I kinda read thru driveline vibration issues with current gen. TLs...
I dont think my problem is the driveline vibration.
My TL has wheel vibrations which occurs *sometimes*

mostly in the cold start (way to work in the morning)
i get on the highway within 2mins from my place. then while acclerating, the car vibrates very noticebility. especially between 40MPH to 60MPH. after 60MPH it still vibrates.

but mostly afernoon driving (going back home, or at nite) the vibration is mostly gone.

I tried to shift into N during high speed and it still does vibrate, so i am assuming its not the driveline problem.

maybe its just simple wheel balance issue....

anyone have any clue what my problem is ??

 

Flat spotting? Perhaps someone knows better than me, but this is my guess. What tires are you running?

 

i am using yokohama es100? (not sure) it's the one with A-SPEC rims

 

Yeah, those will flat spot. Typically this lasts for 6-7 miles (maybe 10) and is more pronounced on colder mornings...

 

well... my Tire pressure reads (in the morining) 28PSI FRONT : 27PSI REAR
then after 10 mins of driving, it rises to 32PSI FRONT : 30PSI REAR

and i am wondering if this is normal PSI rate increase.

 

Yeah, that sounds normal, but the increase in pressure itself won't make the flatspotting disappear. It takes a certain number of revolutions for them to true themselves. I would say, though, that your cold pressure of 28 and 27 respectively is a little on the low side. Increasing the pressure a bit would probably reduce some of the tendency to flat spot on cold mornings...

 

Thx for alot of info dug-mac,
i am just scared of putting more air into the tire since my tire completely blew on the highway 2 times on my previous car.

 

What is the tire pressure specified on the placard in the car?

 

i dont know about aspec (18inch tires)

but the 5AT 17s are somewhere like 34or35PSI

 

I would think that the recommended pressure for your 18's would be at least as high as the 17's. Generally you run a greater chance of failure (including blowouts) by running your tires too low than too high. What happens is the tire heats up more when it is underinflated. I would stick very close to what the manufacturer recommends. Remember too that as the outside temperature goes down so will your tire pressure. Good luck!...

 

Agree^^^^. Dug-mac is right, simonsez- you are running too low. Bring your COLD tire temp to at least the F/R pressures on your driver's side door placard. My 05' AT is 32F/32R; 6Ms were 35F/32R. Otherwise, put your 18s at 35F/32R and see how it works. FYI, I'm running 36F/33R on my 5AT to decrease understeer/plow.

You should feel sharper handling, and likely a better ride with less "flat-spotting." You may also reduce the wear on the outer tread blocks near the sidewalls with additional air pressure.

Don't bother to check on pressure when tires are hot- they do heat up, and sometimes inconsistently.

 

I would definitely suggest running higher pressure with those tires.

35 front, 33 rear, seems to be a great balance for my tastes. This has reduced the flatspotting for me and the ride is very comorftable.

As for the pressure rising, yes, this is very normal. 2-5 PSI depending on outside tempratures and driving habits.

As mentioned above, the variation of this change will go down somewhat with proerly inflated tires.

Cheers

 

I am having a similar problem with my TL. The drive to work in the cool mornings (around 70º)are rough but the drive home (90º and up) are smooth. At first, I thought it was this driveline vibration that everyone talks about but the vibration is the same if I shift into neutral.

Is this "flatspotting" a problem with TL's specific or do other cars with similar tires have them?

I'm going to check my tire pressures tonight and see what that does.

 

Great use of the search button! I don't believe "flatspotting" is TL specific problem. Methinks it's the tires.

 

What about flatspotting with a slightly bent wheel?

 

I've been to the dealer atleast 6 times to try to get rid of my steering vibration and basically have come to the conclusion that one of the wheels is just slightly bent and will never allow my vibration to go away. It's very annoying because it's a constant shake in the steering and the vibration kills the smooth ride. I have noticed with the right balancing, a tire pressure of about 33-34 reduces the vibration to almost none but it definitely is there when the tires are cold in the morning with less pressure.

 

If the vibration/shaking is felt on cold starts, I would say it's the tires if they contain nylon belts. Most all performance or speed rated tires contain nylon belts which are used to contain the "inside" of the tire at high speeds, give better steering response, higher cornering grip, but are also the cause of the feeling of riding on "square" tires when cold. All tires having at least one nylon belt experience cold tire shake, and the stiffer the tire carcass, the more you'll feel the cold flatspot.

Here's some additional information:
http://www.tirerack.com/tires-techpage-1/42.shtml