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hi ppl,

just wondering about these options in hubs... what do you guys prefer?.. guess i'm just wondering why record thru to centaur hubs come with loose bearings, but veloce rears come with sealed, but the fronts come yup, u guessed it, in loose !? weird.

Pretty sure that the rear veloce hub is the exact same unit on the 06 ventos i have. The front however is different b/c of the high track-style flange and sealed bearings. I've noticed they have a bit more resistence than my other wheels that are loose ball, but that is only when spinning the axles by hand off the bike... free spinning the whole wheel with the bike upside down gives a very smooth and free action caparable to my other hubs. OTOH, i'm loving the lack of maintenance that comes with the sealed units, rear bearings get pretty dirty IME. My only issue is i dunno where to get new sealed bearings from ! Some website i saw (maybe banford?) even suggested buying a velcoce rear hub and swapping the internals out !

Thoughts? Are all high end road hubs loose ball? or do some manufacturers favour sealed?

cheers,

joe
 

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wankski said:
hi ppl,

just wondering about these options in hubs... what do you guys prefer?.. guess i'm just wondering why record thru to centaur hubs come with loose bearings, but veloce rears come with sealed, but the fronts come yup, u guessed it, in loose !? weird.

Pretty sure that the rear veloce hub is the exact same unit on the 06 ventos i have. The front however is different b/c of the high track-style flange and sealed bearings. I've noticed they have a bit more resistence than my other wheels that are loose ball, but that is only when spinning the axles by hand off the bike... free spinning the whole wheel with the bike upside down gives a very smooth and free action caparable to my other hubs. OTOH, i'm loving the lack of maintenance that comes with the sealed units, rear bearings get pretty dirty IME. My only issue is i dunno where to get new sealed bearings from ! Some website i saw (maybe banford?) even suggested buying a velcoce rear hub and swapping the internals out !

Thoughts? Are all high end road hubs loose ball? or do some manufacturers favour sealed?

cheers,

joe
The lower end campagnolo hubs use catridge bearings which are sealed and the higher end ones use loose ball bearings... Note that the loose ball bearings also have seals but they are part of the hubs design where else in catridge bearings, the seals are part of the bearings unit...

Actually it is not weird for campagnolo to use loose ball bearings for their higher end hubs. Shimano also uses loose bearings and these two companies make the smoothest and sturdiest hubs in the industry. These two companies understand the superiority of loose ball over catridge bearings in real world applications... Loose bearings last longer, are better at handling shear forces and are stronger...
 

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Radial cartridge bearings vs. cup and cone bearings

Like Vinokourov said, the issue here isn't sealed vs. non-sealed (since virtually all hubs have bearing seals), but radial cartridge bearings vs. cup and cone bearings.

Like Vinokourov said, cup and cone bearings have several technical advantages - they can take more axial load, and they have better tolerance to misalignment (misalignment can quickly destroy radial bearings). In addition, cup and cone bearings generally can use larger balls, and usually have a full complement of balls (vs. many cartridge bearings, which, due to their use of a ball retainer, can not use a full complement of balls). This additionally increases their load capacity and life. Finally, the larger balls and the single line of contact (vs. the dual lines of contact necessary for radial bearings) means that cup and cone bearings have lower drag.

So why do so many "boutique" hub manufacturers use cartridge bearings in their high-end hubs? It generally comes down to economies of scale. It is much cheaper and easier to design a hub around a standard cartridge bearing than to manufacture (or have manufactured) custom cup and cone bearings, at least in the quantities that boutique hub manufacturers produce.

Which do I prefer? I like the bearings in the latest Campagnolo hubs. They are full complement cup and cone bearings, and yet the races are easily replaceable, so you can completely replace all the bearing components if necessary.
 

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Inconclusive data

divve said:

Unfortunately, the bearing friction test performed for this report only spun the wheels under no load conditions. The main component of the friction measured was thus seal friction, and not rolling friction. Nothing can be gathered from this test about the friction of radial bearings vs. cup and cone bearings under load.

In Edmund Burke's book "High-Tech Cycling", 1st Ed., he refers to a study by Danh at Oregon State University on the friction of different bearing types in bicycle applications. According to the conclusions of the study, cartridge bearings produce about 7 times more friction than cup and cone bearings. (To keep things in perspective, he also states that ball bearings produce about 1/20th to 1/50th the friction of a high pressure racing tire).

BTW, the bearings were compared with out seals, and with identical lubricant. Also mentioned was that cartridge bearings with seals have about 10 times the friction as without seals.
 

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Mark McM said:
According to the conclusions of the study, cartridge bearings produce about 7 times more friction than cup and cone bearings. (To keep things in perspective, he also states that ball bearings produce about 1/20th to 1/50th the friction of a high pressure racing tire).
Wow! A factor of 7 is huge... but then I don't understand the 1/20th to 1/50th ratio... if there is a factor of 7 difference then there needs to be a factor of 7 range in the ratio.

Makes me wonder about all the ceramic bearing hype, too... they are claiming a greater *reduction* than total drag (even in the cartridge bearings) should be to start with.

Mark McM said:
BTW, the bearings were compared with out seals, and with identical lubricant. Also mentioned was that cartridge bearings with seals have about 10 times the friction as without seals.
I'm confused... is that unloaded or loaded data? How does that relate to the factor of 7 between the two types?
 

