Jughed

Since you didn't respond to my other post where I pointed out that it would take over 30#'s of additional weight to create the 16% time difference you were spouting off about... I don't expect you to respond to this either. But anyhow...

I got to looking last night - found an Emonda SLR 7 with Sram Force DISC brakes and 50MM deep CF wheels.

A fairly aero bike, with deep wheels and disc brakes - and not top spec equipped.

Total weight for a 56CM frame- 15.6#. 1/2 a pound over the UCI minimum weight limit - and its not a top spec bike.

1/2 a pound.

As a 180# rider - that 1/2 a pound means diddly squat in a group ride or race. I'm not losing anyone's wheel, not getting dropped...

Now, the UCI minimum weight - that's the standard. It was set back in 2000. Well before disc brakes, well before deep section wheels were common, well before the big aero push.

Yet, one can purchase, off the shelf, a disc brake bike with aero wheels that is = to the UCI weight min.

So, if the disc brake bike with aero wheels is the lightest it can be legally - what is your point again?

Koyote

Hyperbole much?

Failing to understand the math (the physics, really) doesn’t change it.

If you’ve built your bike (or your whole cycling experience) around the notion that lighter is always better, then sure, evidence to the contrary is upsetting. Science has a history of upsetting people…just ask Galileo.

smd4

Well, I haven’t done that. My bike is a balance of weight, style and performance.

Steel Charlie

It's been long time established that belief systems are immune to empirical data/evidence or rational argument. Opposition to the system only serves to strengthen it.

A situation easily observed in certain elements of the population relative to political beliefs.

Trakhak

It's a shame that emotion-based assessments of reality aren't confined exclusively to utterly inconsequential topics. Such as everything that gets argued over endlessly on Bike Forums.

delbiker1 

I guess I got a touch of this ism. Though, I tell myself it is just curiosity. I have a 9000 Dura Ace group, minus the cranks set, with a set of C24 wheels, that I acquired from a friend. I purchased a couple of the Aerothan tubes that were on sale, this morning I mounted those with GK 26mm slicks on the DA wheels. I put those on my 1X Airborne Zeppelin, that dropped the weight from 17.5 pound s to 17.2. I'll feel like I am riding a crotch rocket.
I was going to sell the 9000 group, and still might. But, I pick up the components individually and am amazed at how light they are. So, maybe my 1X will go back to a 2X, or, my Smoothie can become a DA Smoothie. Never even considered Dura Ace in my past.

Eric F 

Galileo. Figaro?

Eric F 

I don't agree with you very often, but in this case, I do. Unless the slower rider is doing something to disrupt the vibe/flow of the group, someone sitting on the back isn't generally an issue, even with a smaller group. Larger packs tend to settle into whatever people can handle - cycling Darwinism. The strong thrive at the front and drive the pace. The weak get dropped. Those in between do what they can do, and may develop into a stronger rider.

Eric F 

Although our aesthetic preferences are different, I tend to be the same. I am excited by the way my bikes look, and I have taken some measures to make them lighter (basically to the limit of what I consider financially reasonable), but high-performance is still a top priority.

rsbob 

https://www.globalcyclingnetwork.com...tweight-design

jonathanf2

After having built several bikes, I believe a lightweight bike is just more enjoyable to ride, plus I live in a hilly area that requires climbing every direction I go. Lightweight deep dish aero wheels exist, so there's not really a major weight penalty to put aero wheels on your bike unless you're aiming to build a 4kg climbing build. Also the older I get, a lightweight bike puts less strain on my body and especially my knees. I can easily build a 7kg disc bike for less than $1500 USD. I could probably build a 6-6.5kg for under $2k. I know there's extreme weight weenism, but I think being a practical weight weenie is perfectly fine.

I'm beginning to think wheels matter more than any other component on a bike. I'd rather own a cheap alloy road frame and have a budget groupset, but ride the best wheels I can afford.

