who can figure this out for me---I am begging

There has been a lot of discussions on highway speed handling issues:

http://priuschat.com/forums/gen-ii-prius-technical-discussion/55978-unstable-higher-speeds.html

http://priuschat.com/forums/gen-ii-...0-prius-handling-problems-highway-speeds.html

http://priuschat.com/forums/gen-ii-...ting/4508-poor-steering-handling-highway.html

http://priuschat.com/forums/gen-ii-...ing/2054-twitchy-steering-freeway-speeds.html

Some say alignment, some say tires, some say needing stiffening plates, some say driver subjective judgment ....

Hope you will find a good solution for you. Good luck!

 

I also had this problem when I first got my 2004. In my opinion, the problem is due to a combination of factors that add up worse in some cars than others:
- poor tires
- touchy steering that takes some getting used to
- possible alignment problems
- aerodynamics optimized for minimum drag and not for high-speed stability

I was able to solve the high-speed handling problem (except in high headwinds or crosswinds) by replacing the Integrities with better tires (TripleTreds) and adjusting the plastic "chin spoilers" in front of the front wheels as suggested by jayman in one of the related threads. For high speed aerodynamics, a small change can have a big effect. I angled the chin spoilers a bit so they now divert air to the sides of the car to reduce the pressure underneath. I think, at high speeds, the front end can lift up a bit resulting in poor steering control. Maybe the shape of the car acts like an airfoil. The change was very easy -- just drill a new screw hole ahead of the old one on the inside side of the spoiler to create a slight angle.

In my opinion, this issue is another example of a significant safety problem that Toyota has swept under the rug. But, with the fix, I love my Prius!

 

i don't know what you mean by high speeds, but i have had none of these issues with my 04 or 08. factory tires, 55-65 mph any wind or road conditions, and i have owned many cars to compare it to. i don't see how any of these four issues can be a problem. but maybe i'm just lucky!

 

I don't have any answers, but I do want to note that my 2004 Prius has some similarities:

- One of the rear angles is off just barely out of spec
- One test showed the Rear being off on the Left, another test showed vice versa: it being off on the Right while Left was centered.
- After a new set of 2 tires and alignment, it felt really unstable like there was something clearly but subtly wrong with the alignment.

However in my case the feel seems to be getting better every day; I think the unstability I felt was mostly from the new tires breaking in, and the old tires needing to get worn down in certain places to compensate for their new surroundings.

There definitely is an overall instability to the Prius; it is simply not as stable as other cars on the highway, but you get used to that.

I think you are best off driving another Prius to compare. Ideally have the two cars in the same place so you can switch back and forth. It can be hard to tell the difference between unsafe alignment and alignment that's just unfamiliar.

 

I don't know anything except that in the infamous Prius Owner's Manual it says:

"0.05 DEGREES of Toe IN each side, for a total of 0.10 DEGREES."

My Prius is a bit wavy on the road also.. especially during windy days I've noticed. I get more tired in my arms driving my Prius than I ever got driving my Toyota Celica.

I do agree that the steering is a bit dodgy. It is hard for me to estimate how bad, cause my Toyota Celica had the awesomest, tightest steering ever.

 

It is quite common for a blacktop paved road to have depressions or ruts that are made by constant use, especially by large trucks. It is worse in areas of hot climate where the blacktop gets softer with heat. Some stretches of pavement can be real bad if the hiway department opened the road for use too soon after being newly paved.
Driving on a road like this, the car would like to ride in the ruts if the tread width of the car is the same as the distance from groove to groove. If not then the car climbs in and out of the tracks in a random fashion. In the case of the Prius (and some other cars) where the front tread width is different than the rear tread width then the problem is even worse.
Walt

 

Ivorz I don't know the effect of removing the chin spoilers. Using them to reduce air pressure under the car seems to have helped for me. Here are some pictures of what I did.

Here's a link to a thread where jayman discusses this mod.

http://priuschat.com/forums/gen-ii-...prius-handling-problems-highway-speeds-7.html

 

Before I start a new thread I thought I'd look for an answer in this one. Our 2010 Prius II does little self-straightening on the highway. It doesn't drift to one side, but even a tiny input will go uncorrected. We are used to cars that self-center at speed, and I was wondering if the alignment (caster? Camber?) can be tweaked to get better on-center feel.