Loose bearings
 

Need some help with wheel bearings on my 91 300E. Seems my front wheel bearings loosen within 1000 miles after adjustment. Someone explain to me what I am doing wrong or how to do right. I have repacked wheel bearings and replaced wheel bearings using the procedure in the manual. No matter if I repack or replace, seems the bearings loosen within 1000 miles or less. When I say loosen, I grab the at the top and push/pull vigorously. I can feel movement and hear 'clunk'. I purchased and used a metric dial indicator the last time and tightened to an indicated .02mm. Everything seemed fine for about 750 miles and when I re-checked, loose again. Talking with the local MB techs, seems i may not be tightening the bearings enough on the initial setting. The manual states to tighten bearings until they turn "with effort", loosen and then tighten to .02mm. The MB techs @ the dealership dont use the dial gauge and they say that they have no problems with come backs. Is this true or does every 124 out there have loose bearings?
Any help or suggestions would be appreciated. I have replaced all tie rods, drag link and rebuilt the idler arm. The front end is tight enough that the loose wheel bearings can be felt.:confused:

I concur with the MB techs. I don't use a dial indicator either, but the again you get the feel after several hundred times. I suggest you use the factory method for safety sake. There are two keys to remember. Don't over pack the hub with grease and tighten and back off the nut several times before you set the final preload. Tighten the nut down with about 45 ft lbs, spin the hub, back off the nut, re-tighten to about 45 again, spin the hub, back off the nut, and do this several times before setting the bearing to specs.

I've never used a dial gauge to check freeplay and I've changed and adjusted front wheel bearings on my 123, 124, and 126 models for over 20 years and I've never had a problem. It's kind of hard to describe how they should feel, but that said I tighten them real tight initially and try to turn hub to get them to seat. Then I loosen and tighten again. Go thru that process several times, then tighten till they are hard to move and then back off maybe 1/2 turn and then turn to tighten till you feel the adjusting nut starting to seat. Then put wheel on and spin it around a few times and then grab tire at top and bottom and feel for freeplay, to do this I remove brake pads. Keep in mind that I'm not a professional but this seem to have worked for me for a very long time.

Well, you do it just like a professional. As a professional, I can't recommend this method, but is how I do it.The only part I would say is not necessary is removing the brake pads, but if that is your comfort level, keep doing it.

I believe the only answer can be that the bearing races weren't seated properly. Ron is correct. When you put the nut back on, you're supposed to wrench it hard while turning the wheel (or rotor), until it is difficult to turn the wheel. This seats the races and squeezes the excess grease from the working contact surfaces so the clearance can't creep any further during use. Only then do you set the clearance.

Don't worry about damaging the races this way, they can take it.

I am glad you guys do it this way as well... tightening and backing off is the only way I have ever done wheel bearings.... I don't think I have ever replaced one

Hi
If they keep getting loose they might be too worn?
Regards, Bruno

If a bearing loosens up from wear, then that bearing has very serious problems and will destroy itself in short order. Anything less than the original honing marks on the race, and the bearing will go south rapidly. Bearings don't wear as you may think of other wear parts (journal bearings, seals, ball joints).

i am wondering
 

if it was run with the bearings loose the race might be worn between the race and the hub.

tom w

You're out of your freakin mind. You don't seat races by tightening the nut. You seat races by pressing or hammering them home with a race installer. Then you install the bearings and set the preload by the means that have been described earlier in this thread.

easy there
 

autozen

i bet he meant to seat the bearings against the race.

tom w

Actually, its unlikely that you can sufficiently accurately seat the races using either a press or a drift. Nothing will apply the pressure as evenly as the actual adjusting nut, when a few thousands of an inch clearance is the spec. It IS the races you are seating properly - the bearings do not need 'seating' between their mating parts, so the 45 ft-lb torque would accomplish nothing if this were the case.

