Does rotating weight really matter?
05-03-21, 11:06 AM
#51
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From the usenet archives:
Although it may seem daunting, when another rider pulls away on a hill
or in a bike race on the flat, these accelerations, except in standing
starts, are so small as to make the rotating mass story a hoax. Sure,
the mass counts twice as much when accelerating but two times zero is
still zero, and how long does a rider accelerate. Weight of bicycle
components for climbing is the main consideration, not acceleration.
The rotating mass story is a fable that sounds good and has just
enough technical truth to be one that will probably sustain itself
indefinitely. Making equipment choices by it are a matter of faith,
not fact. Jobst Brandt, 26-Mar-2000
or in a bike race on the flat, these accelerations, except in standing
starts, are so small as to make the rotating mass story a hoax. Sure,
the mass counts twice as much when accelerating but two times zero is
still zero, and how long does a rider accelerate. Weight of bicycle
components for climbing is the main consideration, not acceleration.
The rotating mass story is a fable that sounds good and has just
enough technical truth to be one that will probably sustain itself
indefinitely. Making equipment choices by it are a matter of faith,
not fact. Jobst Brandt, 26-Mar-2000
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05-03-21, 11:34 AM
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You're saying these companies are lying about what their wheels weigh? Because this thread started off with you thought the benefits from light weight stuff wasn't enough to justify the price, but now it sounds like fraud (false advertising) is going on??
05-03-21, 11:50 AM
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but I think generally folks are looking for a tangible benefit when they decide to shell out cash on wheels and higher priced bikes. So its fair to temper peoples expectations. Ive seen videos where the time savings of nice carbon wheels vs basic aluminum wheels is about 1min per hour, I certainly cant justify spending that much.
I have the most basic of bikes, a base model allez with Claris and axis sport branded wheels and I get lots of enjoyment on the bike, the only limiter is me. And I go way faster than a lot of folks because Ive put in the work on myself. I think a lot of people buy into hype and then come up with nebulous things to justify spending way too much in absence of any tangible benefits they may have been looking for. Yeah its all about fun, but I think most folks have priorities outside of cycling and helping people make smart purchases is just as important as getting enjoyment.
I have the most basic of bikes, a base model allez with Claris and axis sport branded wheels and I get lots of enjoyment on the bike, the only limiter is me. And I go way faster than a lot of folks because Ive put in the work on myself. I think a lot of people buy into hype and then come up with nebulous things to justify spending way too much in absence of any tangible benefits they may have been looking for. Yeah its all about fun, but I think most folks have priorities outside of cycling and helping people make smart purchases is just as important as getting enjoyment.
It sounds like you're thinking the only thing any bike equipment can do for anybody is make you faster. But you've seen how disc brakes took over road cycling, the time savings is zero. Negative time savings if the wind is coming from the rotor side. A lot of people will never buy a rim brake road bike again and are happy about it. I've seen a lot of people complain that they can't get high end wheels anymore, I've never seen anybody complain that riders can't spend money on increased safety on the basis of minutes saved per hour.
I have not especially light, but deep, carbon hoops. The main benefit I get out of them is I enjoy riding more when I use them. Did they make me faster? Yes. Do I care? A little. Mainly I like the way the bike feels, looks, and sounds (when I'm going fast). Would I do it again? **** yeah!
Sometimes it's really fun to be fast, but there's so much more to cycling and the difference between 27.3 and 27.4 mph doesn't really affect my smiles per mile.
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05-03-21, 11:51 AM
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05-03-21, 03:12 PM
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You said "Because this thread started off with you thought the benefits from light weight stuff wasn't enough to justify the price," That's not what I started off with. I will agree that the "benefit" real or imagined does not justify paying $2,000 or more for a CF wheel set. But, that's just me. If someone else does feel it's justified....go for it. Also, I did not say anything about lightweight "stuff." The video addresses wheels, not stuff. My question is about rotating weight vs weight in general. But, that's just my question. I thought the presenter raised some interesting questions.
Last edited by bruce19; 05-03-21 at 03:32 PM.
05-03-21, 03:19 PM
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You said "Because this thread started off with you thought the benefits from light weight stuff wasn't enough to justify the price," That's not what I started off with. I will agree that the "benefit" real or imagined does not justify paying $2,000 or more for a CF wheel set. But, that's just me. If someone else does feel it's justified....go for it.
05-03-21, 03:53 PM
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I'm talking about *your* statements -
So, what's being advertised and unmet w/r/t rotating weight?
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05-03-21, 04:09 PM
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05-03-21, 04:10 PM
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I have seen ads which tout the reduction in rotating weight as a significant advantage. Any search I've done says this is a myth or, at best, there is a minimal advantage in specific situations. IMO this does not justify a large expenditure of money. Especially when I could, and should, lose 10 lbs.
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05-03-21, 04:15 PM
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05-03-21, 04:35 PM
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Yes, I think that Bike Forums is the perfect venue for us to be critical of each other's statements, semantics, and intent like we are all doing peer review of each other's posts.
