Hub rolling resistance demo

Ted Bennett said:

Could anyone devise a simple test to demonstrate the difference in rolling resistance between hubs?

A friend adamantly argues that Hub A will definitely allow faster speeds than Hub B for the same
power. I say that for properly adjusted cup and cone hubs, the differences are so tiny that they
are overwhelmed not only by aerodynamic effects (bike and rider) but probably also by RR
differences between tires.

Build the hubs into otherwise identical wheels (spokes, rims, tires, tubes, inflation, etc). From a
dead stop, coast down a long steep grade and time the run. Swap wheels and repeat, taking care to
keep the same riding position. Repeat this process several times to compensate for variables like
wind speed, etc. It would be a good idea if the rider was unaware of which hub was which.

John Albergo may have said:

Ted Bennett said:

Could anyone devise a simple test to demonstrate the difference in rolling resistance
between hubs?

Build the hubs into otherwise identical wheels (spokes, rims, tires, tubes, inflation, etc). From a
dead stop, coast down a long steep grade and time the run. Swap wheels and repeat, taking care to
keep the same riding position. Repeat this process several times to compensate for variables like
wind speed, etc. It would be a good idea if the rider was unaware of which hub was which.

Since the bearings are the only part that ought to be able to have an effect, any bearing
manufacturer should be able to measure the running torque of the two units and provide a direct
comparison. As was suggested to be the case, though, I suspect that the difference would be
negligible if they're both from decent manufacturers. Because bearing are small and well concealed,
they tend to get hot quickly if they aren't doing their job well, so their manufacturers work hard
to ensure that their inherent drag tends to be tiny. (And, let's be honest, after far more than a
century of progress, making an efficient ball bearing assembly isn't steam-engine science anymore.)

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Werehatrack said:

John Albergo may have said:

Ted Bennett said:

Could anyone devise a simple test to demonstrate the difference in rolling resistance
between hubs?

Build the hubs into otherwise identical wheels (spokes, rims, tires, tubes, inflation, etc). From
a dead stop, coast down a long steep grade and time the run. Swap wheels and repeat, taking care
to keep the same riding position. Repeat this process several times to compensate for variables
like wind speed, etc. It would be a good idea if the rider was unaware of which hub was which.

Since the bearings are the only part that ought to be able to have an effect, any bearing
manufacturer should be able to measure the running torque of the two units and provide a direct
comparison. As was suggested to be the case, though, I suspect that the difference would be
negligible if they're both from decent manufacturers. Because bearing are small and well
concealed, they tend to get hot quickly if they aren't doing their job well, so their
manufacturers work hard to ensure that their inherent drag tends to be tiny. (And, let's be
honest, after far more than a century of progress, making an efficient ball bearing assembly isn't
steam-engine science anymore.)

--
My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
don't respond to something, it's also possible that I'm busy.

There's also drag from the free-hub ratchet design, and on mountain bikes -- the water seal design.
I've noticed a definite difference between a cheap hub and some more expensive ones on my mountain
bike (as I went through hubs trying to find one strong enough not to self destruct in a couple k
miles <sigh>😉.

And, when you do this test, you should consider new hubs vs. a well broken-in one of the same
make, etc.

David

David Kunz may have said:

There's also drag from the free-hub ratchet design,

True, but that's only a factor when coasting down, and I was considering the drag when
pedalling. The coasting dgag should bbe taken into account in the evaluation, though; I hadn't
thought about that.

Quoted message said:

...and on mountain bikes -- the water seal design. I've noticed a definite difference between a
cheap hub and some more expensive ones on my mountain bike (as I went through hubs trying to find
one strong enough not to self destruct in a couple k miles <sigh>😉.

Hmm. Yes, seal drag might be a factor until the seal's well seated; is it possible that some of the
mtb hubs are being assembled with the seals dry? I know that in the world of engines and
transmissions, one sure way to shorten the life of a seal (and increase drag from it) is to fail to
lube the lip with some grease during assembly.

Quoted message said:

And, when you do this test, you should consider new hubs vs. a well broken-in one of the same
make, etc.

