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Old 12-05-17, 02:14 PM   #26
Racing Dan
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Quote:
Originally Posted by Andrew R Stewart View Post
I think what Racing Dan is talking about is when there's excessive (and there's that qualifier once again. Our passion is full of judgments and opinions) bearing preload the rolling surfaces go through a work hardening process as they are indented and rebound under the pressure of the balls. I think of it like a too heavy truck for the road's surface. The layers of road will flex and then in time crack.


Not every situation has had scientific research and a published paper. But the decades of hands on findings do speak just the same. Andy
I mean preload in the sense the bearing is loaded, to some degree, even if no external load is applied (no one is riding the bike). Bearing preload is the opposite of bearing clearance.
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Old 12-05-17, 03:52 PM   #27
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With a properly adjusted bearing, which has absolutely no play in it, then all of the ball bearings always make contact with the Cup and Cone, evenly Distributing all of the forces and weight over the entire assembly. Back in the day when I used to race, many many years ago, people were obsessive about resistance, and ran their beautiful campy hubs with play in them. Within a couple of months, either the cup or the cone was ruined in one section because all of the forces were concentrated on one or two bearings, instead of being evenly distributed over all of them.

So do not adjust hubs so that they have play in them.
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Old 12-05-17, 04:03 PM   #28
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Originally Posted by 3alarmer View Post
...ball bearings and how they work have been thoroughly researched. Cone and race surfaces are case hardened, at the very least, in a quality bearing assembly. I honestly do not see how what you have described can occur.

Certainly excessive bearing load (to the point where the wheel no longer spins freely under the weight of the valve stem) ought to be avoided. But like @davidad, Mr Brandt, and a lot of other people I have preloaded both headset and wheel bearings on bicycles for many years now, with no noticeable ill effects.

But I'm a test subject group of one, which is why I asked for a source.

Bingo! Because this well adjusted hub is not the usual for the vast majority of bikes sold, at the time of sale. Just about every bike I have pulled out of a box, and had cup and cone hub bearings, had bearings too tight to achieve this standard. The time to adjust the hubs as well as their grade can be isn't time that makes the shop any money, so most shop assemblies I see have really tight bearings. There's so much leverage at the tire over the bearing, that when the bearings are new the preload is hard to notice. Unless the wheel is removed from the bike this preload isn't likely to be discovered until the bearings start to wear badly.


The preload thing is a shade of gray. A tiny amount is good, much more gets bad fast. (and I draw a difference between radial and angular contact WRT radial's sometimes need for end play). Andy
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Old 12-05-17, 04:14 PM   #29
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Originally Posted by Andrew R Stewart View Post
Bingo! Because this well adjusted hub is not the usual for the vast majority of bikes sold, at the time of sale. Just about every bike I have pulled out of a box, and had cup and cone hub bearings, had bearings too tight to achieve this standard. The time to adjust the hubs as well as their grade can be isn't time that makes the shop any money, so most shop assemblies I see have really tight bearings. There's so much leverage at the tire over the bearing, that when the bearings are new the preload is hard to notice. Unless the wheel is removed from the bike this preload isn't likely to be discovered until the bearings start to wear badly.


The preload thing is a shade of gray. A tiny amount is good, much more gets bad fast. (and I draw a difference between radial and angular contact WRT radial's sometimes need for end play). Andy
The leverage issue is real. If you adjust a cup and cone wheel to have a tiny bit of play at the rim, when mounted, it will often feel somewhat tight if you rotate the axle, between thumb and index, holding the rim.
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Old 12-05-17, 07:42 PM   #30
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Originally Posted by Racing Dan View Post
A wheel that spins freely under the weight of the valve is not preloaded.
...that's an interesting observation. Again, what's your source ?
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Old 12-05-17, 08:50 PM   #31
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One of the final steps in the bearing manufacturing process is the assembly of the individual bearing components: the outer ring, inner ring, balls and retainer (or ball separator). When the bearings are assembled, it is necessary to have a controlled amount of internal clearance, or looseness between the rings and balls. This is referred to as radial play in most bearing catalogs.

