I recently put a new set of Bridgestone Potenza RE750s on my 05 GT...They have probably 500 miles on them to date... I took them on my first road trip and interstate driving and have noticed some problems... I increased the tires from the 235/55-17 to the 255/50-17 all around... On the interstate the tires feel as if they are swirving all over the road... Its not a bad bad swirve and its not truely a wobble that would stem from the tires being off balance but its bad enough to worry me... When driving in a strait line the car seems to be moving back and forth some from the front and rear end... truely its hard for me to describe... and the bump steer is almost unbearable anywhere I drive... one little bump and the car feels like it gets squirrely... I did not have the front end aligned when I had the tires put on because the front end still tracked strait as an arrow... Sorry for the long write up but I dont even know how to go back to the tire place to describe my problem

 

Have you checked the tire pressures? Maybe they are way too high?

 

Some tires just do that on streets, especially if they are high performance unilateral treaded tires and wide. Also if the road has a crown in the middle or slightly lower where the tires run like a rut they will do that. Sometimes you cant even notice it driving along it just looks flat. I haven't heard of too much complaints here on TMS though so you might want to get them checked out.

 

Did you have new bands (TPMS) put on the wheels? It could be that they arent set tight enough and they are spinning around the inside of the wheel.

 

I never heard of putting new bands on the wheels? no telling there... Im going to check the tire pressure now sometimes it does seem that the tire pressure it too high...

 

I say that, because it happened to me. One of the tires was out of balance, so they fixed it, still a wobble/vibrations. Then I noticed they had 48 psi in each tire, instead of 32. And last but not least, I have them take each tire off and check the wheels and its then, that they discovered the bands were rotating, causing the vibration, etc.. Changed them to tightest setting, and now its perfect.

 

The RE750's are a wet and dry tire vs. the all season rubber you replaced, along with another inch of rubber per wheel put down on the road. Its probably just grabbing at every imperfection in the road (trammeling IIRC is the term used to describe that). Tires should not have affected bumpsteer, unless of course, you have lowered the car.

Check the tire pressure to make sure it is consistant from side to side and front to back, also check the lugs - did the shop use a properly calibrated torque wrench - did cleam the mating surfaces - did they snug the wheels down or just slam them on with an impact. Also, if the tires were not properly lubed, they may have hung up on the wheel and aren't properly seated. This actually occures more often than people might think. if you've ever had a tire wear out in one spot, take a look down where the rim meeets the tire, most tires have a refernce line which should appear concentric to the rim. If not, then the tire was not seated correctly.

The proper method for mounting a tire would be;

1. Lube the rim and mating beads on the tire.
2. Inflate to 40 PSI, then drain the tire completely
3. Inflate to vehicle manufacturers specifications.

This allows the the bead to relax and seat itslef properly on the rim.

Unfortunately its a time consuming procedure and 99.99999% of the shops out there are under the gun when it comes to time and its much easier to just inflate and set to the vehicle manufacturer's specs.

Also a good thing to ask about, is the type of lube the shop uses, a tire specific lube should only be used (the worst being a water soluable lube), perferably a non aqueous type lube, and defintely not WD40 or something similar (consider the tires ruined if WD40 or a petroleum product is used to lube the tire).

 

is your car lowered? i am thinking of going to this tire size next....

 

The car is not lowered... I will be checking the pressure of all tires as soon as I find my tire pressure guage

 

All good things mentioned.

Did you ever find your tire pressure gauge?

colbymh, he has an 05, doesn't come with tpms.

 

Ya no tire pressure monitor for me on the 05 sadly... Its somewhere in my shed I just managed to misplace it... It will probably turn up where I least expect it.

 

I put on BFG 255/50/17's also. Mine follows every rut in the road.

 

I put on Nitto's 555, they follow every groove that is cut into the freeway.

It drives like a hyper active kitten. It keeps you on your toes!!

 

Something's not right, then... I've got the 555s in 255/45 and 285/40 18" sizes, and the car just tracks. It gets a little dodgy when going over a metal-grate drawbridge, but actually less so than the stock tires. Try running a little more toe-in and a bit more negative camber, and see if that settles things down. I'm running 1/16" toe-in, and -1.5* camber on both sides.

Toe-in will help with stability, and toe-out will help with turn-in.