How to inspect wheel bearings

[gabenheimer]

I had my car on jack stands this weekend and discovered the front wheel bearings are loose on both sides. Rather than just tightening them up, I plan on taking the hubs apart and inspecting the bearings up close. This seems like a good idea since the car has 124,000 miles and I don't know if they have ever been replaced or serviced. My question is this, after I have the bearings out and cleaned up, how can I tell if they need replacement? Is there a certain spec or should I just look for pitting and other corrosion?

[jtratza]

I replaced mine early this year. Seems to me I remember they didn't cost enough to fool around using the old ones.

[Oh Haha]

Look for pitting and corrosion BUT since you have to take them apart anyway, why not just replace them? 124,000 miles is a good service life for the bearings. You may never have to do them again. Do a search here using the words " front wheel bearings" and you'll have plenty of reading to do. The inner race can be a PIA to install so the reading will help you understand what to do.

[gabenheimer]

Originally posted by Oh Haha
.... The inner race can be a PIA to install so the reading will help you understand what to do.

So, should the races be replaced along with the bearings?

[Oh Haha]

Yes, you should ALWAYS replace bearing races when installing new bearings.

[randywebb]

when a front bearing reaches replacement stage you will see tiny flecks of shiny metal stuck in the grease between rollers. No flecks? Re-pack them and put in new seals...
Peter Zimmerman

(from a current thread on RennList)

[Eagledriver]

I wouldn't replace them if they don't need it. Pushing out the old races and pushing in the new ones is not easy nor without risk of error. They don't have a mileage limit. If they are bad you'll see pitting and discoloration in them when you inspect them. If they look shiney and silver with no pitting or scoring on the races then they are fine. Grease them and reinstall. They are tapered so they will go as tight as you make them. Installing new ones will not make them tighter.

-Andy

[Zeke]

Lightly grease them and install to spec. Mount the wheel and turn it and listen when things around you are very quiet. I you still don't hear anything, you might be good to repack fully and drive some more. However, I agree that once you're torn down this far, just do it if you have the skill and the right tools.

Do you have Wayne's 101 Projects book, a Haynes, or something of that order?

[Formerly Steve Wilkinson]

Nobody in the aircraft world would try to figger out whether or not they saw microscopic "flecks of shiny metal," much as I admire Peter Zimmerman. If it's a wear-sensitive part, you "change it out," as the aviation phrase has it. Because maybe if you ran it for 15 minutes and then took it apart again, you _would_ see flecks of shiny metal.

I don't meant that you should replace wheel bearings every 15,000 miles, but if they've been in there for 124,000 miles and have been running loose for awhile, happiness is changing 'em out.

Stephan

[randywebb]

I agree that the cost is so low one is well advised to just replace them, once they are removed.

Pete's comment is on a Rennlist thread that is live now if you want to post there.

[rusnak]

I've found that if you can't adjust out the "wobble" or if excessive clunking returns soon after re-packing, then that is a definite sign that the bearings need to be replaced.

I've had good luck with the new Japanese made bearings for the 911. I've also had good luck with V-power synthetic grease. You have to pound out the old races with a long hardened steel punch, like the kind you get from Sears. You may have to re-surface the punch on a bench grinder for the second pair of bearing races. Lisle tool makes a good tool to punch or press the new races back in. Lightly coat with oil, like air tool oil or something light, then press back in with a hydralic press. It's important to make sure the new bearing race is fully seated and square to the hub.

Good luck!

[Brad01mc]

Hi!

I'm not sure about p-cars, but in the past, I've used the 6 inch extension from my socket set as a drift to drive out the race. There is usually some form of a cut-out, on the hub, that allows you to get at the back of the race.

Once I've pounded the race out, I use the old bearing race as a means to drive in the new one. You have to be careful, since you can damage the edge, or even "mount" the old bearing with the new!

The 3rd thing is to use the extension, or drift to listen to the sound of the metal hitting the hammer. Being very careful, you can rest the (rounded) extension on the lip of the race and give it a good hit with a hammer.

