How often do you change or re-grease Rear wheel bearings?

Driver side of my car rear took a big hit against a tire wall and that caused looseness in the bearing.  I disassembled the hub and noticed how terrible the grease smelled.  Burnt and nasty.  This was a 'pro' (not ESR) rear hub assembly with special grease that I bought in 2013.  I took a few years off between then and now but it has been on the car since.  This made me wonder how often you guys are servicing, replacing, regreasing, whatever the rear wheel bearings.  

 

What maintenance do you do?

What intervals?

 

Thanks.

Drive it until it passes me on the track!

Have you ever had a rear wheel bearing come apart on you on the track. I have had both types of failures. the flange failing and the bearing failing. In both cases the wheel can and often will separate from the car. So I like the way my body is today that all my appendages work and are attached so this is what i do.

Replace immediately after any impact to the rear wheel. If no impact press in new bearings annually.

 

I don't try to repack them. Its difficult to take them apart without damaging the bearing cage, and IMO not worth it.

I’ll try to avoid another debate on the risks and rewards of doing certain kinds of maintenance for no particular reason other than an abundance of caution, but I’d be interested in hearing from people with rear bearing failures not at least plausibly attributable to an impact. We’ve never had a flange failure for any reason, and as far as I can recall never had a bearing failure not likely caused by an impact. That includes many seasons on the bearings that came in our first two donor cars with over 100k miles on them. I’m not saying they never fail on their own but if someone is having failures in anything less than at least a few seasons of racing, including some enduros, then I question whether they are being correctly installed.

And for the bearings, I question whether they fail quickly to a catastrophic level. If checked at each wheel change, there should be no problem spotting it early and swapping before the next event. In the later years we often carried spare complete hubs but never pulled one out of the trailer.

I do recall a race here at Gateway, probably around 2005 give or take, when someone was running around asking for either a bearing or complete hub, or maybe just the correct socket, because they needed to replace a rear before the next session. It’s sticks in my mind because it was the first and still only time anyone ever asked to borrow something for a rear bearing repair at the track. If I’m not very much mistaken, it was on Jim Drago’s car, though back then he would have been just “the other Jim”.

Maintenance interval: replace bearings at first of year, with a thorough inspection of the flange at both the portion inserted into the bearing and the areas around the lug studs in addition to a check of the upright itself in the suspension jigs.

 

During the season: check for play after every session/weekend and if play detected, R&R/maintenance process kicks off (see above).

Contact: check for play which will plausibly be present and thus require replacement. R&R/maintenance process kicks off (see above).

 

I always keep a pair of rear uprights with me at the track and don't monitor the hours on the bearings. With the bearing cost, the jigs, a 20t press, & a gear separator tool, swapping bearings isn't much of a hassle.

 

For our endurance Miata (NA6 on RE-71s), it's essentially the same but depending upon the track, one of the uprights will most likely require replacement absent contact (9 hour races).

I had a left rear hub fail (break off) at the flange inside the lugs last year.

 

Heading through Big Bend at Lime Rock (fast right turn) I was passed on the outside by an SM7 traveling at a high rate of speed. Car seemed to suddenly develop a bit of oversteer as well.

 

We had been running the alternate course, and coming back onto the old track at the top of the hill past West Bend, there was a hole where the pavement from the new section joined the old track surface. Of course, I hit it hard. That was only about 15 seconds before the failure. 

 

The upright looked fine to the eye, but Magnaflux dye revealed that it wasn't.  

 

So, I'd suggest that the hubs and uprights also get a very close look anytime you get off track and take a hard suspension hit on any corner. 

Maintenance interval: replace bearings at first of year, with a thorough inspection of the flange at both the portion inserted into the bearing and the areas around the lug studs in addition to a check of the upright itself in the suspension jigs.

 

Since it reads like you've done this a few times, How does the grease look and smell at your annual replacement?

 

I've never had a rear wheel bearing go bad on my Mazdas even with over 170k miles of street and years of track days so I would tend to think that they don't need regular replacement.  Every season seems a bit excessive unless regular monitoring proves otherwise so I'm curious if you or others have noticed anything that would truly warrant a certain replacement interval.

 

 

 

The upright looked fine to the eye, but Magnaflux dye revealed that it wasn't.  

