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83 GSL Rear Bearing Failure - Endurance Racing

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83 GSL Rear Bearing Failure - Endurance Racing

Old 09-12-14, 10:55 AM
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83 GSL Rear Bearing Failure - Endurance Racing

Hey Folks,

First post in the race tech side. Normally I just post in the 1st gen.

Car Background:
83ish GSL (for all intents and purposes: has GSL drivetrain)
Stripped and caged
1.5" Wheel spacers
-40mm offset wheels (brings them back to around stock)
OD of tires is 0.5" less than stock ( lowpros on 16" rims)
Sticky by road legal tires (200 treadwear)
Stock rear suspension

We were at the Chumpcar race at the Ridge near Seattle just a few weeks ago, we experienced rear wheel bearing failure which is something I couldn't find a great deal about on the forum.

When I say failure, I mean the outer race became twisted off the inner race and we lost all of our ball bearings from the bearing. What became even MORE peculiar, is we did an axle change mid race, sent the car back out and the other side failed within 40 minutes. We are now trying to figure out what the root cause of our issue as when you read the list below, you will find there are a number of areas that could contribute. Right side bearing failed first, left side second. Track is a counter clockwise track (largely left).

Bearing 1: Unknown Age
Bearing 2: Relatively new (1 season on them ~30 hours of hard driving)
Both "stock" bearings

Basically I am starting to wonder where to look. One factor is the wheel spacers, obviously it is not ideal and does add a bit longer of a moment arm which will magnify the forces a bit higher than if we did not have them.

Another possibility is, is our rear end bent/out of alignment? Are there easy ways to check? If the rear end was misaligned, is bearing failure where you would see it?

Could it be we are getting too much side play in axle retaining plates and that is causing the outer race to flex and as a result fail (it was a hot day, we were pushing HARD)? Rear axle Q

That thread shows that the stock retaining plates are a bit weak but is this our issue? Could it be that side forces on the axle are twisting it out of the outer race and thats what is causing a failure mode?

Any pointers on where to start looking would be appreciated. As I said, I didnt see much except for your typical "my bearing is worn out and making noise" vs we had dual bearing failure within 40 minutes of each other of different aged bearings.

Let me know if I am missing any important info.

Jesse
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Old 09-12-14, 12:30 PM
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I eat rear wheel bearings, I believe due to bent housings. I reinforce them and they still bend...

The spacers will not matter as long as the track is roughly the same. All the same, you are using the small axles, not the large ones, and this makes things a little more whippy. Just because the tires are "200 treadwear" doesn't mean much, since the number is something that is kinda made up and does not correlate (much) to how much grip the tire has anyway. Modern rubber is grippier than what was available in 1983, and also bear in mind that even then, Mazda saw fit to increase the size of axles and bearings in 1984.

When Mazda went racing, they used full-floating rearends, which solves the problem. Not an option for racing under a strict budget. For your situation, I'd install new bearings and "life" them to 24 hours' use.
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Old 09-12-14, 12:54 PM
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My bet would be a bent housing, most likely at the flange ends or somehow cambered/toed housing. The 1.5" spacers will most likely not help that either. Could also be a bent caliper bracket (not sure if the 83GSL is drums or disc in the back). However if it is both sides, you are most likely have a bent housing.
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Old 09-12-14, 01:48 PM
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Thanks guys.

Is there an easy way to check for a bent housing as theres a bunch of different ways it could be bent?

Could bent links causing a misalignment of the housing also cause this? Wouldnt it be more likely to bend the links than it would be to bend the housing itself?
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Old 09-12-14, 04:58 PM
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Links have zero to do with it.

Checking for a bent housing is easy, what's the rearend alignment?

