W202 wheel bearings.

dbanbery

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How hard are they to do? do i need special tools? i have noticed some play in my front wheels when i wobbled them, so i will be investigating further at some point.... more than likely going to see if i can tighten them up and if that doesnt help then i'll be wanting to sort them.

i know on the 203s you have to have them pressed out and in. if this is the case i would rather buy the tool and do it unless its going to be prohibitively expensive. i have done rear bearings on my E30 BMW a while back that involved hammering out the old one and knocking in the new one, not too difficult when you got the hang of it to be fair.
 

Number_Cruncher

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You'll need a dial gauge to set the end float on the bearing properly. The MB spec is very difficult to acheive by any other means.

Replacing them is just a hammer and drift job, or, more ideally, work for a press, while setting them up is the only part that needs anyting approaching a special tool - the dial gauge.

You'll need to check the specific clearance for your model, but on this type of bearing since at least W123s (and probably before!), the clearance is 0.01mm (about half a thou in old money!), and is way to small to be set correctly by feel or by other approximate recipes.
 
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dbanbery

dbanbery

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right,

i take it the dial guage measures how tight the bearing should be tightened? like a torque wrench?
 

Number_Cruncher

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Not quite like a torque wrench.

With the wheel off, you put the magnetic base of the dial gauge onto the flat part of the hub/disc, where the wheel bolts go, and you put the pointer of the gauge onto the spindle itself. You also squeeze back the pads, so they don't restrict movement, and you push and pull the hub in and out, and see on the gauge how far it moves.

So, with your wheel being a bit loose, you'll read a large movement. As you slowly rotate the locknut to tighten the bearing, if you repeat the pushing and pulling, you'll find the distance measured, or "end float" as it is known will reduce. Eventually, you'll reach a stage where you will no longer be able to feel any play, but the dial gauge will tell you that there is still too much (but, you're getting near), keep going until you read an end float of 0.01mm (or whatever is appropriate for your car)

Edit: Having consulted a previous, the end float for your car is 0.01 to 0.02 mm
 
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dbanbery

dbanbery

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right. what is the name of this tool? i have had a look on ebay and i cannot seem to find anything. to be fair i'm not even sure what one of these looks like!
 
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dbanbery

dbanbery

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ah right.


so basically it measures the play in the wheel bearing when you tighten it up on the hub?
 

Number_Cruncher

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>>it measures the play

Yes - you need a gauge to do this because the play is so slight, the clearance so small, you can't actually feel it.
 
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dbanbery

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right.

going shopping for one tomorrow when SWMBO is at work. what make are the OE bearings from mercedes?
 

Number_Cruncher

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Surely you have got to be joking ? Using guages to replace a wheel bearing ?

Get back to the basics, This type of job requires no guages and requires no books or internet surfing.

This is a simple job, so why complicate it.

You are giving members unecceasarry worries. This is a simple job, why add complications ?

Go and read the MB procedure for the job.

Yes, you can bodge the job if you want to, but, it's not difficult or expensive to use a gauge and do the job PROPERLY.

A DIYer who buys a simple dial gauge and stand will still be doing the job much more cheaply than taking it to a garage, and, unlike many garages, the DIYer will be doing the job correctly. i.e., they get a better job and cheaper.

I guarantee that you cannot set these bearings up, and meet the MB specification, without a gauge.
 

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Go and read the MB procedure for the job.

Yes, you can bodge the job if you want to, but, it's not difficult or expensive to use a gauge and do the job PROPERLY.

A DIYer who buys a simple dial gauge and stand will still be doing the job much more cheaply than taking it to a garage, and, unlike many garages, the DIYer will be doing the job correctly. i.e., they get a better job and cheaper.

I guarantee that you cannot set these bearings up, and meet the MB specification, without a gauge.

as you have said, even MB dealets wouldnt use the guage! and most cars have some form of measurement to check the free play. but without exception, everyone ive ever worked with, in every garage ive worked at, in fact even at college, we were told to tighten gently till free play (you could feel) was eliminated, or tighten up and then release the nut by 1/4 turn. ie nip up to squash grease etc to where it needs to be, wheel/hub will be tight to turn, release by 1/4 turn, bearing will have no detectable free play and hub etc should rotate freely. ive always done it that way and never had a problem on any taper roller bearings ive fitted, and they were common on mk3/4 escorts etc and i undid thousands of those! only way to access the rear brakes on most models!
 

