Go Back  Bike Forums > Bike Forums > Road Cycling
Reload this Page >

Does rotating weight really matter?

Notices
Road Cycling ďIt is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.Ē -- Ernest Hemingway

Does rotating weight really matter?

Old 05-01-21, 06:28 AM
  #1  
bruce19
Senior Member
Thread Starter
 
bruce19's Avatar
 
Join Date: Jul 2006
Location: Lebanon (Liberty Hill), CT
Posts: 7,791

Bikes: CAAD 12, MASI Gran Criterium S, Colnago World Cup CX & Guru steel

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 1445 Post(s)
Liked 835 Times in 500 Posts
Does rotating weight really matter?

bruce19 is offline  
Likes For bruce19:
Old 05-01-21, 06:33 AM
  #2  
Racing Dan
Senior Member
 
Racing Dan's Avatar
 
Join Date: Aug 2015
Posts: 1,772
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 1026 Post(s)
Liked 132 Times in 98 Posts
Weight matters no matter if it rotates or not. However the effect is greatly exaggerated on the forums and the reasons why is not generally understood by the forum "experts".
Racing Dan is offline  
Old 05-01-21, 08:57 AM
  #3  
mstateglfr 
Sunshine
 
mstateglfr's Avatar
 
Join Date: Aug 2014
Location: Des Moines, IA
Posts: 12,615

Bikes: '18 class built steel roadbike, '19 Fairlight Secan, '88 Schwinn Premis , Black Mountain Cycles Monstercross V4, '89 Novara Trionfo

Mentioned: 99 Post(s)
Tagged: 0 Thread(s)
Quoted: 5309 Post(s)
Liked 2,593 Times in 1,516 Posts
When starting from still, sure.
When trying to accelerate, sure.
When JRA, not really.

I dont need to watch a GCN 'experiment' though.
mstateglfr is offline  
Likes For mstateglfr:
Old 05-01-21, 09:08 AM
  #4  
bruce19
Senior Member
Thread Starter
 
bruce19's Avatar
 
Join Date: Jul 2006
Location: Lebanon (Liberty Hill), CT
Posts: 7,791

Bikes: CAAD 12, MASI Gran Criterium S, Colnago World Cup CX & Guru steel

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 1445 Post(s)
Liked 835 Times in 500 Posts
Originally Posted by mstateglfr View Post
When starting from still, sure.
When trying to accelerate, sure.
When JRA, not really.

I dont need to watch a GCN 'experiment' though.
FWIW it wasn't a GCN experiment. Some Formula 1 tech guy ran some tests with a computer program is what I took from it. Apparently he's the founder and CEO of this company: https://www.swissside.com/?locale=en

Last edited by bruce19; 05-01-21 at 09:14 AM.
bruce19 is offline  
Old 05-01-21, 09:27 AM
  #5  
noodle soup
Senior Member
 
noodle soup's Avatar
 
Join Date: Nov 2015
Posts: 8,884
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 4669 Post(s)
Liked 1,799 Times in 974 Posts

Does rotating weight really matter?


it depends
noodle soup is offline  
Likes For noodle soup:
Old 05-01-21, 10:31 AM
  #6  
Doomrider74
Senior Member
 
Join Date: Mar 2021
Posts: 209
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 103 Post(s)
Liked 73 Times in 41 Posts
Is that the video where the conclusion was "no, unless you're accelerating"? Isn't climbing a whole series of micro accelerations, once it gets steep enough for inertia to be negligible for a given speed? Also, what about crit racers constantly accelerating out of corners? It seems to me even casual cyclists are accelerating quite a lot.
Doomrider74 is offline  
Likes For Doomrider74:
Old 05-01-21, 10:51 AM
  #7  
zandoval 
Senior Member
 
zandoval's Avatar
 
Join Date: May 2010
Location: Bastrop Texas
Posts: 2,031

Bikes: Univega, PR-10, Ted Williams,UO-8, Puch, PHLE, UO-18 Mixte

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 91 Post(s)
Liked 67 Times in 55 Posts
Mass in motion and more than that, Harmonic Mass in motion. Not so much easily attainable but a little easier for bicycle riders. Looking at the technical aspects bicycle riders attempt this physically, mechanically, and metaphysically on a good ride...

__________________
No matter where your at... There you are... Δf:=f(1/2)-f(-1/2)
zandoval is offline  
Old 05-01-21, 11:15 AM
  #8  
HTupolev
Senior Member
 
Join Date: Apr 2015
Location: Seattle
Posts: 3,806
Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 1741 Post(s)
Liked 862 Times in 423 Posts
Originally Posted by Doomrider74 View Post
Isn't climbing a whole series of micro accelerations
Yes. Technically speaking, power variation across the pedal stroke creates speed oscillations in all riding, although this is much less pronounced in situations with more inertia.

