124 front wheel bearings

[Chazchuzzlewitt]

Hello, recently replaced the front pads & discs on my E300D and thought I'd check out the front end while I was there- both wheels had a little (but noticeable) play in the bearings so I tightened them (with brake pads out) 'till the disc wouldn't move without hard work, then backed off 1/4 turn.
With everything back together the wheel spins about 3 full turns with a decent tug... and there's no more play... does this sound about right or too tight (accounting for brake drag)?

cheers...

 

[jibcl500]

Chaz

Sounds a little too tight, the wheel should rotate for a lot longer than 3 rotations. Take it back another 1/4 turn and check for play, best checked with wheel on but I think you knwo that.
jib

 

[television]

Yes back off a lot more,,if you tightened them without rotating the wheel you could have damaged them

 

[Chazchuzzlewitt]

thanks for the quick replies, I did tighten them finally after rotating the wheels but I'll have another go...

 

[Chazchuzzlewitt]

actually, I meant 3 seconds worth of spinning, not 3 rotations... doh

 

[jibcl500]

Should aslo spin for more than 3 seconds.

jib

 

[Number_Cruncher]

The only way to set up W124 front wheel bearings is by using a dial test indicator.

The specified end-float is 0.05 mm.

There is absolutely no way that you will get anywhere near this specification using any of the tighten, and then back off a bit types of solutions. A dial gauge is the only way, as 0.05mm is a truly tiny distance. If you can feel *any* play in the bearing, there's already way too much!

A dial gauge and magnetic stand isn't expensive, and allows you to do the job properly.

 

[wireman]

0.05mm = 0.002" that is not tiny and you can feel that much slack (if you reduce the mass by taking the wheel off), my figures (from haynes book of lies I'll admit) are 0.005 to 0.01 mm.
Can somebody verify this?

The DTI method is of course the best by far, but if you tighten the nut by hand only(with the pinch bolt slackened only just enough to allow the nut to be turned by hand) untill the spacer washer can only just be turned the bearing assembly will pass the end float spec.

Do not use a spanner to over tighten the hub assembly or the running surfaces of the bearing rings and rollers will get damaged beyond repair, this will result in premature failiure of the bearings.

 

[Number_Cruncher]

>>Can somebody verify this?

The figure of 0.05mm is an absolute upper limit. If adjusting, the bearings should be set to between 0.01 and 0.02mm [MB work instruction 33-0300].

Until you've tried to set a bearing to these sorts of clearances using a DTI, you won't realise just how far off the rule of thumb methods are. You'll get nowhere near.

I have been used to various methods for setting taper roller bearings on various makes of car over the years, but, in terms of end float specification, these bearings are a set very small clearance and a tight tolerance, and normal techniques really aren't suitable.

>>will pass the end float spec.

I would be amazed if this were true. I'm sure the method won't result in a failed bearing, but, it is unlikely to get the clearance within spec.

When the bearings are right, you can't actually feel any play by hand, but, the DTI shows the movement - so, if you can feel play, they're too loose, and if you tighten to remove all play, nine times out of ten, you'll over-tighten. The DTI is absolutely necessary, if you want to do the job correctly.

 

[television]

The figure of 0.01 -0.02 is correct, achieved by turning the nut and vigorously shaking the wheel