Bad Grounds Can Lead to Wheel Bearing Failure

Now that I got your attention, I was looking up some typical Subaru wheel bearing failure and came across this thread. As crazy as it sounds it actually makes a lot of sense. This would make sense on why Subaru's suffer from throw out bearing failures too.

Subaru's rear wheel bearings tend to die more often then front, which is odd since they are not exposed to as much heat as the fronts. One thing I found is, there are no grounds on rear differential to the frame. The last ground before the drive shaft is the transmission one up front, which is fairly small too. The only other reason that I can think of for rears failing more often is Subaru using cheaper bearings for rear and better ones for front.

I also think our high throw out bearing failure is related to the same grounding issues.

Source Thread

FYI, bad grounds also destroy wheel bearings.

 

Electricity WILL find a ground, and if the closed circuit in your automobile is compromised, it will simply find a ground through the suspension, wheel bearings, and tires.

 

If that happens, tiny micro-sparks travel from the rolling elements to the races, causing microscopic pitting in the races. It doesn't take long for those microscopic pits to get larger and larger and start spalling, etc., and wheel bearing failure. It can easily happen in under 10k miles.

I don't blame you [for being sceptical] ... people constantly talk to me like I have brain damage when I try to explain the phenomenon. NOBODY EVER believes it.

 

From my experience in the field, I'd say 99% of bearing failures are misdiagnosed by well-meaning but not well-informed folks who also don't believe bad grounds ruin wheel bearings. Come to think of it, I'd have to say I have NEVER seen anyone outside the bearing industry ever correctly diagnose a grounding induced failure. I'll have to think about that.

 

Of course, as a guy who made a very nice living for quite a while running a company that manufactured automotive wheel bearings, you could say bad grounds have been very good to me. Especially all those thousands and thousands of Omni/Horizon wheel bearings we sold because Lee Iacocca's engineers saved a couple bucks on ground wires. We literally were running those bearings 24/7 and couldn't keep up with demand, even after Chrysler had a big TSB announcement and started recalling cars to install more grounds. I even had one do-gooder engineer on staff who wanted to put a notice in the bearing boxes, notifying customers about the fix. I sure put a stop to that (does it make me a bad guy?).

 

In fact, I've seen studies by all world's largest bearing manufacturers, and everyone points to bad grounds as right around the third most-common reason for automotive/light truck wheel bearing failure. The first is installer error, of course. The second is accident/driver inflicted damage, and the third is bad grounds. Contamination and dragging brakes and old grease and flooding and etc. all come later.

 

Yes, we do a ****-poor job in the bearing industry of explaining these most common reasons for bearing failure in automobiles and light trucks. The heavy truck and industrial applications get a lot more of the attention and tend to do better with diagnosis. Part of that has to do with the very high cost of a bearing failure in a piece of production equipment or an over-the-road truck. With cars and light industrial equipment, they often don't get the attention. Not a snipe at anyone, just my experience.

 

I ran a little Google search, and here's the first hit it came up with regarding bad grounds ...

http://www.tomorrowstechnician.com/tt/t2100322.htm

See "Story 4"

 

Which DOES bring up another bad ground failure which I totally forgot to mention, and that's transmission bearings. And that includes clutch release bearings. But tranny bearing failures are, thankfully, less common than wheel bearing failures. With transmissions, you see damage to the gears (particularly pinion gears) before you see bearing damage. The loading is higher on the gears, damage is exacerbated by the forces at work.

 

PLEASE check out the various bearing company web sites; they all have excellent technical information areas, even though some are hidden or at other URLs. SKF, Timken, NSK, NTN, INA/FAG, and several other bearing manufacturers have sections on their web sites dealing with how to identify particular bearing failures, and then determine their causes. Definitely worth visits, and they do a better job explaining the bad ground situation with pictures, etc., etc. Here's one of the Timken TechTips links, written with the semi-trained technician in mind:

Industry Solutions

 

(see electric current on page 2) Note that Timken gives two versions ... pitting and fluting. In fact, we rarely see bad-ground pitting in cars and trucks, it's virtually all seen as fluting.

 

It's not limited to cars, however. Another I dealt with was (industrial) bearing failures in the conveyor system used in the Neon power steering assembly line. Out of the blue one day, DaimlerChrysler notified us they were billing us $30,000 an HOUR while the line was down due to repeated bearing failures. I sent our guys up there and in about fifteen minutes they identified stray grounding through the bearing races as the cause (bad maintenance of the conveyor drive system). After that, they were SO nice, we showed them a couple other problem areas for free.