The thing is, rotational inertia works in both directions. Heavy wheels won't accelerate as quickly at the peak of your power stroke on a climb, but they also won't decelerate as quickly when the power isn't flowing.
HTupolev is online now  
Old 05-01-21, 11:29 AM
  #9  
tyrion
Senior Member
 
tyrion's Avatar
 
Join Date: Oct 2015
Location: San Diego, California
Posts: 3,381

Bikes: Breezer Radar

Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 1816 Post(s)
Liked 1,158 Times in 550 Posts
I don't know much about racing, but I thought very small differences in acceleration can make or break a break away attempt. That video completely ignored that aspect of wheel weight.
tyrion is offline  
Old 05-01-21, 12:01 PM
  #10  
Atlas Shrugged
Senior Member
 
Join Date: Mar 2010
Posts: 519
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 302 Post(s)
Liked 314 Times in 167 Posts
People use the rotating mass argument as a justification tool when trying to explain why they are riding multiple thousand dollar wheel sets while they are 20 or 30 lbs overweight.
Atlas Shrugged is offline  
Old 05-01-21, 01:06 PM
  #11  
rubiksoval
Senior Member
 
Join Date: Nov 2015
Location: Music City, USA
Posts: 4,415

Bikes: bikes

Mentioned: 52 Post(s)
Tagged: 0 Thread(s)
Quoted: 2601 Post(s)
Liked 1,396 Times in 698 Posts
Originally Posted by tyrion View Post
I don't know much about racing, but I thought very small differences in acceleration can make or break a break away attempt. That video completely ignored that aspect of wheel weight.
The peloton is what makes or breaks most break away attempts.
rubiksoval is offline  
Likes For rubiksoval:
Old 05-01-21, 01:13 PM
  #12  
SoSmellyAir
Method to My Madness
 
Join Date: Nov 2020
Location: Orange County, California
Posts: 354

Bikes: Cannondale Synapse, Trek FX 2

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 153 Post(s)
Liked 105 Times in 75 Posts
Originally Posted by Doomrider74 View Post
Is that the video where the conclusion was "no, unless you're accelerating"? ... It seems to me even casual cyclists are accelerating quite a lot.
Yes, especially if you are out of shape like me, freewheeling now and then to catch my breath.
SoSmellyAir is offline  
Old 05-01-21, 01:37 PM
  #13  
WhyFi
Senior Member
 
WhyFi's Avatar
 
Join Date: Jan 2010
Location: TC, MN
Posts: 34,293

Bikes: R3 Disc, Haanjo

Mentioned: 343 Post(s)
Tagged: 1 Thread(s)
Quoted: 16482 Post(s)
Liked 5,182 Times in 2,705 Posts
It may not manifest on the stopwatch, but it certainly affects handling feel. Bikes with lighter rims/tires feel much more fun and responsive to changes in orientation (less weight, lower angular momentum)

WhyFi is offline  
Old 05-01-21, 02:01 PM
  #14  
sfrider 
Asleep at the bars
 
sfrider's Avatar
 
Join Date: May 2006
Location: San Francisco, CA
Posts: 1,683
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 209 Post(s)
Liked 169 Times in 109 Posts
It matters for acceleration since you not only have to accelerate the wheel mass forward with the rest of the bicycle, but you also have to add rotational energy to the wheels. And the rotational (angular) energy grows with the square of the rotational speed (angular velocity). (For the technical people, there is an w^2 factor where w=omega.) Forward kinetic energy only grows linearly with speed.
__________________
"This 7:48 cycling session burned 5933 calories. Speed up recovery by replacing them with a healthy snack." - Whoop

sfrider is offline  
Old 05-01-21, 02:06 PM
  #15  
HTupolev
Senior Member
 
Join Date: Apr 2015
Location: Seattle
Posts: 3,806
Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 1741 Post(s)
Liked 862 Times in 423 Posts
Originally Posted by sfrider View Post
Forward kinetic energy only grows linearly with speed.
This isn't true at all. Kinetic energy for linear acceleration is quadratic with velocity.

https://en.wikipedia.org/wiki/Kineti...f_rigid_bodies

The inertia of mass at the tire requires double the kinetic energy to reach a certain forward velocity than mass at the frame.

Last edited by HTupolev; 05-01-21 at 02:09 PM.
HTupolev is online now  
Old 05-01-21, 02:36 PM
  #16  
walnutz
Senior Member
 
walnutz's Avatar
 
Join Date: Jun 2010
Location: ATX
Posts: 604

Bikes: CO-OP ADV 3.1 aka Beeftank, All-City Super Professional aka Bulldozer

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 78 Post(s)
Liked 119 Times in 64 Posts
Disclaimer: All of the following may only have taken place in my head and is not based on anything scientific.

