Tire Problems
 

Hello to all,

I have a 2000 base that I purchased in May of this year. Have really enjoyed the car so far. Chased a CEL light issue for the first 2 month but finally replaced the MAF sensor and all is good. In August I decided new tires were needed. It had Michelin Pilots and ran very smooth but tread was thin. I purchased a set of Hankook V12's from Discount Tire on Line. Had them shipped to my Indy and he mounted and balanced them. I had a bad shake after the car sat overnight. Once they warmed up the shake would go away. Temperature didn't seem to make a difference. Hot or cold morning it still would shake for the first 5 to 10 miles. I felt it in my rear end more than the stearing wheel so I thought I had a bad rear tire. I took them back to the indy and he rebalanced the tires. Same issue. Once they got warmed up the shake would disapear and tires ran real smooth. I called Discount tire and they suggested I replace the driver rear tire and see if that helps. I put a new tire on the driver rear to no avail. Same issue.
Obviously I have thought the tires an getting flat spots from sitting. The unsual thing here is that the car can set for 4 to 5 hours at work and i get in and go and don't have the morning shakes. I'm toldy by my Indy that flat spots don't ususally happen from overnight sitting. Maybe if it sat for a couple of weeks but not overnight. So, I took to a local tire store and had them road force balanced. I watched as they balanced them and they were spot on. I then take the car out for a spin and get a bad steeing wheel vibration at all speeds but worse at 70 to 75 mph, right where you want to cruise on the highway. I am ready to give up. You have now heard my winning story, but I really am looking for someone who may have had a similiar situation. Is it somthing mechanical that is causing the bad vibration in the morning. The car is stored overnight in a non heated garage with a cement floor.

Any help would be appreciated.

1st step in any ride disturbance troubleshooting is check tire air pressure. 29 front & 36 rear. IF rears are already @ 36psi I would set at 40 psi & check for any changes the next morning drive. You have changed from the best quality tire to a lower quality tire with a softer tread compound so it will be more likely to have cold weather flat spots. If the increased psi reduces flat spoting this may well be the only issue you have. Keep in mind extra psi amplifys imbalance issues so you will have to find a happy medium. I only buy Michelins & they will flat spot overnite if cold enough also. Tell us mileage on your car, what wheels & what size tires ? Do you still have Pilots on front?

Tire Problems
 

The car is a 2000 Boxster base with 55,000 miles. 5 speed. The tire sizes are 215/40 18's up front and 245/35 18's on the rear. The pressures are currently set properly as you noted. I will try to add some pressure and se what happens.
Thanks,

Any other suggestions let me know. I know i downgraded to a cheaper tire but there are a lot of reviews on this forum that are positive about the Hankooks. Any body else having issues with the V-12's?

I am going back a few years, back in the 60-70's. Most cars had what are called Bias tires. Most tires did not have steel belts, they where a blended type rubber with Nylon Belted Cords. These tires would ride very smooth, but would thump for a few miles until they warmed up. Hankook might be using a softer rubber for the grip, but they may thump until they warm up or they may have sold you seconds. I purchased Falken 912's for mine and the perform very well. Nice smooth ride with a very decent handling feel to them. They thump a little when cold but not much...now I live in Florida and do not need a tire for snow...that's why I went with the Falken's.

What wheels/tires are you running ?

A good RF balance job should have revealed any rims being bent. How many miles are on it? How bout ball joints, cv's, tie rod ends ? even worn shocks can do it although being speed specific is not usually the way a bad shock behaves.

Ah yes, you have chosen to install undersized tires on your car. Porsche psi specs are for Porsche recommended tire sizes, you have smaller tires so you must increase air psi to maintain load carrying capacity. So basically you are starting off your driving with flat spotted tires.

tires
 

Johnny,

Check out my garage and you will see the rims and tires. They are 18 in. I thought the 2000 base came with 16 inch so these must have been special ordered or put on my the PO.

I tend to agree with Ghost Rider. Regular dynamic balancing simply is not enough when it comes to larger diameter high performance tires . Try getting them road forced balanced . In the process, you may discover that one or more of your tires is in fact out of "spec" .

Hunter GSP9700 Wheel vibration Control System solves wheel vibration and tire pull problems that balancers and aligners can't fix

Tire Tech Information - Match Mounting to Enhance Tire & Wheel Uniformity

Sounds like either a little flat spotting due to cold weather or worn out struts. I had an issue with the car being pretty bump unfriendly for the first 10 minutes of driving. After the car warmed up the suspension worked much better/smoother. I installed fresh struts last year the car is more firm overall but negotiates bumps in the road gracefully right out of the garage.

Your tire sizes should be fine as a base 2000 came on 205/55/16 and 225/50/16 tires. Try running 36 psi cold pressures all around and see if the flat spotting improves. The V12 Evo tires are a good choice with a lot of drivers raving about their grip.