Jack Tone 

upthywazzoo 

Cool video. Seems that psychology is king, yet again

rubiksoval

"Unless you're accelerating."

So...yeah, I'll go with the light weight wheelsets. Thanks.

WhyFi

It's a good thing that the guy selling the heavier wheels put together simulations to show how they're not at a disadvantage to the lighter wheels.

walnutz

MoAlpha

Cool. That consistent drop in my times this Spring was all me!

Iride01 

If getting lighter wheels is the only way to easily lighten your bike by a pound or so then the battle of rotational weight and just weight is meaningless anyhow.

So what's the point? I tried to listen but the audio quality was poor and evidently neither interviewer or interviewee could talk in full sentences.

But did they ever talk about to bikes of the same overall weight and one with lighter rims? Seems to me that the bike with lighter rims will accelerate faster. And about the only time that is needed is in a sprint. So if they didn't look at the models for just a 200 meter sprint, then they were making a big deal about nothing.

Carbonfiberboy 

What do you bet that this guy paid a lot of attention to unsprung weight on his cars? Speaking of that, of course it's not only rim weight, but tire weight also which should be considered. Using his own aero wheels in this experiment is an absolute no-no, taking away all credibility.

That nitpicking aside, the data files supplied are much too coarse to be useful in making the kind of statements this guy made. To see any rotational weight differences, one would have to look at data intervals on the order of tenths of a second or finer. What's not being considered is the minor accelerations which happen with every pedal stroke, especially when standing. Of course the energy put into the wheels by tiny power variations comes right back out again because momentum. However it takes a tiny bit more muscular effort to accelerate and decelerate than to maintain an absolutely steady speed. It's probably possible to take these micro-efforts into account if one had sufficiently fine data and knew the exact physiology of the particular rider, but of course no one's going to do that.

I think we could say that over the decades, riders have decided that light wheels climb better, using only their subjective feel for it, much the same as that light bikes climb better, even if the computer says there's only a few seconds of difference for that little bit of weight. In both cases, it could be that the act of rocking the bike feels different with lighter wheels and a lighter bike, For sure even I notice large differences in weight, just by feel, therefore small differences must be there, too.

jbchybridrider 

They weren't saying you don't need light wheels. They saying go by there total weight and don't think to much of the rotating weight. So total weight and aero.

noodle soup

+1

Some people only hear, what they want to hear.

79pmooney

I don't buy it. I raced as a skinny climber. The constant little and not so little accelerations of a competitive race took its toll on me. Having very light tires and rims were a Godsend. Being able to very quickly jump up a few MPH to grab that wheel going by or pulling out could save chasing hard for 100 yards. Making the break vs falling 3 feet short could be the difference between top 8 and 25th place 10 minutes back.

Now if you are strong enough to make those repeated jumps on heavy wheels, its a different story. (The big, strong guys couldn't ride the light rims I did unless they had an endless supply of sponsored wheels. 290 gram Fiamme Ergal rims and 250 gram silk tires. (Yeah, everyone rode those tires. My budget didn't allow me to ride Seta Extras. But I could get two seasons out of the Ergal rims on New England roads.)

Ben

Iride01 

I know, and I didn't hear a thing about how they compare in just a 200 meter sprint. Otherwise I'd agree that it's pretty much just weight.

In the grand scheme of anything longer than maybe a kilometer, there is more going on that will cost the win.

jbchybridrider 

Some of you guys are only focused on one aspect of rotational mass thats when accelerating. In say a crit yes you can feel the acceleration but less felt is when you take your power out of the cranks you loose more speed faster than a wheel with more rotational mass which maintains forward momentum.
A rider with less rotational mass needs to apply more power sooner to regain the speed of a wheel with more mass. This is kinetic energy.
In Formula one racing it's the continued energy "momentum" after power has stopped being applied that is stored in batteries. In cycling light wheels are always an advantage and biggest benefit when there's climbing because it's the easiest fastest way to reduce total mass, it's not about rotational mass so aero becomes the biggest advantage when looking for faster wheels.
On a climb you could say a light accelerating wheel can get a breakaway from the bunch and can but still you can't maintain that power on a long climb and when you explode loose momentum faster than a rider that maintains a constant effort and may have a wheel with more rotational mass.

SHBR

I'm not sure I'd EVER trust rim brakes on carbon rims, after seeing this.

nomadmax 

If I "think" lighter wheels make a difference; they make a difference.

datlas 

I do think weight of wheels matters a bit more than the video suggests. On most rides except TT’s, there are lots of micro-accelerations of a few seconds. The heavier wheel requires a bit more power relative to a lighter wheel, and these accumulated marginal extra efforts are going to have an effect. Yes I know you “get it back” in momentum but we are looking at a human engine which is not factored in by the model.

rubiksoval

Or you could just learn how to properly ride and brake. It's not like we haven't been using carbon rims and rim brakes for the last two decades...

SHBR

That crash gives new meaning to the term "unglued".

Its possible those wheels weren't up to spec, good luck proving it though!

With alloy rims, they tend to show cracks, before they fail.

upthywazzoo 

+1

Pretty much this. Even though Conservation of Momentum would dictate that the energy required to keep two geometrically identical bodies of mass in motion would be the same, regardless of the differences in mass--if a rider feels that they have to mash on the pedals to get their bike moving, this will take a toll after repeated efforts--even if the benefit of heavier rims manifests itself on rolling terrain. That said, it seemed to me that the guy in the video is showing that over time aero will trump wheel weight, which is pretty much indisputable at this point. If you have to choose between light, semi-aero rims and heavier, aero rims--the better choice is aero rims.

If you have money though--Bora Ultras, Aeolus XXX, 1100 Dicut, etc are all under 1500 grams.

upthywazzoo 

Personally I'm a lot more worried about getting doored, a car making a sudden right turn, a pedestrian not looking both ways before crossing the bike lane, etc etc than my chinese wheels randomly failing.

WhyFi

It's the same ol' thing - math showing that increasing rotating mass doesn't affect average speed very much... and I actually agree with that. Where I disagree is that, IMO, this always overlooks what makes lighter wheels feel so different - angular momentum/the gyroscope effect.

Anyone that had ridden light wheels can immediately feel the difference - it's not in your head. But it's more side-to-side than straight ahead - lighter wheels change direction/orientation much more readily than heavier wheels and make the bike feel much, much more snappy and responsive whether you're cornering or thrashing out of the saddle - you don't feel like you're fighting the bike as much.

If anyone needs to demonstrate this to themselves, it's easy: the next time your changing a tire/tube, hold the wheel in front of you, by the ends of the QR/TA. Give the wheel a good spin and then try tilting the wheel side-to-side. It'll resist very noticeably. Next, take out the tube (or tire, if you're tubeless), give it another spin and try tilting side-to-side again. Very big difference and that difference is magnified with speed.

Robert A

When I went from OEM to custom alloy wheels, I saved a measured 500g and the difference in bike handling was quite noticeable.

tyrion

Well people don't accelerate in races, do they?

asgelle

If you actually look at the numbers, accelerations are so slow* they virtually don't.

*Scaled to the forces needed to maintain a steady speed

tyrion

I don't race, and I don't know much about racing, but I thought marginal gains in acceleration were critical for breaking away.