Steve

Ok, Tom, I'll back off til I get an answer. I'm just concerned about seriously bad info about something as important as wheel bearings. I once saw a DIY tighten wheel bearings down to tight and go for a test drive. He ruined all the spindles and bearings, but what concerned me most was that he could have killed someone. We professionals take our job very seriously. I have always maintained a standard of sending out a car knowing that I have done my best to be sure nobody was ever stranded or at risk, because I was lax in my diagnoses. Anything less comes from a pseudo professional.:)

Where are you people coming from?

I disagree. The O.D. of the race is smaller than the hub. You must freeze the race if you want it to fit at room temperature. It will expand and effectively be clamped in place by the hub. When a mechanic "hammers" the race into place with a drift, he is attempting to overcome the interference fit between the race and the hub. There is quite a bit of force that secures this race and there is zero clearance between the OD of the race and the hub.

Tightening down on the adjusting nut won't move the race within the hub whatsoever.

The procedure of tightening the adjusting nut past the desired operational point is to ensure that the hub is fully seated against the inner bearing. If you simply brought the nut up against the face of the outer bearing, you could be misled by any clearance that existed between the rotor/hub and the inner bearing. Once all the clearance is definitely zero (or negative), then you can back the nut off and set it properly to the desired operational point (.0005" end play IIRC).

You could use a dual set of angular contact ball bearings like I do when I manufacture my spindles for balancing jet engines. The set costs $3000. But, you just clamp the outer races together and the two bearings load themselves up with the proper preload and the internal clearance is zero. The bearings run fantastic in this situation and they are eminently suitable for measuring unbalance that approaches .000010" displacement of C.G. Truly amazing. This could never be done with a tapered roller bearing that requires clearance to run safely.

I don't know the pitch of the spindle thread, but let's say for argument that the diameter is 1", and one revolution displaces the nut axially by 1/20". I.e., the nut displaces that 1/10" for every 3.14" of tangential displacement. At 45 ft-lb torque applied, the axial force will be 2826 lbs. In other words, you have just used a precision 1.5 ton mechanical press to seat the inner and outer bearing races into near perfect parallel planes while you spin the wheels.

If someone would like to measure the actual diameter and pitch, this could be refined.

Steve

Sounds to me like the out bearing were replaced but not the inners.

Rick Hall, did you replace both?

If you did the inners, how did you replace the inner races? If they are slightly crooked the bearings will beat themselves out of adjustment.

Haasman

Oops, problems with posting too close to sleepitime - forgot torque-to-force conversion, among others. Tangential force at 1/2" radius from 45 ft-lbs is 1080 lbs, then tangential-to-axial conversion factor of 62.8, and we actually have 34 tons of pressure. That will seat about anything.

Steve

Brian, you basically said the same thing I did but perhaps more eloquently.

To everyone alse on this thread:
My # of 45 lbs was an arbitrary #. That # has no meaning other than to tighten the nut a little which would be an arbitrary amount. I'm reminded of the time I bought about 4 cases of oil at one of those super stores. The sign on the end of the cash register conveyer belt said not to put heavy objects on belt. I piled all the oil on the belt. The cashier really cycled through. I told her that to me the cases of oil were not heavy. My point is that if I had tighten the nut to remove excess clearance, someone might have used a small pair of water pump pliers.

As an aside has anyone ever given any thought to how rugged wheel bearings are? A 3600 lb Mercedes is supported by four little surfaces that don't amount to much more area than a U.S. dime. In my opinion wheel bearings take every bit as much punishment as the reciprocating parts of the engine.

You're missing the point. You can't "seat" the outer race because it's already squeezed into the hub and stopped against the hub face. You could use 1000 tons and it's still going nowhere.

As far as seating the inner race, it lives on the spindle with a very slight clearance in most cases. So, seating it, axially, requires very little force. So, your desire is to simply take up the clearance between the rollers and the outer race and ensure that the bearing, with the inner race, is sitting on the axial stop within the hub. Adding more force, once the clearance is zero, won't accomplish anything. As your calculations show, you don't need much torque (5 ft.-lb. would be more than sufficient) to remove the clearance in the bearing.

