tar6day

On the race track today and my car started to make a "thump, thump, thump' noise that would only be heard from inside the car on right hand turns. It was coming from the passenger side rear wheel area. Wheel bearing problem??

Thanks,

mooty

assuming all other things are fine and your have no rubber accumulationg on your tires, it's most likely bearings. i just had the samething happen to me and bearing it was.

Tom W

Jack the front up and tug on the tires. If there is any wobble, it's a wheel bearing.

I think that it is most likely rubber that you picked up off the track. My first few track events caused some concern due to noises like that that were due to clumps of rubber.

tar6day

I'll check for rubber. I was going to change wheel bearings anyways...... so this just gives more of a reason.

thanks

Alon

No humming noise and grinding feeling? Those are both common symptoms of a failed bearing.

Greg Fishman

Sounds like CV joint. When was the last time you had the axles serviced? Good idea to take them off once a year and repack the bearings. That is the only service you can do for the stock units.

As Alon said, failed bearings don't thump.

KASH '95 993

I have been getting this humming/ mild grinding noise, but I'm unable to determine if it is coming from the front or the back (how can I tell?). Is it relatively easy to change all four corners? Any ideas on the cost of the parts and a good source is greatly appreciated. TIA

Alon

It does sound like a wheel bearing but could be something simpler like a bad tire too. I'm not really sure how you could determine front or rear while driving unless you get someone to stick their head way out and try to listen but I would jack the side up that the sound is coming from and check for any wheel play by shaking the wheel while grabbing the top and bottom and then side to side. For the front wheels, expect some play side to side due to steering but you should feel no play otherwise. For install, check www.p-car.com I remember seeing a write-up on a bearing replacement. It's not that easy or cheap to do all four and I wouldn't rush to change any unless you know for a fact that it is a bearing problem.

Does the sound/feeling change when you corner? Is it speed sensitive?

Martin S.

Drive the car in a wide open space, put the car through some hard lefts and rights. If you hear a howl when you load up the suspension in a corner...suspect wheel bearings...

"Whem you hear hoof beats, look for horses, not Zabras." Note: This advice does not work in Africa...but it is good most other places. I would be doing the following:
1. Look for debris build up on tires,
2. Jack the car up and tug at the top of the tire. If the wheel moves...not a good thing.
3. If there is no move,emt, take the car to the trusty mechanic for have it inspected, and of course you will check the CV joints..they can also diagnose wheel bearing failure.

If you drove nearly any Porsche up to the 993, wheel bearings would be relatively inexpensive. On the 993 car, the rear suspension has to be severely torn apart to get at the wheel bearings...not so tough on the front. When I had all four replaced...the car was howling on the left to right under load test, the bearing were about $200 for four, and the labor was about six (6) hours...this is not a cheap fix.

Note, we are putting one hell of a load on those bearings with our huge tires and R compound rubber. They will wear out sooner than a street only car in which the bearings will last a longer time, much longer I suspect.

kkim

To troubleshoot between a tire problem and a wheel bearing, just mount another set of wheels/tires and see if the noise goes away.

KASH '95 993

Alon,

I haven't detected any changes with respect to cornering and the humming seems to start building at about 30 MPH when accelerating and usually tapers off at about 70 MPH (drowned out my the higher RPMs maybe???). If I let the car coast down from about 40 MPH to a about 5 MPH, the grinding sound becomes evident right around 30 MPH with the humming sound at its loudest all the way down to 5 MPH. New tires on 18" Twists (still awaiting steering rack brace from dealer).

Thanks for the feedback Martin, $200 for all four is not too bad (will be doing the work myself if it comes down to it).

Martin S.

I forgot that one GEM of advice that Kelly mentions...swap out the tires. I had a set of Kumho Ecsta MX tires on the car, my street wheels, and I could have sworn that the bearings were going out again! I changed tires...the noise went away. Note the tires went away soon thereafter; I sold them to a guy who just loves Ecsta MX tires. As they say, there is an *** h*%e for every seat!

If you are hearing a Grinding Noise....it can't be the tires....good luck with the project.

Alon

Great suggestion. If there is a spare set available, swap them out and have a listen. You mentioned that the noise seems to go away at higher speeds, perhas drowned by engine sounds. Get up to speed and drop the clutch or put in neutral and listen for the sound. I don't know that I have ever heard of a noisy bearing losing its noise at higher speeds.

Jeff96-993

Tim,

What part of Ohio are you in? I did a wheel bearing replacement DIY here on Rennlist and p-car.com, so I spent some time diagnosing and replacing. If you're close to Cincy I'd offer to drop by for a quick run through.

Two things I found... first, when I did the "wiggle" method, I didn't feel a thing. The brakes pads limited the movement leaving no wiggle at all. Unless you back off the brake pads you might not feel anything. I didn't figure it out until I took the caliper off and then the rotor flopped around.

Second, the best way I found to find the suspect bearing was to push the car on level ground. With the engine off you can hear the bad one (at least I could on mine).

Good luck.

Greg Fishman

Jeff,
Another way to check the bearing is to remove the wheel and the brake pads and spin the hub/rotor assembly. Very easy to tell when you have a bad bearing as it feels like it is full of gravel.