|
Originally Posted by sweeks
(Post 22990461)
These changes are very small and hard to measure... but they can be measured.
I hope this helps settle the matter. :thumb: Has any matter ever been settled here on BF ? now there's a topic for discussion. food for thought and grounds for further research /markp |
Originally Posted by mpetry912
(Post 22990492)
Has any matter ever been settled here on BF ?
|
Gokiso hubs from Japan claim to be the smoothest, lowest friction hubs on the market. Can anyone speak to how to purchase a set of these outside of Japan?
http://www.gokiso.jp/en/products/hub_06.html |
Originally Posted by mpetry912
(Post 22990492)
Thank you for those quotes. "interesting"
Has any matter ever been settled here on BF ? now there's a topic for discussion. food for thought and grounds for further research /markp |
I recently bought a new carbon wheelset and did a free spin test on the front wheel compared to the front stock wheel from my 2016 Trek Domane. The old front wheel free spun for almost 2mins, the new front wheel spun for less than 20 seconds. I checked the brakes several times to make sure there was no interference. There just seems to be a ton of resistance/viscosity in these new hubs.
I realize that all the comments here disagree, but this rolling resistance must add up over time. I can genuinely feel a difference in resistance when spinning the wheel slowly by hand. Could this all come down to extremely heavy grease being used in the hub? Any other thoughts? |
Originally Posted by leon6782
(Post 23265873)
I recently bought a new carbon wheelset and did a free spin test on the front wheel compared to the front stock wheel from my 2016 Trek Domane. The old front wheel free spun for almost 2mins, the new front wheel spun for less than 20 seconds.
|
Originally Posted by leon6782
(Post 23265873)
I recently bought a new carbon wheelset and did a free spin test on the front wheel compared to the front stock wheel from my 2016 Trek Domane. The old front wheel free spun for almost 2mins, the new front wheel spun for less than 20 seconds. I checked the brakes several times to make sure there was no interference. There just seems to be a ton of resistance/viscosity in these new hubs.
I realize that all the comments here disagree, but this rolling resistance must add up over time. I can genuinely feel a difference in resistance when spinning the wheel slowly by hand. Could this all come down to extremely heavy grease being used in the hub? Any other thoughts? It's like putting on a new pair of of cheap jeans without washing them. |
Originally Posted by leon6782
(Post 23265873)
I realize that all the comments here disagree, but this rolling resistance must add up over time. I can genuinely feel a difference in resistance when spinning the wheel slowly by hand. ? Here’s how you test it: put a power meter on your bike. Ride a time trial course at a sustainable power level. Record your time. Go home, switch wheels, then ride the same course at the same power level. Record your time. Do that 9 more times. Remember to record all the variables: weather, tire pressure, what you ate for lunch, etc. Now, is one wheelset consistently faster? There’s your answer. Is there no consistency? That’s also an answer. |
Tiny numbers do add up over time. To what are still tiny numbers because all the other numbers add up over time too.
|
If the wheels were identical in every way, including in levels of hub resistance, except that the new rim was substantially lighter than the old rim, the difference in rim weights would explain your results. Less mass means less inertia.
Example: drop a ping pong ball into water. Then drop a steel ball the same size into water. The lower mass of the ping pong ball accounts for the fact that the resistance of the water halts the ping pong ball almost instantly whereas the steel ball is barely slowed. If the new wheel has a lighter rim, there's less inertia, and so wind resistance becomes a more important factor. |
Bouyancy also plays a role in that example (but is related to mass too - but if you could reduce the volume of a pingpong ball enough to match the density of the steel one, it would sink pretty damn fast even with its much lower mass inertia) but yeah I completely agree a lighter rim will slow more quickly.
Also don’t think this has been mentioned, inertia of the bike and rider is 0 when spinning the wheel but high when rolling along the flat, makes the hub bearing friction even more negligible. |
Originally Posted by choddo
(Post 23266001)
Bouyancy also plays a role in that example (but is related to mass too) but yeah I completely agree a lighter rim will slow more quickly.
Also don’t think this has been mentioned, inertia of the bike and rider is 0 when spinning the wheel but high when rolling along the flat, makes the hub bearing friction even more negligible. |
Yeah that’s what I meant when I said it was still related to mass but added a bit :)
|
Originally Posted by Jeff Wills
(Post 23265952)
Here’s how you test it...
|
Wheel bearing resistance is a tiny source of power consumption in comparison to both aerodynamic drag and tire rolling resistance.
If you're not already using them, changing to tires with a low rolling resistance is the easiest way to get a significant savings in power consumption while riding. The downside? That type of tire is typically more expensive, easier to puncture, and wears out more quickly than average. Pick your poison. |
Bearing friction in properly working equipment is negligible.
|
Originally Posted by Trakhak
(Post 23265993)
If the wheels were identical in every way, including in levels of hub resistance, except that the new rim was substantially lighter than the old rim, the difference in rim weights would explain your results. Less mass means less inertia.
Example: drop a ping pong ball into water. Then drop a steel ball the same size into water. The lower mass of the ping pong ball accounts for the fact that the resistance of the water halts the ping pong ball almost instantly whereas the steel ball is barely slowed. If the new wheel has a lighter rim, there's less inertia, and so wind resistance becomes a more important factor. |
Originally Posted by leon6782
(Post 23265873)
.....
Could this all come down to extremely heavy grease being used in the hub? Any other thoughts? But it barely matters anyway. When comparing rolling drag it's important to consider the torque rather than just the drag. Because the bearings are so close to the neutral axis, hub drag would have to be staggering to matter. Small differences between various hubs are comparable to worrying about the pennies in a jar when the mortgage payment comes due. |
Originally Posted by wheelreason
(Post 23266397)
Ah, no. The steel ball will slow down or come to a stop (or even bounce up) depending on the specifics of it's velocity at impact and the size and shape of the "container". Then it will accelerate downward due to graivity. The ping pong ball will initially do the same, and then be acted upon by the opposing force of bouyancy. And none of this has anything to do with the rotational forces at work ina wheel.
