Instability

Bob,

Get decent tires. The Goodyear Integrity tires have very soft sidewalls that lead to highway instability and tread wear at the shoulders (from turns - somewhat improved by higher PSI). I have Nokian WRs (now get the WRg2's) and they do not exhibit the highway instability. They also have much better traction in all conditions as well as 4% better MPG. I also have had Michelin MXV4+ tires and they also did not exhibit the instability. I ran/run all three tire models at 42/40 PSI.

JeffD

 

Some new Prius arrive with bad alignment. The dealer will do a free alignment for you on a new car.

Most likely the problem is that stated above. The Goodyear (lack of) Integrity tires are marginal at best, and bad in snow, rain, side winds, and at freeway speeds. Other than that they are okay.

Get new tires. I gave mine away at 8,000 miles.

Tom

 

+1

And put the pressure back up if you want to even get moderatly cheezy life out of the Integrities. Then if that's not enough to stabilize your ride, go here:
PriusChat Shop : BT Tech Chassis Stiffening Plate - $195.00$165.00

 

You might also wait and see whether you simply get used to it. Mine also felt squirrelly in the first freeway trip, but after a month my reflexes accommodated and ever since it feels completely fine. And less expensive than a new set of tires and a stiffening plate.

 

Oh! In that case I must ask: how often do you check the tire pressures, and what were they shortly before that 2nd long trip?

If the tires pass inspection I wouldn't think that wear is the problem, but if you don't do a lot of highway driving you may be especially sensitive to the phenomenon.

 

Hi Bob. I'm 72 by the way, have had my 2008 Prius for 17 months now and like many others on PC run my tires (the original Goodyear Integritys) at 42psi front and 40psi rear. The 2psi differential front-to-back is important. I have absolutely no problems with stability, though the car can be sensitive to strong side gusts. The steering does require fine and delicate control. I have taken a number of long-distance trips from Southern California to Southern Oregon (800+ miles) with no discomfort. Handling in snow, ice or very wet conditions is another matter.

Obviously, correct wheel alignment is important so maybe you should have that checked. Other than that, together with the higher running tire pressures, I find the car handles beautifully. It is not a sports car, however, though some people seem to like treating it as such.

 

I agree with the strong wind. My 2006 prius is pretty stable unless a strong gust of wind is blowing, then I really need to hold onto the steering wheel tightly.

 

The Prius steering is super-tight with lack of feedback, so it's easy to over correct.

My Prius felt squirrelly until I had an alignment done, including the critical "Zero Point Calibration." It was much improved after that

Note that if the rear beam axle is out of alignment, it could require custom shims be made to fix. This could get complicated

However, I doubt a "soft" suspension or "soft" tires are the culprit. I've driven plenty of land barges with suspension compliance *far* softer than a Prius, and they tracked with no effort

Eg: my folks used to have a 2003 Buick LeSabre Limited. Actually, it was a nice car, especially for road trips. You never felt bumps on bad roads. It easily tracked with one finger on the wheel, even at 75 mph with snow tires on

Kind of wish I had kept that car now. When my mom died in 2005, my dad moved in with me and I decided to sell the car. It only had 27,000 km on it.