What do we think of Zipp's 'stance' against cup-and-cone hubs?

[531Aussie]

Just wonderin', 'sall....
Is any of it bollocks?

ooopsl...spelling

http://www.zipp.com/_media/pdfs/technology/hubs.pdf

Radial Contact instead of Angular Contact

One area that we feel strongly about with our hub design, that is not shared by any other manufacturers in using radial contact bearings with ideal ball location. This means that we utilize deep groove cartridges, but confine their location to be optimal for friction and life, and do not allow them to be preloaded or adjusted by the consumer. Why are we so adamant about this design? And what does that mean for you, the consumer? First, radial contact bearings much better handle the loads seen in a bicycle hub, and nearly ½ the manufacturers out there are using them. The radial ball loading better distributes the load fed into the hub, and can handle higher loading using lighter weight bearings that generally spin smoother than cup and cone type setups. Granted, that cup and cone bearings can be carefully adjusted to feel near perfect in your hands, but once the
wheel is on the bike, the loading of the cup and cone bearing actually results in higher ball friction and reduced
life.

The key to notice in the Radial vs the Cup and Cone design is that the force Fn is the Normal (vertical) force fed to the bearing through the weight of the rider. In the radial bearing design, Fn is the same force resisted by the ball, but in the angular contact situation, the normal force is only one component of the ball force, since the ball contact line runs 45 degrees to the force line, the ball must generate √2 times more force (and a lateral force component represented by FL). This means that Factual is 1.41 times greater than Fn, so the ball in the cup and cone scenario sees 41% higher load than the radial ball bearing. This higher ball load results in higher friction,
decreased ball and race life, and increased wear of the internal components meaning that the hub will have to be adjusted more frequently.

The reason for the cup and cone design is quite simple, it is much less expensive to machine and assemble since the components are adjusted for preload by the consumer. This means that the bearing race diameters can have nearly twice the tolerance, and there is little to no need to axial tolerances in the assembly as any slop can be accounted for in the adjustment of the cone. Contrarily, the radial ball situation, requires exact dimensional
control of both bearing bore diameter, as well as axial length of both hubshell and center spacer, as well as requiring bearing planes to be exactly coplanar to each other. One design variant now becoming popular is to utilize radial cartridge bearings but to use an adjustable cone design, allowing for user adjustability for bearing preload, but this essentially negates the gains to be had in using radial cartridge bearings (other than the better seals).

The precision necessary for a perfect radial cartridge hub is on the order of +/- 0.0002” in 3 axes, this is simply unachievable in Asian production, and is not even achievable in most types of CNC equipment, so it is very, very expensive to obtain. However, with proper machines and fixuturing, the Zipp hub is manufactured to these exacting tolerances and specifications, the only hub in the world to do so. The result is a hub that spins with as much as 1 watt efficiency improvement over competing designs! What’s 1 watt mean? Well, that’s roughly 2-3 seconds in a 40k time trial, and it was all achieved through design and process control measures.

 

[Resistorlead]

It makes sense, other than the BS about the inability of Asian producers to hold tolerances. You get what you pay for and they can equal anybody else in the world if they want to. IMO, cup and cone designs are pretty lousy compared to any commercial bearing design found in an industrial setting. Consumer products are more price sensitive and the users less knowledgeable, so corners get cut. Once you start loading things by mounting in a frame and riding the bike, the alignment due to flexing is nowhere near what you might think compared to what it was during a static adjustment. I don't think they're saying anything that isn't well known at an engineering level, OTOH, how good does a bike bearing need to be? Cups and cones have served us well (they work fine for me at Clydesdale+ class) and unless that last watt really means anything, you just have to decide how much punishment your wallet can take.

 

[dhk2]

I think there are some questionable assumptions made which exaggerate the advantages of their design. First, why do cup-and-cone bearings need to run at 45* contact angles, which implies the axial preload is equal to the design radial load? Bikes generate very low lateral forces, so I believe the conventional hubs can be designed and adjusted to function with much lower preload.

