2010 IS250 with only 20,000 miles on it in great shape. When a tire needed to be replaced, I noticed the age date on the tires and they were so old I was concerned I could get a blowout. So I go to a good solid place to get new tires. They put Michelin tires on there that cost me like $1000 and now I can feel every bump in the road I can feel it through my spine coming through the steering wheel and I think the seats but I can literally feel every tiny stone in the road.

Appointment tomorrow with the car guy who's being very cooperative but to be honest this happened once before and he replaced the tires and there's the same problem. He says that he is doing road force balancing (after some reading, I asked).

I have the suspicion maybe he put a sportier tire on there? At one point he said something about it really being a sports car or something and I wonder if maybe I had like a touring tire on there before and this tire is I don't know lower profile or something. I really don't know what I'm talking about so I would very much appreciate anybody who would like to chime in. This is definitely the tires or the way they were installed, because the car was driving smoothly and beautifully with the old tires

Thank you for responding – yes I think they are stock size. Certainly nothing is altered on the car and I'm looking at the paperwork right now.

The set that's on there now is Michelin. 2ea 225/40 ZR 18, and 2ea 255/40 ZR 18, with all four changed at once. I just noticed on the paperwork it looks like they put sport tires on there (don't sport tires provided noisier ride then I touring tire?). It should be noted that I specifically asked them to put the quietest tires they could find on there (I gave them no other specs but I have a special problem with sound and the car was completely quiet before we changed tires).

I should note that the road is bumpy enough that I actually believe the metal is twisting (this go-round I've had these tires on for months but I've been miserable) and my passenger door is not quite fitting the same. I can hear a tiny bit of air coming through the closed window.

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Sorry I've been tied up all day so sorry it took me so long to respond.

Not clear if you are saying that a Z rating is too much or what but I just can't quite understand what you're saying there.


QUOTE=kitabel;10109139]Let me explain my remark.
The speed rating is partially determined by the chemical formula of the rubber (which always includes petroleum distillates, sulfur, carbon black, and other things they won't tell you).
The tire is designed to have maximum grip near it's speed rating, and is colder than its efficient temperature at normal cruising speed. Watch F1 and Indy cars warming up by zig-zagging across the track to torue the sidewalls, and instantly crashing if the tires are cold at the first turn.
For most people, a tire rated "H" (130 mph maximum) is all you'll ever need.

Summary: a "Z" rated tire has less traction than an "H" rated tire (other factors omitted) at speeds up to 130 mph.[/QUOTE]

No - what should my air pressure be?

Why, would he have put a Z rated tires on there? I'm unlikely to hit 149 mph. I'd find it hard to believe my car goes that fast.

if quiet was the priority and Z tires were not already on there, why would he have put them on there, and why would that never have been discussed? I assumed he would put a tire that was virtually equivalent on the car.