 

Not so free was when an inadequate chassis ground on a huge rotating telescope drive system damaged the high-precision bearings AND forced them to disassemble the entire observatory to get the darn things out of there. Our guy told me the electrical connections for this big powerful motor were just tiny little wires, and they were all held in place with drywall screws. Nice.

 

Here are a few other non-bearing-company resources:

Magnetic Products & Services

(that one has a nice long list of reading material which should satisfy your desire for documentation) In fact, the fine folks at gaussbusters make most of their living from bearings ruined by bad grounds.

1951 DeSoto Suburban cars - long term report / car review with trailer towing

Here's a guy who found out when he honked his horn, the ground wound its way through the steering gear box, and the pitting erosion caused it to wear oddly.

 

But like I say to everyone, please DON'T believe me ! Do your own research via those bearing manufacturer sites. You'll learn a lot more there than I can put into an email. (Disclaimer: I did write some of the stuff that shows up on Timken, SKF, Minebea and INA/FAG technical sites, and maybe a couple others, but I don't remember ever writing anything about electrical damage, so it'll all be non-Bruce resources; my foci tend to be OEM installation, mechanical failure diagnosis, and cost/performance analyses).

<snip>I am talking about bad ground in terms of an errant electrical path to the (-) terminal. You know, errant as in not as designed by the auto manufacturer but as induced by time / wear / error.

 

For those of you who have some shred of sense in your brains (rather a fewer of you than I used to believe, unfortunately), some other information to answer questions I got in various emails:

 

- 300mV in a car/light truck is still too high; quick death for automotive-sized tapered roller and ball bearings. We know 100mV will create (minor but) observable damage in one revolution, so I'm guessing right around zero is quite nice ;-)

 

- To people who emailed and got to the stage of thinking about grease dielectric. Yes! Wheel Bearing + grease = Capacitor YES! Someone finally suggested high dielectric protects bearings, even in bad ground situations, by keeping that ground going somewhere/anywhere else. Take a cigar! Oh, how my heart swells; I am proud of you. Sadly, in a Real World wheel bearing, grease dielectric performance degrades to crap very quickly, for a long, boring set of reasons. NASA has some nice stuff that holds its dielectric, but the cost is -cough- high.

 

- Yes, there are bearing-failure-related ground problems being sorted out right now. I really shouldn't comment on any of them, sorry.

 

Okay, I'll now pitch a softball out to all you earth = ground people who were so condescending in your emails, (I'll assume you were just having a bad day):

 

- Ford has TSBs out on most of its recent vehicles, using rear wheel hub assemblies (TSB 97-18-4 is an example, old enough to be on the Internet), if a customer complains about static on the AM radio. Turns out (usually rear) bearings aren't cleanly conducting rear tire / pavement - induced static electricity to the chassis. Brand new, the grease dielectric stops the juice getting through, but (as above), grease degrades. And so, gradually, that static electricity starts arcing across the bearing races to get to the chassis ground (electricity's will to live is amazing, eh?). Symptom = customer complains about AM radio buzz. Solution = add a little ground strap thingie between the hub and axle stub. SYMPTOM IGNORED = every spark is another step in DESTROYING THE REAR WHEEL BEARINGS! (industry secret: we sell more Ford rear wheel hub assemblies than statistics say we should, and we ain't killin' no Golden Goose). Don't you think it's interesting Ford can issue a series of TSBs for AM radio buzz, but ignore the fact that the reason for the buzz is that the wheel bearings are being arc-welded to death?

Here is another great article which talks about different kind of bearing failures, electrical included.

Lubrication of Rolling Bearings - Technical Solutions for Critical Running Conditions

As shown in Figure 12, the actual electric current crater is small and can be identified only under an SEM. Today, the typical diameter of the nearly circular craters present in most common failures ranges from 1 to 4 µm. Practical experience shows that bearing surfaces will be damaged, even with a minimal load. These arcs also lead to a catastrophic oxidation-induced aging of the grease in the rolling contact area, which dramatically shortens grease life (Figures 13 and 14). At the roller contact points, the deteriorated grease can no longer lubricate effectively, while the outer portions of the bearing retain fresh grease. This condition is sometimes characterized as underlubrication, which may be an accurate depiction of a secondary failure mechanism but is not necessarily the fundamental contributor to failure. Corrective measures are usually not successful when the actual cause is not correctly identified and amended.

 

http://media.noria.com/sites/archive_images/_Backup_200601_fluting-fig15.jpg

Figure 15. Typical Fluting Pattern

(Courtesy of MH Electric Motor and Control Corp.)

