djessence

Folks,

It's been a bit since I've posted but I've been working away on doing some racing (currently working on a build thread). At the last race in 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.

Track is a counter clockwise track (largely left).
200 treadwear tires (sticky road legal)
Wheel adaptors for bolt pattern (spaces the wheel out ~1.5")
-40 Offset rims (brings the tire back close to stock spacing)
Bearing 1: Unknown Age
Bearing 2: Relatively new (1 season on them ~30 hours of hard driving)

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)? https://www.rx7club.com/1st-generati...xle-q-1021417/

That thread shows that the stock retaining plates are a bit weak but is this our issue?

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.

Jesse

t_g_farrell

iTrader: (1)

I've heard that it is common to have failures like this in racing rx7s. I think you have to do a few
mods to deal with it. Not sure what they are. You may want to try posting in the racing section
to see if anyone can shed some light on your situation.

bwaits on here may have some advice as well since he has been involved for a long time racing
various rotaries.

WJM ROTARIES

Standard rear axel bearings are useless on a race car , U need to replace them with wider and stronger ones and replace the retainer tin plates with some machined aluminium plates .I do this to all the race cars I build

DivinDriver

iTrader: (15)

Any chance that your rear-end lube had gotten contaminated, or was low, before the first failure which exposed both bearings to inadequate lube and high stress?

Lubrication breakdown would be one of the few factors common to both bearings on a solid rear.

djessence

There is a chance that we blew our seal first. As soon as we saw smoke, we slowed down and brought it into the pits to diagnose. So I guess there is the chance that the axle seal failed first, causing a loss in fluid and then as a result bearing failure I suppose.

Other than that, the fluid level is replaced and checked before every race. We run new amsoil synthetic gear oil for LSDs.

djessence

Do you have recommendations on brand/model number or specifics surrounding the bearings you use?

How does the wider bearing affect the use of the rear bearing spacer?


Are the spacers required with the re-speed axles? (I just can't recall exactly what hardware is on the axles right now).

djessence

On second thought, they are sealed bearings on the OUTSIDE of the axle seal and therefore would not use the diff fluid to lubricate is my understanding. Therefore this scenarion would not be the cause of our bearing issues.

DivinDriver

iTrader: (15)

[blush] You're right. My memory failed me. Apologies.

j_tso

iTrader: (2)

Are you running the bigger S3 axles?

Wouldn't hurt to check the alignment for bent arms or casing.

Carl

iTrader: (2)

I would say that most, if not all, ITA RX7's, ChumpCars, LeMons, Spec RX7's, Pro7's in the U.S. race with the stock rear wheel bearings. The design of the bearings is not your problem. I don't know what is, but it is not the basic design. No need to change to wider bearings.

Carl

WJM ROTARIES

The bearings I use are rw6206ccr on series 1 & 2 with 24 spline axels and 62207-2rs on series 3 with 26 spline axels.

I have photos of drawings for ser 1 & 2 bearing aluminium spacers I make for larger bearings Plus u need to make a replacement spacer of 2mm thickness to go on outside of bearing to replace the original one .

djessence

I am/was running 1 S3 axle and 1 Re-Speed/Moser axle (with the 4x110 pattern)

mustanghammer

iTrader: (3)

I raced an RX7 in SCCA IT for 7 years with the smaller bearing rear axles. I wore axle bearings out and the retaining collars would also get loose after time but nothing this catastrophic. I typically installed new axle bearings and seals every other year. We also tacked the bearing collars in place to help them stay in place. I also used ISC steel bearing retainers instead of the wimpy OE dust shields.

The only time I have seen bearings fail the way you describe was on a E Production car raced by a friend. His axle housing was bent. A good alignment shop should be able to tell you if your axle housing is straight or not.

WJM - that is a hell of a good idea. I will be looking into this!

LongDuck

So, I know you guys are talking race cars, but my street car has a clicking from the left rear bearing which I believe to be caused by a bearing 'falling out'. How that might happen, I'm unsure - but I can attest that you can hear the click increase with speed and it sounds like a ball bearing falls as it rounds the top.

I figure this can't be safe to drive, so I bought the new bearings and collars at Mazdatrix last night. Any tricks to installing those? Thanks,

j9fd3s

iTrader: (3)

you might wanna check the axle shaft for runout, other than that its very easy to do bearings. you do need a press though.

a bent axle causes the rotor to move side to side, which moves the caliper, and usually that makes some kind of noise.