Some things are huge in comparison to wheelset weight. Ride a MTB on pavement with the tires it came with and then put on 1.25 slicks -- yes you WILL feel the difference. Other examples in no particular order are: reasonable fit, properly working shifters, appropriate gear range, ditch that suspension seat post, lock out suspension fork or replace with non-suspension (for riding on good surfaces.) Once the bike fits you, shifts reliably, has a suitable gear range for your circumstances and has nothing actually wrong with it, returns diminish rapidly as the cost of upgrades increases rapidly.

The more you spend, the less bang/buck but there will always be some. You could spend $5000 on a $3000 bike but don't expect a quantum leap in performance.

Don in Austin

In the sense that I think you are intending, no. If we are talking about the energy required to accelerate and decelerate a given amount of inertia then the energy is the integral (the area under the curve) and the average is the quotient of the integral and the length so by definition the ratio between the total and the average is constant (= the length)

The bit that is confusing you is that since aerodynamic drag increases as the square of speed it actually does take more energy to maintain speed in the higher speed parts of the varying curve. That's not what anyone is talking about.

LOL I'll overlook the tone. This last sentence is incorrect. Because of the drag (which I do understand), it takes more energy to maintain the speed accelerating and decelerating.

Also, unless I'm having a brain fart, you have an energy cost to acceleration that you're not making up coasting to maintain a given speed.

I don't think anyone is challenging the law of diminishing returns. Diminishing returns apply to the cost/weight proposition for all components, not just wheels. As I read you posts you are singling out wheels.

The marketing people are selling good old American bull****!

When I switch from regular 26 x 2 all-purpose tires and tubes to my Pasela 1.25's with the ultralight tubes, the bike takes off like a rocket from a stoplight. I'd have no problem identifying the two configurations in blind testing, that's for sure. The weight difference is about... lessee here... 1100 grams or so. The cost difference is reasonable.

For me as an arterial commuter, getting up to cruising speed quickly is definitely useful. Surging from cruise to ~30mph is also useful at times. I don't always use the Paselas, but when I do, there's no mistaking the change in acceleration.

I expect the rolling resistance difference is more responsible for the performance improvement than just the weight. Knobby or coarse treaded tires absorb a lot of energy compared to slicks.

I don't really agree with that. For one thing, when launching from a stoplight, you start at a speed of zero. What's rolling resistance at zero mph? Yeah, it's zero too Those first few pedal strokes are all about the accelerability. For the record, the 2" tires I mentioned are relatively smooth street-oriented semi-knobbies, namely Bontrager LT3s. Not a bad cheap tire. Big enough to handle potholes with a load of groceries onboard

Knobbies don't have to be slow, either. I have some extremely fast-rolling 2.2" XC race tires that cruise as fast as the Paselas do in a steady-state situation, and have set the course record for our local paved-and-gravel Midnight Century three years in a row on my XC bike. The key is really rider aerodynamics, which is why I spend a large part of that ride in this position: https://www.midnightcentury.com/supercruise.jpg


In the bigger picture, it's possible to overthink anything. I don't scowl if I have the LT3s installed, or even my extremely heavy studded tires, if they serve the purpose at hand. But it's not a waste of time to look at rotational weight if you want your bike to be more perky.

Technically yes, due to the non-linear drag from air resistance there's slightly more energy required to travel at varying speeds rather than maintaining the same average speed but without any variation. But in practice while bicycling this effect is insignificant. Let's say you have someone on a light bike who averages 20 mph but does so by speeding up to 21 mph during part of the pedal stroke and slowing down to 19 mph at another portion of the stroke. If we simplify the problem and assume he spends half the time at 21 and half at 19, then the power he puts out could propel him at 20.05 mph if he used it to maintain a perfectly uniform speed. Actually the benefit would be even less since the speed would vary roughly like a sine wave rather than abruptly switching between the two speeds.

Now putting extra weight in the rim will help to even out the speed since it acts as a flywheel, but it'll also add some rolling resistance. And since the potential gain from maintaining a uniform speed is so small (less than 0.05 mph in this example) it doesn't make sense to add the flywheel - even on a totally flat course.

Yes, you are having a brain fart.

I didn't say it was significant, I said it existed and that its existence led to confusion. This thread would be QED for that last point.

There is a point of diminishing returns on all attempts to reduce bicycle weight. Like lostarchitect says if you are replacing steel rims and steel hubs with aluminum, you'll get immediate return. If you are replacing OEM wheels with higher quality wheels, the return is less. If you are replacing $200 to $500 wheels with $1500 wheels, you'll have a hard time noticing any difference at a nonelite level.

As for your question, look here for a pretty good answer from a physicist. The answer to your question is that it's not overblown...too much...as long as you are talking about accelerating. And even then, the differential in speed has to be taken into consideration. If you are accelerating from a stop to cruising speed, wheel mass is important. If you are accelerating to change from, say, 12 mph to 14 mph the wheel mass is far less important.

Torque X speed = power, not energy and is measured in units like watts or horse power.
Torque X speed X time = energy and is measured in units like watt-hours. Any competent engineer or scientist should be aware of this.