Rolling resistance for the bearing will change as the bearing wears in, but I think you may have
nailed it when you mentioned the seals. Also, perhaps some of the hubs have a flexure problem that's
de-aligning the bearings under load. Putting the bearings farther apart (as is done with freehubs)
helps to overcome the old axle flex problem, but I wonder if it has introduced a hub flex factor
that wasn't present before. I have to think the engineering types would have thought about this, but
not all of the engineering is always done by engineers, so who knows?

Somehow, I have to expect that tire rolling resistance will dwarf hub inefficiency in most cases, so
I'd say that someone interested in trying to get a more free-running unit would be better off
starting at the outside of the wheel. Once that's been addressed, if the result isn't satisfactory,
the hub and the driveline is the logical next place to look. If somebody gets to the point of
worrying about aerodynamics, they probably weigh a lot less than I do, and go a lot faster.

--
My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
don't respond to something, it's also possible that I'm busy.

[email hidden] schreef ...

Quoted message said:

There's also drag from the free-hub ratchet design, and on mountain bikes -- the water seal
design. I've noticed a definite difference between a cheap hub and some more expensive ones on my
mountain bike (as I went through hubs trying to find one strong enough not to self destruct in a
couple k miles <sigh>😉.

The answer to the last bit is: Chris King. Even holds up in mountain tandems, actually used
off-road :-)

--
Regards, Marten

Marten Hoffmann said:

[email hidden] schreef ...

Quoted message said:

There's also drag from the free-hub ratchet design, and on mountain bikes -- the water seal
design. I've noticed a definite difference between a cheap hub and some more expensive ones on my
mountain bike (as I went through hubs trying to find one strong enough not to self destruct in a
couple k miles <sigh>😉.

The answer to the last bit is: Chris King. Even holds up in mountain tandems, actually used
off-road :-)

So I've discovered (my wallet and wife are happy 🙂).

David

Werehatrack said:

David Kunz may have said:

There's also drag from the free-hub ratchet design,

True, but that's only a factor when coasting down, and I was considering the drag when
pedalling. The coasting dgag should bbe taken into account in the evaluation, though; I hadn't
thought about that.

Quoted message said:

...and on mountain bikes -- the water seal design. I've noticed a definite difference between a
cheap hub and some more expensive ones on my mountain bike (as I went through hubs trying to find
one strong enough not to self destruct in a couple k miles <sigh>😉.

Hmm. Yes, seal drag might be a factor until the seal's well seated; is it possible that some of
the mtb hubs are being assembled with the seals dry? I know that in the world of engines and
transmissions, one sure way to shorten the life of a seal (and increase drag from it) is to fail
to lube the lip with some grease during assembly.

My experience and the experience of the wrench that I chat with at my LBS is that most bike bearings
/ seals come either dry or starved. He always checks and greases everything on a new bike.

Quoted message said:

Quoted message said:

And, when you do this test, you should consider new hubs vs. a well broken-in one of the same
make, etc.

Rolling resistance for the bearing will change as the bearing wears in, but I think you may have
nailed it when you mentioned the seals. Also, perhaps some of the hubs have a flexure problem
that's de-aligning the bearings under load. Putting the bearings farther apart (as is done with
freehubs) helps to overcome the old axle flex problem, but I wonder if it has introduced a hub
flex factor that wasn't present before. I have to think the engineering types would have thought
about this, but not all of the engineering is always done by engineers, so who knows?

Somehow, I have to expect that tire rolling resistance will dwarf hub inefficiency in most
cases, so I'd say that someone interested in trying to get a more free-running unit would be
better off starting at the outside of the wheel. Once that's been addressed, if the result
isn't satisfactory, the hub and the driveline is the logical next place to look. If somebody
gets to the point of worrying about aerodynamics, they probably weigh a lot less than I do, and
go a lot faster.

If you use quality, broken in, well adjusted hubs this will be true. But, I'd do some cross testing
(same tire/tube on all test rigs) to see if it changes the results.

David

Thought you couldn't have both, it's either one or the other. -tom

"David Kunz" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

So I've discovered (my wallet and wife are happy 🙂).

David

Quoted message said:

"David Kunz" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

So I've discovered (my wallet and wife are happy 🙂).

David

Tom Nakashima said:

Thought you couldn't have both, it's either one or the other. -tom

My wallet's no longer putting out for additional hubs which makes it and my wife happy 🙂. (Although
that initial outlay for the hub was done very quietly).

David