Mercedes-Benz Forum banner
1 - 2 of 2 Posts

·
Registered
1981 240D
Joined
·
185 Posts
Discussion Starter · #1 · (Edited)
I recently reviewed a how-to on replacing rear wheel bearings. The one issue I have, is I am not sure how to use a dial indicator. I have a dial indicator with a magnetic base (actually, it is the same one used in the how-to). Once you stick the magnetic base to the wheel carrier, what do you use as reference point? If you look at the photos he put in the how-to, you will see two photos of his dial measurements. One is approximately 58 and one is a little over 59. He says it is "pushing" and "pulling". So what was his reference point? In other words, where is 0? What is he measuring from? Also, this is probably a really stupid question, but why is it 58 and 59? The end-play tolerances for the hub is 0.04-0.06mm or SAE .0015"-.0023". Each mark on the dial indicator is .001", so shouldn't it be between 15 and 23?

Here is the how-to I used to do the job:

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

·
Registered
1984 300D
Joined
·
5,534 Posts
When I clicked on the site it would not open for me so I am going to make a wild guess and say that what it means is that who ever did the Dial Indicator Reading did not set the Indicator at Zero to take their reading. and when he moved the Hub in and out he is saying that the needle moved between 58 and 59 (thousands?) which would be 0.001 of end play on the Hub.

In theory you when you setup the Dial Indicator and push it in against the spring tension of the Plunger (preload it) you are supposed to rotate the Dial to Zero; push or pull the Hub and take your reading.

But, after I preload the Indicator it I could simply make a note of where the Indicator Needle is pointing (like 58 (0.058")) on the Indicator and push or pull the Hub and take a reading (the Indicator Needel moved to (599(0.059")) and note the differance in how much the Indicator Needle Moved (0.001").

Remember the write ups are sometimes done by regular folks and sometimes done by professionals. Neither are technical manual writers.
Professionals often use Jargon that the none professionals do not understand and the regular folks often do not know the terms or how to describe what they have done.

The reason everyone likes to see pictures of the job being done.

A lot of folks keep avoiding getting the Factory Service Manual CD set or searching the internet and finding the online one that is out there. I recommend reading the Manual and then going and reading the various write-ups on the job. It will give a much fuller understanding of what needs to be done.

In short it is a bad idea to blindly follow an instruction without understanding as much as you possibly can what you are doing.
 
1 - 2 of 2 Posts
Top