Wheel bearing preload tool
 

I'm doing my homework for the next project.

Pads and rotors.

In reading the old threads, it seems I need to remove the front hubs on my 123 which will lead to wheel bearing repack. I'm done this numerous times on American cars and know the procedure and feel for setting the bearing preload by hand/feel.
However, the old threads keep talking about the manual calling for using a tool to set the bearing preload.
What is that tool and where do you get one. Is it just a variation of a torque measing device?
Couldn't I just use my torque wrench?

Better still, why would MB need to be more precise? It looks like the bearings and races are standard 3, 5's like I have worked with on American cars. What would make the MB special?

The bearing clearance is set with a dial indicator. M/B wants .0005" free play in the bearings. Good luck trying to get that by feel. Others have tried and failed...........and cooked the bearings in the process.

Like most tapered roller bearings, they are intolerant of any preload and it shortens their life dramatically.

If you must do it without the indicator, be absolutely sure you can hear the slightest bit of movement in the spindle when you push and pull on the rotor. This amount of clearance is much greater than .0005" but it's far better than the alternative.

The spindle nut that the W123 uses renders "feel" relatively useless.

Wheel Bearing Service
 

Charles ;

That's a good question you posed ~ every Mercedes I've bought (and most I've serviced) have bad outer wheel bearings .

However , I have also adjustem the new bearings by feel and so far , not one has failed .

If you know how to do it , no special tool is necessary .

The main thing is to not pre-load the bearing .

Ditto on the above.
I tried to do mine by feel as I had done since 1969 and ended up overheating the Grease in the hub and had to start over again. Cleaned the roasted Grease out and re-greased and used the Dial Indicator and that was over 1.5 years ago.

Harbor Freight sells an inexpensive Dial Indicator and Magnetic base that is sold as a set or separately.
In the DIY section there is a step by step with pics.

Link please
 

I spent about an hour in the DIY section looking for such a step by step. I didn't find it. If someone has a link, I'd really appreciate the short cut.

OK, so it is not a torque setting. It must be how far to back off from snug? I gotta find the link with the pictures.
Must be this type of dial indicator, right?
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=623

You can use that..........it's a bit coarse for this job...........the setting is one half of one line and the dial isn't quite that accurate.

When you get the proper clearance, the needle moves 1/2 line.........not more..........not less.

Thanks Brian,
I didn't look at the scale, just the design of the device.
I changed my search terms for the thread and finally found this one

http://www.peachparts.com/shopforum/tech-help/100590-wheel-bearing-adjustment-dial-indicator.html

It only has one picture and subsequent post question the mounting in that picture. Is there a better thread with better pictures?

That's a good thread.........some knowledgeable folks there.

I don't know of any better threads..........the process is not difficult. The indicator is set onto the end of the hub and you push and pull the hub toward you and away from you while watching the indicator. If you're getting more than 1 line.........tighten the retaining collar very slightly and repeat. The final goal is 1/2 line.

OK, thanks.
I'll invest in a dial indicator or borrow one from the university machinist and use that method.
I'd almost be willing to bet it will correspond to about a 10 degree backoff using the old fashioned method. I'll see if I can make a correlation.

10 degree rotation from an unknown starting point is not accurate. You cannot be precise in the starting point.

Sorry I let you down suggesting the DIY. I went back an looked and I could not find one either. Only rear Wheel Bearing stuff.

Yet I have seen pics somewhere. I did a search and found a brake pad replacement thread but most of the pics no longer have a good link and the person who started the thread did not use a dial indicator?
So that was a dead end too.
Here is A pic of the indicator setup
http://www.peachparts.com/shopforum/attachment.php?attachmentid=50329&d=1197263926

Thanks,
That's a better picture than the one I found.

I have been a machinist for several years now, and I cant see getting the play in the bearings to a tolerance of 5 tenths, and by the way, is this +/- .0005, or is the total tolerance .0005, meaning +/- .00025? If you can move the rotor out .0005, then you could also bring it back to zero, and push it in another .0005, making your total play as .001. Besides, I write programs for, and setup machines to manufacture rollers for aircraft bearings, and the rollers themselves have +/- .0002, Just because you have .0005 play in the bearings, doesnt mean that this tolerance is the same on each roller.... Sorry for being so picky guys, but this is ridiculous. I go by feel, and always have. Half a thousandth of endplay is a higher tolerance than aircraft parts would need. I know Mercedes is a high quality car, but not aircraft grade.