Second, to me an adjustable-preload hub is always desireable to one which is "perfectly" machined at the factory. One of the disadvantages to the (cheap and common) radial cartridge bearings that most "boutique" wheels use is that they aren't designed for axial loads, meaning any axial preload causes the bearings to feel rough and generate extra drag. With normal tolerances in hub and axle clearances, the choice in production comes down to "building in" some preload, or accepting some freeplay in the finished hub. While a small amount of freeplay isn't really noticeable when riding, believe most of us buyers would complain if our new wheels had freeplay which couldn't be adjusted out. So, I fail to see how even a very-tightly controlled hub could be better than one I can carefully adjust at home. The adjustable hub can allow for bearing wear, as well as variations in replacement bearings later on.

In summary, the ad copy may be overstating the issue with cup and cone hubs, and understating the real issue of keeping preload at zero so that pure radial bearings have an advantage. The best of both worlds might be the shallow angular contact cartridge bearing combined with an adjustable preload hub....believe the new DA hubs use this design.

 

[garage sale GT]

45 degrees, eh? Looks more like 25 degrees to me. Haven't these guys ever looked at their cones???

 

[alfeng]

Of course, Campagnolo & Shimano hubs still use loose bearings + cup & cone design ...

And, "real" Track hubs have loose bearings + cup & cone, too.

 

[dhk2]

I think your 25 degree estimate is closer to correct, unless the preload is seriously cranked down. It only needs to be a small fraction of the radial load on the bearing to prevent lateral play in the hub; no advantage I know of in exceeding the minimum preload.

In fact, I shimmed my (non-adjustable) Circuit hubs years ago to remove the preload entirely. The bearings felt rough when turned by hand, which was caused by built-in preload. I shimmed one cartridge out by placing a ring of .008 wire (finest I had) between the OD and the hub. The bearings now feel perfectly smooth, but there is a slight amount of lateral play, 1 mm or less at the rim which is undetectable to me.

Just checked a reference book which estimates the friction coefficient for a properly adjusted cup-and-cone bearing as .001. So, for 100 lbs (450N) load on a wheel, this results in bearing friction of .45N at the bearing race, or .0145N drag at the wheel rim. Translating that to a speed of 10 m/sec (22 mph) would indicate a typical power loss of .145W, just a fraction of the claimed 1W that the Zipp bearings could save. Also the reference notes that this bearing loss is only a small fraction (about 1%) of the rolling loss of the tires.....essentially it's "noise level". If Zipp can exaggerate bearing losses this way, makes me suspicious of any aero claims they make.

 

[alfeng]

The best of both worlds might be the shallow angular contact cartridge bearing combined with an adjustable preload hub....believe the new DA hubs use this design.

Interesting!

 

[Johnnycatt]

Credentials: I own a company that sells bearings! I have sold bearings to industry and agriculture for almost 15 years. I currently represent NTN, Nachi, KOYO, Peer (cheep Chinese bearing, but it has it's place), and some others that have no use in a racing bike.


My Take:
I had been curious as to why my bike had angular contact bearings in the hubs...it never really made much sense to me!! The first time I ever opened a hub, I fully expected to see a RADIAL ball bearing! When I saw the loose balls, I was stunned and wondered WHY?!?! It's a multi-thousand $$$ bike, and the FIRST place I would think I need "precision," I have a "cut corner"....

Angular contact bearings are for "thrust laoads." In other words,if you were trying to drive the shaft out of the hub with a hammer they would work much better for keeping the shaft in the hub. Alas, MOST of us are not doing that, besides, RADIAL ball-bearings can handle up to 20% of their radial capacity in "thrust loading." Now, when you consider that a bearing the size of one that would be in a hub can handle 3,000 lbs, then you can have as much as 600 lbs of PURE trust loading... most of us don't ever "Slide" sideways on our bike, and if we do, it is at an extreme angle where the bulk of the load is still be transmitted "radially" from the inner race to the balls to the outer race.

The first problem with "angulars" in the hubs was that I was able to adjust the amount of "clearance" or "axial movement" of the shaft. When Angular contact bearings are used as "duplex pairs," (they way we use them in bike hubs) the "races" are specially ground to ensure they are parallel. There is a set amount of "axial" movement that is considered acceptable... many times this "axial movement" is NONE and there is actually a LIGHT pre-load on them. The average Joe HAS NO IDEA how to set these and no matter how I try to help, they get it wrong and end up buying bearings MORE often than they should! These tolerances are so close, the TEMPERATURE of the work environment, Machinery and work play a part in the clearance!