You misunderstood me. You don't use the nut to mount races, only to seat them. I happen to be a bearing engineer and this is the terminology we use. I hope I didn't word it such that it can be misinterpreted. Mounting may not be enough to seat the races. And even if they weren't replaced it's always a good idea to take the extra step and make sure they're seated because of any micromovement that can unseat the races, which can happen for any number of reasons.

If the outer race is pressed into the hub and lives there with an interference fit, and if it is seated against the stop in the hub face, how will you cause it to move via adding torque to the nut??

Where, exactly, is it going to go??

Wow, this is gettin interestin. I'm beginning to believe we all know how to do it. We just can't splain it. The newbies must be really gettin confused.:D


Is there a tribologist in the house?

Well, here is where all I can offer is my experience. I have drift tapped in cold bearing races until they stop, carefully tapped the circumference to verify I can accomplish no further seating, packed and re-assembled all, torqued to the spec'd 12 ft-lb, then adjusted to finger tight. Everything seems and sounds and rotates flawlessly. In less than 100mi of driving, there is slop. Re-adjust, and all is hunky-dory forever. This would not be possible if the problem was a fit issue among mating bearing surfaces - it is a basic problem when pressing the inner race.

Now, you can decide I do sloppy work and this should never happen, but luckily for me, I know what I do and am satisfied that I do precision work within the limits of my tools at hand. I do NOT have or use a precision press to install the races. That, if available, should do a better job. Still, seating of the race will be incomplete due to flexing of the race and friction of the fit.

Steve

Well said, Steve. There's just something about metal and machined surfaces where you don't get things perfectly snug. I too ask myself where's it gonna go when it's mounted and bottomed out?.... but it still moves. Experienced machinists know this when they clamp parts on a fixture for machining, and they develop protocols for minimizing slop or movement during machining. I find it difficult to explain this phenomenon.

Not being an expert on this subject and one who has been thinking about replacing my bearings for all four wheels, my head is spinning. Makes me think twice about having this all done by my indy. What would be a fair cost to have all four wheels done, inner and out?

Firstly, do we agree that the inner race is a slip fit onto the spindle........so.........no pressing involved there??

Second, if the procedure that you have used to seat the outer race is not satisfactory, and, as you noted, the bearing actually seates the outer race in the first 100 miles of driving, how much do you believe the outer race can move? I'm going to take a stab at the number and say that it cannot be more than a movement of .0005".

And, when you find "slop" when you return and pull on the hub, how much is this slop? Would it be something around .001" or would it be considerably more than this? If you find .005" axial play in the bearing, I think you would have a very difficult time attempting to make a case that the outer race moved sufficiently to generate this level of play.

I'm not questioning the mounting procedure...........simply suggesting that there is another variable that you are unaware of. It cannot be the seating of the outer race.

450slcguy, why do you want to replace ALL bearings? Automotive wheel bearings usually aren't replaced until there is imminent failure. Though if you're looking to refresh an older car, I would agree or regreasing and replacing seals on all four corners.

Brian, MB specs the bearings at 0.01-0.02 mm axial play for proper installation, yet allows for 0.01-0.05 mm axial play as a check after use.

If I may take a stab at where this extra play comes from, it can be grease or grit that finds its way onto the mounting surface that hasn't been squeezed out or crushed down. Also, there are asperities on the surface that preclude a perfect mount. During use there is some flexing of the components and micromovement of the surfaces that act on these irregularities and increase play. Large amounts of it are called "fretting". This presents itself as polish with perhaps some brown discoloration on the mount surfaces. The brown is iron oxide products from the fretted surfaces.

I'm aware of the specs. I like to work in inches. The limit is .0008" axial play during a proper installation.

I agree with all of your statements regarding where the extra play comes from. All of those possibilites will give a variable on the order of .0005" or so. None of them can be of significance to the point where an axial play of .005" would be realized.

So, the question remains. If the axial play increased to approximately .005", where did it come from? It's not from flexing of the components, micromovement of the surfaces, or fretting.

