rpeterson

Not my fault you guys don't understand basic physics.

celticfrost

Basic physics tells me that when going up a hill the force of gravity is greater on an object w/ greater weight (or mass). When I'm hauling something up a hill I want that weight/mass to be less.

I'm not disagreeing w/ what is being demonstrated in the article only noting that the testing is done on flat ground.

zigmeister

When not going uphill.

canam73

So when you add a 70kg rider to the bike you are at 1.5/77=2%.

njkayaker

Criminy! People are dense!

Campag4life

The controversy of response here...as many are engineers that have interest in the subject including me is...about relative difference in performance. 400 grams is < 1 lb and << 200 lbs for the average bike + rider whether you have to drag that 400g up hills or not. Of course in racing you want to optimize everthing so why not opt for uber light + very aero wheels for $2K...but for the average guy that doesn't race a 1800g wheelset works fine...what I ride and I can keep up with most out on the road including hills.

If you want relative contribution...I know most of you guys live only on the road...look no further than off road. This particular debate about wheel static weight...but also wheel diameter wages on pretty much every mtb forum on the web contrasting the performance of 26 inch mtbs to the changing landscape of 29ers starting to dominate mtbing. 29er wheels are taller and heavier. It is unavoidable in fact. They have a greater moment of inertia. Anybody who has ever raced a 26 inch mtb and a 29'er knows this. A 26 inch bike will win a drag race pretty much every time with equivalent riders. And yet 29ers have some clear benefits and now vastly out selling 26 inch mtbs including in professional racing circles. So wheel weight disparity even racing isn't all about acceleration...which btw is still pretty important in mtb racing....and plenty of small hills to climb over as well. Heavier wheels also hold on to their speed a bit better. It depends on the track which is faster. I believe the same applies to this discussion only to a lesser degree. 400g is only significant if racing. For average road bikers it is foo foo dust. Most here would also concede that if wheel strength is given up in favor of weight...or a wheel needs a lot of truing this is also a bad trade off for the average guy who doesn't have a wheel car following him around on his daily training rides.
Aerodynamics does trump static and dynamic weight on the flats where most of us live. TT bikes prove that.
Anyway...reason I believe there is lack of consensus here is we are disagreeing only in degree. Of course light is right...but less than a lb...even rotating mass is pretty miniscule unless counting seconds in a race for the average rider.

tfro

You clearly don't get it.

We all agree that extra weight takes more power to go up a hill at a given speed.

And we all agree that increased drag from air takes more power to move at a given speed.

What you fail to understand is that wind drag makes a bigger difference compared to weight on all but the steepest and slowest hills when we are talking about the increased weight and reduce wind drag of aero wheels. You can 'trust' your 'feel' all you want, but it just isn't supported by the data.

fly:yes/land:no

to elaborate a bit more, system mass makes a much, much bigger difference than rotational mass even on the steepest of climbs. (i.e. the difference between two riders with identical system mass -rider+bike+wheels- and power outputs on a 20% slope with one rider on a 1kg wheelset + 71kg of bike/rider vs the other rider on a 2kg wheelset + 70kg bike/rider will be very, very small.) almost all of the improvement that you "detect" on climbs, although i would be highly suspicious that you can consistently predict performance with one wheelset vs another, comes from the reduction of mass to the system, not from the fact that it is rotating. if you had a similar reduction in mass to either the frame or the rider, the benefit would be nearly identical. and that is what the article is pointing out - not that mass is insignificant, but that rotational mass isn't much different than non rotational mass in terms of cycling performance.

spock

TDF is pretty much the cutting edge of measuring performance and how things have changed over the years.

TDF stats: https://www.bikeraceinfo.com/tdf/tdfstats.html

Just compare the stats from 1980's and 2000's... Given that bikes have changed monumentally in the areas of weight, aerodynamics, and materials for the sake of speed, performance and efficiency, the change is not really that monumental. Getting the bike to drop almost half the weight is the biggest factor in about 1.5 mph increase on an average, and that's probably all gained with climbing.

zigmeister

Are you calling me dense? That is nice, your grasp of the English language is astounding.

When in a thread talking about science/physics and technical information, making statements with the word "generally" is a faux pas and laughable.

Science doesn't deal with "generalizations" well.

wphamilton

Yet they all swear it makes a big difference, and I believe them! That's what makes this so entertaining.

