Bairs rebuilt rear spindles seem too stiff ???

[Joe R.]

I sent my trailing arms to Bairs for a complete rebuild, and they came back looking great. However, I was surprised that the spindles were rather hard to turn. I'd like to know whether this stiffness is normal.

If the spindle has been sitting for a while it requires moderate force to start turning it by hand (maybe a few foot-pounds). Once it starts turning the rotational resistance is reduced, but if it sits for a while it goes back to the high-resistance mode.

I decided to check the end play using a method similar to what is described in the service manual. I mounted a dial gage to the trailing arm using a magnetic base, with the gage indexed on the center flange of the spindle. Then I used a large screwdriver as a lever to put pressure on the spindle, first trying to force it outward axially, then inward axially (using alternate pry points on the inside and outside of the spindle bearing assembly).

The result was that there was no measurable end play at all, not even one mil. This concerns me because the factory spec is 1 to 7 mils, and I have read on this tech board that the bearings will fail prematurely if they are assembled with a preload.

I called Bairs to ask about what I had measured. They told me that the stiffness I feel in turning the spindle is due to the seals, not the bearings. They said they set up the bearings dry with 2 mils end play, then pack them with grease and assemble the spindles. It sounds like they do not perform a final check of the end play of the finished assembly. Their basic view was that my measurement procedure is probably not accurate and I shouldn't worry.

It just seems to me that there should be some measurable end play in the assembled spindle. The absence of measurable end play, combined with the relative stiffness in turning the spindle, has me concerned.

Does anyone on this board have experience or advice to offer? Am I worrying unnecessarily? I know that Bairs has a good reputation for this type of work, but I'm uneasy with what I am seeing.

[Michael H.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Joe,

While it is true that the seals will cause a resistance to rotation of the spindle, the fact that you have measured zero end movement is definitely not a good thing. It sounds like you have used enough force to move the spindle in and out to over come the normal seal resistance so I have to agree that the clearance is zero. Bearing failure is the result of such settings.

Also, if someone tells you that the clearance will be ok after a few hundred miles of running, it's not true. This style of tapered roller bearing absolutely must start life with at least the minimum .001 clearance.

[Joe L.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Joe-----

The measurement of end play is perfomed with no grease in the bearings. While it might seem that the addition of the grease should not affect the end play very much, in my experience it definitely does affect the MEASUREMENT of the end play. I don't know why it does, but it does. I don't think that the actual end play is changed much, though.

It is true that the bearing seals can also affect the rotational force required to turn the spindles. However, this was more a factor with the old style seals which used a flat rubber seal sandwiched between two steel surfaces. The more recent seals are a lip seal bonded to the shell of the seal. Some of these use no circumferential spring to increase the tension on the sealing surface; some use a spring. Those without the spring (usually CR seals are of this type) exert very little force on the rotational assembly and, consequently, the spindles turn much easier. Those with the spring (usually National brand are of this type) or the old style seals I described exert considerable resistance to rotational effort. So, it may be that Bair's uses the old style seals or the newer style with spring. Actually, I prefer these type seals.

It's hard to say if there is a problem with your spindles. However, from your description, I really don't think that there is. At "0" end-play the spindles require considerable rotational effort to rotate; at a pre-load they are, essentially, "locked up".

[Michael H.]

Re: Bairs rebuilt rear spindles seem too stiff ???

If the measurement was zero with just a light pull in and out on the spindle, I wouldn't be as concerned. However, Joe R mentioned that he "forced" the spindle in and out with a large bar and the results were zero end movement. That, to me, is absolutely not acceptable, grease or no grease.

[Rob A.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Joe,

Although I didn't check any of the tolerances on the assemblies Bair's rebuilt for my '67, I can tell you that I experienced no problems with them, and as you say, they have a reputation for doing quality work. I believe that if they thought from your description there was a problem, they would tell you.

[Harmon C.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Joe
Install them that is why you paid them to do the work and if they fail Bairs will fix them free. Set at .002 dry the grease will make them very tight after they set and the next time do the repair yourself as it only takes time and you can set the clearance to what you want.

Lyle

[Wayne W.]

Re: Bairs rebuilt rear spindles seem too stiff ???

