Bad Grounds 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 TOB failures too. Nissan's are generally pretty well grounded, I remember seeing some OG folks questioning why we loved grounding kits when our cars are fairly good already.
Subaru rear wheel bearings tend to die more often then front, they are not exposed to as much heat as the front either. There are no grounds on rear differential to the body, the last ground is the transmission one up front, which is fairly small too. The only other reason for rears failing more often could be Subaru keeps on using different cheaper bearings for rear and better ones for front?
Source Thread
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
Subaru rear wheel bearings tend to die more often then front, they are not exposed to as much heat as the front either. There are no grounds on rear differential to the body, the last ground is the transmission one up front, which is fairly small too. The only other reason for rears failing more often could be Subaru keeps on using different cheaper bearings for rear and better ones for front?
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.
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).
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).
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.
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).
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).
Last edited by Vadim
on 2014-12-10
at 17-47-31.
Originally Posted by wnwright
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