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Here are some interesting figures from Hans Smolik's German website. He's a mechanical engineer now heavy into bicycles:

"Frictional wheel bearing losses (frictional moment divided by wheel radius) are extremely small. Depending on type and quality of the bearing, they range from 0.006 to 0.015 Newton (N) for the front wheel, and from 0.011 to 0.025 N for the rear wheel. At 35 km/h, you'd need from 0.06 to 0.14 Watt (front wheel) and from 0.11 to 0.23 Watt (rear wheel) to overcome this frictional loss. To put this into perspective: at the same speed, chain friction robs you of 3 - 6 Watt; the rolling friction (resistance) of the tires will cost you from 45 - 60 Watt."
 

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rruff said:
Wow! A factor of 7 is huge... but then I don't understand the 1/20th to 1/50th ratio... if there is a factor of 7 difference then there needs to be a factor of 7 range in the ratio.
Here's an excerpt from the book (High-Tech Cycling, Edmund R. Burke, PhD, 1996, ISBN 0-87322-535-X, published by Human Kinetics, pages 18-19):

"Bearing Friction
Bicycle wheel bearings are of two basic types, the cup and cone type and the cartridge type. As supplied by bicycle manufacturers, bearings are lubricated with grease. Ball bearings have a very low friction, and cause about 1/20th to 1/50th as much drag as high-pressure racing tires. Friction in bearings is so low that it can be measured only with a very accurate laboratory apparatus. Cartridge bearings usually contain seals that add to the bearing friction.

"In 1991, Danh and his fellow researchers at Oregon State University measured the friction of bicycle wheel bearings of several types (Danh, K., Mai, L., Poland, J., & Jenkins, C. (1991). Frictional resistance in bicycle wheel bearings. Cycling Science, 2(1), 9-13). They found enormous differences between lubricants and between bearing types (see Figure 1.10). Their conclusions were:

"- Cup and cone bearings, properly adjusted and lubricated with 20w oil, have the lowest friction. The friction of a cartridge bearing having no seal and lubricated with 20w oil is about seven times higher than that of cup and cone bearings. For racing, therefore, standard cup and cone bearings are superior.
- Bearings with grease have a friction about six to seven times higher than the same bearing with light 20w oil. For racing, therefore, the bearings should be cleaned and lubricated with light oil. The losses resulting from use of grease are the equivalent of climbing a 15-m hill during a 20-km time trial.
- Cartridge bearing seals can cause up to 10 times the friction of a free running bearing without a seal. For racing, therefore, cartridge bearings should be of the shielded type, not sealed (the shield doesn't rub). For racing, the inner shield should be removed and the bearing lubricated with light oil.
-The friction of the bicycle wheel bearings does not seem to be affected by the load; however Danh and coworkers found that the friction increased linearly with the speed. Friction approximately doubled from 50 to 600 rpm.

"The conclusions are generally correct with one qualification; Danh used new cartridge bearings, which give very high friction measurements. Worn bearings and seals that have been run in have a much lower friction than new bearings. Using a different test procedure, Kyle (Kyle, C.R., How friction slows a bicycle. Bicycling, June, 1988, pp.180-185) reached basically the same conclusions as Danh. According to Danh's data, cone bearings could produce a 7-m lead in a 40-km time trial against an equal opponent using cartridge bearing with the seals removed and lubricated with light oil."


The graph (Figure 1.10) accompanying this text shows Torque vs. Speed for several types of bearings, all of which are straight lines:

Cartridge, grease, seal: 18 N-mm @ 100 rpm to 56 N-mm @ 600 rpm
Cartridge, grease, no seal: 4 N-mm @ 100 rpm to 9 N-mm @ 600 rpm
Cartridge, 20w oil, seal: 3 N-mm @ 100 rpm to 8 N-mm @ 600 rpm
Cup and Cone, grease: 2 N-mm @ 100 rpm to 3 N-mm @ 600 rpm
Cup and Cone, 20w oil: 1 N-mm @ 100 rpm to 2 N-mm @ 600 rpm

For 700c wheels (664mm dia.), each N-mm of friction torque represents 0.0335 Watts of power per wheel at 40 kph (319.5 rpm). The values from Danh, et. al. fall into the same basic range as those reported by Hans Smolik.

(As a side note: up to about 15 or 20 years ago, many hubs used dust covers, referred to above as shields, instead of seals. Dust covers did not drag on the axle, and instead limited the intrusion of contaminants into the bearing by creating a long narrow gap between axle and dust cover. With the advent of the mountain bike in the 1980's, which are used in harsher environments and have greater bearing sealing requirements, rubber contact seals began to be used, and now virtually all hubs use rubber contact seals of one type or another.)

rruff said:
Makes me wonder about all the ceramic bearing hype, too... they are claiming a greater *reduction* than total drag (even in the cartridge bearings) should be to start with.
They are complete, total and unadulterated hype. Far greater reductions could be achieved by replacing the rubber seals with non-contact labyrinth seals. However, this type of seal would require that the hub builders apply high tolerances to their own components and manufacturing processes, instead of just buying pre-manufactured ceramic ball cartridges off the shelf.
 
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