Bike hub angular contact bearings also have no retainer (cage) to keep the balls separate. This is what is commonly referred to as an "un-ground bearing." These are common non-precision bearings that can be found in such things as lawnmower wheels, hand-truck wheels, and other "carts"... Not exactly what I want holding up my $2,000 GIANT, even if she is "old" by most standards! My hub bearings are little "above" a lawnmower wheel, but in my world, NOT by much!

No retainer (part deux)... with no retainer to keep the ball separated, they rub against each other creating friction... well, the point of a bearing is to reduce friction, not create it... this can also have the effect of taking the "round" out of the ball and creating even more friction and damaging the inner and outer races and causing MORE friction, that cannot be corrected by simply replacing the balls.

No retainer (part three)... no retainer means that the shaft will tend to sit "in-between" two balls at the the bottom of the bearing and force the rest of the balls closer together around the sides and top of the bearing...this can cause "skidding" of the balls as they try to pass under the shaft from one side to the other..again, MORE friction, more wear, less speed...

ABEC 7 ???? I have seen this offered.. ABEC 7 is an extremely precision bearing commonly used in aircrafts and VERY high-speed applications. Their tolerances are held SO closely that they are virtually the same when measured by "standard" equipment.... only a few nations in the WORLD have the technology to produce such a bearing (USA, Japan, Germany, Russia, Sweden, and some other "western" nations). CHINA, ROMANIA and INDIA are NOT capable of it, even though they claim they can. WASTE OF MONEY!!!!! UNLESS YOU PLAN ON RIDING STRAIGHT DOWN THE FACE OF THE ALPS WHILE DRAFTING A FERRARI, SKIP these and use a standard "C3" fit (angulars have no "C" fit, just get "standard bearings"... you can get ABEC precision in an angular, but since no one can really set the clearance, it's a waste of money).

No seals... there is absolutely NO sealing mechanism on my hubs that can prevent dust from entering the bearing space. Now, I can see this as a distinct ADVANTAGE in a race since there is no "drag" from a rubber seal rubbing against a steel shaft. I see this as a DISADVANTAGE for the other 99% of the time I am on my bike. The dirt, grime, water, etc serve to break-down the lubricant on the balls, thus we are back to more friction, more wear and less speed...

Lubricant... I wanted to touch on this too... I don't have a clue what grease is used in most hubs, but to be honest it should be oil! VERY LIGHT oil and small amounts, thus creating the least amount of drag and still offering protection. Oil DOES require a contact seal, and since seals add drag, it is wiser to utilize a super thin AGLI #0 or #00 grease. I would even say it would be a good idea to use one with an EP (extreme pressure) additive... I am certain that no bike shop in the world offers such a thing, but the day I changed to #0EP, I CUT time on my next ride and have maintained the cut time (in general)...


Now, I am talking mostly on a microscopic scale, but the difference in life and performance would be most noticeable as our components wear or age. The other thing you will notice about my old bike is that she is quiet as a church-mouse in coma... why? Noise is vibration...vibration is friction.. friction is a loss of energy... I adjust my chainring for the different sprockets in the back to prevent the "rubbing" of the dérailleur by the chain... again, that is a waste of energy -- no matter how small!

One day I will get rid of the chain since it is only 97% efficient Cycloidial gearing (not helical) is 99% efficient, but too heavy...for now!

pass me on the left, please!

JOHNNYCATT

 

[garage sale GT]

Credentials: I own a company that sells bearings!

The first problem with "angulars" in the hubs was that I was able to adjust the amount of "clearance" or "axial movement" of the shaft. When Angular contact bearings are used as "duplex pairs," (they way we use them in bike hubs) the "races" are specially ground to ensure they are parallel. There is a set amount of "axial" movement that is considered acceptable... many times this "axial movement" is NONE and there is actually a LIGHT pre-load on them. The average Joe HAS NO IDEA how to set these and no matter how I try to help, they get it wrong and end up buying bearings MORE often than they should! These tolerances are so close, the TEMPERATURE of the work environment, Machinery and work play a part in the clearance!