However the general public uses the terms interchangeably and it doesn't help that the "power company" encourages "energy conservation" and so on.

Check your math please - I estimate much higher difference using power equations. Assuming a frequency of 90, I get an average about 49 watts for simply accelerating the mass. (with each stroke in 2/3 sec, time accelerating t= 1/3 sec,delta v is .9 m/s,mass is 80 kg, = 32 joules for .3 sec = 97 watts. divided by 2 since only half the time is accelerating)

Solving in the familiar drag equation: using (estimated 1/2rho CdA =.28) power at the average 20mph plus 49 watts, solve for the higher speed as I assume you did something similar, I get almost .3 mph difference.

Did you subtract the power saved during the period when he's decelerating?

Yes, when dividing the energy by two. I didn't assume an unpowered coast-down to 19mph. Did you?

As measuring devices, us humans are quite sucky when it comes to quantifying change in absolute terms, but we can be surprisingly good at noticing relative change.
I've got 3 sets of tires and two sets of wheels that I commute on, one rather nice build, and one bog-standard. Tires range from 1.2 slicks to mid-count(106-160) studded winter tires to high count(288-294) winter tires.
While the difference in feel between nice wheels in slicks, and crummy wheels in either mid, or high stud count is absolutely massive(the high-counts I think are 800+ grams each), the difference in time really isn't that much. I can easily be faster on the heavy gear, if I have someone to pace, than what I am on a solo ride on the nice wheels. There are plenty of times where a winter ride has felt like a really boring slog, but when I get home it's only added maybe 5% on the time. And that's for a change that is more radical than most riders will see on road bike wheel set.
But sure, for someone whose level of effort is more closely linked to how the bike feels, I can certainly see how a moderately lighter wheelset can translate into an unproportionally large improvement in riding.

(this is "dry" winter of course. Icy patches, a bit of sand on the roads. If I have to churn my way through inches of snow/slush, the speed drops radically)

+1. Anyone who thinks the benefits of lighter wheels = the benefits of a lighter frame have never taken a class in physics

That's not accounting for the energy saving while decelerating. Not only are you only accelerating for half the time and having to apply more power only during that time, but the rest of the time you are decelerating and applying LESS power as compared to the rider who goes at a totally steady speed.

Nobody's mentioned that lighter wheels brake better.

No, the hub might have been a part of it, but most of it was due to having to put more energy into the heavier wheel to accelerate it to the same speed.

Lighter bikes are definitely more fun to ride, and doubtless the placebo effect magnifies the difference to a varying extent. But it does matter where you shed the weight; definitely wheels first: tyres, then rims, and who cares about the hub.

They're over-rated as a performance issue. I bet I could build a high-performance wheel on a $20 hub, and the only aspect to suffer would be durability. Drag from hubs is meaningless unless you have a serious issue potentially leading to seizure. Their weight really only matters as far as overall bike weight does, and when you hand your friends your wheel. Their quality is all about durability, engineering of the wheel (for non-traditional spoking), and aesthetics.

After losing weight from the wheels, the next best place to drop it is from the seat and post; as soon as you stand on the bike, it feels like you've lost a lot more than you have. More fun. Then the front end, I guess... I remember trying out some clip-on aero bars, and loving the fact I could cruise in a taller gear, but hating the extra weight hanging off my stem. Also a bit of a bummer when you go from DTs to brifters.

I'm not an engineer but I am an unfrozen caveman lawyer. Some scientists found me in a glacier, thawed me out, and sent me to law school. Your inventions frighten and confuse me. But I do know one thing: lighter wheels accelerate better than heavier ones and during a race, especially a criterium on a technical course, it matters a lot.

Back, oh, 30 years ago or so, Bicycling magazine had an issue where they tested a Klein (which, if you were cycling 30 years ago you would know was at the top of the super bike heap back then) and an UJB. Everyone on staff raved about the Klein. As an experiment, they swapped the wheels from the Klein and the UJB and had everyone on staff ride the bikes. They all preferred the UJB with the wheels from the Klein over the Klein with the wheels from the UJB.

Like many things we buy it comes down to the "best bang for the buck" situation. Upgrading from $100 factory wheels to something like a $500 to $600 set of boutique wheels will give the biggest increase in performance from the biggest reduction in weight. But shaving off the next few grams from that $600 price point becomes increasingly more expensive per gram of reduction. It may well be that to achieve a noticable gain in actual performance we'd need to buy wheels that are well over $1000. But even then the doubling of the price won't produce a doubling of the advantages. We may only be looking at a small reduction in weight over the mid priced wheelset. The rider may not even be able to feel the difference. But if they are a competitive racer the stopwatch will be able to tell.

You're right prathmann. I actually get even less than 20.05 in the example.

There is still something I'm missing though. Perhaps differences in metabolic efficiency, but something about it feels imcomplete.

This is a good thought experiment to get a better feel for how much acceleration the different weighted wheels require. Does a lighter wheel brake better - yes - but it also breaks better. That is something to worry about because if your gossamer tire or rim blows/bends out just once you've lost way more time than you could have ever saved by going ultra lightweight.

Lighter wheels certainly do "feel" faster and liven up the bicycle, but that is not physics!