Like Kestas, I have machining experience that has taught me to pay attention to the details of a procedure, and to try to understand when my experience does not match my expectations. When you press in the seat, you might expect that when it 'bottoms' that you have removed all play and slack. Many things can be undermining that. The seat may be contacting at just one point, there may be minute shavings or hard debris that have scraped into the gap, and certainly there will be rebound of the race when you release pressure or impact. This is just the nature of real systems.

As to my experience: I do a final adjust by backing off the nut until I can finger tighten it. Then I go slightly forward or back to the closest cotter pin alignment. When slop develops, you can easily tell by the difference in play shaking the raised wheel at 6 and 12. With my technique, I find the new cotter alignment will be usually one hole beyond previously.

I find actually driving around the block a few times will usually seat the race, followed by the readjust. But, 'over' torquing the hub nut on initial adjust may be as effective.

Steve

And, like I mentioned to Kestas, I ask you for a numerical figure that represents the amount of movement of that outer race caused by the fact that the seat only contacts at one point, hits minute shavings or hard debris, or has rebounded a specific amount after impact.

If this numerical figure is approximately .0005", then you don't have the data to support .005" axial play after the vehicle has been driven for 100 miles or so.

I design and manufacture spindles for jet engine balancing and it's nearly impossible to get an outer race to move .001" after it's frozen and installed. The retaining plate for the outer race has 18 socket head cap screws that are torqued to spec, thereby providing significant clamp load to the outer race. The errors due to the conditions mentioned by both you and Kestas are not significant.

First, this is getting kind of hairy, and anybody looking for simple wheel bearing maintenance advice should not have gone past the first page.

Brian, I agree that it's hard to develop 0.005" movement after properly mounting a bearing.... though this may mean little to large bearings.

Also, the bearings (and spindles, and other related components) you're working with in your industry are probably made of premium, hand-finished material, made with a fine Scothbrite finish, robust geometery, and no nicks and dings.

Automotive, on the otherhand, is mass-produced and quite different. There's lots of nicks and dings (outside the raceway). Surface finish is no better than it has to be (outside the raceway). Metrology often shows the races are not round (but within spec). The bearing metallurgy usually has high levels of retained austenite whereas in aerospace it's quite low, making it a "precision" bearing. High levels of retained austenite in bearings can transform during use, causing the components to warp.

I'm not surprised that your assemblies can behave within 0.001".

I've seen lots of lousy automotive bearing designs. If you take a look at some American (and Japanese) wheel hub, you'll see the races are mounted on the hub with one big rivet (actually called "orbital roll-forming"). This riveting action also sets the preload on the bearing and is not adjustable. There's not even a mounting nut on the spindle! I've seen them work loose at times and develop horrible axial play and failure. But the Big Three want these designs because they're cheap to manufacture and they're willing to deal with the warranty cost. I just hope MB doesn't buy into this design.

I agree completely.

However, take a close look at the cage and the races on the 20 year old bearings. For a mass produced item, I have to say that the surface finish is very close to 32...........a ground finish. Now, purchase the same bearing today and it's a completely different story. I've no doubt that you might find an outer race out of flat by .002" or so.

But, we still need to put a figure on this "problem" with regard to the outer race. Even if it's low quality and has a poor finish on the O.D. and faces, I would say that you would have a difficult time to get it to move more than .001" after it's installed. Remember, it's compressed and rounded up on it's OD by the very nature of its installation in the hub.

With regard to the inner race, it's free to move around slightly on the spindle (.0001-.0003" or so), therefore it doesn't take much force from the nut to allow it to seat in it's operating condition.

The entire discussion is probably over the top for the purposes of this thread, however, there needs to be some closure regarding whether loading the bearing races with the nut will allow them to "seat" closer to their "preferred" running condition and therefore not cause the axial clearance to increase.

I don't buy it for a minute. There has to be additional variables that cause the increase in axial play when the vehicle is driven for several miles.