In certain applications, this internal clearance must be removed for a pair of bearings to operate properly. The application of an axial load across a pair of bearings – for the purpose of removing free internal clearances – is called preload.

Benefits of preloading ball bearings include:

Rotational accuracy and precise shaft positioning
Elimination or reduction of ball skidding
Control and reduction of axial and radial deflection under applied load
Noise reduction
Load sharing between bearings
Quote:
Axial adjustment requires great care, accuracy, proper tooling and cleanliness during the assembly process to avoid excessive preloading and ensure correct conditions. First, two bearings are mounted with the desired axial offset. The shaft and/or housing are threaded. Finally, the internal clearance in the bearings is removed by installing precision ground washers and then tightening the nut or threaded collar.
Quote:
How much preload should be applied?

In general, provided the design requirements are met, the least amount of preload is desired
...all from Preloading Ball Bearings: Full AST Guide - Bearings : Blog : AST Bearings
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Old 12-05-17, 09:57 PM   #32
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Originally Posted by Racing Dan View Post
A wheel that spins freely under the weight of the valve is not preloaded.



My wheel bearings have zero play, NONE, and are therefore preloaded. They are not tight, which would be excessive preload, resulting in an interference fit.

Once spun, my wheels will eventually "pendulum" for a few cycles before they finally come to rest.


Quote:
Excessive preload can cause increased heat, fatigue, and torque. Insufficient preload can allow resonant vibration causing fretting of the raceways.

Bearing Preload - National Precision Bearing
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Old 12-06-17, 04:32 AM   #33
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Originally Posted by Reynolds View Post
+1. Better to have no play, but a little doesn't cause any harm IME.
This speaks more than words:



Just add that play won't result in (at least not measurably) lower drag when a bearing carries rider's weight (compared to an optimally preloaded bearing, not overtightened one), and will result in wheel's play.
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Old 12-06-17, 11:24 AM   #34
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That graph is super helpful! The takeaway being, better to err a little on the side of loose than tight
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Old 12-06-17, 12:25 PM   #35
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Er, I think you read the graph wrong. Peak bearing life happens with just a little more than zero preload.
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Old 12-06-17, 12:39 PM   #36
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Not sure if this is helps but last winter I rode with play in the hubs for several months without any noticeable difference. Took it to a bike shop and they couldn't figure out why the wheel shimmied from side to side. Rode it a while longer and took it into another shop which immediately realized the cartridge bearings were shot. Replaced them and the wheel spun like new. Pretty sure the first mechanic thought I had a cup and cone bearing and tried tightening up the hub...
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Old 12-06-17, 12:44 PM   #37
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Originally Posted by RubeRad View Post
That graph is super helpful! The takeaway being, better to err a little on the side of loose than tight
I added a sentence below the graph, just in case, but obviously didn't explain well enough. The no-play zone is what you should aim for - i.e. preload, no play. Just make sure not to overdo with it. Tightening until the play has just disappeared is usually good enough.
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Old 12-06-17, 12:45 PM   #38
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Er, I think you read the graph wrong. Peak bearing life happens with just a little more than zero preload.
I think what Rube is saying is that once you begin to move away from "perfect", the consequences are greater and occur more rapidly if you move towards increased preload vs towards increased clearances.

I think. And that's if I am reading the graph correctly as well.
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Old 12-06-17, 12:56 PM   #39
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Yes, the Squid understands. 'perfect' is not possible, so if you keep getting what you percieve is a little too far on either side, one type of error is preferable.
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Old 12-06-17, 04:29 PM   #40
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My setup uses Polk speakers (fronts, which I have bi-amped, central, subwoof, rears) and a Yamaha RX-V1000. The RX-V1000 came with a microphone that you plug in, and then you run a calibration routine, and the unit sets the equalization constants. Sounds great.