 

The last stage is characterized by the typical fluting pattern as a result of bearing currents (Figure 15).

Here is what my wheel bearing looked like on a 2004 Forester XT. Looks like it was just starting to happen:

http://legacygt.com/forums/attachment.php?attachmentid=256627&stc=1&d=1507728380

2017 Update: Here is the rear wheel bearing from my 2012 Outback, similar pitting. Bearing has 107k miles on it, and started making noise a couple months ago. Was surprised to see this on such a new car, so I quickly re-grounded the rear diff and rest of the car to avoid further bearing damage.

http://legacygt.com/forums/attachment.php?attachmentid=256628&stc=1&d=1507728404

I'm not convinced but for the sake of discussion:

Assuming that electric current is passing thru the bearing and causing the failures, what is the proposed solution? Ground straps from the hubs to the frame? Don't suspension components already provide direct metal connections between the hub/knuckle and the frame? I suppose if the charge is travelling down the axle it would have to exit thru the bearings to go back thru the hub/knuckle to the frame...Ground straps from the rear diff to the frame? Additional ground straps from the tranny to the frame?

I'm trying to figure out which way the electricity is flowing:

A) Is it coming from too much un-grounded electricity in the car not making it's way to the negative on the battery, so it tries to go thru the wheel bearings to the tire then to the ground, therefore we need more neg battery terminal to frame grounds, and grounds from rubber bushing isolated components like the rear diff to the frame?.

B) Or is it some form of static electricity being produced by the wheel rotation, which goes thru the bearing to the frame to the neg terminal on the battery? The only solution I can see to that is some form of "brushes" touching the spinning part of the outside hub or brake disk with a ground strap to the frame.

Plausible. It's of concern with welding on cars or other things that have bearings that might be between the ground path and the welding arc.

I think the cause of the fluting (failure) hasn't so much to do with the ground traveling thru the bearing but moreso with the bearing spinning at the same time the ground is traveling thru it, creating the micro-sparks and thus the fluting. You don't weld while driving do you?

Here is what my wheel bearing looked like on a 2004 Forester XT. Looks like it was just starting to happen:...

How many miles on that bearing?

I think the cause of the fluting (failure) hasn't so much to do with the ground traveling thru the bearing but moreso with the bearing spinning at the same time the ground is traveling thru it, creating the micro-sparks and thus the fluting. You don't weld while driving do you?

The fluting is clearly rotational wear. The theory posted above is that the rotational wear at that level is due to micro pitting that is caused when electricity arcs between the balls and the race. The arcing will happen because there's not a great mechanical bond between a ball and a race, kind like a loose electrical wire can cause heat buildup and arcing. The micro pitting will occur whether the bearing is rotating or not. Once there is a pit in either the ball or the race rotation will cause the pit to transfer defects to other balls and other parts of the race.

I can easily cause pitting around a poor welding ground clamp. I can also weld with a car battery, jumper cables and standard stick welding rod, so it's not like we're out of the realm of possibility on a car from either the battery or from the alternator. 12v dc at 90+amps is sufficient to throw a very strong electrical arc and vaporize metal.

So, I'll stand by my statement of plausible.

Plausible. It's of concern with welding on cars or other things that have bearings that might be between the ground path and the welding arc.

Great point, I never really considered this side of it, I remember people making an emphasis on grounding close to the weld spot when trying to weld onto the cam bolts to remove them.

How many miles on that bearing?

Car has 160k miles. Knowing that it's a Subaru, and the fact that the bearing was a ball bearing design and not the tapered design, tells me that it was replaced at least once.

The new bearing I put in, Timken 513248, is a tapered design, which I'm not too happy about (I prefer ball bearing designs).

I'm not convinced but for the sake of discussion:

Assuming that electric current is passing thru the bearing and causing the failures, what is the proposed solution? Ground straps from the hubs to the frame? Don't suspension components already provide direct metal connections between the hub/knuckle and the frame? I suppose if the charge is travelling down the axle it would have to exit thru the bearings to go back thru the hub/knuckle to the frame...Ground straps from the rear diff to the frame? Additional ground straps from the tranny to the frame?

 

I'm trying to figure out which way the electricity is flowing:

A) Is it coming from too much un-grounded electricity in the car not making it's way to the negative on the battery, so it tries to go thru the wheel bearings to the tire then to the ground, therefore we need more neg battery terminal to frame grounds, and grounds from rubber bushing isolated components like the rear diff to the frame?.

