bearing, joint, or tire - 986 Forum - The Community for Porsche Boxster & Cayman Owners

oc-boxster · 11-27-2012, 09:46 AM

i know its difficult to diagnose without audio, but im getting a speed dependent rumble from what i think is my right rear wheel, thers no clunking or change in sound turning left or right, its more of a hum like a dirt tire on asphalt but im not sure whats causing it, the ppi i had done revealed a torn cv boot which i havent addressed any ideas? the tire on that side doesnt show any abnormal wear from what i can see,

Kenny Boxster · 11-27-2012, 09:59 AM

Check to see how worn the tire in question is, and if any of the nylon thread is showing. That will give you a bad noise and shaking. Run your finger and see if you can feel the wear bar in between the rubber. That would probably be the easiest to check out.

thstone · 11-27-2012, 11:17 AM

Check the wheel bearing by lifting that corner of the car and pulling on the tire/wheel from top to bottom and from side to side. There shouldn't be any play. Then rotate the wheel while lifted and listen/feel for noise/vibrations from the bearing. A bad bearing will usually sound rough or feel like there is some grinding or skipping from smooth to rough.

Check the tires by swapping the rear tires from side to side. Does this change where the noise comes from? If it moves to the other side, then its the tire.

If the bearing and the tires check out ok, then the last place to check are the inner/outer CV joints. They can be hard to diagnose but if its not the bearing or tires, then you're left with the CV's.

Ghostrider 310 · 11-27-2012, 11:20 AM

Does the noise speed up and slow down in tandem with acceleration and deceleration?

oc-boxster · 11-27-2012, 01:08 PM

Quote:

Originally Posted by Ghostrider 310

Does the noise speed up and slow down in tandem with acceleration and deceleration?

yes it does, and i can hear it start at a pretty low speed, and is constant even wiht the car in neutral coasting.

Ghostrider 310 · 11-27-2012, 02:09 PM

Then we know it's rotational, I'd guess wheel bearing, CV joint or least likely warped rotor or hanging brake pad. It could be the tire too but that seems unlikely as well, easy enough to check as another member pointed out. If it were me and I was swapping the tire I'd take the extra time to pull the caliper and rotor, inspect, clean and reassemble.

oc-boxster · 11-27-2012, 02:40 PM

I'm gonna take everything apart on that side and then maybe ride around the block with my spare on that side to see if it makes any difference it's getting so loud it's hard to stay in there very long

Ghostrider 310 · 11-27-2012, 02:46 PM

If it's that loud you will likely find it when you take it apart, it also means the possibility of it being rubber is reduced. Once it's jacked up spin the wheel, concentrate your vision on one spot and inspect for any hop or out of round look as it rotates, listen for the noise too and try to isolate it.

oc-boxster · 11-27-2012, 02:51 PM

Ok thanks for the help-the tires on the rear are Pirelli p zero Nero that are down to about 15-20% tread left I thought I remember reading Pirelli tires tend to be loud

Ghostrider 310 · 11-27-2012, 03:24 PM

Without hearing the noise and with each of us having a differing perspective on loudness it's tough to make the call over the net. Ruling out the rubber is next and if it happens at very slow speeds I guess using the spare is not a bad call.

Frodo · 11-27-2012, 06:21 PM

Quote:

Originally Posted by thstone

Check the wheel bearing by lifting that corner of the car and pulling on the tire/wheel from top to bottom and from side to side. There shouldn't be any play. Then rotate the wheel while lifted and listen/feel for noise/vibrations from the bearing. A bad bearing will usually sound rough or feel like there is some grinding or skipping from smooth to rough.

Check the tires by swapping the rear tires from side to side. Does this change where the noise comes from? If it moves to the other side, then its the tire.

If the bearing and the tires check out ok, then the last place to check are the inner/outer CV joints. They can be hard to diagnose but if its not the bearing or tires, then you're left with the CV's.