No retainer (part three)... no retainer means that the shaft will tend to sit "in-between" two balls at the the bottom of the bearing and force the rest of the balls closer together around the sides and top of the bearing...this can cause "skidding" of the balls as they try to pass under the shaft from one side to the other..again, MORE friction, more wear, less speed...

Your last paragraph is exactly why you want preload. All the balls under the axle bear the load then. Surely you realize that with a cone-shaped inner race and a cup-shaped outer race, you take up the radial clearance while simultaneously taking out the axial play. If there's radial clearance, then the bottom ball (and the corresponding contact points on the races) will take all the load, because the clearance will be at a minimum at the bottom due to the weight.

Furthermore, if there's clearance, the balls will leave their track when they're away from the bottom-when they have clearance to move both axially and radially they'll move outward due to centrifugal force or inward due to their weight depending on your speed-then, when they try to roll back into the bottom position where the clearance is minimum, they'll have to slide back into their track while under tremendous load. If you spin a wheel while holding the axle ends in your fingers and it's got clearance in the bearings, you'll feel it grab.

Loose ball hubs must be adjusted with just enough clearance so the compression of the skewer would take out the clearance and provide a very small amount of preload.

A cartridge ball bearing is a radically different situation because the balls have no radial clearance even if they had a great deal of axial clearance.

 

[alienator]

So, after a page, there's nothing that shows that in actual everyday use, there's nothing superior between cups and cones and cartridge bearings. Some conclusions:

• White papers are not scientific publications. They're written to sell something.
• We all know that how a bearing feels in your hands means little. The important factor is how the bearing operates under load.
• Zipp's numbers might be from one extreme end of the spectrum, but they may not be unrealistic. After all, how many cups and cones are perfectly adjusted, with the perfect amount of lube?
• The only time bearings cause bike problems are when they're small (AC front hubs...have been known to die quickly), when they're insufficiently lubed, when the bearings are contaminated with particulate matter, or when they're installed incorrectly.

Zipp had a rep for not making great hubs. It looks like with a white paper and revised design, they're looking to turn that opinion around.

 

[Johnnycatt]

I will admit that I do NOT have much experience with "bicycle" bearings, but I do have a pretty firm grasp of "bearing theory."

Forgive me... the bizarre nature of the "cup and cone" ball bearing is a little archaic to me... I am not extolling the virtues of angular contact bearings here. While they may be "suitable" for bicycle wheel application, they are far from "ideal." I mean, I could sit here and make a case for using oil-emprgnated bronze or babbit bearings, too, but they would be as out of place on a bicycle wheel as an angular contact...although they would be "suitable"... if that was what someone wanted! WD40 is a fine lubricant, too but I am not too sure it would be a good choice for the hinge of 20-ton dump truck!

If you need a "cup and cone," then why not taper roller bearings.. they are capable of higher speeds, higher load capacities and higher thrust loads... all around a better "bearing" choice than angular contacts!


Now, for a novice such as myself, I am sure the angular design is "suitable," although I would like to get away from them since the bicycle wheel is far better suited to "radials".

The manufacturers of wheels that have "radials" don't have to convince me that it is a superior design to "angulars".. to me, it is intuitive.. I see similar applications EVERY day!

I would never arbitrarily choose a "duplex pair" of angular contact bearings when a generic pair or "radials" would handle the load better...

Just my two cents...

JOHNNYCAT

 

[Johnnycatt]

After all, how many cups and cones are perfectly adjusted, with the perfect amount of lube?

umm, EXACTLY NONE!

...A problem easily remedied with a radial ball bearing! They come lubed, sealed, spaced and aligned right out of the box!

 

[Johnnycatt]

A cartridge ball bearing is a radically different situation because the balls have no radial clearance even if they had a great deal of axial clearance.

Please expound on this... I am assuming that when you say "cartridge bearing" you are referring to a "radial ball bearing."

I guess I have no idea how "radials" would ever have any "axial clearance" unless they are realllllyyyy worn out! (defining "axial" as the inner race moving parallel to the outer race) More over, WHY would you want any axial clearance????????

I think the chief difference is you are thinking of how bicycles work and I am thinking of how bearings work.

And "radials" do have radial clearance: the "C3" fit I mentioned..they also make a C4 which has MORE clearance, although it would be ridiculous in a bicycle wheel unless you were doing some SERIOUS off-road stuff where longevity was an issue... they also make a C2 fit which has a light pre-load (in case you wake up one morning in Antarctica and the only method of transport is a bike).