When the race is seated, the sound of the hammer blows will sound different. It will turn from a tinny "ting" to a solid "thud".

Of course this method is probably not popular with many of the folks out there, but it is a hardened steel cup and I've never had a problem doing it this way.

I'm not saying my way is the best, however, it's a cheap alternative to a simple problem!

Brad

[balleta]

Gabenheimer

Just think "How many times that little bearing have turned in 124K miles? Don't think thats enough?
(That's a mathematics assignment?)

[Green 912]

Late night ramblings... Not an expert opinion by any measure.

A bad wheel bearing is kind of like Porn. You know it when you see it. Asw as said but worth repeating. Replacing races is not without risk to the hub. Just hammering a new race in and having it cock during will more likely damage the cast aluminum hub than the race. New bearings and races always go together!

A wheel bearing, that after being properly adjusted, still lets the wheel slop side to side is more likely a bad spindle or a race that is not fully seated and moving. If the bearing were this bad it would likely growl and or look and yes, smell bad. To differentiate you can over snug the pinch nut and wiggle the wheel up and down. No wiggle? Loose seat. Still wiggles but a bit less? Check the spindle diameters where the bearing run. Even a small amount or wear will translate into a lot of movement. Also, fully clean and inspect the hub for cracking. Even more so if you have a 951 which are know for fracturing in spectacular faction.

If you install new bearings and races and the wheel seems to keep getting loose after you adjust it a race is likely not seated all the way given a good spindle. This is not uncommon but must be fixed ASAP. A loose race will destroy a bearing in short order.
Clean the hub real well then inspect and feel the race seat areas in the hubs. They must be clean and burr free. It makes for much less force needed if you heat the hub to 300 deg or so and cool the races. Often times the races will just drop in with no force, pressure or impact. Even if they drop in they need to be seated fully and true and checked as they can bounce and stick up off the seat. I give each race a seating stroke even when installing in heated hubs. You cqwn press or impact a race without heat added to the hub but there is less force involved when you heat them. Makes me clean them well and I can inspect then while cleaning them too.
I then use a 90 deg dental pick to feel if there is a gap at the race /hub seat face on each race as well as look using a bright light. Clean out the inside of the hub after you press, drive and fully seat the races. Your work can leave crud or metal shavings behind. Wash your hands or put latex or nitrle gloves on before you handle or pack the bearings and reinstalling the hubs. Inspect the bearings and pack with lots of grease but don' fill the bearing cup.
Does your 1/2 full slimy plastic pot of bearing grease come from this decade? If not chuck it and get new grease.
Don't forget to get and install a new hub seal! Cardboard is a big help. i cut some one foot squares of new like clean card board and swap out to a new one during packing and assembly. Be aware of where you set greasy things that are supposed to be clean or used where clean grease might be.

[gabenheimer]

Thanks for all the great advice. I just bought the car a month ago and the PO didn't have many records. So far, it looks like it was maintained fairly well based on some of the work that I have done. I'm not sure if the bearings have ever been replaced, but the wheels are slightly loose. Based on what I'm reading, it sounds like I should replace the bearings and races for good measure. Basically, cheap insurance.

I have a press and several punches to remove the old race. I've done it before, just not on a Porsche. Here's a pic of the project car. Thanks for all the great advice.




I plan on selling the ducktail soon. Let me know if anyone is interested.

Randy Gabe

[gabenheimer]

I forgot to ask. What is the complete list of parts that should be replace when doing front wheel bearings?

[Green 912]

Good grease. gloves. cardboard. brake cleaner or other clean solvent.

Inner and outer bearing and seal. one of each per wheel.

Project car! nice looking project car. this is a project car where I come from.

[gabenheimer]

Wow, that really is a project! Looks like wheel bearings are waaay down on your list of things to do.

Randy

[Formerly Steve Wilkinson]

Oh, god, talk about porn...stop me before I Project again.

Stephan