Axle bearings

[Hib Halverson]

Just for the record, the original '63 design used slip fits for both the inner and outer bearings, and the drive flange nut was torqued to 50 ft-lbs.

As a result of a spindle failure at the Proving Grounds (which resulted in the wheel, brake drum, and part of the spindle coming off the car), the design was changed, and went into effect at Chevrolet-Warren between November 2 - November 19, 1962. The spindle was revised to provide a press fit for the inner race of the outer bearing, and a chamfer was added at the shoulder of the bearing seat area of the spindle to provide for tool (bearing separator) access.

The diameter at the inboard end of the spindle was revised to provide a .0005" loose to .0005" tight fit for the inner race of the inner bearing, and the thickness of the washer under the spindle nut was increased from .140" to .210"; the drive flange nut torque was increased from 50 to 100 ft-lbs.

The above indicates the change was made as a way to prevent drum brake cars from loosing wheels after an axle breaks, not as a solution to "spun" inner races.

But then, this....

Courtesy of JohnH, Mike McKown and Mike Hanson, here are pages 1 and 2 of the TSB issued by GM on this subject. Note that they do mention the occurrence of the races rotating (spinning) on the spindle which I believe is the primary fault. Mike Hanson further explained the mechanics of why a slip fit inner race can be used successfully on a fixed spindle (like a front wheel) but is not the best strategy in an installation where the spindle rotates. Similarly, this explains why a slip fit outer race would be disastrous for a fixed spindle. Neat stuff.

...indicates the change was made to address "spun" bearings.

Nothing like confusing the issue, eh?

I think I'm going to stick with my slip-fitted bearings and spindle nut torqued to 100 ft/lbs plus whatever additional torque is needed to get the cotter pin hole to line up. It's worked for 20 years...(knock, knock, knock)...so I'll stick with it.

The second post cited above refers to a "Mike Hanson" further explaining the mechanics of slip fits in different applications. Can you post this discussion?

Once again, this has been an interesting exchange of ideas...just what the CAC should do.

 

[Vettehead Mikey]

...indicates the change was made to address "spun" bearings.

Nothing like confusing the issue, eh?


The second post cited above refers to a "Mike Hanson" further explaining the mechanics of slip fits in different applications. Can you post this discussion?

I'm not the one that's confused. If we accept that the primary issue was spinning races which resulted in wheel liberation due to axle fracture then all make sense. On the other hand, you've proposed that defects within the bearings themselves initiated the failures essentially leading to the same end result.

Note that there was no change to the bearings via this TSB, only the spindle. If there was an ongoing issue with the bearings, the failure would still be present but without the wheel liberation events. This does not seem to be the case.

As to the point about wheel retention being the primary motivation for engineering revision, providing a tight fit on the outboard bearing race won't achieve anything in this reagrd. If the spindle fractures anywhere inside the bearing cavity- ie 'outboard' of the 'inboard' bearing assembly then the wheel is gone walkabouts nonetheless.

The Mike Hanson I mentioned is a well known enthusiast, racer, collector and restorer and has been in the hobby far longer than most. He's mentioned here

Corvette Action Center | Model Center | C3 | 1981 Corvette Center | 1981 Last Saint Louis Corvette

for being one of the guys that tracked the very last St. Louis car go down the assembly line. He's also regarded as being a real go to guy for '63-'64 stuff. His recent efforts to update the NCRS manuals are legendary in many ways.

In any case, he makes the point that a fixed spindle can tolerate a slip fit bearing as the race is always loaded radially in the same direction (a non-varying load path) whereas the direction of load constantly changes with a rotating spindle. Any radial clearance will allow the race to move axially by the same amount, with ensuing friction and wear until the axial preload from the spindle is lost and a spun race becomes a possibility. Mike's terminology was the that the races tends 'to walk around the spindle' as the wheel revolves.

The same would occur on front wheels if the outer bearing races were a slip fit in the hubs.

 

[Hib Halverson]

You present a good, "anti-slip-fit" case.

As for my experience and observations in re: my 71, the reason I'm not seeing inner races rotating on the spindles must be the 100 lbs/ft torque of the spindle nut.

 

[Rod75]

As I've read almost countless threads on this subject over the years, this has been one of the more interesting ones. I file the slip fit in the personal preference slot.
I guess what ever you can live with that gives you peace of mind.
But damn Hib, I just couldn’t go 10-20 years without an inspection. It would drive me nuts! (worse than I already am, that is…) Especially if I made the change to slip fit to start with.

Quote: “Here's a little anecdote which underlines the importance of preventive maintenance.”
I like to add that I don't promote that gizmo that claims to lube your rear bearings without disassembly. Do it right, disassemble, clean and inspect.

Fact is, I’m more concerned with the quality of bearings and seals these days than I am with anything. The last seals I purchased were (what I call) the flat washer style lip. After some review on the bench, they were exchanged for the orig factory style.
The parts vendors I deal with are selling the bearings separate from the races these days. WTH is with this? When did they start piece-mealing this stuff out? Another profit margin idea?

And Hib, with the aluminum T-arms: I would first like to see some testing done. Take them to the point of destruction in multiple scenarios, then I’ll give ‘em a consideration.
I can only imagine them coming from China, with that wonderful quality and craftsmanship we see in their products!

 

[VetteV8]

The application of the front and the rear wheel bearings is not the same and hence should not be seen as equal loading; as has already been pointed out, the front axle has a stationairy spindle, and the rear has a rotating spindle.
That is the single most important observation.

