Wheel Bearing Adjustment - PeachParts Mercedes-Benz Forum

qwerty · #1 12-09-2007, 09:10 PM

'84 300D W123
When adjusting the front wheel bearings, what is the target end play when using a dial indicator calibrated in inches? (One increment is .001".)

Bama1 · #2 12-09-2007, 10:16 PM

No joke. I really don't understand...but I always look forward to learning.

Hey, I'm Red Farmer old school where you just grease em good, snug them up and then back off a notch...then floor the pedal.

What do you mean by end play? How do you measure it? What does that have to do with the price of eggs in China?

Actually, this forum is the place to ask if you are looking for some great experiencial advice...

Dave, what information is he asking for?

dmorrison · #3 12-10-2007, 12:18 AM

Your talking a about the inward and outward movement of the bearing assembly once the assemble is tight. The attached photo is how you set up the dial gauge and base to measure it.

This post shows how it is set up on the rear wheels. Same philosophy on the front wheel.

http://www.peachparts.com/Wikka/W123RearWheelBearings

Limits for the front wheels are

.01-.02MM

SAE 0.00039-0.00078 inches

So on your dial it's 4/10ths of a increment to 7/10ths of an increment.

Dave

Diesel911 · #4 12-10-2007, 01:02 AM

I think that what he wanted to know is what the specification was for the end play on his front wheels. The dial indicator will not do you any good on the front as the bearings are preloaded. Also you do not want your brakes draging while you are adjustin the preload so I would remove the calipers and hang them safely. The instrustions pick up after you have packed the bearings with grease and installed the seal.

This is from the Haynes Mercedes-Benz Diesel 123 series book. Consider the following to be quoted:
22 install the lock nut and adjust the bearing preload using the following proceedure.
Adjustment
23 Rotate the hub while tightening the locknut until the bearings will no longer turn and then back off the locknt 1/3 turn
24 Give the kingpin a sharp blow with a hammer to loosen the bearing tension and then tighten the locknut Allen head screw securely and install the radio static supressor.
25 Pack the cup with grease up to the bead and install it, tapping around the outer circumference with a hammer and punch to seat it.
26 Install the brake calipers.

Here is where it gets confusing at the beginning of the the section they have a "check".
1 With the vehicle securely supported on jackstands, spin the front wheels and ckeck for noise, rooling resistance and free play. Now grab the top of the tire with one hand and the bottom of the tire with the other. Move the tire in-and-out. If it moves more than 0.005-inch, the bearings should be removed for inspection and replaced if necessary.

My understand of this is that when you adjust the bearings you follow the preload procedure and there is no dial indicator setup used. When you do the check the whole wheel is attatch and you use an indicator but they do not say where to put the indicator.
This was my personal experience on my 84 300D.

When I adjusted mine I tried to follow the preload procedure. This resulted in me ending up with them too tight and overheating. I found that I could not get a good feel while rotating the wheel until it was tight before I backed off that 1/3 turn.
What I did was (I had to replace the overheated grease anyway) I romove as much of the overheat grease as I could re-installed the wheel with no grease. Did the preload procedure and rotated the retainer nut 1/3 back. I scribed a mark on the axle and the retainer nut and measured the exposed end of the axle that was sticking out. I removed everthing, repacked the wheel bearings with grease and re-installed the hub on the axle. I threaded on the retaining nut as per my measurment than lined the nut up with the scribed line and tightened it. After which I have had no problems.

What ever method you use I suggest that after your done you drive a block or 2 and get out of the car and carfully put you hand on the hub to see if it gets abnormaly hot. Drive some more and check it again until you are sure it is not overtightned.

I also tried the yanking on the tire/wheel to check for play thing but found that I could not tell if the play was comming from the wheel bearings or other worn suspension parts. I have not looked this proceedure up in the factory service manyal yet as I only got it several weeks ago.

rivermasternc · #5 12-10-2007, 06:28 AM

Quote:

Originally Posted by Diesel911

I also tried the yanking on the tire/wheel to check for play thing but found that I could not tell if the play was comming from the wheel bearings or other worn suspension parts. I have not looked this proceedure up in the factory service manyal yet as I only got it several weeks ago.

Diesel911:
Put the mag base on the rotor and the dial indicator tip on the axle end. This will isolate the suspension question.

Bama1:
The end play must be measured. See the shop manual.

-Scott

qwerty · #6 12-10-2007, 09:46 AM

Quote:

Originally Posted by dmorrison

Limits for the front wheels are

.01-.02MM

SAE 0.00039-0.00078 inches

So on your dial it's 4/10ths of a increment to 7/10ths of an increment.

Dave

Thanks, Dave. That's exactly what I came up with, but I wasn't certain that the service manual specs were in mm or if they were in some arbitrary units specific to the MB dial indicator (service manual just says ".01 - .02" without defining the unit of measure.)

winmutt · #7 12-10-2007, 11:27 AM

Quote:

Originally Posted by rivermasternc

Bama1:
The end play must be measured. See the shop manual.