To make it clearer for you: Drop a solid steel ball the diameter of a ping-pong ball from a height of 12 inches into a bathtub filled with water to a depth of about 10 inches. Observe the behavior of the steel ball. Does it bounce from the water surface? If not, how rapidly does it descend in the water? Do the same with a ping-pong ball. Does it descend as rapidly as the steel ball? Why not? And: why quotation marks for "container"? Those words are spelled "gravity" and "buoyancy," by the way. (Not grammar police; spelling police.) |
Originally Posted by Trakhak
(Post 23266442)
Others understood the comparison.
To make it clearer for you: Drop a solid steel ball the diameter of a ping-pong ball from a height of 12 inches into a bathtub filled with water to a depth of about 10 inches. Observe the behavior of the steel ball. Does it bounce from the water surface? If not, how rapidly does it descend in the water? Do the same with a ping-pong ball. Does it descend as rapidly as the steel ball? Why not? And: why quotation marks for "container"? Those words are spelled "gravity" and "buoyancy," by the way. (Not grammar police; spelling police.) |
For those who fret over stuff like hub friction, may I suggest some DIY scientific research.
You'll need a friend who weights 20# or so more or less than you, a hill, and of course, a "slow" wheel, and a nice loose one. Take the two bikes to the top of the hill, and do a coast race down. To be fair, each do their best aero tuck. Repeat the test switching bikes. Odds are the same person will win. If you have a number of friends you can repeat this until you find two matched closely enough that the bike actually determines the outcome. Friends and I did this years (decades) ago and managed to find 2 close enough that 10psi tire pressure made the difference, but we never found two close enough for the hubs to determine the winner. |
Originally Posted by leon6782
(Post 23265873)
I recently bought a new carbon wheelset and did a free spin test on the front wheel compared to the front stock wheel from my 2016 Trek Domane. The old front wheel free spun for almost 2mins, the new front wheel spun for less than 20 seconds. I checked the brakes several times to make sure there was no interference. There just seems to be a ton of resistance/viscosity in these new hubs.
I realize that all the comments here disagree, but this rolling resistance must add up over time. I can genuinely feel a difference in resistance when spinning the wheel slowly by hand. Could this all come down to extremely heavy grease being used in the hub? Any other thoughts? |
Originally Posted by wheelreason
(Post 23266548)
Quotations for container because the size and shape can vary from a solo cup to an ocean. Spelling police not reqired, reading glasses police required. The coomparison still isn't valid, steel sinks, hollow thin walled plastic balls float, duh!. What does that have to do with spinning wheels?
An object's rotational inertia depends on both the total mass of the object and the distribution of that mass around the axis of rotation. Mass farther away from the axis of rotation contributes far more than mass close to the axis of rotation. Example: take the case of two wheels, identical except for one having a heavy rim and one having a lighter one. Once spinning at the same rate, all else being equal the wheel with the heavy rim will spin far longer before it comes to a stop - because it stored more energy (as rotational kinetic energy) and had far more rotational inertia than the wheel with the lighter rim. (The "flip side": the wheel with the heavier rim will require more energy input to spin up to the same rate of rotation as the lighter rimmed wheel.) Calculating either inertia or stored kinetic energy is possible for both translation and rotation. However, calculation is significantly easier for translational inertia (m x v) or translational kinetic energy (1/2 x m x v^2) than either rotational inertia or rotational kinetic energy. In contrast, both rotational cases are dependent on size, shape, and distribution of mass around the chosen axis of rotation. |
Originally Posted by Hondo6
(Post 23267762)
Like a mass moving in a straight line (such as a dropped bearing ball or ping-pong ball), a stationary spinning object (such as a spinning bicycle wheel on a truing stand) also has inertia. The object traveling in a straight line has translational inertia, while the stationary spinning object has rotational inertia. That is the analogy.
An object's rotational inertia depends on both the total mass of the object and the distribution of that mass around the axis of rotation. Mass farther away from the axis of rotation contributes far more than mass close to the axis of rotation. Example: take the case of two wheels, identical except for one having a heavy rim and one having a lighter one. Once spinning at the same rate, all else being equal the wheel with the heavy rim will spin far longer before it comes to a stop - because it stored more energy (as rotational kinetic energy) and had far more rotational inertia than the wheel with the lighter rim. (The "flip side": the wheel with the heavier rim will require more energy input to spin up to the same rate of rotation as the lighter rimmed wheel.) I can agree with that, I still don't see what that has to do with splashing a ping pong ball though, I used to be a pretty good ping pong player at one time... Calculating either inertia or stored kinetic energy is possible for both translation and rotation. However, calculation is significantly easier for translational inertia (m x v) or translational kinetic energy (1/2 x m x v^2) than either rotational inertia or rotational kine :)tic energy. In contrast, both rotational cases are dependent on size, shape, and distribution of mass around the chosen axis of rotation. |
Originally Posted by Trakhak
(Post 23266442)
Others understood the comparison.
To make it clearer for you: Drop a solid steel ball the diameter of a ping-pong ball from a height of 12 inches into a bathtub filled with water to a depth of about 10 inches. Observe the behavior of the steel ball. Does it bounce from the water surface? If not, how rapidly does it descend in the water? Do the same with a ping-pong ball. Does it descend as rapidly as the steel ball? Why not? |
| All times are GMT -6. The time now is 06:21 PM. |
Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.