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#31
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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. |
#32
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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.
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95 E320 Cabriolet, 159K |
#33
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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. |
#34
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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!!
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#35
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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?
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.
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Auto Zentral Ltd. |
#36
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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. |
#37
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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. |
#38
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#39
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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?
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95 E320 Cabriolet, 159K |
#40
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#41
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#42
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#43
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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
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC] ..I also have a 427 Cobra replica with an aluminum chassis. |
#44
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But, I have a difficult time believing that they "wore out". I wonder if they were manufactured this way? |
#45
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The reason I'm asking is I think I didn't get one of my bearings cranked down enough. |
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