-Scott

Oh ah. I had been using the caliper bolt hole but I bet this works much better.

rwthomas1 · #8 12-10-2007, 05:50 PM

My "procedure" is very similar to the Haynes version posted by Diesel911. The difference is after spinning the hub while tightening and then backing off the spindle nut, instead of backing off 1/3rd of a turn I retighten by hand. As in, grasp firmly with finger and turn tight as possible WITHOUT spinning the hub. I was taught this trick by my HS shop teacher. The resulting preload is usually a bit snugger than backing off 1/3rd turn and while not dependent on thread pitch it is dependent on hand strength. Its never failed me on any vehicle. RT

Diesel911 · #9 12-11-2007, 03:12 PM

Quote:

Originally Posted by rivermasternc

Diesel911:
Put the mag base on the rotor and the dial indicator tip on the axle end. This will isolate the suspension question.

Bama1:
The end play must be measured. See the shop manual.

-Scott

Thanks for the info. Up until 3 days ago some of tha parts of my magnetic base had been missing in action. I have not used my dial indicatos for anythin since 1995 and the accessory clamps and stuff are scattered around various tool boxes and so forth.
I normaly use as one of the members said the "country boy" method. Turn the lock nut in and jerk on the parts until you feel you got just enough end play and tighten the lock nut. Instead I tried to follow the proceedure as in the manual.

rrgrassi · #10 12-11-2007, 03:29 PM

I do the preload version, like Haynes. I also use a 3lb hammer to hit it. To avoid damaging threads, I use a spare nut and put it on the spindle. I learned this trick from a farmer for preloading bearings on a tractor. Never had the bearings "loosen" later, or wear prematurely.

rivermasternc · #11 12-11-2007, 03:32 PM

Quote:

Originally Posted by Diesel911

Thanks for the info. Up until 3 days ago some of tha parts of my magnetic base had been missing in action. I have not used my dial indicatos for anythin since 1995 and the accessory clamps and stuff are scattered around various tool boxes and so forth.
I normaly use as one of the members said the "country boy" method. Turn the lock nut in and jerk on the parts until you feel you got just enough end play and tighten the lock nut. Instead I tried to follow the proceedure as in the manual.

You're welcome. I learned the hard way. The last time I had the front rotors replaced on my 300SD, I took it to a local shop (not an MB specialized shop). The second time I took it there (with the first set of replacement wheel bearings and grease tube in hand and original set howling at every curve), I walked through the procedure with the tech and left the manual open on the passenger seat for him. Two weeks later (2kmi) I ended up installing the second set of replacement wheel bearings at home. Never another problem. Lesson learned: Don't take the German iron to the local shade-tree mechanic done good.

This is not rocket science, but those procedures were written for a good reason and they work. Why try to deviate?

-Scott

qwerty · #12 12-11-2007, 06:53 PM

After spending a little time with the dial indicator, it became crystal clear to me that the various "shade tree" methods of bearing adjustment are unlikely to even come close to getting the job done right. The line between no end play and the specified end play is a fine one, indeed.

I tried the "tighten and back off 1/3 turn" method; too tight every time. The "loosen then hand tighten" method was too loose every time. Getting it right with the dial indicator required some pretty precise adjustments of the spindle nut. And, if you can feel the end play, it is way too loose.

Bottom line: If you are not using a dial indicator, you are fooling yourself.

qwerty · #13 12-11-2007, 06:59 PM

Quote:

Originally Posted by rivermasternc

Lesson learned: Don't take the German iron to the local shade-tree mechanic done good.

The bearings are the same as on a comparable domestic vehicle with a tapered spindle. I doubt that your man would have done any better with a Chevrolet.

rivermasternc · #14 12-11-2007, 07:26 PM

Quote:

Originally Posted by qwerty

After spending a little time with the dial indicator, it became crystal clear to me that the various "shade tree" methods of bearing adjustment are unlikely to even come close to getting the job done right. The line between no end play and the specified end play is a fine one, indeed.

I tried the "tighten and back off 1/3 turn" method; too tight every time. The "loosen then hand tighten" method was too loose every time. Getting it right with the dial indicator required some pretty precise adjustments of the spindle nut. And, if you can feel the end play, it is way too loose.

Bottom line: If you are not using a dial indicator, you are fooling yourself.

This is the same sage advice offered to me by Stu several years ago. He told a great story of a new hot-shot mechanic he had hired. Following a small wager, the hot-shot began using the dial indicator.

I'll leave this posted for a couple of days for those who have not gotten their shop manuals yet.

http://web.infoave.net/~ontheriver/automobiles/download/33-300.pdf

I should add that I compared my print versions of the 123 manual to the 126 manual. They are the same for all practical purposes.

-Scott

rwthomas1 · #15 12-11-2007, 10:02 PM

Quote:

Originally Posted by qwerty

Bottom line: If you are not using a dial indicator, you are fooling yourself.

Do what works for you my friend. I have greased the MB wheel bearings twice in 50+K miles and they are just fine. Same ones that came with the car. No howling, no scoring, no heating up, nothing. While I understand the reason for procedures if the end result of another method provides satisfactory results then there is no issue.

RT