Wheel bearings bad?

Ziggy925 · 07-25-2015, 07:05 PM

I have a '79 911 SC and my mechanic, an independent good with Porsches, is telling me my wheel bearings need to be replaced. How do you know when your wheel bearings need to be replaced? I know what "bad" wheel bearings feel like, but right now the car seems to be rolling fine -- to me. No noise or grinding when steering side to side. The car has 120 K miles on it and I've had it since '89.

Help me. I don't want to throw money away, but I also don't want the wheels to fall off. Assuming there is some play in the bearings, don't you usually adjust that?

ben parrish · 07-25-2015, 08:17 PM

Ask the mechanic why he thinks they need replacing and have him show you the deficiency..

ninelevenick · 07-25-2015, 08:39 PM

Did he tell you that all four need to be replaced? Did you get your wheels off the ground and do the 12 o'clock/6 o'clock and 9 o'clock/3 o'clock tests?

sugarwood · sugarwood's Garage

The wheels will not fall off.
You may hear a sound if bearings are bad.

And they will be loose.

safe · safe's Garage

Quote:

Originally Posted by Ziggy925

I have a '79 911 SC and my mechanic, an independent good with Porsches, is telling me my wheel bearings need to be replaced. How do you know when your wheel bearings need to be replaced? I know what "bad" wheel bearings feel like, but right now the car seems to be rolling fine -- to me. No noise or grinding when steering side to side. The car has 120 K miles on it and I've had it since '89.

Help me. I don't want to throw money away, but I also don't want the wheels to fall off. Assuming there is some play in the bearings, don't you usually adjust that?

You hear it... but it can be hard to. If you have the wheel in the air you can hear a bad bearing if you spin the wheel, that can be hard to do in the rear with the CVs attached.
Listen to the sound in the video above in the end, it may sound "fine" and spin freely, but it should be dead silent and have a little more drag.

In the rear there should be no play, if there is, they are seriously worn...

In the front there should a small amount of play.

jason2guy · 07-26-2015, 12:51 AM

yeah i wouldnt go messin with those unless you NEED to. its tricky work and if your mechanic is a gorilla itll be a nightmare. i would say if you dont hear them they are probably ok. it wouldnt hurt to take apart the fronts and clean that 100yr old grease out of there and repack them

mhackney · mhackney's Garage

I replaced my front bearings 2 years ago after my local mechanic mentioned that they were a bit loose after my annual inspection. The car had been feeling a little squirrelly but it had also been pretty windy for the previous month. He was right even through the bearings were not making any noise.

Check by jacking up the front end of the car and grab the tire at 12 and 6 o'clock and rock back and forth. Same at 3 and 6. If there is any excess play, it's time to replace the bearings. I did the work myself because of all the warnings I read about gorilla mechanics. I do have a large press and an oven and the proper tool I borrowed from a friend to press out the bearings. It was actually a straightforward job if you have the tools.

mreid · 07-26-2015, 05:22 AM

In general, if it rocks an equal amount at 12/6 and 3/9 and can't be adjusted and makes noise, wheel bearings. If it rocks more at 12/6, ball joint and more at 3/9, tie rod. This is a general guideline and is then used to pinpoint where to investigate further.

Ziggy925 · 07-26-2015, 11:00 AM

Quote:

Originally Posted by sugarwood

The wheels will not fall off.
You may hear a sound if bearings are bad.

And they will be loose.

Great video! I will definitely talk to the mechanic about the "why," and I've done the 12-6 and 3-9 test before on other cars. I guess one of my questions is how do you know when to just make an adjustment vs. inspecting and repacking? I would assume if you go so far as to have the bearings in your hand you may as well replace them.