Michelin Primacy MXV4 on Prius TOURING !!

Alignment.
.
_H*

 

+1 on alignment, if it is actually spot on install an upgraded under body brace and a front upper strut bar.
Are the roads it wanders on heavily marred by truck traffic, any car will wander on roads the trucks have dug channels into and a Prius with excellent rubber will definitely wander...

 

Stock was 185/65 15 and now you're on 205/55 16 must be new rims also, anyway the tread is 1" wider so the tire just grabs more of everything, check with the alignment people, if it's not spot on make them adjust it, human error is always possible...
I used to run 18" 40 series tires on an Audi and it was horrific on the highway, on my Prius I run 17" 45 series rubber and with the front upper strut bar it's not to bad unless the road is ridiculous.

 

It's an alignment problem, imho; I'm wondering why you would have an alignment done in the first place, unless you ran over a curb, etc, etc. Cars nowadays very seldom go out of alignment, except when in an accident. Like previous posters, my recommendation is to take it back and have them go over the alignment again, at no charge, of course.

 

I disagree w/ derkraut on recent models not going out of alignment. With frt wheel drive cars, they require alignments more frequently to maintain proper alignment. I DO agree however with the increase in tire size being the most likely contributor. 10 extra mm on the width of the tire could most certainly be the cause. It is more noticeable w/ electric p/s too. Very sensitive steering feeling accompanied w/ a slightly wider tire will accentuate any sensation while driving in the steering system. Either switch back to factory size tires of a different brand, or double check the availability of a 195 size tire in the Primacy. The Primacy's are a great tire, so hopefully they make them in the correct size.

 

Did you receive a report from the first alignment? If so what is the front and rear toe-in?

I agree that it sounds like the alignment should be checked again given the handling issues you've experienced. Ideally the alignment shop would be willing to reperform this work at no charge.

 

By changing to different tire size, you increased the diameter from 24.44 in to 24.87 in. Since the diameter is different, it is probably best to get an alignment.

 

I second the suggestion by Patrick to post the alignment data. My car was very squirrely at highway speeds when the rear toe settings were out of whack.

 

Re: Michelin Primacy REDUCED tire pressures !!

Well, I think your car has a problem which has not yet been identified.

I'm using 44 psi on Bridgestone Ecopia EP100, 185-width tires which is standard on non-Touring, no problem driving at 75+ mph on rural AZ highways.

 

I know that when my rear toe settings were uneven, it did not matter whether I used the door sticker inflation settings (35/33) or higher settings (40/38) it still felt unstable at freeway speeds. Correcting the toe to be even and in spec helped drastically.

I now have Michelin X-radials and the car feels much more stable than with the OEM Integrity tires. I'm running 44/42 with the Michelins.

 

I need my car aligned - did that involve shimming the back?