One can also get a "standard fit" which has a little less clearance than the C3. The reason I recommended a C3 fit was for that little extra clearance... of course, a "standard fit" would do just fine as I doubt the conditions of 99% of bike wheels would ever reach the point where the C3 would actually be beneficial in allowing for expansion due to heat, but I guess it depends on how well maintained the bike is, what conditions one was riding in and the condition of the hub.. better safe than sorry if you get the C3's... besides the cost is about the same; C3 may even be cheaper!

Not to mention, you can race ONE time, pop 'em out and replace... shouldn't even get your hands dirty! and not worry if they are dragging you a few seconds slower every mile...

 

[Resistorlead]

Today was "clean, lube & adjust all bearings day" around here, so the topic is timely. I'm pretty sure that if our bearings are seeing much lateral loading, we've probably tipped over. I ride vintage stuff and even when I was a kid and didn't weigh so much, I'd always end up with slightly bent rear axles. If the frame dropouts aren't parallel, or you hit a bump, the traditional axle isn't strong enough to prevent serious flexing or even bending. When that happens, all thoughts of proper preload and alignment go out the window. Maybe the cone profile helps things a bit, but the bearing will still suffer. Add a little fine grit to the equation and you'll see damage pretty fast. I assume if modern hub designs have fixed anything, it's that. IMHO, bearings sized for the typical cup and cone would last the life of the bike if no flexing occurred and grit could be kept out. Johnnycatt- my old Shimano hubs have an oil hole in the middle and a clip that closes it off. I assume the intent was to squirt in a little light oil every now and then. I've never seen anybody do it, but it might have been a good system unless one let it get dry.

 

[garage sale GT]

Please expound on this... I am assuming that when you say "cartridge bearing" you are referring to a "radial ball bearing."

I guess I have no idea how "radials" would ever have any "axial clearance" unless they are realllllyyyy worn out! (defining "axial" as the inner race moving parallel to the outer race) More over, WHY would you want any axial clearance????????

One could hypothetically make a radial ball bearing cartridge with excessively wide grooves in the races which still had no radial slack. Why anyone would want to is beside the point. One cannot, however, have axial play in a cup-and-cone ball bearing without also having radial play, which, as I have explained, can be ruinous to a cup-and-cone ball bearing.

The hypothetical radial bearing with axial clearance also contrasts with cup-and-cone bike hubs in another way. You have to deform some pretty thick solid steel rings to get the clearance to open up.

However, a cup-and-cone ball bearing hub can develop momentary excessive clearance just when it needs load resistance the most, because the angular contact can stretch the axle or compress or otherwise deflect the hub when a load is applied, causing your adjustment to change. Consider that tightening the skewer, a force you apply with the palm of your hand, can significantly alter cone adjustment, but all your weight and pedal torque and the force of bumps cannot?

As an aside, it's utterly ridiculous for you to report that some radial cartridge bearings have some slop in the radial fit, but none in axial. Is it somehow easier to make the bearings run perfect axially but not radially??? Is it more important that your wheel not be able to move even .0001 side to side than to not have any radial clearance so as not to allow only one ball to take the bulk of the load?

 

[garage sale GT]

I ride vintage stuff and even when I was a kid and didn't weigh so much, I'd always end up with slightly bent rear axles. If the frame dropouts aren't parallel, or you hit a bump, the traditional axle isn't strong enough to prevent serious flexing or even bending.

I like old stuff too. I have a 1980 Gitane Tricolore with full Spidel gruppo.

I would say the very reason for a slight preload is that stuff deflects under load, especially with multispeed freewheel hubs.

Freewheel axles fail in fatigue according to the opinion of at least one expert, Jobst Brandt, who is a mechanical engineer. In case you don't know, that means they'll be OK for a few hundred or a few thousand miles(depending on the severity of the load), then they'll give up. So after each ride, check your rear wheel for a bit of wobble (when not turning, as if loose on the axle,) and get a new axle if you detect any. It IS strong enough until it fatigues. Think of it as having a short life, not as being too weak.

You can also buy solid, chrome moly axles from Niagara Cycle Works or Harris Cyclery, though not all the axles they sell are chrome moly.

