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  #1  
Old 11-08-2003, 09:01 PM
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wheel bearing question?

Is it OK if i use a procedure out of this old car book i have, it says to tighten the wheel bearing nut with a pair of slip-jaw pliersuntil either the brake disk will be hard to turn, or until the plier jaws open, back off nut until it is free, and then fingertighten it. Will this work on a MB?
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  #2  
Old 11-08-2003, 09:20 PM
JetForeman
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Your method sounds suitable but I copied this for you for specific instructions just in case your bored and want to check end-play!!

1. Release internal bolt of clamping nut, and tighten clamping nut while simultaneously turning the hub until hub can only just be turned. Loosen clamping nut approximately 1/3 turn and relieve tension by striking stub axle with a plastic mallet.

2. Position a suitable dial indicator onto front hub assembly.

3. Check endplay by pulling and pushing on the flange. Turn wheel hub several times before each measurement. End-play obtained should be 0.00039-0.00078 inch (0.01-0.02mm).
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  #3  
Old 11-08-2003, 09:24 PM
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If i had a dial gauge, i would do that, too bad Grainger wants $100-300 for one, since they are the only place locally that has one.
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  #4  
Old 11-08-2003, 09:36 PM
JetForeman
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Good for you because if I had a dial gauge I probably wouldn't bother with it
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  #5  
Old 11-08-2003, 10:46 PM
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You can skip the pliers. You can spin the nut by hand tight enough to keep the wheel from turning.

What I do set it for the smallest perceptible play. After 4 or 5 tries I figure it's good enough.

Harbor Freight has dial gauges for under $20. I don't know how much for the clamps. There's a Harbor Freight store in Vallejo (5201 SONOMA BLVD #7 707-645-0185). http://www.harborfreight.com .

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  #6  
Old 11-08-2003, 11:36 PM
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The dial gauge magnetic clamps to the wheel mounting surface and the gauge itself reads off the axle stub.

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  #7  
Old 11-09-2003, 12:01 AM
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The setup needs to be clamped to the disc hub and the indicator needs to read off the spindle end in the axial direction. I was fortunate to borrow a good dial and magnetic base when I set mine. The spec of 0.01 to 0.02 mm is rather difficult to do by feel. I couldn't feel any play when it was set correctly.

Edit: Why is this post out of sync? It should come right after the third nthach post.
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  #8  
Old 11-09-2003, 12:09 AM
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http://www.pindelski.com/cars/W126/W126_brake_job/imagepages/PIC00053.html

so in a way, like this?
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  #9  
Old 11-09-2003, 12:29 AM
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so the dial indicator needs to be setup on the wheel bearing thrust washer or the disc carrier?
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  #10  
Old 11-09-2003, 01:42 AM
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This is the way I set mine up

Agree with Kestas......no play felt when at spec
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wheel bearing question?-wheel-bearing-endplay.jpg  
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  #11  
Old 11-09-2003, 02:55 AM
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I'm suprised that the hub would be true enough to read .00039 you'r talking jet engine tolerances.I don't think a Harbor frieght dial indicator is up to that ,I would rely on feel if I didn't have a machine shop quality tool..........
William Rogers........
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  #12  
Old 11-09-2003, 03:09 AM
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Looks like that rig could have .01mm of play in it.

One of my previous cars had a torque spec for the front wheel bearings. The manufacturer shop manual had you wrapped a cable around the lug bolts and measured resistance on a spring scale. I don't know if it was accurate but it was fun

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  #13  
Old 11-09-2003, 01:12 PM
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I've always wondered about the .01-.02mm spec. The spec for my '63 Corvette and '76 Cosworth Vega is .001-.005" based on a 20 thread per inch spindle, a six point castle nut, and two pependicular cotter pin holes, which varies the clearance about .004" with each twelveth turn of the spindle nut. The front wheel bearing setups are basically the same, but the Mercedes allows you to achieve an exact clearance with the pinch nut.

On my vintage GM cars I've found that shaving the washer to achieve clearance in the range of .001-.002" makes the steering feel more precice.

These tapered roller bearing designs must operate with slight clearance or they will fail, but Mercedes spec of .00039-.00078" seems to be cutting it too fine. Could it be that the .01-.02mm spec is a misprint and it should really be .1-.2mm. The .01-.02mm spec is in my 1984 introduction manual. Is this consistent with other Mercedes service publications?

Trying to read half a thou with a typical dial indicator setup (as shown in the photo) is iffy at best. I've checked/adjusted the front wheel bearing clearance on my '88 190E by snugging the nut until I could not feel any play while wiggling the assembly by grabing the top and bottom of the tire and then backing off the nut until I could just feel a tiny amount of play. It's almost something you can "hear" more than "feel". The RH side was okay. The LH required a bit of snugging. The spindle shoulder that the inside bearing inner race rides on takes the cornering load, so it can wear slightly in many thousands of miles, which will tend to loosen the clearance a bit.

Duke
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  #14  
Old 11-09-2003, 02:39 PM
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That is the spec as I recall. Loose but so tight you can't detect it.
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  #15  
Old 11-09-2003, 10:29 PM
I told you so!
 
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Quote:
Originally posted by Duke2.6
...the inside bearing inner race rides on takes the cornering load, so it can wear slightly in many thousands of miles, which will tend to loosen the clearance a bit....
Bearings do not wear in the conventional sense. Any increase in clearances is the result of additional seating that occurs during use. If a bearing does wear, then it is experiencing a condition that will eventually lead to failure.

The reason most manuals dictate tightening the nut down to either a certain torque or until the wheel is hard to turn is so the bearing components are properly seated and the excess grease is squeezed from the races. Only then can the assembly maintain the set clearance.

The spec in my manual says clearance should be set at .01-.02 mm. A clearance check allows play to be .01-.05 mm.
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