wphamilton

They all know that. Someone was arguing that an axle can't compress, someone pointed out that it might bend slightly whether or not it compresses, etc etc but it's all trivial to the point that the QR tightens up the cones.

Kontact 

Hey Steve,

I saw that you PMed me, but being new I can only post 5 timers per day and have to send 10 posts before I can PM. I'll get you later today, hopefully.

sweeks

No worries!
Steve

RowdyTI

Agreed. Bearings are loaded when you get on the bike. If there's more than slight preload before you get on the bike, the load on the bearings is going to be excessive and cause premature wear. The more loaded, the more rapid the wear.

shelbyfv

sweeks

I used an improvised set-up for years, and eventually bought one of THESE, which makes the job much easier.

sweeks

Well, since someone woke the Dead Thread, I was looking it over.
Wouldn't the fact that the load on the cone's bearing surfaces is applied radially account for the wear being asymmetric on the races?

Andrew R Stewart 

The load on the cones isn't radial. Typical bearing contact angles are 20-30* and with the angular forces that a wheel sees during pedaling alternate sides of the bike as well as turns the cones see various non radial forces. My point (if I can think that far back) is that when the cones are miss aligned axially, as with a bowed axle, the balls track both at an angle to the cone axis and that the ball tracks will see more loading where the two cone tracks are closer together. Andy

sweeks

I agree... it's complicated! Maybe I should have said that there is a *component* of radial loading that is not symmetrical around the race.
If you imagine a loaded wheel which is not rotating, the balls in the top half of the bearing could be completely removed without changing the loading of the balls in the bottom half, which are supporting the entire load. There are those other loads that you mentioned, but there is more load on the bottom of the cone than on the top. This would explain why the bearing cones always (in my admittedly limited experience) start wearing on one half of their circumference. It's also consistent with the change in cone orientation with axle flex during wheel loading. This hypothesis would be confirmed if the orientation of the cones could be known... of course, it never is, so it's nothing more than a reasonably plausible explanation.
Would it be correct to say that this is a justification for having a very slight pre-load (or at least *zero* free play) on the bearings? It seems to me that if the bearing was loose enough, the entire load might be carried on one ball at a time as they rotate in position. This would account for increased wear on bearings that are too loose.
Or... maybe I'm over-thinking this! But there should be no doubt that axle compression occurs under quick-release pressure, and this is sufficient to change bearing adjustment.

Andrew R Stewart 

An axle could be marked to track it's rotational position WRT the frame. Sounds like a "science" project for some one here to do.

I've adjusted thousands of hubs and other bearings over the years and have spent some many moments thinking about this stuff over and over (like each time I adjust a bike's front wheel bearings, the wheel that is already off the bike when initially assembled and it's bearing access is so easy to deal with, yet so many are rough and notchy miles/years later. My belief is that most hubs are not properly adjusted during the shop assembly and that most are left way too much preloaded.) If someone does a study on cone rotational position and ball trach wear I will pay attention. Andy

70sSanO

The issue with hub play will never be completely resolved as long as manufacturers fail to include acceptable lateral tolerances for an installed wheel.

It is possible to use a dial indicator and determine the amount of lateral play. While I understand that any wheel, just by its construction, can be forced laterally, it would be helpful if a tolerance, just as an example, of .001” to .003” is maintained.

The hub adjustment “feel” and QR test are really based on people’s experience as to what works best. But I’m not sure that obtaining .000” of play is better than .003” for longevity. So a “perfectly” adjusted hub may in fact not be so perfect.

But in the end it is probably just moot. I remember replacing front wheel bearings with a little bit of play and a crown retainer that was anything but precise. Then jumping in and going 70mph on the freeway. Lol!

John

davidad

Bearings should have a slight amount of preload or they wear out sooner.

RowdyTI

Exactly. This is my conclusion as well. Even having zero preload, even some clearance -- even a lot of clearance -- is better for bearing life than excessive preload, and it doesn't take much preload before it becomes excessive. Do up the QR or thru axle tightly and you're adding more preload, and you're adding more load just getting on the bike and riding it.

There's a forum member named rydabent who is adamant against preload of any kind. He knows what he's talking about too.

shelbyfv

Is this still true with cartridge bearing hubs?

RowdyTI

Yes, it is still true.

Andrew R Stewart 

Me thinks it depends on the design of the cartridge bearings, "cartridge" being a term of assembly more then actual bearing design. The usual reference of cartridge bearings is for radial contact designs, I would say this is the vast majority of cartridges we see in the bike world. But angular contact types, like what Chris King specs, exist and do take a somewhat different set up. I'll also say that what a bearing designer stipulates and what any specific hub's tolerances are can and do drift. So that the axial end play (which with radial contact designs is not an indication of lacking preload) that many radial contact cartridge bearings are designed around doesn't happen very often for a few reasons. Axle compression/bowing from QR tightening, drop out miss alignment, hubshell/axle bearing seats/shoulders not being exactly the same are all frequent aspects of "fudge", let along the hubs that have threaded axles with a sleeve supporting the bearing's ID. With new and fresh bearings it can be very hard to really know of the true peloads and what direction they are being applied in.

Years ago Southerlands' manual gave a good start to radial cartridge bearing application in our bike world. But after so many decades of adjustable angular contact cup and cone designs we all have as out base line the thought of bearing end plat as felt at the rim is still thought as "wrong" Andy

rydabent

"preload" means you are deforming the bearing races at all times. that is not good.

madpogue 

FAKE! Shadows in the wrong direction cf. the moon. No gravestone shadow.

shelbyfv

Well, it was the best I could find at the time. Figured it was more polite than "Why did some moron dredge up a three year dead thread...." BF should have a flag of some sort or alert saying "Do you really want to do this?" for necro-threaders.

madpogue 

If they ever add this functionality, they should incorporate your graphic.

RowdyTI

Exactly. I've read many of your posts and you know what you're talking about. Also just getting on the bike and riding it adds a lot of extra load versus freely spinning the wheels in the stand. Those bearings will heat up and expand as well. A heavy application of quality grease will be for naught if the load on the bearings is excessive. It's clearly documented excessive preload destroys the ability of the grease to do its job.

andrewclaus

On the other hand, endplay means your hub is not contacting all the balls, with too much load on too few balls. It's not hard to achieve zero endplay with good technique.

And it's easy enough to avoid excessive preload. Hitting that sweet spot on the curve just to the left of zero is the goal.

70sSanO

With all this deforming and heavy loads are we still talking about bikes?

You know... two wheels, handlebars, kids ride and abuse them all over town.

John

shelbyfv

Yeah, maybe a little context. Necro-man posted a half dozen threads related to his reluctance to tighten his thru axle to spec. That seems to have expanded to a general fear of anything more than finger tight. I don't have any explanation for the choice of rydabent as a mechanical reference.

RowdyTI

The bikes we ride are precision instruments, not bikes for little kids. None of us want to ride deformed bearings that don't roll optimally. rydabent has decades of experience as an industry professional. His knowledge is sound and corroborated by other professional sources.