I agree with Lyle and Joe, and the builder. I do a bunch of these in my shop and when you set them up dry you can easily feel the clearance. Just adding grease will cause you not to feel the clearance if it is set up on the low side. As Joe mentioned the seals have changed styles over the years. Actually I thought the originals were shaped and the new ones were straight, but no matter. Even the new straight seals are different. Most that I see now have a very thick rubber, unlike the old ones that were very thin. This causes a very tight feel and the fact that they are pinched, they will make checking clearances almost impossible.

[Michael H.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Wayne,

I agree that the addition of grease would reduce the end movement of the spindle when checked by hand but in this case, Joe R used a large screwdriver to pry the spindle in and out. As the spindle and bearings are rotated, there is a film of grease that will have some effect on rolling clearance but when the assy is checked statically, under pressure, the grease is displaced and has no effect on the clearance, especially when forcing the assy with a bar.

Using this pry bar method to attempt to move the spindle in and out, there couldn't possibly be enough resistance from the seals to have any effect on the clearance. They're just not a factor. They're only a factor if you are trying to feel the clearance by hand.

Also, grease is easily displaced when the load is as localized as it would be while there is no movement of the bearing. A round roller on a semi flat surface under pressure will not be affected by the lubricant. The localized load at the point of contact between the roller and race under force is hundreds of times higher than required to displace the lubricant at the exact point of contact.

Most Corvettes today never see serious road mileage so if spindle bearings are assembled in this "too tight" condition, it will most likely never cause any problems. I suppose a bearing set at zero, or even slightly preloaded, would last for years with the limited number of miles these cars see today. And anyone that has a bearing set to these dimensions will probably want to agree that it's ok to use this zero setting but if you're heading cross country, I'd be very concerned.

I want to guess that most professional builders use a dummy spindle to establish the initial clearance???? This is a used spindle that has been slightly turned down or polished in a lathe so the new bearings slip on/off easily. If that's the case, and I'll bet it is with most builders, thats where the missing .002" went. I "splain" later.

Rear spindle bearings are the same as front spindle bearings. If you set the clearance at zero, you can still spin the wheel freely. If you tighten the nut further, the wheel still spins freely. If you crank down on the nut, you can still spin the wheel with only very light resistance. So, the theory that a very slight preload (.000-) would lock up the assembly just isn't exactly correct.

GM spent a lot of money making sure I completely understood exactly how and why these clearances are used. I'd like to think they didn't waste their money and my time.

[Joe R.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Thanks to everyone for the well thought out responses. I really appreciate the good advice from others who have more experience in this area. The information on the seals helps me to feel better about the rotational resistance.

Regarding the end play, I can understand the arguments on both sides, but I am reluctant to reinstall these if there is *no* measurable end play. Eventually I plan to take this car on a minimum 500 mile segment of the Road Tour as part of qualifying for the Founders Award, and I do not want to experience a spindle bearing failure while I am far from home. The whole point of the present rebuild effort is to make this 40 year old car as reliable as possible, because I intend to drive it a lot.

This weekend I will repeat the measurements using an alternate setup, and hopefully I will be able to see at least one mil of end play. If I can't confirm any end play, I will talk to Bairs again about returning them to Bairs for evaluation.

[Joe L.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Michael------

Regardless of what you say, I stand by what I said initially. Furthermore, I'll bet that there are absolutely no problems with Joe's spindle set-up, at all.

REGARDLESS OF HOW LARGE OF A BAR JOE USED TO MOVE THE SPINDLE IN AND OUT, EVEN IF HE USED AN 8 FOOT LONG PRY BAR, IT'S VERY DIFFICULT TO ACCURATELY MEASURE THE END PLAY WITH GREASE IN THE BEARINGS. THIS IS ESPECIALLY TRUE IF THE BEARINGS ARE SET UP AT LOW CLEARANCE. PERIOD. I PERSONALLY HAVE SET REAR BEARING CLEARANCE IN THE .001-.002" RANGE WITH THE BEARINGS DRY. WITH THE BEARINGS PACKED AND INSTALLATION COMPLETE, IT IS DIFFICULT TO MEASURE ANY END-PLAY. I HAVE DONE THIS MANY, MANY TIMES. THERE WERE TIMES WHEN THIS OCCURRED I DISASSEMBLED THE UNIT FOR FEAR THAT I HAD IT WRONG. CLEANED ALL THE GREASE OUT OF THE BEARINGS AND RECHECKED END-PLAY. GUESS WHAT? I NOW HAD THE PREVIOUSLY SET .001-.002"! I WENT THROUGH THIS EXERCISE SEVERAL TIMES BEFORE I FINALLY BECAME CONVINCED THAT YOU CAN'T CHECK THE BEARING END-PLAY WITH GREASE IN THE BEARINGS. IF YOU HAVE A LOT OF CLEARANCE, THOUGH, YOU WILL BE ABLE TO MEASURE END PLAY WITH GREASE IN THE BEARINGS. IN LONG-IN SERVICE BEARINGS YOU CAN USUALLY MEASURE END PLAY WITH GREASE IN THE BEARINGS; IN A FRESH SET-UP, YOU CAN'T IF THE CLEARANCE WAS INITIALLY SET AT LOW RANGE.