Number_Cruncher

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Pete,

Yes, for the thousandth time!, most cars have a very relaxed tolerance on bearing play. On the rear bearing caps of most Vauxhalls, it used to say something vague, lilke "adjust to leave a little play".

MBs are different, and they have a very exacting tolerance which you can't set properly any other way.

I *know* most garages don't do it correctly, but, it's not difficult or expensive to do the job right. MB have gone to the effort of developing and defining a procedure - a simple procedure. Why not simply follow it?
 

turbopete

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my point was, yes it is a simple and relatively inexpensive procedure to do it correctly, but unless they are people like myself or yourself, with trade experience and knowledge, some people may not wish to spend money on a dial guage etc that they may use this once for this particular bearing then may never use again. i can always find uses for such things as i do all my family's work and a few others as well,meaning i will re use the tools at some point! i was merely pointing out that there alternative methods that would probably be "close enough" if they decided they did not wish to purchase equipment they may never use again
 

Number_Cruncher

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Yes, fair enough.

But, a dial gauge can also be used to assess disc run-out in case of judder, and on our cars timing chain wear (and TDC position if someone's disturbed the pointer)

I think it's safe to assume that most DIYers wouldn't be using one to set the crown wheel to pinion backlash, but, they could!
 

turbopete

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correct, but i doubt most diyers would get as in depth as timing chain wear even. still, nothing wrong with a nice healthy, friendly debate!
 

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Well rightly or wrongly I still do them by feel, if you had a lot of play before you started and you could feel virtually none when you had adjusted them, then there would be nothing wrong in that, and it would be a lot better than not doing it at all, as when bearings are too loose there is the danger of a roller damaging the cage when hitting a pot hole
 

Number_Cruncher

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I have done hundreds. No comebacks, no failures. Yes, please send me your procedures for the job.

Note. A DIYer wirh a DTI is more likely to get it wrong than doing the job wthout a DTI. It is a simple job without adding unneccessarry complications,

Would you not agree ?

They aren't my procedures, they are the MB procedures.

The rule of thumb methods rely upon feel and experience. You know what to feel for, I know what to feel for, but, does the average person who's asking on the internet know?

I think that dial gauges are not too difficult to use, and the MB procedure allows anyone to set up a bearing in a consistent way without relying on feel or experience. (It's the same logic as recommending torque wrenches to prevent DIYers from mangling their rocker covers by over-tightening them as in the other thread).

I would wager that 10 DIYers with dial gauges would give more consistency in setting a bearing up than 10 experienced mechanics each with their own variant of the feel and rule of thumb approach.

It also happens to be the case that these bearings can't be set up to the MB spec without using something to amplify the tiny movement.

Next time you have a car fitted with bearings like this on your ramp, have a quick play with a dial gauge, (when the other mechanics aren't looking!) and you'll see what I mean - you'll really be surprised when you try to set the clearance to 0.01mm, I promise you!

If I were stuck in the middle of nowhere and had to adjust an MB bearing, yes, I would do it purely by feel to get me home, but, when a dial gauge is available (they aren't exotic or expensive!), and takes only a minute or two to use, I don't see a good reason not to recommend this approach.
 

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None at the monent, but there's an OM642 in the Jeep Grand Cherokee!
I'm getting a strong sense of déjà vu here ;)
 
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dbanbery

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Okay,


so while i may be a DIYer, i have done wheel bearings before.... well one... on a BMW which wasnt a roller, it was a typical large rear wheel bearing. and that was fine. no dial guages or anything. but that was a ball bearing, not a tapered roller.


i understand about the "feel" etc on doing this, but not having the experience of being a mechanic i would like to use the guage.... however, i have an idea.

i'm going to adjust them by feel and then use the dial guage to see how far off you can get it without, to see how different they can be. to be honest i'm not one to geti n the middle of the cross fire between spec nuts and trade mechanics, but i do want something i do to be spot on, and whether its deemed to be necessary or not by everyone i would want to get it right. i'm not one to go and pay someone else to do it because someone has said that i have to go buy a tool. that is part of the fun. and as mentioned before, there are more things to use a dial guage for other than bearings.

btw both sides have a bit of play - not massive and not by any means unsafe but if a mechanic wanted to fail the car he could quite easily fail it and tell me that he would happily charge me £X parts and labour to do them. i want my car to be as perfect as possible for France, and for the MOT in November. this requires thought, vigilance and some money spending, tools and parts if necessary :)

all in all, any excuse to buy tools.

i wouldnt care about being laughed out for using tools to get a job right, seems a bit of a macho thing to me.
 


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