Instability at hwy speeds

Also, it may also be the change in rim size. I went from 20's on a Venza to the 15's on my IV, and noticed the turn in was instantaneous compared to the taller rims.

 

Toyota performed a EPS torque adjustment calibration which has helped some. It was out of range. Car is now acceptable but still not as stable as my BMW or Honda Civic.

 

Another new Prius owner here who feels the car gets blown around by the wind a bit more than my previous Subaru Legacy. I'll try upping the tire pressure (been meaning to do that anyway for FE reasons). Its not really bad, but noticeable.

 

Well if you think about it, a car designed with proper wind resistance in mind, will get blown around a little more easily.

 

Hi Brad,

There is allot of talk about aerodynamic cars having side wind issues, since the 1930's.

The second Gen Prius was nearly as good as one could expect in those conditions, aerodyanmically. But it structure was flexible, and yea, in my 2006, a good 40 mph side gust at 65 mph was good for half a lane change. Similar to most SUVs.

With chasis stiffening, however, the 2006 was excellent in wind. The CL (Coefiicent of lift ) of both the front and back were nearly neutral. And a 40 mph gust at 65 mph with the steering wheel locked, was good for only a few inches of sideways motion. One could feel how the car just rolled some, with no pitch variation.

My experience with the 2010 is not as nice. Stock, its allot better than the 2006 was stock. But, it definately has allot of front CL, and one can feel the nose of a 2010 pitch upward in sideways gust but with little roll.


At least that is my experience.

 

Hm, sounds pretty serious. I suggest you ask the Ca highway patrol to follow you at 80 to document.

 

funny we should meet up on here mr. maddog

i thought the exact same thing when i picked my prius up last month. it's unusually floaty at higher speeds, almost to the point of being scary. that coupled with the loose steering definitely makes for an interesting drive.

it struck me as weird because this thing should be way more aerodynamic than the M3 and i assumed it would cut through the air like nothing, but that's not the case at all.

i'm definitely curious on a "fix" for this, but i have a feeling it's just how the car is.

 

I would say there is some sense of instability above 75 mph caused by either strong winds or by the grooves that are common on SoCal concrete freeways. My previous car was a Volvo S60R and vs. the Pius the stability at 80 mph was like night and day. After almost two years of driving the Prius I've gotten used to how it drives (braking power is also not as good as in the Volvo) and I don't believe the Pius is an unsafe car to drive in the freeway. Lets put it this way, the Prius is not a driver's car.

 

My Prius is really stable at 75-80mph. I was surprised at how well it did in 50 mph winds. Better than my Subaru Impreza Outback Sport.

 

Heavy cars with low point of gravity (Subaru Legacy -3400 lbs curb weight) are less prone to side wind as lighter cars (Toyota Prius 2010 300 lbs curb weight).

 

My 2011 Four is very unstable at 60+ MPH. I have driven the car for two months. I have tried all of the obvious solutions. I have tried a number of tire pressure settings. I have done the dealer alignment. I have tried driving in winds and with no wind. I have tried the "drive it like a boat" idea where you try not to over-correct for every unwanted course correction. I have driven on a number of different pavement types. I have driven on flats and on hills. None of these things seem to solve the "wandering" at highway speeds.
I love the car, especially around town, however, on the highway it requires way too much attention. I have owned over 40 cars in the past. These include heavy-weights like Olds 98 and big Buicks. It includes Hondas, Saabs, Volvos, Hyundais, and many others. I have never had a car that was this unstable at highway speeds.
I think my dealer must have dealt with this problem before my service visit. When the service manager checked me in I told him that the car was unstable and that I wanted an alignment. He immediately said, "that won't solve your problem." That indicated to me that other owners had come in for the same reason and later informed him that alignment was not the answer. My guess is Toyota is well aware of this problem.

 

It's not that the car is unstable at high speeds. I've had no trouble doing 85mph from Norcal to Socal. Even at 100mph the car felt stable. In high winds there is an issue. The car is designed for low cd AND to maximize interior space. Unfortunately this creates a narrow yet tall profile which when subjected to side winds is easily pushed around. Coupled with a fairly loose suspension and you have a recipe for mild annoyance to white-knuckled fear if you get caught in a bad wind storm.

The last bad storm we had in my area pushed my car all over the freeway (in known high wind areas like the causeway if you are familiar with I-80 near Sacramento). A few early morning commuters actually changed lanes to get away from my car because it was being blown around so much. To be fair this has only happened twice since I've owned the car and everyone else on the road at the time was slowing down because their car/truck was also having issues.

Some suspension work and lower profile tires can help in this case. I feel sorry for those driving on stock 15" tires at 35psi in a major storm. That is one squirrely ride.

 

You need to get a chasis stiffening plate for your 2nd Generation Prius. It will be like night and day. Either the BTTech one off Prius Chat or the cheaper Ebay offered one. You will be asking yourself, "Why did I not do this sooner!?".

 

Various people have various passive response expectations of cars.

That said, there are no adjustments of the rear suspension of the Prius (any of em). Which is why the dealer may have said that. But, there are ways to adjust it. I am not an expert. But, there are some on Prius chat. How about scanning your alignment report, and see if they can help ? They may be able to suggest some shims that can be installed in the rear suspension, to solve an alignment problem, if it exits....

 

I have one. Was one of my first mods.

 

Hi F8L,

I did not see it listed in your modifications block signature.

You probably have an alignment problem as well then.

 

What are the trade-offs with the stiffening plates? If there are none, I
wonder why the Prius doesn't come with these.

 

The Gen III has a new suspension design and does not need a stiffening plate upgrade.

Many of us think the Gen II has greater stability in cross winds with the upgrade. The Gen II comes with a steel stiffening plate that can be replaced with a larger aluminum plate. The Ebay plate was a good buy at about $35.

 

No worries man. until you mentioned it I forgot I had it. i've had two a lignmentsdone and I was always within spec but could benefit from rear shims.

 

If you are planning on driving 70-80 mph, why not consider buying a different auto that was made to cruise at those speeds?