question on replacing front wheel bearings

[markmalin]

Just wondering, is there anything special to know about replacing the front wheel bearings if I pick up a set from our host? Looks like they're only 10 bucks or so each... My car is an 85 Carrera. I've done bearings on older cars, never a 911 though.

Thanks guys.
Mark.

[tharbert]

There's nothing particularly special about changing them. You need to replace the dust seals too. Many folks here suggest heating the hub and freezing the bearing so the races basically drop into place without the use of a punch. You might want to measure the thickness of the rotors before you do the job. If they are close to the maximum wear or have significant groves, go ahead and replace them. They are relatively cheap as well. I would have said "have them turned" until I saw that new rotors arent' much more than what you'd pay to to have the lathe work done. Just replace them.

If you have the "while you're in there" bug, consider installing caliper rebuild kits, replace the rubber brake lines and flush the brake fluid. That will add a whopping 90 minutes to the whole job.

As for reassembly and tightening of the spindle nut, It's important to follow the manual. You don't want to prematurely wear your new bearings because they're too loose or tight.

This is a fairly good thread that covers lots of topics.

[hcoles]

+1 once you are in that deep then rebuild the calipers, consider cutting slots on the strut brackets, in the future this will avoid breaking open the line when changing disks or bearings again. In my experience new rotors run true if mounted on a cleaned hub and nothing else is wrong, check with a dial indicator, and yes don't make the bearings too tight or too lose

[markmalin]

Thanks, guys. This is exactly the information I was looking for.

Come to think of it, if the bearings and races are still good, can a guy just repack them? It's possible the PO had replaced them -- I need to look in my records. It's just that the other day I noticed some play in both front wheels... so perhaps they are warn.

[hcoles]

a bit of play is OK and desirable - there needs to be room for the lubrication to move around and to account for a wide range of temperature differences, one way mentioned to adjust is the washer should be able to be pushed back and forth with a screwdriver, a search will pull up other methods

[tharbert]

Yes, that would be a good first step. Look for play when grasping the tire at 12 and 6.

Still, at a minumum, replace the seals. That will allow you to get the inner bearings out for inspection and repacking. Look closely for pitting or wear. The rollers should be nice and shiney, not dull gray.

It might be a good time to move to a good synthetic wheel bearing greese.

[markmalin]

Interesting... I actually grabbed the wheel(s) with both hands at 12:00 with the car on the ground and was able to feel some play (a faint clunk), but if just a little bit is OK it might be fine. The car was warm, but not hot at the time (just came back from lunch). I could have sworn when I had it up on all 4's doing the trans fluid a week ago I did the same and didn't notice anything, but that was with the wheels suspended and grasping at 12 and 6.

[tharbert]

It's a simple procedure to re-adjust. Then you'll know it's done to your satisfaction. Seals are, what, $7 each? Synthetic grease, another $8?

[markmalin]

Originally Posted by tharbert

It's a simple procedure to re-adjust. Then you'll know it's done to your satisfaction. Seals are, what, $7 each? Synthetic grease, another $8?

Sounds good. I'll try that first.

Thanks, guys!
Mark.

[Bob Kontak]

Don't know if you have been in there yet but the dust cap can be a stinker to get off. I use a ball peen hammer and tap (medium) on the outer diameter from side to side till it starts to back off.

[jason2guy]

i wouldnt mess w/them if they are ok. seems easy but it is a very delicate and finicky job. aluminum hubs are really easy to screw up when dealing w/the races.
if they are ok u could just clean, inspect and repack.

[tharbert]

Originally Posted by jason2guy

i wouldnt mess w/them if they are ok. seems easy but it is a very delicate and finicky job. aluminum hubs are really easy to screw up when dealing w/the races.
if they are ok u could just clean, inspect and repack.

The races are press fit but it doens't take much to remove one as long as you are careful. The key is to place the the punch carfully in order not to score the hub aluminum. Then again, a scratch in there isn't going to cause much of an issue. I would disagree a bit with calling this job delicate and finicky. I consider this to be one of the easier Porsche DIY jobs.

More reading...
Still More...

Originally Posted by 450knotOffice

I'm going to offer up slightly different advice here. The first time I adjusted my front wheel bearings exactly per the Bently manual (in the process of a full suspension refurb a few years back), I ended up with wheel bearings that were too loose. I followed the procedure to the letter and yet every time I checked the wheel play, it was simply too loose.

