Wheel bearings keep loosening
 

I'm having a strange problem. I swapped front hubs from an '85 380SE to my '83 300SD for the brand new brake rotors that were attached. I didn't mess with bearing, just slid the hub assy from one car and put it on the other. I tightened the bearings good then backed off to make sure they were tight. I adjusted bearings until the play was out and everything felt good. In a few days, I checked them and they needed tightening a full turn more to get the play out. A week later, both bearings again needed a full turn again to get them tight.
Has anyone ever heard of this? Are the hubs from a '85SE & '83 300SD the same? My research says they are.
I'm guessing the races in the hubs I put on wasn't seated all the way? I'm going to keep tightening them every week and hopefully they will finally tighten.

Hubs and Bearings
 

Twere me , The bearings would've been cleaned out and repacked...@ a minimum

Then using the tools pictured,set the proper play in the Hub/Bearing(s) fixture.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=5645

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=623

The screw (#35) locks the nut (#32) onto the axle shaft. (Capisce?)

They are not the same hubs. Not saying this is causing your problem but up to and including 84 on the SD is a non ABS hub. From 85' on is the ABS hub which the SE woulda had if I'm not mistaken.

Another thing to consider: If you used the outer roller cage from the SD instead of reusing the SE's you possibly no longer have matched (of the same make) races and roller cages as The Manual (see pic) appears to insist on.

To CI's helpful post I would add that only by the sheerest of coincidence could you ever get the bearing play right by feel. Get the tools CI told you to get. Use them and see how far off you are and let us know. Proper play is 0.01 - 0.02 mm which converts to 0.000393700787inches - 0.000787401575 inches. Readings on the tool are in 0.001" increments so letting the needle jiggle halfway between two lines when pulling on the hub gives you 0.0005" worth of play i.e. 0.0127 mm which should do it.

How do actually use the dial gauge? Is the following correct?

I've got the FSM and it looks like a magnetic base sticks to the hub.
Then you place the gauge on the edge of the spindle that protrudes from the locking nut.
The FSM says a "2 mm pre-load" which I take to mean you compress the indicator first so the resting position is actually spring-loaded so it can travel plus and minus.
You then wiggle the hub/rotor assembly, check indicator travel, then repeat after rotating the hub a few times.

It looks like you can do this with the caliper attached, but the pads removed, correct?
Do you measure un the same position each time, or take a few different spots, like 10, 2 and 4 o'clock?

Is the $20 /set Harbor Freight gauge set-up accurate enough? It almost looks like with this set up you'd need to adjust it to no play whatsoever, or only one-half of one increment on the dial?

I put off using the dial gauge test for bearing adjustment and was going to defer to a mechanic because the Northern Tools set was $130 and was too much for a limited use tool; but at $20 it's a different story.

Sounds to me that your bearings are not a match with the races. If the angles are not identical the bearing will loosen just that fast. The other thing to check is if the bearing races are fully seated into the hubs. I've seen replacement hubs where the bearing races are differnt and where they were not pressed in straight. As for special tools to set the bearing I've never used them. After 40 years of greasing bearing hubs I think I can handle it without.

Don't use reverse that much.

The bearings appeared to have a fresh packing so I didn't mess with them.
Yes, the SE had ABS but I didn't think the hubs would be any different.
I have been doing wheel bearings since 1985, it's not rocket science. It wouldn't matter if I used the micrometer gauge or not, it's still loosening a full turn every few days.
I might just switch the rotors and use the original hub before my wheel goes rolling past me on the interstate.
I had a bad vacuum booster so I switched out that, the master cyc, and all 4 brakes & rotors. Everything was the same except the SD has 3 brake lines coming from the master cyc. I had to remove a plug and everything was fine. What is that third line for anyway?

You put the mag base on the face of the rotor and the contact point of the indicator rests against the end of the spindle.

If you adjust it to 1/2 increment on the dial........it's perfect. In reality, anything between 1/2 increment and 1 increment will work just fine.

When you actually perform this task with the gauge, you'll be amazed that anyone could claim that they properly set the bearings "by feel" because they "have been doing it that way for 20 years".

I happened to have had the calipers off which I was also replacing but I don't think that even the reduced play as a result of the tightness of even fresh pads would arrest play of hub at spindle.

Retest, retest, retest before and after tightening hexagon socket screw of tightening clamp. Don't mistake needle movement caused by hard to restrain turning of hub with back and forth movement along axle of spindle which is what you do want to measure. Retest.

No matter how inaccurate the HF gauge, it WILL be more accurate than doing it by the mythical "feel". 1/2 to 3/4 increment gives you a range of 0.0127 mm to 0.01905 mm which corresponds close enough to the prescribed 0.01mm -0.02mm I hope you agree. Retest.

Did I mention retest? If not, retest.

Not claiming it makes a difference but The Manual both states "Place tester (15) on front wheel hub" and shows photo of such placement.

Disclaimers: I don't have any dial gauge, but I may get one. I have had a rear wheel come off at speed due to a failed bearing (VW Jetta, a long time ago). I didn't do the repair then, but the experience gives me an appreciation for doing it right. That's one reason my car is mostly sitting in my garage until I can get the bearings and alignment done correctly.

I would disagree that 1/2 to 3/4 increment is "close enough" though if you're going to recommend a tool. I'll agree that the $10 HF gauge is probably better than doing it purely by feel, but if you adjust to 1/2 of the smallest increment you are still out of tolerance. 0.0127 of travel lets the bearing move from 0.01 to 0.0227, 3/4 of one tick is 0.01 to 0.03. And this is talking about fractions of the smallest possible movement.

The least precise standard spec for a non-metric gauge that you can use seems to be around 0.0002 inches, although a 0.0005 inch probably does get to the "close enough" limit. That one at least lets you use 90% of the smallest possible increment.

And since they seem to be available for less than $25 on e-bay, maybe I'll get one.

http://cgi.ebay.com/BRAND-NEW-PRECISION-DIAL-TEST-INDICATOR-GAUGE-GAGE-C92_W0QQitemZ380154536867QQcategoryZ58239QQcmdZViewItemQQ_trksidZp3907.m263QQ_trkparmsZalgo%3DSIC%26 itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D12%26po%3DLVI%26ps%3D54

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260378828974

The hubs for the ABS and non-ABS are different within the 123 series, probably true for yours as well. The hubs coming loose might be more a correct parts issue than a tightening-technique issue.

That's sort of like falling 13 stories after jumping off a 10 story building. How does it get to 0.01 if there was no movement prior to that?

Instead of worrying about the accuracy of dial indicators, perhaps you should focus on the accuracy of your computations. Measurements should be from 0.00, not 0.01, which places a 3/4 increment deflection on a 0.001" indicator slightly below the maximum limit.

Adding to the above I have owned my own Vehicles since 1969 and have always adjusted my Wheel bearings by the "Feel Method".

When I used the Feel Method on the Mercedes the result was I over heated the hub to the point were I had to remove everthing and clean out replace the Roasted Grease.

After that I had to take the time and search through my stuff to find my Dial Indicator and Magnetic Base; that I was too lazy to look for the 1sr time.

Since I did it the correct way I so far have had about 1-1/2 year of driving with no problems.

All I can say is that because I did not do the job right the first time I ended up doing the job 2 times.

If you insist on using the Feel Method at least drive your car a few Blocks and get out and put your hand carefully on the Wheel to see if it is getting too hot.

First things first: Mixing used bearings into a hub with a used race is a sure formula for failure. I wouldn't even worry about the tightening method until you start with a matched set. New ones are not that much considering the risk you are taking!