W126 Front wheel bearing replace
 

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.

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.

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.

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.

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.

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..

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