 

B) Or is it some form of static electricity being produced by the wheel rotation, which goes thru the bearing to the frame to the neg terminal on the battery? The only solution I can see to that is some form of "brushes" touching the spinning part of the outside hub or brake disk with a ground strap to the frame.

Here is how I understand the electricity to flow. Someone more knowledgeable in this topic please chime in and correct me:

Alternator/Battery -> Engine -> Transmission -> Drive Shaft -> Rear Diff -> Rear Axles -> Rear Bearings -> Rims -> Gets Stopped at Tires

Same thing happens with front axles, I didn't include them for simplicity sake.

Electricity gets to the transmission in two ways, one through direct bolt on connection, another is through the Flywheel -> Pressure Plate -> throw out bearing & Input shaft. I am willing to bet this is why our throw out bearings die so often (besides bad quality). If they use NSK TOB's then they are quality and I've never had this issue on my Nissans. Front transmission does have a single ground strap though, something like a 12 gauge weak wire though. All grounding points end at the drive shaft on these cars.

Now you asked about ground points on suspension components. Most of them are rubber isolated, especially in the rear. Front MacPherson Strut does bolt to the knuckle directly, which means electricity will travel to the front strut right before the bearing, but even front strut has enough rubber to not have a good ground.

Front Suspension paths looks like this:

Front Strut: Knuckle -> Strut housing -> (Spring -> Rubber -> Top hat -> Body) -> Strut Rod -> Rubber Insulator -> Plastic Top Hat Bearing -> Top Hat -> Body of the car

Control Arm: Knuckle -> Lower ball joint -> Lower control arm -> Rubber -> front rubber bushing and rear rubber bushing

Rear Suspension paths looks like this:

Rear Shock: Knuckle -> Rubber insulator -> Shock body -> (Spring -> Rubber -> Top Hat -> Body) -> Shock rod -> Rubber -> Top Hat

Top Control arm: Knuckle -> Rubber insulator -> Top control arm -> Rubber -> Body

Toe bars: Knuckle -> Rubber -> Toe bars - rubber -> Body

Lower control arm: Knuckle -> Rubber -> forward control arm -> Bubber -> Body

As you can see ground paths on both front and rear suspensions are not good, especially for the rear since we don't have MacPherson struts in the back, which could explain the more common rear bearing wear.

In my opinion relying on grounds at the strut/shock level is too late, electricity already travels through the transmission gears (which get can get pitted too) and through axles. Plus it's right there next to the bearing, so it might still go through the bearing.

I would say the best course of action is to ground the engine, ground the transmission case as much as possible, then ground the rear differential to the body. Going to a carbon fiber drive shaft might also reduce/eliminate electricity from going to the rear differential, then you just have to worry only about static electricity on the rear differential.

Long post, time to get some lunch

Assuming #00 wire is good enough?

I'm personally using 8Gauge, not sure if anything heavier is really a must.

After replacing another wheel bearing (rear right), figured I should try regrounding the diff. Made it from 8gauge wire and gold coated connectors. Finding a spot where to ground on the car was hard, but luckily there were some spare threaded holes under the muffler.

http://legacygt.com/forums/attachment.php?attachmentid=256621&d=1507701253

http://legacygt.com/forums/attachment.php?attachmentid=256622&d=1507701253

I would say the best course of action is to ground the engine, ground the transmission case as much as possible, then ground the rear differential to the body. Going to a carbon fiber drive shaft might also reduce/eliminate electricity from going to the rear differential, then you just have to worry only about static electricity on the rear differential.

 

Don't forget that you have several chassis grounds as well that push current into the body...it's not just the drive line, it's the entire car. I've often put additional grounding from the alternator to the body and the battery to the body to eliminate ground loop noise in audio components. If the audio is noisy just imagine how dirty the electrical signal is to the rest of the electronics.

Correct, for that reason you don't always want the ECU to be grounded on the chassis for say. ECU is grounded on the intake manifold, even with the plastic manifolds (it has a metal L). I always ground any additional sensors, ie widebands, to the same grounds as the ECU.

The grounds that Subaru put on the engine are tiny and tend to rip easily (under valve cover ones as an example). I re-grounded my engine/front a long time ago with my Nissan kit, it's too long though, so will make it myself and post up some pictures.

Considering the massive voltage (but little amperage) produced by static electricity generators, essentially spinning friction wheels of non conductive materials, I wonder if brakes/wheel on cars can create small amounts of static electricity that seeks a ground. Since the tire insulates the charge from the natural ground, that leaves a path thru the bearings to the neg terminal on the battery.