I think if you have a ballsy enough amp, and you work hard to get the EQ set right, the 901s (any version) will sound fine. If your amp is a good one, but not so powerful (e.g. 20 or 30 W per channel), you might be better suited to using another speaker. Other folks here, more expert than I, have suggested some names.
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Old 12-06-17, 05:28 PM   #41
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.
...42.
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Old 12-06-17, 05:38 PM   #42
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In response to WizardOfBoz, I would just say that my preferred bread to bake is the no-knead refrigerator dough recipe from Artisan Bread in 5 Minutes a Day.
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Old 12-07-17, 04:49 AM   #43
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Originally Posted by RubeRad View Post
Yes, the Squid understands. 'perfect' is not possible, so if you keep getting what you percieve is a little too far on either side, one type of error is preferable.
If you tighten until all the play is gone (for QR axles it is tested with the QR locked - loose QR should allow a bit of play) - then you are usually getting somewhere between the zero preload (and zero play) and optimal preload. Loosening further, so that there is play is not a good choice in my knowledge and experience. Bearnings get pitted and the wheel has play - (bad for braking, little less for steering as well).
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Old 12-07-17, 08:52 AM   #44
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I was taught a loooooong time ago, to adjust hub bearing to a point, there is very slight play when wiggling the axle side to side. When the wheel is installed and QR closed, there should be no play and the wheel should rotate under the weight of the valve. I have 4 sets of wheels from the 80's, using this practice, and absolutely no wear to the cones and races.

A few years back, I bought a new replacement wheel for a bike at the LBS, and the adjustment was so tight, you could feel the indexing of the bearings.

I will continue with this practice.

Oh, found the reference. The Best Of Repair Stand, by Don Cuerdon.

"Check the adjustment by alternately turning the axle between the thumb and forefinger sideways. The axle should turn freely and feel slightly loose (to allow for compression when the wheel is fasten to the frame).

When the wheel is installed, there should be no side play at the rim, and the weight of the valve stem (positioned at 3 or 9 o'clock) should be enough to turn the wheel . Keep fusing until you get it right."

KB
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Old 12-07-17, 09:06 AM   #45
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Originally Posted by Slaninar View Post
This speaks more than words:

I think it speaks the same thing as "I'd rather have a little play than too tight with no play", but try to get in between those two.
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Old 12-07-17, 09:09 AM   #46
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Originally Posted by wphamilton View Post
I think it speaks the same thing as "I'd rather have a little play than too tight with no play", but try to get in between those two.
It is far from that. From the graph it is visible that no play part give shorter lifetime. As well as wheel that... well - has play.

It is just important not to overdo the preload - but that is not hard - just stop tightening as soon as all the play is gone. There is a margin - as you can tell from the graph.

One thing that isn't shown in the graph: for cup and cone bearings, leaving play will result in pitting on the cones (at least), which is more bother to source and more expensive to replace (than just balls). Making it tight just enough to eliminate play allows for hubs to last for decades - just replace balls from time to time.
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Old 12-07-17, 12:23 PM   #47
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Originally Posted by Slaninar View Post
It is far from that. From the graph it is visible that no play part give shorter lifetime. As well as wheel that... well - has play.
Seriously? Too tight has a very steep line for rated life, and just too the right of the maximum (a little play) has much less slope. Best is anywhere in the immediate region beyond "too tight'. It is precisely what I said.
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Old 12-07-17, 12:27 PM   #48
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Originally Posted by SquidPuppet View Post
My wheel bearings have zero play, NONE, and are therefore preloaded. They are not tight, which would be excessive preload, resulting in an interference fit.

Once spun, my wheels will eventually "pendulum" for a few cycles before they finally come to rest.


Bearing Preload - National Precision Bearing

That makes no sense. "Inteference" is almost the definition of preload. That is, Preload is the opposite of clearance. Also the post I replied to claimed a wheel should be both free spinning under the weight of the valve(!) but be preloaded as well ... This sounds suspiciously like having your cake and eating it too.

