W126 Front wheel bearing replace

[jerryb1]

i had to replace my front wheel bearings on ny 91 300SE. The manual calls for 2mm preload. This seems too much, it's almost a tenth of an inch(.080). Maybe they mean 0.2mm? I'm tempted to tighten them up then back off a little instead. With the 2 mm, I can shake the wheel and see the movement and hear clicking of the bearings? Is that correct??

Also, I think I did something stupid. I used the old outer raceway on the inner bearing as it looked to be in good shape, but I just read where I should not have done that. It looked like it would be a bear to get out without the proper puller. At this point, it's all back together and I'll see what happens. The bearings are not that expensive, I bought Timken's from ********, for about $7.00 each.

[MattBelliveau]

Do you haqve the tools to measure the preload? I've always just tightened the collar nut while turning the wheel, until I start to feel friction on the wheel. Then back off 1/4 turn (I think this is the procedure from the Haynes manual). I've never had a problem just doing it this way.

[280EZRider]

In the W123 maintenance library - probably the same for the W126 wheel bearings - it says to tighten the nut and then back off 1/3 turn. There is no measurement involved. I too left the rear race in place over 5 years ago w/o problems to date.

[jerryb1]

Thanks guys. i do have a dial gauge to measure the movement, however, 2mm of movement of the rotor in and out seems too loose. I tightened it until there was no movement and backed off 1/3 turn. I'll let you know if the bearings fall apart! The problem is that i think maybe you can wreck the cages if you tighten too much before backing off.

[280EZRider]

One thing I should have mentioned: only reuse the rear bearing race if the existing races have no blue burn marks & if there are no indentations from the bearing rollers.

[jw46]

If I am going to replace wheel bearings.. replaces races as well.. not much cost.. not all that much time to get them out...Better to have all new..

[jhodg5ck]

Running on the old races is a sure fire way to prematurely wear out your new bearings. I've replaced quite a few bearings Very early in their lift after the PO/PM decided the old races looked fine...

Jonathan