Tony356993

Rennlist - Please Help!

Background:

1996 TT, 56k miles, PSS-9's (Setting #1 all around), Fikse Profil's & Michellin Sport Cups - stock sizes (Runnig 36 psi F and 40 psi R - Hot), Techart ECU, S spoiler w/ brake ducts, Pagid Oranges, track alignment. Mainly driven only on the track. DE's only no racing.

Advanced DE Run Group.

Situation -
Friday was an "open" track day with our local PCA for advanced run groups. I drove the Pocono North track for about 200+ miles on Friday. The longest stint was about 1 hour in duration. It was by far the biggest test the car had in my ownership. The car was phenominal with no problems whatsoever.
Saturday was a regular DE with 25 minute sessions. My wife (Beginner group & slow....for now ) and I both drove the 1st 3 sessions without any problems. On the 4th session, I thought I picked up a "booger" because I had a thumping sound that sounded like rubber/plastic hitting the wheel wells. After another lap I pulled off and had someone look on the tires and under the car. There was no sign of anything so I went out again for another lap. The sound came back and I came off the track.

Additional facts -

1. The sound does not start right away while driving. It starts at about 30-40 mph and has a loud sound inside the cockpit.
2. The sound REMAINS if you put the car in neutral while driving.
3. The sound REMAINS if you depress the clutch.
4. The sound REMIANS if you left foot brake slightly.
5. The sound is there no matter which direction I drive L/R or straight.
6. It does not sound metallic.
7. There is no sign of any vibration through the pedals, shifter, dash, or seat of my pants.
8. The sound does not increase rythum proportionally with speed.

What we tried so far (At the track - No lift and No Manuals)

1. No signs of anything loose of hanging.
2. All wheels off and all brake pads examined.
3. Under trays removed and no signs of anything loose or flapping.
4. Console removed and examined.
5. It sounds like the noise is coming from the front of the car but I know noises can travel.

I dropped the car off at my P-car specialist/race shop and I'm sure in a few days I'll get some answers but I'm not the patient type.

Can a bearing start this abruptly? Will it sound this way?
Does it sound like a CV or differantial problem?
Is it a 4WD specific component?

Thanks for looking.

Tony

Jim Morton

Tony:

Did you have any vibration(s)???

I would jack up each front wheel and check the wheel bearings and the front half shalfs for play / slop. If you do not find anything, there is another possibility...

If the noise is merely a thumpa-thumpa sound in time with the tires, check your treads for scramp rubber stuck to them. Many times you can get a thump noise when a nice "blob" of rubber adheres to your tire(s). I typically run my car down a concrete highway after a track day to get the scramp rubber off. Usually all of the odd little noises go away with the stuck on rubber.

Might be worth a try if there is nothing obvious...

Tony356993

Jim,
No vibrations felt anywear. I looked at the tires and the have some rubber on them but the sound is not right. I will bring my street tires to the shop and do a quick switch just to see if the sound goes away. Thanks for the idea.
T

Kevin

As soon as you rule out your tires, I'd check your wheel bearings and CV joints.. When was the last time since you repacked you CV's

fc-racer

I bet money its your wheel bearing. Most likely, the rear one which took the most load during the track day. They are pretty expensive to replace, I had to replace my rear left as the PO had tracked the car frequently.

John H. in DC Area

Just a couple of thoughts ...

If you've thoroughly checked the tires (including for bulges on the inside edge that's difficult to see), wheels, bearings, cv joints, and coupling area, then check the plastic liner that attaches where the wheel well meets the lower back edge of the front spoiler. It's never happened in my TT but it was loose in my Land Rover and would only start to flap loudly over 40 mph when the wind resistance was strong enough to move it. The other idea relates to the Turbo S foglight/duct assembly ... did you tie/tape down the unused wire/socket set? It could be flapping around in there at speed.

Good luck, sounds annoying.

Rassel

If it is the bearings, I think you can get them cheaper if you order directly without going through Porsche spareparts. I'm not too sure, but I think it's a F.A.G or a SKF bearing. Your local car-part store should be able to order those. Changing bearings shouldn't be more difficult than on any car.

Faulty bearings can some times be undetected at slow speeds, and then reveal themselves after a while. However, usually the sound is changing proportionally to the speed. Also see if the noise changes when breaking. The weight of the car is transfered forward and should put a different load on the bearings.

If you have Turbo S ducts in the front. Check if those are clear, and also try to put some tape over them to see if it changes/removes the noise.

If you have another set of wheels, you can always try to change and see if it bakes any difference.

Have you checked your belts in the engine bay?

Just a few suggestions..

Jay993turbo

I had a clicking noise that sounded like a bad CV joint, I took it in for inspection and it turned out that the inside lip of one rim was cracked in two places.

Tony356993

The problem was.............................a loose piece of windsheild trim. It would start to flap at about 40mph and start hitting the b-pillar and windshield. It was not visible to me while driving but that was the culprit. Sounds stupid and IS stupid but at least it wasn't expensive. By the way, Pete on the 993 board had the correct guess. Rennlist is great. The savings at the mechanic can pay for a lifetime Rennlist membership.
Thanks again,
T

KRA993tt

Tony,

Great news! See you at the Glen.

Tony356993

Thanks Keith.
What did you say your hot pressures were your sport cups?
T

AndyT

Tony are you number 119 when you run with NNJR ? I think you may be. I saw your car at Poc North this year. That car is beautiful I was meaning to ask you if those were Aeros or Profil 13s. What finish did you get ? Also what are the spec on those wheels. If you don't mind I'd like to get the exact same setup. Thanks Andy NNJR member #109 Black 97 twin.

Tony356993

Andy,
My wife and I were driving with NNJR an April. Thanks for the kinds words about the beast. The wheels are profil 13's. They are the same size as the stock wheels and I run Pilot Sport Cups that are stock size. I really like the look but is is quite hard to keep them clean at when you track the car. I'm going to try and get into NNJR Glen and Porscherama. Be sure to say hello if you see me.
Tony

AndyT

I'll be there as well assuming all the problems go away with my car. Hey I like that you took off the Turbo badge. Very sneaky !! haha I had Fikse FM10s on my 930. I got the anodized centers and that helped with the brake dust. The outer lips though I had to polish very often. Thanks Tony.

KRA993tt

Tony,

The info I have is from a Michelin presentation for our tire size and the weight of our cars. 32 - 34 F and 37 - 40 R Hot. 160F - 220F temp is optimum.