Dave Mayer

The Factor 'climbing bike' at 6.8kg is almost 15 pounds... The Trek Emonda SLR (rim brake) could have been brought below 13 pounds without any extreme weight-weenie measures. Of course you'd shed the extraneous discs. Anyone around here need to comply with the arbitrary UCI weight limit that could be revoked at any minute?

Actually I did go hunting for one of these at my local Trek dealer a couple of years ago with a short discussion that went like this:

PeteHski

Sure, we can do just that then. Let's look at the power required to accelerate the mass (both static and rotating) from say 0-20 kph in 3 seconds and then see how much power or time we can save if we reduce the wheel rim weight by 500g.

So my simple bike model:-

Static mass m = 85 kg
Rotating Mass (wheels and tyres) mw = 3 kg


Kinetic Energy of static mass = 0.5 x m x v^2 = 1309J
Kinetic Energy of rotating mass = m x v^2 = 92J (Simplification with 100% of rotating mass at the tyre radius)
Kinetic Energy total = 1402J

Av Power total = KE/t = 467W
Av Power for total rotating mass = 31W

If we saved 500g from the rotating mass:-

KE static = 1309J
KE rotating = 77J
KE total = 1386J

Av Power total = 462W - a saving of 5W over baseline

So a saving of 5W for a 500g wheel rim weight reduction when sprinting from 0-20 kph in 3 seconds. Or expressed in terms of time gained at the original power level it is 0.03s.

Also consider that this calculation doesn't include the additional power required to overcome air resistance and rolling resistance. It is only the power required to accelerate the mass. So the power saving will be even less of a percentage of the total power required to make this very hard acceleration.

Atlas Shrugged

The calculations affirm that when a rider is pushing their limits, head down, tongue hanging out, teetering on the edge of being dropped from the local group ride, rotational weight indeed plays a crucial role. That mere .03 of a second is the determinator of whether the rider is bound to endure the solitary journey of shame for the remaining 100 miles, with vultures circling and coyotes howling in anticipation of their impending feast. As your cheerful group of fellow riders fades into the sunset, eagerly anticipating a cold beer and a hearty laugh at the individual who underestimated the significance of rotational weight.

PeteHski

The qualified physicists and engineers are actually saying that rotational inertia is the least important factor in wheel design. You are stating that it is the most important factor and wondering why everyone who understands the physics is strongly disagreeing. Then you invent an industry wide conspiracy theory to fill in the gap between your superior knowledge and the reality of modern road bikes.

HTupolev

Due to the quadratic term, that's not how the math shakes out. 20->40 is not the same as 0->20. For the static portion, it's not...
.5*85*(5.55556^2)
...but rather...
.5*85*(11.1111^2 - 5.55556^2)
...which is 3935J.
Similarly, the rotating KE difference is about 278J, or 231J for the 2.5kg example.

On the flip side, if we're talking about performance road bikes, you're using incredibly high numbers for mass-at-rim equivalence. (Although the 500g difference is realistic across the extremes).

What's also notable is that, if the weight difference is arising from different styles of rim (such as aero depth), the heavier rim can have a reduction in other losses. And aerodynamic benefits do not disappear during acceleration.

It's a bit more complicated of a problem, but things get interesting when you start comparing mass-versus-CdA tradeoffs in difference realistic acceleration profiles and air conditions.

I think it's an especially big issue in bicycle performance because people can actually feel things that their brain interprets as certain types of performance differences. Like how cyclists often feel the rumble from excessive tire pressure as "speed."

The rotational inertia of the wheels have a huge impact on how a bicycle "moves" beneath a rider. The way it torques the steering column, or resists being tossed side-to-side. Cyclists can't really discern the acceleration difference for a given applied pedaling effort*, but they can feel the handling change, and their brain is trained to feel the latter as the former.

