers into someone else's simulator, much less just watch a video of someone doing the same.

IIRC, Mr. Chung stated that the effect of the rotating-mass/polar-moment-of-inertia stuff was so little when working with a women's pursuit track team that he could just take it out of the equations. And I believe him. If he were modeling a points race, I would not; I would say more work is needed, and ask (rhetorically, I suppose) if he ever asked the gals to to add a pound to each wheel at the circumference, to improve their momentum...

When you're trying to go faster, an ounce off the wheels is worth two off the frame.

I believe my signature, captured above for posterity, is a concise statement about the physics of the matter, or more exactly, the simplifying assumption that a wheel with mass distributed between the axle and the circumference can be modeled by the relative proportions of its mass at the axle and at the circumference. It's a good simplifying assumption, much better than the simplifying assumption that wheel momentum returns useful energy to the competitor, or the underlying one that race placement success is simply inversely proportional to energy expended...

So, I assert that nobody has shown anything of the sort. Arguments about the relative importance of weight vs. aero, and arguments pointing out that every racer has light wheels these days, simply have no bearing on the matter of whether heavier wheels accelerate slower. They do; that's the physics, and the reality. Funny how it seems that relatively 'naive' recreational riders understand it much better than many of the internet-learnin' dweebs posting otherwise.

I can't help that.

tomato coupe

No, he's not. The physics is pretty simple, and it tells you that the moment of inertia of a wheel isn't very important because the typical accelerations encountered while cycling are not very large.

PeteHski

Your posts are about as creepy as it gets here!

Eric F 

This varies WIDELY with the situation. If you're on a fun group ride with a few buddies, you might be right...unless those buddies are quite a bit stronger, and have no issues with you just taking a short pull when you're able. Nothing wrong with that, either. Riding with better riders is an effective way to get better yourself. As a former racer of the sprinter variety, I'm pretty sure there were lots of races where my time in the wind was just a few hundred yards. My job was to be in a position to be able to use my best weapon at the finish, and do as little work as possible to get there. That's how the sprinter's game works. Taking pulls that don't benefit your success (or the success of your teammate, if that's your role), are a waste of effort. There is a local group ride I often do where I do a bigger share of time at the front that some others. That's fine. The fitness level of the riders in that group varies quite a bit, and the stronger riders set the pace. There are other rides I do which are populated by a LOT (100+) of strong, young, racer-boys/girls, and I'm sometimes stretched to the limits of my fitness. Most often, my time in the wind is closing gaps left by folks struggling more than me.

Eric F 

I learned a while ago that it's often a mistake to assume where people gained their knowledge. Some of the people in this thread who have an opinion contrary to yours have deep knowledge from areas of study/work that directly apply to the topic. Just to be clear, I'm not one of those people.

As a non-educated person, I remain puzzled by the assertions that wheel lightness is the most critical factor in going fast, but the people who spend the most money to help riders go fast (pro teams) don't seem to put light weight as a top priority. I would understand if all the pro bikes are bumping against the minimum weight limit, but they aren't.

PeteHski

Nobody is saying that heavier wheels don’t accelerate a tiny bit slower. But aero wheels are much faster overall despite their slight weight handicap. Pro teams have shown this to be a fact.

Btw, I didn’t get my engineering qualifications off the internet. What qualifies you to say who’s right and wrong anyway? Last time this was debated you had the arrogance to dismiss all the physics modelling with a blanket statement that they must all have “missed” something.

calamarichris

As one with thousands of miles on both the Dura Ace C23s and C50s, I must agree.
I never noticed much of a detriment while climbing on the C50s, but during flat/level riding, it was a lot easier to sustain >24mph solo on the C50s. It were as if the wall had been lifted. Same avg watts, same avg HR, but several avg MPH faster.

Fredo76

You have vacillated on this subject before. However, your kernal of truth is showing. Now all we are left with is to answer is how tiny is tiny. And BTW, people are saying exactly that


Again you conflate aero with something I am talking about. This is tiresome.

Last time you vacillated similarly, then joined the ignorant, shouting side. But what I found especially creepy was starting a new thread about 'how to learn' simply to mock other members, after they got tired of your bs, and stopped shouting back.

3alarmer

.
...today, out walking, I witnessed a murder of crows mobbing one of the neighborhood hawks (a red shouldered hawk, I think, but it might have been a Cooper's hawk).
It reminded me of General Cycling in its current incarnation. Say anything that threatens the current roadie canon, and the same guys circle around, squawking, taking turns pecking away.


The resemblance is quite remarkable.

calamarichris

Hey man, some of us are just sparrows doin our own thing in our own time. And who's the hawk in this metaphoric scenario? Thou?
Not all of us are peckin at each other.

Atlas Shrugged

I can relate to your experience. Whenever I post over in C&V questioning any religious dogma expressed, I am quickly scolded to go back to General as my opinions and proselytizing are not wanted, as the their saying goes, never destroy a good story with facts.

The problem you are experiencing is that General is a place where facts and reality matter, not dated beliefs and myths told while repairing a tubular on the side of a road 50 years ago.