I'd be more inclined to believe, given the nature of the failure, that the axle itself is flexing and putting a cockeyed load on the bearing, which because the axle is turning at 500-1000rpm is going to put a lot of side to side cycles on the inner race and the *****.
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Old 09-12-14, 07:13 PM
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Originally Posted by peejay View Post
I'd install new bearings and "life" them to 24 hours' use.
with the honda we need to buy new wheel bearings, take them apart, and repack them with synthetic grease to even get them to go 25 hours.

actually they will go 25 hours, but if you have any kind of wheel to wheel contact they will die.

here is Mario holding the wheel bearing with 30 hours on it...

and you should be glad you're running an Rx7, because just about every part of the honda needs to be replaced at 25 hours, ALL the bearings, tie rods, engine (actually its limping after 18), trans, axles.

shoot the body is only good for about 48 hours before it starts tearing, and popping spot welds, its not built like a Mazda
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Old 09-12-14, 07:34 PM
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I recall one team who were running a Grand Am in Lemons. The last bodystyle where the tie rod ends were on top, a legacy of being descended from the Opel Kadett. (Which was sold here in direct-from-Daewoo form as the Pontiac LeMans, but I digress...)

They had swapped to the "American N" chassis knuckles, which gave much beefier wheel bearings, but they would still life out the wheel bearings every eight hours. They would just unbolt the whole knuckle and swap in a replacement, take maybe five minutes.

From what I have seen of WRC servicing, they replace the struts/uprights/axles at EVERY service. The wheel bearings on those are huge... maybe 4" wide, and so large in diameter that the CV joint is actually inside it...

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Old 09-13-14, 09:59 AM
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people replace all kinds of stuff in a 25 hour race, its pretty amazing. we even pulled the frame straight with two trucks and a tie down straps one year.

here is the after of our 2007 car, the cardboard and duct tape are functional, and please notice the hole in the windshield there was some shackle that bounced off the track, it went through the windshield and dented the floor...

oh yeah, it set its fastest lap like this

EDIT, the really funny part is for the 06-07 season we had two cars, and the other had this delrin splitter that was really low, and they screwed up the shake and bake and hit each other. when we tore down the silver car we found that the splitter had actually sliced most of the way through the B pillar, the INNER section. so keep in mind your splitters and tow hooks are very very dangerous
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Old 09-13-14, 10:47 AM
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Originally Posted by djessence View Post
Any pointers...

Jesse
here are three:

for a short (1-5 hour) race, you don't have time to pit and change anything without being last, so fresh bearings, lifed at whatever hours, 30 is good, and just run.

for the longer racers you want to do one of the two following

1. build a complete backup rear end. from disc to disc, minus the hydraulic part of the calipers (you should have spares of these, but not plan on changing them). plan on changing the rear about half way through the race. you should practice this once or twice, and the rear should be setup to swap the fastest (which links stay on the car). when you do this swap, you should swap the fronts too, add 4 tires and a new driver and you have a fresh car for the second half of the race.

3. have a complete backup rear end, with new(ish) parts, but only use it for parts as needed. imo i'd rather plan on swapping the whole diff as an assembly than having to swap just an axle and dealing with hot gear oil and stuff.
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Old 09-13-14, 10:59 AM
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It's pretty easy to redo the brake lines so you unbolt the calipers from the rearend, hang them up, cut some zipties and leave the hydraulics on the car.

In a racing environment like this, swap whole assemblies. You can repair the failed assembly at your liesure while the car is back out. Gives the service crew something to do between pit-ins - proper time management is in minimizing downtime by maximizing unallocated uptime. Although an axle swap is simple enough that I'd rather swap axles than entire rearends. Two bolts and the caliper is off, three nuts and the axle is out, and if your housing is bent then the bore is usually wallowed out so you can just get the axle out by hand, no slide hammer needed...
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Old 10-19-14, 09:46 AM
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Originally Posted by peejay View Post
Although an axle swap is simple enough that I'd rather swap axles than entire rearends. Two bolts and the caliper is off, three nuts and the axle is out, and if your housing is bent then the bore is usually wallowed out so you can just get the axle out by hand, no slide hammer needed...
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