CLK (A209) front wheel bearings play, advise please.

[Reggie-rock]

My 2006 CLK 350 Convertible passed it's MOT with an advisory that there is some play in both front wheel bearings.
I was wondering if anyone knows if these are adjustable or do they have to be renewed?
Thanks.

 

[optimusprime]

Should be adjustable one way or the other .Some had a colar with an allen bolt through it ,you just slaken it off and screew it on a little more ,not tight or it will bind ,over heat and damage the bearing .Others have a castle nut and cotter pin ,you remove cotter pin and screew up the nut ,same as bofore not to much or you will damage it ,replace cotter pin after...Some you replace the whole nut for a one off locking nut, . Take it in to your local garage and let them do it ,if your not sure .If its a front wheel drive it will be more complicated to do it .And might mean replacing the bearing complete.

 

[Codger49]

My 2006 CLK had the same MOT advisory.

W209s have the collar with an allen bolt and as optimusprime said, it can easily be adjusted. Mercedes WIS specifies use of a dial gauge (end float of 0.005-0.022mm for W209), but in the real world I expect most time served mechanics just 'nip' it up by feel. Tightening torque of the hex bolt is 11 Nm.

I had mine adjusted by my indie when he was replacing springs, I would have thought its something you ask to be done at its next service.

 

[markjay]

In the olden days we used to adjust this by hand, the rule was tighten slowly until there's no more play at all, then loosen-up a touch so that only a very minute slight 'knock' can be felt.

 

[190]

Taper roller bearings are happy enough with a slight pre-load but the problem is short of trying to measure rotational drag the average mechanic can't determine the amount of pre-load where as they can easily measure end float so to be on the safe side manufacturers specify a minute amount of play. Knowing this makes it acceptable to me to set them by feel and I aim for close to zero play.

My 79 BMW motorcycle has essentially the same taper roller wheel bearing set up as a car but any play on a 2 wheeler is to be avoided if possible so we do actually aim for a small amount of pre-load and shim the bearing stack to get it right. Even with some pre-load the bearings will still last hundreds of thousands of miles if properly maintained. This experience persuaded me to forget about trying to set end float on my MB and aim for close to zero.

I'll just add that I realise that if you want to play mind games with the concept, zero end float is impossible to achieve and inevitably you end up with a a minuscule amount of either end float or pre-load - but it doesn't matter.

 

[markjay]

I think the issue is that you can measure play by feel - it gradually increases - but you can not measure pre-load because once you've reached the zero point it will feel the same regardless of how much additional pre-load there is.

So aiming at a minute amount of play is the safest guideline to ensure that the bearing is not overloaded when setting by hand and measuring by feel.

And while you could well argue that using measuring tools is more accurate and offers standardisation across workshops - the main reason that we now have measuring tools and torque setting for almost everything is only in part the extra accuracy, it is also in great part that setting by 'feel' requires plenty of skill and training, while setting using a measuring device is a simple skill (in comparison) and so quicker and easier to train people to use.

 

[190]

I think the issue is that you can measure play by feel - it gradually increases - but you can not measure pre-load because once you've reached the zero point it will feel the same regardless of how much additional pre-load there is.

So aiming at a minute amount of play is the safest guideline to ensure that the bearing is not overloaded when setting by hand and measuring by feel.

And while you could well argue that using measuring tools is more accurate and offers standardisation across workshops - the main reason that we now have measuring tools and torque setting for almost everything is only in part the extra accuracy, it is also in great part that setting by 'feel' requires plenty of skill and training, while setting using a measuring device is a simple skill (in comparison) and so quicker and easier to train people to use.

That's basically what I was saying. They spec a small amount of end float because it's easily measurable even though a small amount of pre-load is the optimum condition for bearing life.

The learning point for me was just how much pre-load a taper roller bearing will handle without materially reducing the bearing life below the life of the vehicle. It's far more pre-load than a reasonable person would ever apply when aiming for zero play. Basically if you can't detect an increase in rotational drag then the pre-load is not too high. On their motorcycles BMW were known to apply grossly too much pre-load at the factory and still the bearings survived in my case for 28 years before it was then properly shimmed.

Perhaps one reason for end float being common on cars is that the old castellated nut method effectively dictated that it was needed because the adjustment increments were relatively large. MB's method is smarter than that and much easier to adjust to closer tolerances.

 

[coupefan]

judder

That's basically what I was saying. They spec a small amount of end float because it's easily measurable even though a small amount of pre-load is the optimum condition for bearing life.

The learning point for me was just how much pre-load a taper roller bearing will handle without materially reducing the bearing life below the life of the vehicle. It's far more pre-load than a reasonable person would ever apply when aiming for zero play. Basically if you can't detect an increase in rotational drag then the pre-load is not too high. On their motorcycles BMW were known to apply grossly too much pre-load at the factory and still the bearings survived in my case for 28 years before it was then properly shimmed.

Perhaps one reason for end float being common on cars is that the old castellated nut method effectively dictated that it was needed because the adjustment increments were relatively large. MB's method is smarter than that and much easier to adjust to closer tolerances.

If there is too much play in the bearings might this cause "judder" on braking?

 

[streethawk]

If there is too much play in the bearings might this cause "judder" on braking?

More likely you're disc's are warped