The situation regarding the effect of the grease in the bearings that you have described above is the INTUITIVE and THEORETICAL. I would agree with that; it's what I once thought, too. However, it's NOT backed-up by the EMPIRICAL. In this case, the EMPIRICAL is all that matters. You've stated previously (with respect to original configuration of the cars) that what matters is the way it was actually done (i.e. EMPIRICAL evidence from known-original cars) is what matters, not the way it was supposed to have been done. So, you support empirical evidence in that case, but in this case you apparently feel that INTUITIVE and THEORETICAL is more powerful than the EMPIRICAL.

Also, I never said that setting the bearings at a "slight preload" would lock up the bearings. I said, essentially, that when you get to "0" preload, the bearings will turn with greater resistance and when you tighten beyond that point, they will, essentially, lock-up.

Furthermore, folks that perform this operation use a special tool for bearing set-up, not a turned down spindle. A turned down spindle could, of course, be used, but a special tool is manufactured for this operation and that's what most folks, particularly professionals, use. The special tool makes it easier to check the bearing set-up than using a turned down spindle.

Finally, no one, including myself, EVER said that the effect of the seals would affect measurement of bearing end play. I said that the effect of the seals may, varying with the seal type, affect rotational force required to turn the spindles. If you will note, that was ONE of the factors which Joe noted as being evidenciary in his assessment that the spindles were set-up improperly.

[Michael H.]

Re: Bairs rebuilt rear spindles seem too stiff ???

I totally disagree with just about everything you just posted but you do it your way, I'll do it my way.

[Tom Dooley]

Re: Bairs rebuilt rear spindles seem too stiff ???

Joe, I worked at Chrysler engineering in the final drive and axle laboratory in the 60's and 70's, then worked for Smokey Yunick for several years, and finally to Crane Cams as an engineer, so I think I have "some" knowledge on the subject. One of my specialties at Chrysler was bearings and the durability there of. In my opinion..... your wrong. I think Mike has it right.

Tapered roller bearings can only operate with zero clearance when they operate in oil, such as a differential pinion bearing. This type of tapered roller bearing, when used in a "grease only" application must have at least a few tho of clearance.

As far as the grease having any affect on the dial indicator reading, that's not likely if the bearing is stationary. You can do this test yourself by measuring the stacked height of a new ungreased bearing and race assembly, then measuring that same new bearing after you pack it with grease and rotate it at least a 1/4 turn back and forth. I doubt you will be able to find ANY difference.

Just the opinion of an old retired engineer. Tom.

[Joe L.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Tom-----

First of all, I never said that a tapered roller bearing could operate at "0" clearance in a wheel bearing application. Quite the contrary. I have previously advised folks that wheel bearings MUST have at least .001" end-clearance and that any pre-load is not acceptable. I've stated that position quite a few times; I'm 100% sold on it and believe it.