*Compare how easy it is to feel a 500g difference at the rim to how difficult it is to feel a 1kg weight attached below the bottom bracket. Kinematically, these things create exactly the same resistance to forward acceleration.

terrymorse 

Yes, aerodynamics may be more significant than weight on a climb, but that depends on how fast the rider is going.

When the best cyclists in the world are going full gas up a 9% grade, they're still moving fast enough that aerodynamics is significant.

For the rest of us on a 9% grade (actually, the end of TdF TT was an 8.5% grade), we're better off dropping as much weight as possible and ignoring the aero.

tomato coupe

Do you think people are too stupid to notice the dishonesty of your "Bike A is xx pounds" vs "Bike B could have been yy pounds" comparison?

Does this story have a point?

Eric F 

Old bikes good. New bikes bad.

OldsCOOL

When one rather spend hundreds for a 100gr weight loss in a component and fail to realize what losing 5 pounds of fat will do.

PeteHski

Good catch, I had forgotten that my spreadsheet was starting with u=0
So those figures are actually for 0-20 kph

20-40 kph in 3 seconds requires around 1400W with a 15W saving for 0.5kg rim mass. Time saving is the same at 0.03 sec.

Either way it's not a lot for a seriously major acceleration and very large rim mass saving.

Eric F 

Not once have one of my cycling buddies picked me up and said, "Wow! So light!!". Isn't that the real reason why we want a light bike?

Maelochs

This thread ... and so many others ... is a perfect demonstration of why I never argue with Flat-Earthers. "Yes, the Earth is flat .... you are so smart not to be fooled." Then I walk away.

I mean, we all Know math was invented by the Illuminati and the pedophile cannibals and the Bilderbergers and the aliens to keep the masses under control. We know they are lying to us when they say 1+1=2 ..... and then they show us what they call "higher math" ... and there are hardly even any numbers!!

I mean, how can e=mc^2 be an "equation"?? How can you "square" the letter "c"?


We are not fooled.

I cannot follow the math .... I am not one of you brainwashed "scientists" with your fake math ..... but yes, people mistake their sensations. As I and a couple people have said, the first two pedal strokes feel different with lighter wheels, so we think we are faster, even when measurements show we are not, I mean, it is only two pedal strokes, when I am pedaling 80 rpm ... that is not a higher speed for much time ... 0.03 seconds? Whatever ... you brainwashed "scientists" fight it out.

The human brain is easily fooled. Our preconceived notions can even affect our perceptions so that we don't notice or incorrectly interpret what we feel to make it support what we want to think we already know.

Yeah, you mind-controlled "science" types think you get around that by performing experiments multiple times using "controls" and such to minimize variables .... but we who are not alien-controlled sheeple know your science is bunk.

Hard tires on light rims are faster, and aero only matters to aeroplanes ..... I know, because that is what I want to feel and think ... You Cannot Control my Thoughts and Feelings. Take you alien magic elsewhere.

The Earth IS flat ... except for the hills, of course. And it's not just because some guy on YouTube told me .... several other people on YouTube agreed. And since that makes me feel good and think I am right ... obviously I am.

I really feel sorry for all you guys who wasted your lives in "higher education," getting conditioned by the Illuminati and the aliens to spread their propaganda. I hope some day you can all see the truth.

By the way .... I am way too smart to think that just because the fastest cyclists in the world find, through testing, that aero adds more benefit over the course of an actual race than does marginally lighter weight .... We Insiders know that UCI stands for Universal Control Institute, and is wholly run by lizard-people. They are so obviously part of "The Plan," it is shocking they have not been exposed yet. Just another part of the mind-control we really smart people reject.

Okay, I am out. I have to go buy some shoes with velcro closures, because I am not smart enough to tie my own shoes ..... but I am smart where it really counts. YouTube told me.

OldsCOOL

Thanx for the grin

3alarmer 

...cheer up. You don't need to be very smart to construct a straw man. Some old clothes, some straw or hay for stuffing. Boom, you're there.