i have the coupe, but got a sedan loaner a while back, when i got up in speed, maybe over 70, it had some pretty bad shaking and was difficult to control.

Not at all like my coupe. I just thought that it was the design of the sedan, since the wheels are smaller and has a different body. Apparently not.

Seems like many people have this problem on their sedan.
I would think that this is not a tire balance issue, unless the design is causing the tires to fall out of balance somehow??



6MT coupe, red/willow, premium, aero

 

My sedan is rock solid all the way up to 110 mph.
At that point I'm pretty scared and back down. If my
steering wheel shook at 90, I would be pissed as S&^t
and demand it be fixed. How can the Car of the year
handle like this?

2003 Twilight Blue Sedan 5AT, sunroof, Graphite Leather,
splashguards, GG red 8 wire Hypergrounding kit, 350Z intake duct, K&N filter.

 

I got my car back yesterday. It seems better no visible shake at highway speeds. But I agree with redwillow all the sedans I have driven at highway 60+ do have a wiggly and roughness to them. I bought the car at a dealership in the city and didn't get to really run it fast on the highway. If I did I don't think I would have bought it.

BTW as comparison my 94Probe GT with 97K miles drives more smoothly at 80mph than my brand new G35 or any of the loaners that I have had.... still wishing I got the IS300.

Oh well this might end up being my wifes car in the near future.. maybe I'll get a Mini Cooper

2003.5 5AT Sedan Black/Black Premium/Winter Packages

 

Except here. I had my tires put on the Hunter 9700. It showed three of the tires needed to be deflated and moved to a differnent point. All four tires were rebalanced. Jumped on the highway, same vibration problem at 65mph. I have the Goodyear Eagle NCT-5 tires. What am I missing?

 

A bad tire could be the problem. I would check for anything unusual - bumps, uneveness, cracks, etc.

 

Just got my printout from Discount Tire. Well, I am off to the dealer tomorrow. God bless the Hunter 9700 for telling the facts. All four of my wheels and/or tires are wacked. Look at these road force numbers:

RF - 47 before, 35 after
RR - 25 before, 20 after

LF - 21
LR - 23

I called the dealership and spoke to the service manager. He stated the maximum road force should be 15. Ideally, 8-10. I think it is safe to say 47 is a tad bit out of range.

Is this a tire only issue or could the rims be causing some of this????? Someone said you need to run the rims with no tires on the Hunter 9700 to see if they have defects. Is this true? Please equip me with knowledge so I can kick some *** tomorrow. Peace.

 

Most tire dealerships ballancing machines only go up to 60mph. If you drive higher than that (70, 80, 90 +), they can not be certain that the tire is ballanced for that range. Usually the 50-60mph rotating ballance machines do a decent job but there are those occasions where the tire is defective and can only be identified at the higher speed. It has something to do with the sidewall heat and expansion.

I'm no expert on this but had a similar issue on another car at 65mph. I had those tires ballanced and re-ballanced multiple times before finally changing the rubber. The new tires did not have the vibration at all, at any speed.

 

POKEY...the break-in period requires you to stay under 4k rpms AND maintain moderate speeds. I would say your 90mph exceeds the "moderate" requisite. As for the shake...sounds like an out of balance tire.

 

I've taken mine up to 130 mph and smooth as silk.... Then again I got aftermarket tires/rims and Nismo Suspension...

Is this just a 05' problem? If it is, I would bet money that the tire manufacturer screwed up on the deisgn of the tire... If enough people complain I wouldn't be surprised to see a new OEM tire design soon...

On my brothers 350z they ended up redesigning the OEM tire on that car after the feathering issues....

Long time ago on my Honda Accord I bought new tires and had serious alignment issues and vibration at speed, it ended up being 1 bad tire. They replaced it and it ran great after that..

 

Alderran--
If it makes you feel any better, my IS300 was nothing like the G. The G feels 100 times more solid and grounded at high speeds than my IS300 ever thought about being. And, I replaced 4 wheels on my IS300 trying to get the high speed wiggle to go away...no such luck. Don't get me wrong though....the IS300 was tight and looked great, but I definitely prefer the G...just wish my G were as rattle free as my IS300. I guess there are ALWAYS trade-offs.

 

Also....my 05 G is totally, completely, flawlessly smooth all the way to 120, which is as fast as I've had it up to....so far :-)