As far as your statement that the grease should not affect the measurement of end play, I agree with you that INTUITIVELY and in THEORY, it should not. I believed this for quite a few years until I proved myself wrong EMPIRICALLY. What I described in my previous response is EXACTLY what I observed. Namely, when I VERY CAREFULLY and PRECISELY set up the rear spindle bearing end clearance in the range of .001-.002" with the bearings dry, I could measure no clearance with the bearings packed. Furthermore, as I mentioned, on several occasions I disassembled the unit because, just as Joe R has observed and is concerned about, I found that there was no measurable end-play after final assembly (i.e. with the bearings greased). After removing the grease from the bearings and re-measuring the end play, I found that I, indeed, had the originally measured end-play of .001-.002". Even after having this happened once, I still could not believe that the grease would make a difference. So, on several other subsequent occasions I went through the same exercise until I got tired of all this needless disassembly and re-assembly and just accepted the fact that you can't get an accurate end-play measurement with the bearings greased. It may not make sense, but that's what I observed. And, I observed it repeatedly. As I mentioned, if one sets the bearing end-play at a higher range (say, .005-.008", which is higher, but within the acceptable range), then end-play can be measured with the bearings packed with grease (although I have not measured the full, pre-packed end-play setting). I spent quite a bit of time doing this "experimentally" for my own edification and interest. What I have reported is what I've found.

Furthermore, I have a friend who has been in the Corvette service business for over 30 years. He rebuilds trailing arms as one of his specialty items and does it for many other Corvettte shops in the area. He has probably done thousands of these assemblies over the 30 years of his involvement. Most of his units are for driven cars; not "low mileage" trailer queens. One time (before I discovered reality for myself), I noted that I could feel no end play in the assemblies he had in stock. I questioned him about it. He said that he often gets "complaints" from customers or other shops about this. However, he told me that it's because it's very hard to measure or feel end play in the units after the bearings are packed and with the low-range end play which he sets them at. I didn't completely believe him (although he's usually right about such things) but that's EXACTLY what I later found to be true on my own.

I do greatly appreciate your response in this issue, though. All input and information is welcomed here. However, I do have one question for which I would appreciate a straight and honest answer. I don't think that I've seen you post on the board previously. Perhaps you have, but I don't recall it. Maybe you've just been a frequent observer and infrequent poster. Howver, my question is: did you post in this matter "spontaneously" having read the thread OR did you post at the specific instigation and request of someone else? I'm just curious.

[Tom Dooley]

Re: Bairs rebuilt rear spindles seem too stiff ???

Joe, I've been here on the discussion board off and on for a few years now. I don't post often but I do follow the 63 and 64 information. I am the real thing and all of the things that I said about my history and experience are true. This can easily be verified. The last time I actually posted was I think during the discussions about fuel injection air cleaner paint gloss at least a year ago. I do know mike hanson and i do sometimes get information about our cars by email or phone but i haven't lately. My post was in defense of what was correct, not in defense of anyone.

Mike started to touch on the problem with the missing few thousandths but never finished the story. Heres what happens. When using an old spindle that has been turned down, a dimension can be established for the built spindle. but when that same set of bearings is pressed on the spindle that has not been machined down the inner bearing race expands a little bit. It doesnt expand much but when you multiply the amount by the angle of the bearing rollers, a little bit turns out to be quite a bit as much as the .002 that everyone is talking about. If youre good at math you can figure out how much this dimension shrinks when the bearing race expands. I don't know how to better explain it but thats how it happens. In engineering, we always added at least .002 or .003 to the check dimension if we werent using the actual press fit part. In other words, if you build it with a test shaft you should automatically add at least a few thousandths to your reading. I'll try to explain it better if this is to confusing.

You are correct on the fact that the seal doesn't have much to do with all of this.

If you have a bearing and race handy, try the test with the greased and non greased measurement. I think youll be surprised at what you find. Thanks for putting up with me. Tom...

[Wayne W.]

Re: Bairs rebuilt rear spindles seem too stiff ???

Ok, I understand that everyone has good points, what this should be and that should be, in theory or practice. But the fact is, that in practice with todays parts, you will not likely be able to detect much if any clearance, if the bearings are set up on the tight side. The reason is that the very thick rubber in todays seal get pinched in the installation process. It exerts so much pressure on the unit that it is not easy to tell whether it has clearance or not, and it will drag like the brakes are applied. I have even disassembled them and found the seal to be chewed up on the edges. I try to find the Chicago Rawhide brand that are shaped to fit. Joe, If you want to prove to yourself that it has some play, do this. Put the assembly in a press or a large vise and clamp the unit by the spindle. That is ,from the face of the hub to the nut on the end of the shaft. Leave the trailing arm hanging out in the air. Now pull up and down on the bushing end of the arm. You will feel the play, if it is there. After you install it, the drag will loosen up with time and you will feel the play in the wheel.