Purely anecdotal, but I didnít like when I had lighter wheels, Iím not a heavy person so I definitely felt I had to work more to keep them going on flats, or on any road terrain in general. I felt like if I stopped pedaling the bike stopped. I did definitely notice they felt more touchy/responsive in a way that I actually didnít like, which lines up with what whyfi said above. I understand I am the outlier here though lol. I feel more planted and comfortable with heavier wheels. I may just be crazy though. Thereís also probably other variables Iím too dim to understand here. Long story short, I sold my lighter wheels.

All that said, the above qualities mean on a mtb lighter wheels make sense for me because Iím not rolling as much (inertia matters less) and I can appreciate the quickness and lighter feel more.
walnutz is offline  
Old 05-01-21, 02:48 PM
  #17  
79pmooney
A Roadie Forever
 
79pmooney's Avatar
 
Join Date: Oct 2014
Location: Portland, OR
Posts: 9,508

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 102 Post(s)
Tagged: 0 Thread(s)
Quoted: 2871 Post(s)
Likes: 0
Liked 1,384 Times in 940 Posts
Originally Posted by tyrion View Post
I don't know much about racing, but I thought very small differences in acceleration can make or break a break away attempt. That video completely ignored that aspect of wheel weight.
Yup. I was a skinny, light, long limbed climber with all slow twitch muscles. The "flatties" hated me when the race wasn't flat. But on the flat, all those little accelerations that they did so easily took a much bigger percentage of my max each time. Then there was getting on the wheel going by. Closing a gap. Lets say when you are at your max, super light rims and tires mean you are two feet behind that wheel and heavier rims put you at 5 feet back. 3' at 28 miles per hour comes out to 0.07 seconds. Who cares? In a 5 hour race, totally meaningless, right?

But, you are at your max. 2 feet means you are on that wheel, 5' means you aren't. You may not be able to close that extra 3 feet or it may take you minutes to do it. If you do make it, you may be cooked for the rest of the race. But getting that little extra jump to grab that wheel, that extra 0.07 seconds up the road? You're on! You're in the break. You may will be finishing 10 minutes ahead of that other you on heavier wheels who didn't quite make it.

In my hardest race ever, I was half way up the deciding hill 15 miles before the finish, in about 30th place with an unbroken line of rider in front of me. I was hurting bad. The race had been very fast and I'd been an instigator in an ill fated break. Looked over my shoulder to see how far I could fade back and still be with the leaders (being fully aware this might cause a field split that might never come together again). Next rider was 25 yards back. That's about 4 seconds at the speed we were going. I knew instantly the wheel I was on was going to beat that guy and everybody else back there by 10 minutes. I stayed on and was well rested and had waited in line, then got my drink at the water fountain before anybody else finished.

That was at steady speed and rims didn't matter. It was about holding a wheel at any cost. I paid a LOT to stay on that one. But at the top of the hil, I was there and the guy behind me wasn't. (I was on 270 gm average rims and 250 gm tubulars so they WERE very light and helped me to an unknown degree over the previous 3 hours.) Point being - the little things in races matter far more than any analysis of seconds gained or lost, etc. will ever tell you. If you are strong enough to simple clobber everyone with the raw power of your legs, those light rims might not matter. If you have to race with all your smarts and all your resources to be there at the end, rims can be make or break items.
79pmooney is offline  
Likes For 79pmooney:
Old 05-01-21, 02:53 PM
  #18  
SoSmellyAir
Method to My Madness
 
Join Date: Nov 2020
Location: Orange County, California
Posts: 354

Bikes: Cannondale Synapse, Trek FX 2

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 153 Post(s)
Liked 105 Times in 75 Posts
Originally Posted by walnutz View Post
Iím not a heavy person so I definitely felt I had to work more to keep them going on flats, or on any road terrain in general. I felt like if I stopped pedaling the bike stopped.
Yes, this is scientific; you were after the flywheel effect. Time trial bikes have solid rear wheels for that (and aerodynamic) reasons. This is not a phenomenon that is unique to cycling. Those who have installed aftermarket flywheels in manual transmission cars also go back and forth on this issue.
SoSmellyAir is offline  
Likes For SoSmellyAir:
Old 05-01-21, 04:11 PM
  #19  
smashndash
Senior Member
 
Join Date: Feb 2018
Posts: 1,208

Bikes: 2017 Specialized Allez Sprint Comp

Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 726 Post(s)
Liked 256 Times in 180 Posts
Originally Posted by SoSmellyAir View Post
Yes, this is scientific; you were after the flywheel effect. Time trial bikes have solid rear wheels for that (and aerodynamic) reasons. This is not a phenomenon that is unique to cycling. Those who have installed aftermarket flywheels in manual transmission cars also go back and forth on this issue.
I will also say that this effect is much more apparent on fixed gear bikes. I started riding on a fixie with 3000+g 50mm deep alloy wheels. When I switched to a road bike, my legs would literally stop (not exaggerating) at the top of the pedal stroke because I was so used to the pedals carrying my feet through the deadzone.