 

So, I'd suggest that the hubs and uprights also get a very close look anytime you get off track and take a hard suspension hit on any corner. 

 

Can you describe this Magaflux Dye thing?  

 

 

Thanks

Since it reads like you've done this a few times, How does the grease look and smell at your annual replacement?

 

I've never had a rear wheel bearing go bad on my Mazdas even with over 170k miles of street and years of track days so I would tend to think that they don't need regular replacement.  Every season seems a bit excessive unless regular monitoring proves otherwise so I'm curious if you or others have noticed anything that would truly warrant a certain replacement interval.

 

 

 

 

Can you describe this Magaflux Dye thing?  

 

 

Thanks

 

I'm an IT person and it's been a good practice for me to have a known-good baseline to achieve success with anything which is why I start the year with this type of process. The rear bits are inclusive of an overall review of the major parts and whether they had been replaced during the year prior. In addition to the rear uprights/bearings/flanges, those other parts include front hubs (clean/inspect/regrease), lower ball joints and the upper boots (inspect for play or tears), replace all "lower suspension" hardware (adjustment bolts, rear outer long bolts), clean/lube sway bar bushings & end links, inner tie rod, ends & boots (inspect for straightness, play or tears), plus a full fluid swap (oil, trans, diff, brakes, blinker).

 

The odor from the grease has been consistent as has been the observed level of degradation (not measured or anything). The grease doesn't have the smooth consistency and overall coating property like it did when new. This would be expected for a 4-7 weekend race season of varied environmental characteristics (dry/wet, dusty, sandy...) I don't use the inner seal on the rear uprights so that is another reason why I do the replacement annually.

 

One caveat to the odor: when I removed the bearing from the bent upright, there was a distinct smell of burnt oil/metal due to the the heat generated in the bearing. It was not something I had smelled before at any point but it reminded me of how a hot engine with poorly maintained oil smells, like when you take off the valve cover for example.

 

Not to answer your question for the other commenter here, but magnaflux, I believe, is the "name brand" process of using a dye, magnetic particles, and an alternate light source (ultraviolet or otherwise) to identify cracks in steel/iron parts. My exposure to it was around the engine building process when you're building cast iron engines but it is usable across any industry where the integrity of iron/steel parts is a requirement (pipelines, ships...)

 

Here's the wiki entry for the generic term (magnetic particle inspection): https://en.wikipedia...icle_inspection

Edited by Brandon, 02-26-2020 12:30 PM.

Magnaflux dye is just a spray penetrant that is used to illuminate fractures in a piece. Essentially, you clean the piece being inspected, spray the penetrant, let it sit, clean off excess and apply a developer. Small cracks will be illuminated by the remaining dye. In cast pieces it can be a bit tricky, but still very useful. 

 

Here's a couple links to a videos on it. 

 

https://www.youtube....h?v=llHg1ZEctgU

 

https://www.youtube....h?v=a_FeCPWryvU

 

YouTube has several videos on it. 

All depends on how much risk you want to take. The bearings do fail. The hub flanges do fail. Beginning of the season we replace the studs, bearings and flanges. On that interval we have never seen a failure. 

All depends on how much risk you want to take. The bearings do fail. The hub flanges do fail. Beginning of the season we replace the studs, bearings and flanges. On that interval we have never seen a failure. 

wait until we start running 4.5 degrees with slotted arms this year

So Jim your saying that 4.5 camber will equate to more grip thus more part failures. So you are telling me that your current setup (much less than 4.5) is not making the most grip? your leaving grip on the table? Or does what you run make as much grip as possible? thus as hard as its going to get on parts. 

 

From what we have seen and tested if you get that high in camber you start losing a lot in grip. 

 

But if someones car is maxed out at 2.8 they are for sure not able to get max grip and are very happy to get a no cost change to fix that. 

I’m pretty sure Jim was just looking for another jab at the rule change, but either way we’ll never make the grip of a good production class Miata so I’d be interested to know their failure rates. I doubt that any amount of additional grip we might get from setup or tires is even relevant to rear bearing life expectancy. I’ve seen zero data and so far not even heard any anecdotal evidence to support frequent replacement.