05-03-21, 04:48 PM
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05-03-21, 05:02 PM
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FWIW, there's a bunch of discussion here about not much. Typically from what I see here on BF, cyclists get a stock bike. Don't like the wheels -- they're heavy. Lighter wheels save weight -- that's not even a question. This topic seems should be about whether a gram saved on a wheel rim is how much better than a gram saved elsewhere -- is it worth 1.5x, 2x, 3x more than another option (per gram)?
Spending money on saving weight.. whatever -- do what you want to do and buy what you want to buy. I find it an interesting premise though that there's nothing that special about a wheel gram vs another type of gram. Aero however, is a completely different topic.
Boil it down.. if you could get a 1800 gram, awesome looking blingy wheel with a cool 28mm exterior width and 45mm depth for $750, or the same described wheel, at 1400 grams, for eg. $3k, would this be something you'd consider? What's your breakeven?
Spending money on saving weight.. whatever -- do what you want to do and buy what you want to buy. I find it an interesting premise though that there's nothing that special about a wheel gram vs another type of gram. Aero however, is a completely different topic.
Boil it down.. if you could get a 1800 gram, awesome looking blingy wheel with a cool 28mm exterior width and 45mm depth for $750, or the same described wheel, at 1400 grams, for eg. $3k, would this be something you'd consider? What's your breakeven?
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05-03-21, 05:06 PM
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Anyone who reads this thread will see a few pissing contests of no consequence, but in between is the clear point that lighter (and more aero) bikes are more fun.
And yeah, you notice rotating mass more. All the rotating mass, not just the wheels. Not so much the cranks, but consider that the whole bike rotates from side to side with the contact patches as the axis when you stand on it, so if you want your bike to feel light when you do that, start at the top - seat and bars matter like rims. Then you've got the front end rotating around the head tube; lighten all that and you'll notice that more too.
Save crank upgrades for last.
And yeah, you notice rotating mass more. All the rotating mass, not just the wheels. Not so much the cranks, but consider that the whole bike rotates from side to side with the contact patches as the axis when you stand on it, so if you want your bike to feel light when you do that, start at the top - seat and bars matter like rims. Then you've got the front end rotating around the head tube; lighten all that and you'll notice that more too.
Save crank upgrades for last.
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05-03-21, 05:09 PM
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Will people notice the faster accelerating or the faster deaccelerating first?
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05-03-21, 06:15 PM
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Before either of those, how easy it is to carry up stairs.
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05-03-21, 07:13 PM
#72
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FWIW, there's a bunch of discussion here about not much. Typically from what I see here on BF, cyclists get a stock bike. Don't like the wheels -- they're heavy. Lighter wheels save weight -- that's not even a question. This topic seems should be about whether a gram saved on a wheel rim is how much better than a gram saved elsewhere -- is it worth 1.5x, 2x, 3x more than another option (per gram)?
Spending money on saving weight.. whatever -- do what you want to do and buy what you want to buy. I find it an interesting premise though that there's nothing that special about a wheel gram vs another type of gram. Aero however, is a completely different topic.
Boil it down.. if you could get a 1800 gram, awesome looking blingy wheel with a cool 28mm exterior width and 45mm depth for $750, or the same described wheel, at 1400 grams, for eg. $3k, would this be something you'd consider? What's your breakeven?
Spending money on saving weight.. whatever -- do what you want to do and buy what you want to buy. I find it an interesting premise though that there's nothing that special about a wheel gram vs another type of gram. Aero however, is a completely different topic.
Boil it down.. if you could get a 1800 gram, awesome looking blingy wheel with a cool 28mm exterior width and 45mm depth for $750, or the same described wheel, at 1400 grams, for eg. $3k, would this be something you'd consider? What's your breakeven?
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05-03-21, 07:45 PM
#73
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So....Is it easier to carry up the stairs if the wheels aren't spinning?
When sprinting at speed in an important race, The aerodynamic advantage of a heavier wheel might outweigh the tiny loss in acceleration of the rotating mass.
When sprinting at speed in an important race, The aerodynamic advantage of a heavier wheel might outweigh the tiny loss in acceleration of the rotating mass.
Last edited by xroadcharlie; 05-04-21 at 02:04 AM.
05-04-21, 02:27 AM
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From what I have read, because the whoosh from aerodynamic wheels makes you think you are going faster. Some day, when I buy a bike with disc brakes, I will give this a try.
05-04-21, 02:49 AM
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I've never noticed a difference in speed when switching to a light wheelset. The biggest difference is the smoothness of the ride when going from wheels with stiff straight gauge spokes and light DB spokes. Straight gauge spokes, which the majority of stock wheels come with are my pet peeve.
I did buy a Swobo single speed bike than came new with 42mm tires, cheap and heavy ones (that were too wide for the narrow rims). I switched to 23mm Vittoria open tubulars and the difference was very noticeable.
I did buy a Swobo single speed bike than came new with 42mm tires, cheap and heavy ones (that were too wide for the narrow rims). I switched to 23mm Vittoria open tubulars and the difference was very noticeable.
