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Wheel bearing question.


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5 replies to this topic

#1 hebrewhammer

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Posted 07 June 2009 - 08:01 PM

going to change out both front wheel bearings on my 94 impreza awd.
i got Koyo bearings from napa that look to have come packed with grease already but they are not fully packed.
Do i need to pack these or is the supplied grease in the new bearing the correct amount.
Also, is there any specs for the bearing installation, anyone have the pages out of the FSM?
i.e. Depth of bearing on race, clearance for the final press fit when hub and spindle go together.
Thanks for all the info!

#2 grossgary

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Posted 07 June 2009 - 09:41 PM

there's some pretty good information on here about bearings.

in general it's best to assume bearings come in packing grease and just pack them with quality synthetic bearing grease. i would think those come with real grease though.

also - they are not supposed to be fully packed. it's been mentioned a bunch of times here how much to pack them but i can't recall the percent.

good luck.

#3 tcspeer

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Posted 07 June 2009 - 10:03 PM

Gary is right they are not suppose to be packed full, however before I knew this I put as much as I could get in them and didn't have any problem with them. I think most of the extra will be squeezed out when you press it in, and then easy to wipe away.

#4 grossgary

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Posted 07 June 2009 - 10:12 PM

I think most of the extra will be squeezed out when you press it in, and then easy to wipe away.

i've packed other non-wheel bearings too full and that is exactly what happens - the heat causes it to expand and it pushes out through and around the seals. i think the concern would be that it may push a seal out, but with those tight fitting, pressed in seals i can't imagine it doing much of anything.

#5 hebrewhammer

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Posted 07 June 2009 - 10:29 PM

yes have been doing reasearch over the web and found 30% was right on the money.
I have found some say don't add grease and some say clean it fully and pack to 30%.
I have also read that too much grease can cause too much heat which could be a problem.

looking at the bearing again it looks filled to about 30% looks like bearing grease. It is whitish clearish.
did a bearing a while ago and it came in green grease which i assumed was packing grease.
looked over the site here but no real specifics. just did a bearing and it failed within 1k but i'm pretty sure i tighted the axle nuts too tight and did this on the ground.
don't want to make this a 3rd times the charm thing.

#6 CNY_Dave

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Posted 08 June 2009 - 09:00 AM

I went by this guide

http://forums.nasioc...t=wheel bearing

Having just done this on my '03 OBW, a few observations (I think they are relevant to the '96)-

I got my bearings from the dealer. Tongues of semi-clear brownish grease were sticking out in between the bearings, I'd call it 30% packed or a bit better. The dealer said they were packed and ready-to-go, and the two inner races were held in place with a plastic keeper that was not supposed to be removed until the bearing was installed and you were ready to press in the hub.

The manual made a big deal about packing the seal lips with matching grease- the seals from subaru are pre-loaded with grease.

The PDF manual I was following said it was extremely important to put no weight on the bearing until the axle nut was fully torqued. I can see this as important.

Seeing the way the bearing goes together, and following what was happening to the bearing internally as I torqued the axle nut, I am skeptical you could damage the bearing over-torquing the nut. I am fairly sure when fully torqued the two inner races are touching each other, meaning the bearing preload is set by those parts dimensions and not by the nut torque (as long as the nut is tight enough to get the races into contact with each other).
When tightening the axle nut, for a long time all you're doing is pulling the races together. When they meet, the torque goes up dramatically and rapidly, and reaches full torque in less than a quarter turn. As long as you can turn that nut and it's about the same effort, keep turning it!

The hub must be primo- perfect- no ridge. I think the best way to tell a bad hub from a good one is that if there are *any* lines tracing around the hub where the inner race sits (or any 'smearing'), the bearing has spun on the hub and the hub is trash.

I would get a hub and be ready to use it, and if you don't need it, return it. My dealer was fine with this.

The special subaru tools set all the depths automatically so all us backyard guys are on our own on this. Before pressing out the hub from the bearings, measure how far the end of the hub projects from the inner end of the inner race, and re-install the (new) hub to this depth.

The outer race just gets pressed in all the way, until it is hard against the stop it rests against.

When pressing in the hub it is critical to support the inner race of the inner bearing, and that all pressing force pass through that inner race.

If I had a bad knuckle assembly with the bearing installed, I'd cut that sucker apart to see if those inner races truly are touching- that'd be good to know, and would be good to know.

Dave

Edited by CNY_Dave, 08 June 2009 - 09:03 AM.





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