3alarmer

...it seems to vary, depending on who has most recently stated something objectionable to the road racing mindset. Why would you think it was me, based on what I wrote ? FWIW, my hawk today was just trying to get away from the noise.

LarrySellerz

The idea of faster riders being peeved about slower riders drafting the group in order to do a group ride is kind of absurd to me. The only time it makes sense is when you're "training with your team" literally trying to do a team TT thing, and frankly even in that situation I doubt most would mind if a random drafted them. The groups around here are open to everyone (as they obviously should be...) and the strongest people are at the front, with people of all ages and skills in the back. Drafting is the equalizer in cycling

elcruxio

Funny you should say that!

Because that's exactly what the people studying stradivariuses are doing and there are some really interesting results.

Like for one, strads have a lot of placebo. They're great instruments that shaped violins into what they are these days, but a strad can't match up to a high quality modern instrument in a blind study. The best modern violins are made by studying the waveforms of the front and back plates and adjusting graduation and thickness accordingly in order to achieve as neutral as a result as possible. Stradivarius didn't have those tools.

Also carbon fiber violins are a thing and they are beginning to show real promise.

Along with the electric bass I also play the viola and was just given a Cello

Dave Mayer

I think the currently popular erroneous "weight doesn't matter" narrative is due to the bike industry needing to turn over the bike fleet. The dominant trends in the industry is selling new stuff and legal butt covering. Since disc brakes bikes are invariably heavier than rim brake equivalents, especially in the wheels, and since aero is heavy as well, any suggestion from more knowledgeable and experience riders that in fact weight very much does matter is responded to with hair on fire from the industry shills.

Sure, an aero bike may be faster if some is riding solo, or on the front. So say someone strong could maintain 2-3 mph faster on an aero bike with deep section wheels. At a fast pace, a 2mph speed advantage is significant. However, when your porky disc-brake aero bike results in you not being able to keep up with the surges and accelerations in the pack (riding at an even higher pace), then the assumed aero advantage means nothing. The pack slowly recedes into the distance at 30mph, and you are dying at 23mph. But at least with your aero bike, you are dying slightly faster!

tomato coupe

No one says weight doesn't matter. What "they" say is that aerodynamics matter more than weight under most riding conditions.

Eric F 

FYI - Big Bike conspiracy theories do not strengthen the position of your other arguments.

Please explain how your “knowledge and experience” is superior to the knowledge, experience, AND TESTING done by the pro teams who have the most to gain from being faster than everyone else. If weight was the biggest factor, every WT rider would be on a bike that was right at the minimum weight limit, with the lightest possible wheels, at every race. They aren’t. Sometimes their bikes are above the limit by more than a pound. Obviously, there is a tipping point where weight becomes a hinderance, but it’s evident that the line is not as fine as you think it is.

You continue to portray an air of superiority about your “knowledge and experience”. Please share your pro resume. So far, I can’t see where your knowledge or experience is any deeper than mine (or others here). I’m starting to suspect that your choice of wheels actually makes it harder for you to hold the wheel in front of you when things get spicy on fast group rides.

elcruxio

The 2023 TdF stage 16 really drove in the importance of aerodynamics vs weight. Vingegaard did the whole TT with his "heavy" Cervelo P5 with a disc rear wheel no less, whereas Pogačar swapped to a much lighter "climbing" bike before the 2,5km 9 % climb at the end of the stage.

In the end Vingegaard smoked Pogačar and kept gaining time throughout the climbing section even though Pogačar was on a much lighter bike. Granted, Vingegaard was ahead before the climb started, but Pogacar just kept on losing a LOT of time on the climb.
From what I could scrounge up there's almost a kilogram of difference in bike weights between the two and with Vingegaards high profile front rim and disc wheel a lot of Vingegaards weight was rotating weight. Considering how light the two riders are a kilogram is significant.

Trakhak

Vivid (if hyperbolic) example. And an unfortunate choice, given the results of a famous double-blind study conducted with professional violinists and modern violins versus centuries-old Italian violins worth millions.

From the abstract of an article published in the Proceedings of the National Academy of Sciences:

"We found that (i) the most-preferred violin was new; (ii) the least-preferred was by Stradivari; (iii) there was scant correlation between an instrument's age and monetary value and its perceived quality; and (iv) most players seemed unable to tell whether their most-preferred instrument was new or old."

Of course, after the results of the double-blind study were published, violin forums erupted in impassioned rebuttals - "If I'd been one of the players in that study, I know I'd have identified the Guarnieri and the Stadivari!!!" and so on. Science is annoying.

Trakhak

Yes, you and I (5' 8", 118 lbs) would benefit from lighter wheels (to a point; as I've posted before, I disliked my ultra-light Hi-E wheels). We'd also benefit from a lighter frame, or even from carrying one water bottle instead of two. Both would have the same effect as a wheelset that was lighter by the same amount.

seypat

That's an interesting story about the lightweight wheelset simply because I just stepped on the scales. 5'8" and 205lbs. Yesterday was a running/weights day, so I'm retaining lots of fluid today. It's too bad we don't live closer to each other. We could do some testing with the same bike/equipment on these subjects people are always arguing about and get results from opposite ends of the spectrum.