Driver side of my car rear took a big hit against a tire wall and that caused looseness in the bearing.  I disassembled the hub and noticed how terrible the grease smelled.  Burnt and nasty.  This was a 'pro' (not ESR) rear hub assembly with special grease that I bought in 2013.  I took a few years off between then and now but it has been on the car since.  This made me wonder how often you guys are servicing, replacing, regreasing, whatever the rear wheel bearings.  

 

What maintenance do you do?

What intervals?

 

Thanks.

Back to you...if you think the slight play was caused by the impact...odds are your hub is compromised and your lower bolt is bent. When this happens just replace the whole upright and bolt. If your bolt is not bent...good chance hub didnt take that much of an impact. In that case press in a new bearing(the play indicates failure)and keep the upright and hub. But hub failures suck so better safe than sorry to replace that as well. A new bearing cost varies but average cost seems to be $35-$40 aftermarket. Never bother messing with grease on these...because of cost and ease to replace. I dont replace rear bearings unless they show the begging of failure...this could be 3 weekends or 3 years! But I always keep spare upright assemblies with me!

 

EDIT...if it wasn't clear, contact changes everything...at that point being conservative/pro-active is cheap insurance!

 

I'm with Steve on unnecessary parts changes for no reason!

I have had two flange failures One at Mid Ohio and one at Watkins Glenn,both on the left rear, Both scared the poop out of me. I have had 3 rear bearing failures. Since i have had these experiences i have become more proactive about doing the bearings one a year and replacing flanges after a decent direct hit to a rim and/or corner where there is suspension damage.

Since then i have had no more on track failures.

Frank, first thing you need to do is take the targets off your car so people will stop hitting you, then these other problems will fade away.

if you think the slight play was caused by the impact...odds are your hub is compromised and your lower bolt is bent. When this happens just replace the whole upright and bolt. If your bolt is not bent...good chance hub didnt take that much of an impact. In that case press in a new bearing(the play indicates failure)and keep the upright and hub. But hub failures suck so better safe than sorry to replace that as well. A new bearing cost varies but average cost seems to be $35-$40 aftermarket. Never bother messing with grease on these...because of cost and ease to replace. I dont replace rear bearings unless they show the begging of failure...this could be 3 weekends or 3 years! But I always keep spare upright assemblies with me!

 

EDIT...if it wasn't clear, contact changes everything...at that point being conservative/pro-active is cheap insurance!

 

I'm with Steve on unnecessary parts changes for no reason!

 

Yep, I wound up replacing that rear upright, long bolt and the rear upper control arm.  

 

The long bolt and the UCA were bent.  So was the rear subframe and the subframe brace.  The LCA on that corner was straight surprisingly.  I used Advanced Autosport's awesome Spec Miata Suspension Jig kit to check every suspension part on the car with my repairs since I was replacing both subframes and everything was apart.  

 

Interestingly, the rear upright was straight according to the jig.  So I pressed in a new bearing only to find that it didn't rotate smoothly.  Seems like the bearing retainer section or rear hub is no longer truly round.

 

I check for play in all corners regularly.  This corner had no play going into the weekend.  Nor did any other corners.

0 rear bearing failures in SM. Different car (Champcar with RE71’s) started with new Mazda bearings and got about 107 hours out of one that was totally shot. Other one seemed fine but when removed was also toast ( had play and smelled bad). The one that failed made lots of noise but had no play until removing the axle nut. We now change at about 80 hours. Neither wheel was ever hit.

Frank, first thing you need to do is take the targets off your car so people will stop hitting you, then these other problems will fade away.

+1000. I have been trying to do that for the last 10 yrs.

0 rear bearing failures in SM. Different car (Champcar with RE71’s) started with new Mazda bearings and got about 107 hours out of one that was totally shot. Other one seemed fine but when removed was also toast ( had play and smelled bad). The one that failed made lots of noise but had no play until removing the axle nut. We now change at about 80 hours. Neither wheel was ever hit.

Interesting, thanks! To what do you attribute the apparent difference between running SM and champ? Did you ever rack up 100+ hours on a set in SM? If yes, do you think the difference is that temps are climbing in champ and staying there for long stints damaging the grease? If so then it might well be solved by cleaning a new set and injecting a higher temp lubricant and/or adding cooling ducts.