Seeking clarifaction on using dial indicator to set wheel bearing end play
 

After reading several threads about setting the front wheel bearing end-play using a dial indicator vs. 'doing it by feel' I went ahead and purchased a metric dial indicator and stand. As per the FSM I am looking to set the end play to .01 - .02 mm, however I am a bit nervous about setting the tension too high and am hoping for some reassurance I am doing this correctly...

I currently have the clamping nut pretty tight (in my opinion), meaning I can't feel any play in the hub but I can still turn the rotor with one hand. When I set up the dial indicator against the hub and push/pull I can still see the movement on the indicator of about .20 mm.

So assuming I am using the dial indicator correctly I should still need tighten the clamp, however as mentioned it is already pretty tight and I would have to use a large wrench to make it tighter than it already is (which is why I'm nervous that I am over tightening).

Can anyone offer any helpful insight into whether the clamping nut should require a fair amount of torque to get the hub tight enough? Or is that an indicator of something else being incorrect?

Did you overtighten the nut first to set the bearings?

If not, tighten the nut while rotating the hub until you cannot turn it. Then back the nut off, strike the axle end with a hammer. Then proceed to set the end play as specified.

yup. Tango is correct. just tightening the nut until you get the specs is not the correct method to use.

I take a 12" or 15" crecent wrench to the nut, and reef on it, until the bearings are tight, then rotate the hub back and forth with both hands, then loosen the nut, and position the dial indicator, then tighten the nut back down until I achieve the desired play.
if you try to set play without "rolling in" the bearings, you'll be fighting grease that's all over the needles, and trying to set the play when they are not seated against their cage and race.

strike the axle end with a hammer.

I wouldn't recommend that. You'll end up with smashed threads.

... what threads? it's the front axle... unless you are Herculean or Kryptonian... you're not going to damage anything...

ahh... I think you are thinking he meant to strike the spindle... and while I don't see what that would help... I don't think it's going to hurt anything.

I'd strike the flat of the hub, or tap on the rim of the hub...

Thanks for the feedback. I however was never able to get the clamp nut tight enough to the point that the hub wouldn't spin by hand. I think my crescent wrench isn't long enough to put enough torque on it. I could tighten it down to the point where it was difficult to turn the hub, but as soon as I started turning the hub it would loosen up. I would then usually be able to tighten it a bit more and repeat the process.

In the end however I never got it tightened to the point of not being able to spin the hub. Since the car is my dd I had to put it back together with the dial indicator still showing an end play range of about .2 mm. I'll take it back apart next weekend and see if I can get everything dialed in to spec.

That said, even with the .2mm end play the car drives noticeably better. When I replaced the rotors 1.5 years ago I set them up by 'feel' and they were far too loose which eventually was noticeable in the braking (it pulled and could be felt in the brake pedal) and I think was affecting the steering to a small degree.

+1 for investing in a dial indicator

Those possessing poor motor skills would be advised to use a plastic hammer. Which happens to be what the W123 service manual recommends for the procedure.

In my opinion, relieving tension from the bearing set is critical to the adjustment process. Evidently, the folks who wrote the service manual shared that opinion.

That's fine, as long as it took significant effort to rotate it.

So three weeks after doing this work my front bearings seem to dead, i.e. there is a 'roar' coming from the front end particularly at higher speeds. I did re-use the bearings so perhaps they were already on their way out, but I'm still concerned that I am doing something incorrect, e.g. I'm using the dial indicator incorrectly and set everything too tight.

Can anyone point me to good description for how to use the dial indicator to set the correct tension on the bearings?

Also, is there any reason the outer wheel bearings cannot be replaced while the calipers are still on?

Because you cannot inspect the inner bearing which is taking undue load if the outer bearing is shot.

Sixto
87 300D

Question
 

To answer your last question first, the RACE must be replaced with the bearing = a matched PAIR = one bearing assembly..
Servicing Tapered Wheel Bearings - Popular Mechanics
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Please read through the following links about wheel bearing and "race" damage.
Bearing damage chart - SKF.com/Products
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http://www.schaeffler.com/remotemedien/media/_shared_media/08_media_library/01_publications/schaeffler_2/publication/downloads_18/wl_82102_3_de_en.pdf
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Wheel Bearing Service Tips | KnowYourParts
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David Stevens IEng - Bearing failures - Bearing FLAKING
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http://www.rkbbearings.ir/RKB-FAILURE%20ANALYSIS.pdf
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Why are you re-using the old bearings ?
The full kit is only $28.75 per wheel..
I most often use the second one down in the following link.

Wheel Bearing Kit
1163300051
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW TEST


For those wanting heavy education or technical data on bearings:
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http://www.timken.com/AntiFriction/player.html
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http://www.timken.com/EN-US/Knowledge/students/Pages/default.aspx
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http://www.timken.com/EN-US/Knowledge/engineers/Pages/default.aspx
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http://www.timken.com/EN-US/Knowledge/ForMaintenanceProfessionals/Pages/default.aspx
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http://www.timken.com/EN-US/Knowledge/Suppliers/Pages/default.aspx

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And one more, this is why if your bearing set comes with a grounding clip it is essential to use it.

Passage of electric current - SKF.com/Products

I did not read all of the Posts so this could be a repeat.

The reason the instructions want you to tighten up on the nut is to squeeze the grease out from under the Bearing Rollers and it is also why they want you to rotate the Hub.

If you don't do that a layer of Grease between both Bearings can throw the reading off.

Timken wheel bearings don't come with races. Other manufacturers do.