I've shocked the heck out of myself walking across the floor and touching a door knob. And we've all heard about gas fires when the static charged person- car- and a gas nozzle come together.

An interesting experiment that a brake manufacturing company could conduct would be to use one of their brake dynos to try to measure if minute amounts of electricity are flowing from the wheel/brake calipers to ground on the dyno axle.

I hope this isn't becoming Internet BS stupidity!

Well,there are two possible solutions.Buy Timken or just put up with it.There are just not enough amps to create metal degradation.

On the other hand,my experience with high RPM kart motors is that the slightest bit of rust or contaminate can score a bearing. In other words,use NASA type cleanliness when installing bearings.

Sgt.Gator, I don't believe most of the damage is caused by static electricity, I would point my finger to alternator/battery and they are just trying to find path of least resistance.

Well,there are two possible solutions.Buy Timken or just put up with it.There are just not enough amps to create metal degradation.

 

On the other hand,my experience with high RPM kart motors is that the slightest bit of rust or contaminate can score a bearing. In other words,use NASA type cleanliness when installing bearings.

While I love Timken bearings and use them, if you have an inherit design flaw they will fail too. Boxkita mentioned in another thread, which sparked this thread, that he's tried every brand of wheel bearings and they all don't last in racing application.

I and a bunch of people I know race FWD SR20 Nissans and bearing issues are just not existent. Bearing issues are usually from users fault, like removing axle constantly and not replacing the bearing seal. Since it is FWD, rear is not connected to the engine, thus rear bearings just about never go out.

There are just not enough amps to create metal degradation.

 

Yes, there is. Automotive batteries and charging systems are low voltage and relatively high amperage.

While I love Timken bearings and use them, if you have an inherit design flaw they will fail too. Boxkita mentioned in another thread, which sparked this thread, that he's tried every brand of wheel bearings and they all don't last in racing application.

I never asked Sgt.Gator what his failure rate on bearings was, as he's putting just as much load on his bearings as I did. However, his car has a 4 inch cool air duct going to the brakes. Something I don't have.

My suspension guy told me I was cooking the bearings with no cooling. I ran out of money before adding the brake ducts & hoses. Although, I was at the race shop today & they have enough brake duct hoses to do the wagon now. I still have the naca ducts for the front bumper, too.

Sgt.Gator, I don't believe most of the damage is caused by static electricity, I would point my finger to alternator/battery and they are just trying to find path of least resistance.

 

 

 

While I love Timken bearings and use them, if you have an inherit design flaw they will fail too. Boxkita mentioned in another thread, which sparked this thread, that he's tried every brand of wheel bearings and they all don't last in racing application.

 

I and a bunch of people I know race FWD SR20 Nissans and bearing issues are just not existent. Bearing issues are usually from users fault, like removing axle constantly and not replacing the bearing seal. Since it is FWD, rear is not connected to the engine, thus rear bearings just about never go out.

It's not a design flaw,it's a cost flaw.Tapered bearings and shafts are much more expensive to manufacture. One requires close tolerance tapers,the other just requires a close tolerance shaft.

Tapered bearings can withstand much higher loads than spherical bearings.But they cost loads more to manufacture..

I never asked Sgt.Gator what his failure rate on bearings was, as he's putting just as much load on his bearings as I did. However, his car has a 4 inch cool air duct going to the brakes. Something I don't have.

 

My suspension guy told me I was cooking the bearings with no cooling. I ran out of money before adding the brake ducts & hoses. Although, I was at the race shop today & they have enough brake duct hoses to do the wagon now. I still have the naca ducts for the front bumper, too.

When I got the car from Phoenix Performance the left front wheel bearing was bad. It was replaced before my first race season. So far that is the only one I've had to replace. I do carry spare SKF bearings with me to the track. I'm sure the front wheel bearings get cooked, even with my brake ducts, but so far they are still ok.

Thinking about it, my car does have "extra" grounding on the rear diff because of the diff cooler braided mesh fluid lines running to the exchanger bolted to the frame. Same thing for the tranny, although my new 6 speed doesn't have a cooler hooked up <yet>.

It's not a design flaw,it's a cost flaw.Tapered bearings and shafts are much more expensive to manufacture. One requires close tolerance tapers,the other just requires a close tolerance shaft.

 

Tapered bearings can withstand much higher loads than spherical bearings.But they cost loads more to manufacture..

I wonder with the tolerances being closer its more sensitive to dust/electricity/etc. Kind of like an AR15 will jam well before an AK-47.