I get confused when people say riding a fixie gives you a better pedal stroke LOL
smashndash is offline  
Likes For smashndash:
Old 05-01-21, 05:44 PM
  #20  
bruce19
Senior Member
Thread Starter
 
bruce19's Avatar
 
Join Date: Jul 2006
Location: Lebanon (Liberty Hill), CT
Posts: 7,791

Bikes: CAAD 12, MASI Gran Criterium S, Colnago World Cup CX & Guru steel

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 1445 Post(s)
Liked 835 Times in 500 Posts
My take away thus far is that there has been a lot of money spent for not much gain. I am willing to be convinced otherwise but so far that's where I am.
bruce19 is offline  
Likes For bruce19:
Old 05-01-21, 06:30 PM
  #21  
79pmooney
A Roadie Forever
 
79pmooney's Avatar
 
Join Date: Oct 2014
Location: Portland, OR
Posts: 9,508

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 102 Post(s)
Tagged: 0 Thread(s)
Quoted: 2871 Post(s)
Likes: 0
Liked 1,384 Times in 940 Posts
Originally Posted by smashndash View Post
I will also say that this effect is much more apparent on fixed gear bikes. I started riding on a fixie with 3000+g 50mm deep alloy wheels. When I switched to a road bike, my legs would literally stop (not exaggerating) at the top of the pedal stroke because I was so used to the pedals carrying my feet through the deadzone.

I get confused when people say riding a fixie gives you a better pedal stroke LOL
Ride with some slack in your chain and go down fast hills (keeping the top run of the chain tight). Also ride up seated as much as possible. And use some discipline. The vets in my club told me to ride fixed 45 years ago. I've never regretted it. When my pedal stroke needs work, I get back on it. (But I've never ridden heavy wheels outside of big tired gravel.)
79pmooney is offline  
Old 05-01-21, 06:37 PM
  #22  
big john
Senior Member
 
big john's Avatar
 
Join Date: Sep 2005
Location: In the foothills of Los Angeles County
Posts: 16,434
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2742 Post(s)
Liked 2,099 Times in 1,163 Posts
Originally Posted by Atlas Shrugged View Post
People use the rotating mass argument as a justification tool when trying to explain why they are riding multiple thousand dollar wheel sets while they are 20 or 30 lbs overweight.
You say that like it's a bad thing.
big john is online now  
Likes For big john:
Old 05-01-21, 07:29 PM
  #23  
smashndash
Senior Member
 
Join Date: Feb 2018
Posts: 1,208

Bikes: 2017 Specialized Allez Sprint Comp

Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 726 Post(s)
Liked 256 Times in 180 Posts
Originally Posted by 79pmooney View Post
Ride with some slack in your chain and go down fast hills (keeping the top run of the chain tight). Also ride up seated as much as possible. And use some discipline. The vets in my club told me to ride fixed 45 years ago. I've never regretted it. When my pedal stroke needs work, I get back on it. (But I've never ridden heavy wheels outside of big tired gravel.)
So riding a fixie doesn't give you a better pedal stroke. Riding a fixie with the intent to specifically work on your pedal stroke gives you a better pedal stroke. Sure, I can get with that.
smashndash is offline  
Likes For smashndash:
Old 05-01-21, 07:44 PM
  #24  
Koyote
Senior Member
 
Join Date: Sep 2017
Posts: 3,687
Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 3108 Post(s)
Liked 3,968 Times in 1,792 Posts
Originally Posted by bruce19 View Post
FWIW it wasn't a GCN experiment. Some Formula 1 tech guy ran some tests with a computer program is what I took from it. Apparently he's the founder and CEO of this company: https://www.swissside.com/?locale=en
In other words, a guy who makes heavy aero wheels is trying to convince us that rotating mass doesn't matter very much.

Sure, yeah, I trust him.
Koyote is offline  
Likes For Koyote:
Old 05-01-21, 09:38 PM
  #25  
Seattle Forrest
Senior Member
 
Seattle Forrest's Avatar
 
Join Date: Mar 2010
Location: Seattle, WA
Posts: 21,834
Mentioned: 72 Post(s)
Tagged: 0 Thread(s)
Quoted: 14248 Post(s)
Liked 5,292 Times in 3,010 Posts
Originally Posted by bruce19 View Post
My take away thus far is that there has been a lot of money spent for not much gain. I am willing to be convinced otherwise but so far that's where I am.
Having more than one road bike?
Seattle Forrest is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.