Loose Bearings
 

Hey all! Seems I hit a soft spot with everybody!. This subject gets everyone going as well ass the topic of oil. I followed AutoZen's advice and tightened the bearings and released about six times per side. I replaced both inner and outer bearings, both sides and installed with race driver. I may not be a professional but I was properly trained in high school auto shop and also Uncle Sam's joy club. I think my problem was twofold. I was afraid to overtighten and therefore was not "seating" the bearing initially and i THINK i WAS ALSO too concerned with the dial gauge readout. After tightening and loosening bearings about six times before setting final adjustment, I have arrived at what feels to be a better adjustment. During this exercise, I can feel the bearing actually get "smoother" in its rolling. I am headed to Red Cloud Nebraska from dallas texas today so if I dont have it right I will be the black 300E on the side of the Kansas Turnpike somewhere. Autozen, did not get your reply, please try again. Thanks everyone for their input. maybe I will start another fracas and ask about oil or filters sometime. Thanks All!!

Hey guys I think it's time to call a truce, go get another beer, and move on. There is alot of talent posting on this thread, and the key strokes could be better used to help other folks with questions. It has been an exuberant thread. How do you guys feel about health insurance for those who can't afford it?:D

Seriously, my 30 years experience with wheel bearings has led me to the conclusion that they are tough and very forgiving. MB has a special tool to install bearing races, but for all practicallity everyone I know knocks out the old races with a drift punch and hammers the new one in until the sound changes and using the old race as an installation tool. You then pack the new bearings, tighten down a few times to seat the bearings and not the races, and adjust. Lock the adjuster, install the hub cap, and you are done. Don't put too much grease in the hub cap, because as it heats, it will pop the cap off. about 30 years ago an apprentice made that mistake at the dealership in the days when cars came with wheel covers. In the afternoon the customer returned with something clanking around in one of the wheel covers. This is a true story. I know, because I was that apprentice.:D

1989 560SEL

I'd like to ask a follow on question. My bearings make a slight clunk sound when the rotation stops. When I grab the rotor and go in a forward or backwards rotation at each stop or change in direction there is a clunk. Not a huge clunk, but a little one. I thought it might be the brake pads so I removed the calipar but the sound is still there. Is this normal? I don't think it is a ball joint because they were recently replaced and also because I'm not putting that much force on the spindle.

This sounds like the exact discussion that we are having.

If you take the rotor and pull it outward toward you and then force it back in toward the spindle, do you feel any movement or hear any "clunk". The word "clunk" is probably too strong. It's more like a very quiet "chink".

Any movement that you can feel or hear is too much movement. You can't feel or hear .0008". That's the spec.

I only hear the sound when it stops after rotation. Its quiet when I apply an in/out or twisting force. Both sides are the same.

You say the clunk sound is there with the caliper removed?... front wheel?... that is strange. Is the rotor removable from the hub, or is it one unit?

Grease can quiet noises. Can you feel any movement when you push/pull the hub toward you?

...........now that's weird........:confused:

I take 'weird' to mean that something is not right. I have two new bearing kits that I haven't gotten around to installing. I'll install them and look for damage/wear to the old set during the process. Thanks for the help.

No, I can't say that something is not right. I simply can't fathom what item on the vehicle will make a sound with tangential motion of the wheel, but not with axial or radial motion. That's why it's wierd.

i bet
 

the bearings are loose in the race. the little holes where the ends are captured are worn a little too much. i bet changing them will cure the problem.

tom w

Possible.

But, I have a difficult time believing that they "wore out". I wonder if they were manufactured this way?

Out of curiosity, what type of wrench do you guys use on these? I recently did my bearings, and the adjusting nut doesn't fit a hex socket, so it's hard to find a tool to get leverage to tighten the nut. The ends are rounded, which doesn't help.

The reason I'm asking is I think I didn't get one of my bearings cranked down enough.

More data
 

Wheel bearing
http://www.peachparts.com/shopforum/diesel-discussion/148772-wheel-bearing.html#post1125744

Noise Troubleshooting:



Have a great day.

I acyually just use a really large pair of water pump pliers.

visegrip
 

on mine

tom w