Trouble with "internet quote war" is that there is an inherent bias to searching certain terms like "bearing preload". Try searching for "bearing clearance" instead. Then you get this (SKF):

Bearings must have the appropriate operating clearance to operate satisfactorily (→ Importance of selecting correct clearance/preload).
In most cases, bearings require a certain degree of clearance (→ Selecting internal clearance). However, in some cases, they may require preload (i.e. negative clearance → Selecting preload).


As a general rule:

Ball bearings should have an operating clearance that is virtually zero.

Cylindrical, needle, spherical and CARB toroidal roller bearings typically require at least a small operational clearance.

Tapered roller and angular contact ball bearings should have a small operational clearance, except in applications where a high degree of stiffness or positional control is required, in which case they can be mounted with a degree of preload.


Selecting internal clearance or preload

or you can read the SKF catalog that has a lot if interesting info:


"Clearance versus preload

For most applications, bearings operate with
some residual clearance. Normally, a positive
operating clearance near zero is the optimum
(† diagram 2).
A somewhat greater clearance may be more
suitable for:
• high-speed applications to reduce frictional
heat
• form errors on the shaft or housing seat
such as ovality
The initial internal clearance prior to mounting
and permissible reduction after mounting, depend
on the type and size of the bearing. The
reduction in clearance due to an interference
fit may require greater initial internal clearance
than Normal to avoid preloading the
bearing († fig. 15, page 167).
Preload (negative operating clearance) has
advantages, but can also be risky. If a high degree
of stiffness is required, light preload can
be suitable († Bearing preload, page 214).
A light preload may also be required when
there is a very light or no external load on the
bearing in operation.
However, there is a risk that too much
preload causes the bearing to overheat, which
further increases preload, friction and heat.
This cycle can continue until the bearing
seizes.
It could be argued that preload is acceptable,
provided the bearing operates in a zone that
does not exceed light preload († diagram 2,
zone between 0 and –1). In this case, however,
there is an increase in friction and frictional
heat.
Although all bearing types can run with some
preload, SKF recommends a positive operating
clearance. This is particularly important for
roller bearings such as cylindrical roller, needle
roller, spherical roller and CARB toroidal roller
bearings."


https://www.google.dk/url?sa=t&rct=j...tHGX9qtuKpVRpv

Page ~212.


What Im getting at is that yeah, preload is "a thing", but none of the applications that require actual preload has much resemblance to bicycle wheels and usually preload is employed for a variety of reasons other than bearing longevity. Anybody can make up their own mind as to how much, or little, or none, they want to preload their wheel bearings, but claiming bearings should always be preloaded is patently false even if you operate with novel definitions of "preload".

Last edited by Racing Dan; 12-07-17 at 12:31 PM.
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Old 12-07-17, 01:16 PM   #49
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Quote:
Originally Posted by Racing Dan View Post
Also the post I replied to claimed a wheel should be both free spinning under the weight of the valve(!) but be preloaded as well ... This sounds suspiciously like having your cake and eating it too.
...it's magical when you get it right.

Quote:
Originally Posted by Racing Dan View Post
Trouble with "internet quote war" is that there is an inherent bias to searching certain terms like "bearing preload". Try searching for "bearing clearance" instead. Then you get this (SKF):

Bearings must have the appropriate operating clearance to operate satisfactorily (→ Importance of selecting correct clearance/preload).
In most cases, bearings require a certain degree of clearance (→ Selecting internal clearance). However, in some cases, they may require preload (i.e. negative clearance → Selecting preload).


As a general rule:

Ball bearings should have an operating clearance that is virtually zero.

Cylindrical, needle, spherical and CARB toroidal roller bearings typically require at least a small operational clearance.

Tapered roller and angular contact ball bearings should have a small operational clearance, except in applications where a high degree of stiffness or positional control is required, in which case they can be mounted with a degree of preload.