Good advice, though in my case (passenger front) my wheel passed all the tests in the first paragraph---I could not demonstrate any unusual sounds, feel or movement when the car was stationary and jacked up. I did try switching wheel/tire between the fronts, and the sound stayed on the right side. I ended up going on the fact that the sound varied with the speed of the car, worsened as I took the car through a curve, AND there was nothing visibly wrong under there. With a rear wheel, I'm not sure if you get that change in sound as you take the car into a curve or not.

Anyway, I eliminated everything else as well as I could, then dove into changing the bearing. I didn't know for sure that my diagnosis was right until I finished the job and took it for a test drive, fingers crossed. I'd have been one frustrated SOB had the offending noise persisted...but it didn't.

ohhh my · 11-27-2012, 10:15 PM

I'm pretty sure it's a bearing. Sounds exactly like the same problem I had...

BYprodriver · 11-28-2012, 08:50 AM

Quote:

Originally Posted by oc-boxster

i know its difficult to diagnose without audio, but im getting a speed dependent rumble from what i think is my right rear wheel, thers no clunking or change in sound turning left or right, its more of a hum like a dirt tire on asphalt but im not sure whats causing it, the ppi i had done revealed a torn cv boot which i havent addressed any ideas? the tire on that side doesnt show any abnormal wear from what i can see,

1 thing we do know for sure is if the CV boot is left leaking grease long enough it will cause the joints to wear & make noise. If you feel the tread of the suspected tires you can tell if the tread is rough enough to make noise like a dirt tire.

oc-boxster · 11-28-2012, 12:31 PM

so i just pulled both the rear wheels off and inspected the tires they seem fine and i have ruled them out as the cause, checked all 4 cv boots and other than some very small surface cracks they are not leaking and look ok-gave both a side to side tug between the boots nice smooth movement with no clunks-i didnt go as far ast to remove the calipers and rotors but i did turn the whole assemblies by hand there is resistance on both sides and a metallic dragging sound from both-what i did notice on both sides is the outer brake pads were extremely close to, if not touching the rotors-is that normal? but from what i saw i now believe it is a wheel bearing i just cant duplicate the noise just turning the hubs by hand-gonna take it to the mechanic after the holidays, so tired of the noise

Frodo · 11-28-2012, 01:46 PM

Yeah, the brake pads are typically really close to the rotors (in my somewhat limited experience). FWIW, it sounds to me like you are in the same boat as I was: unable to get a definite diagnosis. With his additional experience in such matters, odds are pretty good that a seasoned mechanic would be able to give you a thumbs up or thumbs down on the wheel bearing question. Probably a good way to go.

oc-boxster · 11-29-2012, 07:45 AM

one more question; is it wise to drive the car another 500-700 miles with the bearing making so much noise it will probably be january before i can get it to the shop but i need the car in the meantime?

Topless · 11-29-2012, 10:47 AM

Quote:

Originally Posted by oc-boxster

one more question; is it wise to drive the car another 500-700 miles with the bearing making so much noise it will probably be january before i can get it to the shop but i need the car in the meantime?

No, get it in to a shop sooner rather than later. An Enterprise rental car is $50 but if a bearing fails and your RR wheel passes you as you are going down the freeway it will be a lot more $$. (don't ask me how I know)

Some good qualified shops in SoCal:
::: ZONE 8 - Porsche Club of America :::

Ghostrider 310 · 11-29-2012, 11:45 AM

+1 to topless you can spin the race and ruin the seat that it resides in, sometimes it just welds the entire assembly together.

oc-boxster · 11-30-2012, 11:26 AM

found a great shop with cool guys in orange ca, that diagnosed a definite bad wheel bearing and quoted 3 hrs labor at 110 an hr and 60 dollars for the bearing-so not as bad as i thought..should be back to nice and smooth after that.

Frodo · 11-30-2012, 01:56 PM

Hey, yeah, that's not bad at all. When I was tryin' to diagnose mine I stopped at the local P-car dealership and was asking a few questions about it, gently pumpin' them for opinions. I ended by asking what they would charge to replace it, assuming it was in fact the bearing. (Not knowing yet whether I was willing to try this job on my own or not, but also KNOWING that what he was going to quote me was gonna be way more than I was willing to pay!)

His answer? Around a grand. I was NOT surprised...