Re: can front wheel bearings be damaged

On 2010-12-02, jim beam <me@xxxxxxxxxxx> wrote:
On 12/01/2010 12:08 PM, Brent wrote:
On 2010-12-01, jim beam<me@xxxxxxxxxxx> wrote:
On 11/30/2010 02:39 PM, Brent wrote:
On 2010-11-30, N8N<njnagel@xxxxxxxxxxx> wrote:
...by mounting or rotating tires? I don't see how, BUT keep reading.

At my last oil change, I got new tires installed on my company car. I
immediately noticed an increase in road noise, but chalked it up to
the different tread of the new tires (Uniroyal Tiger Paw vs. Goodyear
Integrity) and since the old, OEM tires were so awful, I figured it
was a small price to pay for actual traction.

I just got an oil change again last week, about 7K miles later. I
asked that the tires be rotated and balanced while there because the
car is a notorious tire eater ('08 Impala.) When I got the car back
the mechanic said that I should take the car to the dealership and see
if they would warranty the front wheel bearings because both felt
loose, and he said that typically one should see no perceptible play
in them. I ASSume that these are not the tapered rollers that I know
and love but are one piece cartridge bearings so no adjustment is
possible. I had to take the car to the dealer anyway to get a
malfunctioning door lock fixed (fleet people wouldn't let regular
garage fix it for reasons unknown to me...) and they replaced both
front wheel bearings under warranty and immediately I noticed a
reduction in road noise.

Now, I can't think of a mechanism by which simply undoing and redoing
the lugs would cause a wheel bearing to fail... right?

I suppose it is possible that they just went bad right about that
time... I remember I had one get really loud on the last Imp that I
had but that was maybe 20K miles later (60K vs. 40K miles) funny thing
was that not three days after I had it replaced I hit a very large and
deep pothole at speed and trashed it *again* - wow, they're not real
strong are they? (I saw the pothole but thought it was a patch so
didn't swerve around it) but anyway, it just seems odd to me that they
would both go bad exactly as I had the tires replaced...

If for some reason they hit the hubs with a big hammer then maybe...
otherwise I can't see how changing the tires would do it. Perhaps the
different tire noise made the bearing noise more noticible?

I am guessing that the impala has ball bearings in the front? The
problem with ball bearings is they can't take much lateral load.

not true.

It is for typical ball bearings.

what is a "typical" ball bearing? single row? double row? 15 °
angular contact? 30° angular contact? full compliment? there's a
/lot/ more to this than you seem to be considering.

A typical ball bearing, an inner race, a cage and an outer
race. No special angles or bullshit, just a ball bearing as found in
all sorts of things, from the very small to the rather large.
Here: http://www.crestock.com/images/1050000-1059999/1054559-xs.jpg
shouldn't need to spell this out so I wonder if you're just playing
games.

most fwd cars use double row angular contact ball bearings -
they most definitely are designed for and can take substantial lateral load.

compared to regular ball bearings, but nothing like what a roller can
handle.

again, you're not considering any of the other factors. rollers are
great for a narrow range of angular loads - the rollers need to be
loaded evenly long their length, not just one end. if they're loaded
outside of that, they don't roll evenly and all kinds of issues occur.
now, you can load them outside of that range if the loading is light,
but then your bearing ends up being overkill.

Now you're just being a usenet nit picker. You're not going to get that
kind of uneven loading in any fixtureed environment. If you're loading
through only part of the cup or cone to get the uneven loading
you are describing you've done a shitty design and/or the shaft in the
inner race isn't concentric with the bearing mount holding the outer
race. The races shouldn't be loaded like that in any kind of bearing
except those designed to have the inner race rotate relative to the
outer.

Anyway for a situation like a wheel bearing, that's what the proper
preload is for. To keep the outer race from tilting and loading the
rollers improperly. Also there is a distance between inner and outer
wheel bearings to prevent them from being loaded at some odd angle.
This costs money. It's not some bearing you can just press in at
one end like the double row angular ball bearings.

Tapered
roller bearings are superior as they are designed to take lateral and
radial loads.

they can take higher loads for a given size, but they have no tolerance
for loads outside their normal config - in that regard, ball bearings
are more tolerant, hence their use on fronts where there's all kinds of
stuff going on.

What do you mean "outside their normal config"?

they're to be used for their specified loading angle which is very
narrow. see above.

Again, this doesn't apply to a fixtured environment.

Using parts as they
aren't supposed to be used can result in failure. Tapered roller
bearings did the job on front ends for years, it's just about cost.

nope. nothing gives a greater range of load angle tolerance than double
row angular ball. that's why they're used.

This is a fixtured environment, what variety of load angles are you
going to be dealing with? You've got primarily a radial load and some
axial load... The vector breaks down into those two components at the
bearing(s). There isn't some point load at some angle being applied to
some location on the OD or ID. If there was that's not the intended
usage and something is very wrong.

This whole concept of "load angle tolerance" seems rather foreign and
sounds to me to be tolerance of shaft and housing not being concentric.
Since a wheel bearing is a cantilevered set up the inner and outer races
and what is mounted on them will always be concentric unless the
bearing(s) is(are) damaged.

Anyway, here:
http://www.skf.com/portal/skf/home/products?maincatalogue=1&lang=en&newlink=1_3_1

Click on the figure that shows the contact angle. See how the ball is
held in place? The races are formed to resist axial loading. Now take a
look at a cross section of a tapered roller bearing.
http://www.efunda.com/designstandards/bearings/bearings_tapered_roller.cfm
See how much more capability there is to take axial load? Now look at a
typical, ordinary, garden variety ball bearing, see link above... hardly
anything for axial load.

If what you mean is that angular ball bearings are easier to deal with
in an assembly enviroment because they are more tolerant of things not
being concentric, not needing a preload, etc and so forth, then yes they
are more tolerant. More tolerant of the wallet becaus making things
more precise costs money. Those are cost motivations. Is it nice that
angular ball bearings can be made assemble and forget? yes. But there's
a trade off for that and that is in the loads they can survive. The
inner/outer tapered roller bearing set up is simply stronger, more
supportive and can take more axial load than a double row angular ball
bearing at one end of the hub.

BTW:
http://www.gizmology.net/bearings.htm
Notice what they call a typical ball bearing.

.

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