It makes me want to exaggerate the effect as an experiment and see if a racer could tell the difference. Put some sliding weights on beefed up spokes, let them slide out to the rim on downhill runs where it won't hurt the speed as much, then slide in when the rotation starts to slow after they level out, and before uphill stretches, or when they want a boost.

njkayaker

Yes.

This isn't true at all!

This isn't true at all!

Dense.

And you completely missed that your "except for hills" comment is a generalization too!

zigmeister

Settle down Beavis. I understand this subject perfectly, unlike most. First, you must grasp English and my response to the person that used the word "generally" when talking about physics and science. Generally isn't good enough when we are trying to discuss the exact methods used, the point of the article written, and many variables and applications as it relates to the subject overall.

Really? It takes more "power" to go uphill at a given speed as weight increases? Nooooooo. Increased speed increases drag? What? Are you serious? You mean like drag quadruples as speed doubles? That old formula?

So, from your last statement, you say that drag is more important than weight except for steepest hills? Ok. Then why don't you go get a moped that weighs 175lbs, and pedal that around? Weight really means nothing and it is the drag that is important right?

As long as you are aero and the drag is minimal compared to a lighter object, let's say a 16lb road aero bike with Zipp 808s FCs on it, that 175lb beastly moped should really fly in comparison!

njkayaker

No, this is not necessarily true.

And you can't really argue against "general" statement with general statements!

Nice straw man argument! Sheesh. No one is saying that weight doesn't matter!

Obviously, all other things being equal, less weight is better. No one is saying otherwise!

Wesley36

Been done, had a measurable effect.

https://www.trainingbible.com/joesblo...ve-spokes.html

merlinextraligh

Unfortunately, there likely not UCI legal. THey violate the rule regarding energy storing devices.

wphamilton

Yes, exactly that Two to five percent improvement in times is claimed.

If the claim is correct, then it stands to reason that different weight rims/tires make a measurable and significant difference in performance, even when the weight is fixed.

I'd call foul on that. It stores energy analogously to storing potential energy when you simply climb the hill. Which everyone does, obviously.

tfro

I have no issue grasping your response, I responded directly to it. And your attack on the word generally is a joke in a forum like this, and that's ignoring that it's a commonly excepted method of conveying a concept in context when presentation of all of the details doesn't fit the forum. Just out of curiousity, I took a look at scholar.google.com and over 32,000 papers were found that had 'generally' in the title or abstract, in 2012 alone (ignoring patents, where generally is just a given). That sure is a lot to be included in published papers when you claim it can't be used on a forum on the internet.

And to your last point, last time I checked this was a bicycle forum and more specifically, this is the road bicycling section, so I'm not sure why you would mention an example that has no relation to those topics? Should we discuss cars too? Maybe donkeys?

I stand by my statements in the context of this sub forum and the quoted article we are discussing.

canam73

If you have to ask this question then the answer should always be yes.

Garfield Cat

Yes, even on an individual time trial.

Campag4life

Zig...you are either being glib or you are missing the point about 'relative'.
Weight increase of a moped isn't relative.
We are talking about 400 grams or about .5 % of total rider + bike mass. This mass increase is being compared to the exponential increase in air drag due to riding at speed approaching 20-30 mph. Air drag on a bike trumps the extra weight of a full water bottle on the flats as the article states whether you fill up your water bottle or not. Whether you fill your water bottle won't make much difference if you climb a lot other than hydrating your body.
That's about it brother.

Garfield Cat

And that variable is the rider, even the pro rider who may be exhausted after all those stages and all those attacks and crashes.

Snydermann

All the science in the world will never convince a guy who dumped a boat load of money into admitting that his uber-light wheels don't make all the difference in the world. There is no known antidote for that Kool-Aid so many cyclists drink.

Lucky for the bicycle industry many of their performance claims are almost impossible to prove.

grolby

Huh? You have a hair across your ass because I think buying multi-thousand dollar wheels for the specific purpose of commuting is stupid? Did you stop to think for a second that maybe that statement doesn't apply to people who happen to use the same bike for commuting and racing? When I commute on my race bike, I'm also riding on my nice, light wheels. But I wouldn't build a set of lightweight, expensive wheels for my commuting bike. I've got boring old heavier, inexpensive but strong wheels on that bike. In any case, I'm not judging or criticizing you. Or anyone else. Get over it.

nhluhr

Foul! Clearly that is not allowed, and also impossible since lightweight wheels wouldn't survive a single commute.