There is a simple and easy rule of thumb, rearding bearingring interference fit vs. slip fit: the rotating bearing ring must have 'some' [depending on the design] interference fit, and the staionairy ring may have a slip fit.

It is actually quite logical: the staionairy bearing ring does not move, but a rotating bearingring, if not an interference fit, will "roll" and could relatively quickly roll and rotate on/into the mating part. A perfect 'rolling mill'.

Hence on a front axle the innerring can be slipfit, and on the Corvette rear axle, the innerring must have an interference fit.

There is another solution, if someone would insist on a slipfit on the inner rings, and that is to "glue" them in place. Lock-tite has a special adhesive just for this purpose, and in my experience has worked and held for many years in heavy industrial axles.
Then, when time for disassembly comes, gently warm the parts to about 170 degr C, and off they come.

Cor

 

[GTR1999]

just getting back to this, interesting reading. I'll stick with my procedures as mentioned.

Aluminum arms? well they could be something but based on the history of the stock arms and some of the offsets I wonder how well they would sell. A new USA powder coated bare arm with bushings and cups installed is $150-$180 each not a bad deal and they're pretty good- as good as originals if not better. Now the new imported arms I've seen are not the same quality and I won't use them.

Bearings and seals. Well I use only the USA Timken, buy them from a non automotive supplier and they come individually boxed, they are not a matched set of bearings as many may think. The seals I use are CR/SKF USA made and I feel they're the best out there. I won't use the flat edge seals I see and have been shipped. National makes some of those now, probably others too. For the few bucks more the Timken and CR's cost the better served. I suppose if someone is building loads of arms to sell on auction sites the cheaper the parts used the lower the sale price offered is and still make a profit margin. But that's for another thread!

 

[SVO]

The parts vendors I deal with are selling the bearings separate from the races these days. WTH is with this? When did they start piece-mealing this stuff out? Another profit margin idea?

Not to go off topic. Ever buy a new set of front rotors and they have the bearing races already pressed in but no new bearings? (NAPA rotors). I always thought that bearings and races were matched sets. I also have my doubts about using used front bearings on new races supplied with the rotors. I won't start on wheel bearings with plastic cages.

 

[Rod75]

Not to go off topic. Ever buy a new set of front rotors and they have the bearing races already pressed in but no new bearings? (NAPA rotors). I always thought that bearings and races were matched sets. I also have my doubts about using used front bearings on new races supplied with the rotors. I won't start on wheel bearings with plastic cages.

Never received the bearing races in hubs yet. And like you, I also thought that the bearings and races were matched. It's just an assumption after receiving them together as a unit for decades.
Could have been somehow tolerance matched prior to the CNC days?

I'd only heard of plastic bearing cages.....OMG!
haven't seen any in use. If the parts guys ever serve me any...ad

 

[Hib Halverson]

Again...this has been an interesting exchange of ideas. On the slip vs press, issue, clearly, there are pitfalls of going that route.

If I had it to do over, would I go the same way?

I dunno...maybe it would have been better, in the interest of easier maintenance, to reduce the press fit by "half", ie: from .0005 to .0002 or so, rather than going "full-slip". In any event, the 100 ft/lbs of torque on the spindle nuts seems to be saving me from "disaster".

I pulled the left side apart today and, again, there is no evidence that the races are spinning on the spindles. What I found was the axleshaft seals were in worse shape than the ones on the right. In fact, I think I was right at the end of the seals' service lives. The seals on the car were hated, flat-edge design. While some here don't like them, they lasted 20 years and 40,000 or so miles which isn't too bad.

The Red Line CV-2 grease was in good condition, but there was evidence of more contamination present then I found on the right side which would be expected considering the condition of the seals.

The outer bearing races looked good. Both had a near-mirror finish. One had a very tiny groove in it, probably from a tiny piece of contamination. The axles showed no signs of rotating races. Once the bearings themselves were cleaned off, the rollers looked to be in great shape.

(snip)And Hib, with the aluminum T-arms: I would first like to see some testing done. Take them to the point of destruction in multiple scenarios, then I’ll give ‘em a consideration.
I can only imagine them coming from China, with that wonderful quality and craftsmanship we see in their products!

They would be made in San Bernardino, California

(snip)

Aluminum arms? well they could be something but based on the history of the stock arms and some of the offsets I wonder how well they would sell. A new USA powder coated bare arm with bushings and cups installed is $150-$180 each not a bad deal and they're pretty good- as good as originals if not better. Now the new imported arms I've seen are not the same quality and I won't use them.

An aluminum T-arm would, obviously, be a high-end product aimed at discriminating C2/C3 owners looking for less unsprung weight and a way to use wider wheels.

I already have aftermarket arms on my car but they are steel. While they are much stronger than an OE arm–even a continuously welded OE arm–and they accept wider wheels, they are heavy. I've been trying to convince the vendor who makes them to do one in aluminum.

 

[Vettehead Mikey]

If I had it to do over, would I go the same way?

I dunno...maybe it would have been better, in the interest of easier maintenance, to reduce the press fit by "half", ie: from .0005 to .0002 or so, rather than going "full-slip". In any event, the 100 ft/lbs of torque on the spindle nuts seems to be saving me from "disaster".

Good point. In reading the GM TSB again there were three simultaneous changes

1) tight fit bearings
2) increased assembly torque
3) thicker washer under the spindle nut

possibly the three together could be viewed as a belt and suspenders approach with any one or two of the improvements being sufficient. Guess we'll never know.

 

[Hib Halverson]

I'm gonna guess that the thicker washer was specified because they found, when the first-design washer was deflecting under double the torque for which it was designed.

I agree with your opinion about the "belt/suspenders" approach.