Selecting internal clearance or preload

or you can read the SKF catalog that has a lot if interesting info:


"Clearance versus preload

For most applications, bearings operate with
some residual clearance. Normally, a positive
operating clearance near zero is the optimum
(† diagram 2).
A somewhat greater clearance may be more
suitable for:
• high-speed applications to reduce frictional
heat
• form errors on the shaft or housing seat
such as ovality
The initial internal clearance prior to mounting
and permissible reduction after mounting, depend
on the type and size of the bearing. The
reduction in clearance due to an interference
fit may require greater initial internal clearance
than Normal to avoid preloading the
bearing († fig. 15, page 167).
Preload (negative operating clearance) has
advantages, but can also be risky. If a high degree
of stiffness is required, light preload can
be suitable († Bearing preload, page 214)
.
A light preload may also be required when
there is a very light or no external load on the
bearing in operation.
However, there is a risk that too much
preload causes the bearing to overheat, which
further increases preload, friction and heat.
This cycle can continue until the bearing
seizes.
It could be argued that preload is acceptable,
provided the bearing operates in a zone that
does not exceed light preload († diagram 2,
zone between 0 and –1).
In this case, however,
there is an increase in friction and frictional
heat.
Although all bearing types can run with some
preload, SKF recommends a positive operating
clearance. This is particularly important for
roller bearings such as cylindrical roller, needle
roller, spherical roller and CARB toroidal roller
bearings."


https://www.google.dk/url?sa=t&rct=j...tHGX9qtuKpVRpv

Page ~212.

Quote:
Originally Posted by Racing Dan View Post
What Im getting at is that yeah, preload is "a thing", but none of the applications that require actual preload has much resemblance to bicycle wheels and usually preload is employed for a variety of reasons other than bearing longevity. Anybody can make up their own mind as to how much, or little, or none, they want to preload their wheel bearings, but claiming bearings should always be preloaded is patently false even if you operate with novel definitions of "preload".
...now you're just making stuff up. If anything, a bicycle wheel most resembles the application in your reference that I have bolded in your quote from it. As to definitions, that's exactly why I've been asking for references in this thread since it started.

Nothing anyone writes here is going to have much effect on how things get done IRL, but it would be nice if we could occasionally have an informed discussion in here on topics that have some real world research and answers without the butthurt that inevitably follows in defense of positions that might be based on something else.


But why would we want to change longstanding tradition at this point, eh ?
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Old 12-07-17, 01:16 PM   #50
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Quote:
Originally Posted by Racing Dan View Post
That makes no sense. "Inteference" is almost the definition of preload.
Interference is when there is binding. Snug to the point that the adjustment is interfering with efficient operation. That is the definition of too much, or incorrect, or poorly adjusted preload.

Correct preload is exactly what it says. Before load. Peload does not mean loaded or tight. It simply means that clearances have been adjusted out.

Correct Preload = zero play. Eliminating clearances is the literal definition of being preloaded.

Correct Preload does not = tight/binding/interfering.

I agree with SKF here, and it sounds like a bicycle application to me. We don't want wobbly wheels or headsets. And we certainly want slopless crank operation.

Quote:
If a high degree
of stiffness is required, light preload can
be suitable
I agree here as well, and this sounds a lot like a bicycle application too.

Quote:
A light preload may also be required when
there is a very light or no external load on the
bearing in operation.
Quote:
What Im getting at is that yeah, preload is "a thing", but none of the applications that require actual preload......
Actual preload is a matter of degrees, ranging from light (and it's many benefits) to excessive and it's destructive consequences.

When we buy and install a brand new cartridge bottom bracket it has zero play. That is because it has been set with a light preload at the factory. Later in it's service life the bottom bracket will exhibit some play or slop. It is worn and that has caused a loss of it's preload. AKA it's toast.

Last edited by SquidPuppet; 12-07-17 at 01:22 PM.
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