I happen to be good friends with a guy who is one of the best Porsche mechanics I've ever met. Over the years he's worked at some of the best high end shops in the area and has also spent time as a mechanic at the local Porsche dealership. The guy is an amazing storehouse of knowledge and experience - 30 years worth. Anyway, when I told him about the looseness issues I was having with my wheel bearings up front and asked him how he tightened the bearings, he shook his head and said that the procedure described in the book was designed to prevent backyard mechanics from overtightening the bearings, but that the procedure almost always resulted in too much play. So I asked him what he does.

He described a much simpler procedure that he said will put a slight preload on the bearings without over doing it, which is what you want. His method, after snugging down the nut to a firm finger tight condition while rotating the wheel rotor/hub, is to simply rotate the nut another 1/16 of a turn. That's it. Tighten down the allen screw and you're done. He also said that the idea of putting a bit of grease in the cap was simply a waste of grease. If it makes you (he meant me) feel better, have at it, but it does no good and simply creates more of a mess next time you need to get at the bearings.

I've used this procedure since then and have not had any bearing looseness or overheating issues since - and I've put a lot of hard miles on my car since. In fact, I just changed my front rotors a month ago and noticed my bearings still looked great.

Give it a try. It's a heck of a lot simpler than the idea of trying to tighten down the nut so the washer behind the nut can just barely be moved by a screwdriver. That's a procedure that leaves a lot of interpretation out on the table.

[KTL]

Agreed you should just start by checking them for signs of wear. The front wheel bearings are very durable on these cars if they've been kept well lubricated with good grease.

Take the hub off the car and remove both bearings so you can get a look at them and their races. If all looks good- no blueing, pitting, staining, gouges, etc., then flush out the old grease from the hub, rinse the bearings of old grease and repack.

You don't need alot of grease. Some people pack the heck out of the whole hub and cap with grease. Not necessary. Just make sure the bearings are well-packed with grease, swab a thin coat (approx. a finger's worth) around each race, swab some on the spindle and you're all set.

Removing the races is only necessary if they're visibly damaged. And you must use heat to remove them. Heat, as in uniformly warmed in an oven (barbeque grill works too....) at approx 200-250 degrees. Then the races tap right out. I've also seen people weld a bead around the race surface. The intense heat transfer heats up the race & hub together and the race pretty much falls right out.

[ben parrish]

I recently replaced mine as part of a complete suspension refresh....discovered they didn't need replacing once I had them removed. Since I had the new ones, I went ahead and did it. I froze the bearing and heated the hub with a propane torch...still had to tap them in.
Mine were original with 120k on them and looked perfect.

[CCM911]

This is a great topic. Does anyone have a list of what to buy when doing this. I figure you'll need the bearings and Dust shields.

What are we missing?

Thanks.

[cmcfaul]

This is a project that can be easier said than done if you don't have a press. It can be messy removing and reapplying all the grease. Getting the old ones out and the new ones in can be difficult as well. I have done it twice and you are working with a very hot hub and a bearing that gets just as hot in seconds. it’s important that the bearing be sealed all the way in and straight.

For the do it at home person, like me, I heated the hub in the oven. The hotter the easier it is to get the bearing in. However, too hot is BAD.

Good Luck,

Chris
73 911 E

[rusnak]

Discussion about wheel bearing brands: Source for wheel bearings - Rennlist Discussion Forums

Discussion about replacing wheel bearings w pics: B90P Wheel Bearing & Hub Kit for Porsche - Rennlist Discussion Forums

I would probably recommend heating the hubs to get the races out, and re-heat them to get the new ones in. It's a feel thing, so go incrementally. Not red hot, just hot.

[dshepp806]

Was wondering about this Job myself.....had ordered the necc'y parts,...rx'g a set of front bearings marked from Japan,.....and the rear's from India.......(all from our host) Guess I'm gonna' have to read up on Rusnak's links,.....and see what the real deal is,....

mmmm..

Doyle

[JJ 911SC]

Originally Posted by Bob Kontak

Don't know if you have been in there yet but the dust cap can be a stinker to get off...

Yeah-per, this was the worse part along with getting the hub off.

[hcoles]

getting the dust cap off the hub is a bear.... I made this, grabs the indent in the cap and then turn the screws