People report Campy axles last well also, but I think they have their own threading and dustcaps which fit your hubs may or may not fit Campagnolo-threaded cones.

 

[alienator]

...my old Shimano hubs have an oil hole in the middle and a clip that closes it off. I assume the intent was to squirt in a little light oil every now and then. I've never seen anybody do it, but it might have been a good system unless one let it get dry.

Campy Record hubs used to have an oil port.

 

[tafi]

umm, EXACTLY NONE!

...A problem easily remedied with a radial ball bearing! They come lubed, sealed, spaced and aligned right out of the box!

Until you put them in a housing which carries machining tolerances and is being pulled open by spoke tension. Then you have a perfect bearing squashed out of alignment or rattling around. But I digress....

To answer the original question (should we trust marketing material from a commercial entitiy?) the answer must be a resounding "NO (non, nein, niet, iie)!" The wool has been pulled down by commercial entities too often in the past for their word to be taken at face value (even if it is right).

In this case Zipp have decided to bombard the consumer with “theory” and some blanket generalisation that Asians can’t do the job properly, instead of actually giving us numbers comparing different hubs. They seem to be able to do that for their aerodynamic tests, so why not do so here?

What we really need is some independently collected data to settle the matter.

Has anyone actually seen any of the following:

Actual numbers representing tests of rolling friction carried out with hubs of the different types (when optimally prepared) in a real world test?
Ideally this would involve wheels with the same rim, spokes, spoke tensions and, if it were done on a roller, the exact same tyre (not just the same model but exactly the same tyre) with the exact same tube at the exact same pressure.
As others have said, I suspect any difference in friction is likely to be lost in the uncertainties related to the other variables. The (null) hypothesis that the two bearing types are no different in this respect would probably be upheld.

Measured or calculated axial loads in hubs and the effect of these loads on friction?
Whether a bearing can cope with this load is one matter, the effect of the load on the bearing friction is quite another and will be related to the construction/type of the bearing.

I have (and enjoy the use of) wheels with both bearing types and am quite comfortable in the knowledge that it is probably not the bearings which are holding me back, so I am not really that bothered with the hype.

 

[alienator]

What we really need is some independently collected data to settle the matter.

Has anyone actually seen any of the following:

Actual numbers representing tests of rolling friction carried out with hubs of the different types (when optimally prepared) in a real world test?
Ideally this would involve wheels with the same rim, spokes, spoke tensions and, if it were done on a roller, the exact same tyre (not just the same model but exactly the same tyre) with the exact same tube at the exact same pressure.
As others have said, I suspect any difference in friction is likely to be lost in the uncertainties related to the other variables. The (null) hypothesis that the two bearing types are no different in this respect would probably be upheld.

Measured or calculated axial loads in hubs and the effect of these loads on friction?
Whether a bearing can cope with this load is one matter, the effect of the load on the bearing friction is quite another and will be related to the construction/type of the bearing.

I have (and enjoy the use of) wheels with both bearing types and am quite comfortable in the knowledge that it is probably not the bearings which are holding me back, so I am not really that bothered with the hype.

I've not seen a test done as such. It can be done though, relatively simply, with an iBike. Calibrate the bike/rider system the coefficients in the quadratic equation that defines the bikes equation of motion. The coefficient of the linear term will be the one of interest as it is the one that includes bearing friction, chain losses, rolling resistance. By only switching between hubs, with everything else remaining constant, you can subtract chain losses and rolling resistance, leaving relative measures of bearing losses. Calibrate each wheel/hubset 10 times (or, ideally, more) to reduce the uncertainty in the final value for bearing losses. A bit of statistical analysis, and you'd be done.

 

[swampy1970]

Granted, that cup and cone bearings can be carefully adjusted to feel near perfect in your hands, but once the wheel is on the bike, the loading of the cup and cone bearing actually results in higher ball friction and reduced life.

This is why you adjust the cup and cone and leave a slight amount of play, insert the wheel into the bike, tighten the skewer and test for play...

I wish sugino would make some hubs with the same 'superlap' treatment to the bearing surfaces that they have in their NJS certified bottom brackets. Godly... They'd be better than the old (1980s) Super Record hubs by far.