Still shaky even with new tires

Upgraded my 8 year old tires to Michelin Super Sports. Was hoping that the shakiness upon higher speeds would disappear. Noticed the function first transmission mount inserts, and am also considering corteco engine mounts. *all stock except for the fister d mod What do you guys suggest? Thanks in advance!

Road force balance, check ball joints,control arm bushings, alignment, make sure wheels are round(including inner lip/barrel).

I have the same issue. Brand new wheels and tires. Hoping an alignment cures things.

have it road tested by a mechanic

Check all of the above. Wheels do go out of round.

I would first have the tires rebalanced.

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Thanks for the input. Previous have owned a mazdaspeed miata, s2000, and 335 coupe and never experienced this... But on that note. None of them were 13 years old...

Also to note, some shops do not have the proper equipment to balance out a 10" wide and above wheel correctly. But some will still try and pass it off to the customer. If you are gonna have it rebalanced, make sure they have done wide wheels successfully before or take it elsewhere.

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This. Road Force Balance will detect an out of round wheel. I'm betting on a suspension issue.

++ on Road Force Balance. I have PSS's on my Cayman. One tire shop that wouldn't fit them said they couldn't be made to run smoothly-didn't have RFB. Another local shop I tried with an RFB machine guaranteed they'd be smooth and they are. Perfect at all speeds-specially high;-) Machog

+1 on re-balancing the tires... although it could be a wheel out of round, you would probably notice that at lower speeds as well.

Could be a bent rim. 2003 Carrera 4S Speed Yellow / 1955 356 Continental 1500 Rust Red

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I had two out of round wheels. The left rear was by far the worst and I had that repaired. I felt vibration around 60 but not below.

If you look on the Hunter website they have a listing of shops that have a road force balancer.

This could be totally off the wall but when I bought my 03 in 2008 after 28 years of driving BMWs, I faced the same thing. I had all the usual suspects checked out and it still didn't feel right, again based on 100s of thousands of miles on road and track in BMWs. It was really disconcerting. At some point I was talking about it with friends at a track event when a mechanic from a local indy overheard the conversation. He said it was a trait of 996s and that the next time I was on open highway at 65 mph or so, I should lightly let go of the steering wheel. He said the car would track normally and not veer left or right on its own volition. I live in south florida with smooth multilane asphalt highways. I did it while in a middle lane one time and he was right - it didn't veer in either direction. Subsequently I tried it at higher speeds with the same results. I just lived with the vibration sensation after that. Potentially unrelated to your experience but I saw this while looking at an unrelated post.

alignment and/or suspension, my tech had to use a noise listening device to find the problem with a control arm -- even after the 30 year service manager told me 2x that it was "normal." No, it was not normal -- on any car let alone a porsche.

Vibration at speed is NOT a characteristic of the 996, I've owned five of them. An out of balance tire or bent wheel would cause a vibration without causing the car to pull. Bad alignment causes the car to pull.

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+1. I can think of things which may be considered "common" in certain marques but should never be accepted as normal.

I found the same slight shaky feeling at speeds with two of my 996's, one of which had new tires and wheels. I had gotten two alignments (one at Gt3 spec and the other was oem spec) and rebalanced the wheels on the hunter roadforce balancer. Nothing helped except filling up with a full tank of gas as often as I could to put some weight on the front wheels!

Where do you live? Ask a fellow memeber to Borrow a set to test out if it's your set of wheels...

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Louusiana

Last yr I was having a problem with my 31 Ford coupe having front tire shake & found due to the floating spacers in the custom WELD wheels no one locally could properly balance them. A shop guy told me to try ceramic bead balancing which I'd not heard of. So, after researching the best source (ebay) I tried them & I couldn't believe they took away the imbalance ! It was inexpensive & an easy DIY --amazing ! Bob -------------------------------- 01 C4 31 Ford cp chp & ch, 302/350 40 ******, 302/350 38 Ford cp, 327/350 57 Belair 62 356B --long ago

I'm having the same issue. Got my tires road force balance twice in the last couple of weeks, alignment done (shop specialize in race alignment with high end equipment) and it's still the same. I noticed the vibration changes on different type of road. It's most likely my A arms or tie rods, the shop who service my car agrees. I also checked my wheel bearing and they are tight with no noise. Will keep this thread updated once i find time to get it done.

My used of the word vibration last Friday was inaccurate. I probably shouldn't be typing on Friday nights. A more apt description is a slight sensation of the front end feeling like it was wandering a little - like if I didn't make continual, tiny corrections it would gradually veer from the intended path. The indy said he'd driven many 996s that had that sensation but not to be concerned - the car wasn't actually wandering. I then tried carefully taking my hands of the wheel while in the middle lane of a near empty 5 lane interstate. The car tracked fine - just like he said it would. The slight sensation never went away but once I knew the car wasn't actually going to wander into another lane on its own, I ignored it and just got used to it. Maybe my particular car had an aero anomaly that caused the sensation but then again the indy, who had extensive experience driving and racing rear engined Porsches as far back as the mid seventies, said it was not unusual on 996s. I don't have the mechanical or engineering expertise to say one way or the other - just passing on my personal experience.

Your alignment is off - you'll probably find that the toe and/or caster is off. If it feels weird enough that you're mentioning it to your mechanic, it isn't normal. My '99 tracks perfectly, even at exceptionally high speed. Yours should be able to do the same.

No vibration at any of the speed ranges I have tested in my 996 (0 to 145 mph)

Having experienced a 99 at 135 with no wiggle wobble shimmy or shake I can say that I am looking forward to figuring out my 02 as the feeling is far less confidence inspiring.

Also keep in mind that not all alignments are equal. When i had mine aligned after i installed my M030 I had a porsche specialist shop do it. I would not just take it to any shop, it needs to be someone that knows what they are doing and is familiar with these cars. And mine feels like it is on rails at any speed.

Hard to put a price on a really good alignment. I had mine done by a friend who race preps Corvettes and BMW's for the track. He's not "known" for Porsches, but he's a wiz... Took him about 3 hours as it was so ****ed up on all corners from the selling dealer. Find someone good, and don't rush them. .02

Ok...just had my car out of the shop with new control arms and the wheel shake is gone!!.. I'm bringing it back for an alignment as the wheel is slightly off center without any pull while driving.

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Which control arms did you buy to fix this?

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I bought the OEM.

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Did you try changing the suspension bushings or engine mounts first? Just trying to figure what to try next...

Would it matter if the previous owner had the vehicle sitting for long periods at a time? In regards to this shaking?

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Flat spot in tires? What about wheel bearings? Mike

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New Michelin Super Sports Balanced with new tires and re-balanced a second time on cones... Thinking of doing the road force balance next... If that doesn't work may check the suspension bushings and engine mounts...