Lean/swerving at high speed/freeway?

Air up your tires to either 44/42psi, 42/40psi or 40/38psi. This will help the car feel more stable.

 

The Prius v is a station wagon, I bet you could add all of these and it would STILL be a station wagon.

Prius V Suspension Upgrades, Coil Springs, Chassis Stiffener & Strut Tower Brace Improves Prius VHandling: JuicedHybrid.com

 

The driver's feeling of "lean and swerving" has nothing to do with the actual vehicle but the "feedback" which the car gives you as the driver. You are NOT the first to notice this effect. There is along history with this issue and previous and current Prius models.

In aircraft design nomenclature, this is called "airframe or control flutter." That's why aircraft builders have test pilots. The design and flying characteristics of a vehicle itself might be absolutely stable and performing perfectly, but if it doesn't feel right, the pilot will react to the "flutter" as he or she would to a real situation.

When I took my 2012 Prius"v," I felt an uneasy feeling, like I've felt on a vehicle, when it reaches the threshhold limitation of understeer and goes to oversteer.

After I installed a custom "box beam" center chassis brace that I designed, the flutter that caused this disconcerting "phanton" feedback that mimics loss of control, is gone.

Toyota, in early 2012 quiely, and without formal announcement, introduced a stillfer but "torsionally" flexible mid-chassis brace made of 5 steel pieces with 7 welds. While this has increased the "feel" of greater stability, I developed an even "stiffer" brace with the same torsional as Toyota's new one. It is a "one piece"box beam" that weighs at least one pound lest than the new Toyota model, with the same weight load as the earlier "thin flexible one." There are quite a few Priuschat users, who have successfully tested the NEW brace and are VERY satisfied.

 

The OP has a PIP not a v.

The Prius sways quite a bit from the factory but adding air pressure to your tires helps stabilize the car a little. A rear sway bar can help but the main effect is to flatten cornering. I've found that 17" wheels and lowering springs make the largest impact on handlingand freeway stability. The wheels make the largest impact but negatively affect mpg and EV range.

 

The chassis of both cars are basically the same and share a lot of the suspension components.

The modifications that you propose will definitely change the performance parameters of the chassis. My findings are for relatively "inexpensive" easy "bolt-on" modifications that improve ride "feel" without creating a harsher ride.

Basically, I have found the standard chassis to be quite good on the freeway. The rails of the exhaust system tunnel, however, is lke an open tube on the bottom that "opens and closes." The effect is that the driver feels the flex, when the wheels are actually really well planted on the road. Eliminating the flex effectively eliminates the driver's feeling of unstability.

 

I can feel another BT Brace argument coming on..... Same stuff 7yrs later.

 

The BT was a good start. In early 2012, Toyota upgraded the brace to a 5 piece design with 7 weld joints. Toyota engineers evidently adopted the complicated design to achieve stiffness to eliminate the sideway movement of the exhaust system rails. They did not just adopt a thckened plate, because they recognized that the brace formed an "H" shaped structure with the right and left rail. These rails must move in a scissors like fashion. A steel tube, as used by Toyota, allows their brace to twist with very little resistance, while still being stiff and hard to bend.

I went back to the history of the early days of Orville and Wilbur Wright, since I am a history buff of the dawn of aviation. The Wrights discovered their invention of a principle they called "helical torsion," when they saw how a rectangular cardboard slide on cover to a bicycle inner tube box twisted with very little resistance. They also noticed, that if they firmly held the ends of the cover, how stiff it was to bemding. The later called this principle "wing warping" and used it to control their first airplanes.

I one can picture the "H" shape with its long arms, it would be redily clear that, if the cross member of the "H" was very resistant to "twisting" like the original BT plate, the up and down thrashing of the free ends of the "H" represented by the four tires would exert enormous stress on the joints of the brace. That would effectively and eventually repeatedly bend the joint back and forth like bending the ends of a paper clip. The result would be cracking of the joint from the separation of the crystals in the metal.

So, BT was a good start. But, it has "unintended consequences."

 

I was wrong, no idea how I made that mistake.

 

it may be just me, but from experience with other cars the feeling is all about the alignment. The prius is aligned to give the most MPG but gives up on freeway stability and steering feedback. From experience on my sport cars, changing toe and camber can help stabilize the car at freeway speeds, but it could also hurt MPG. Just need to consider the compromises. Also changing tire pressure to give the car more neutral feel.

 

The split pressure is recommended by Toyota. Look in your door jamb on the placard. Toyota calls for 35/33psi front/rear. Unless the PIP is different in which case I would follow that specific recommendation but with higher pressure.

 

buy a decent gauge at an auto parts store, sears, etc.

 

Costco has free hydrogen pumps that regulate pressure. Pull up, set the pressure, and fill up.

I have found that the wobbling has gone away after 4000 miles. Or I have gotten used to it.

 

only if i had a Costco membership....

 

Don't put hydrogen in your tires. Hydrogen mixed with the residual air in the tires would be a potentially explosive mixture. It will also leak out much faster than air.

 

You dont need one. The compressor is outside the garage.

And hell, maybe its nitrogen. I am not a scientist and am not standing in front of the pump. I do remember that it was not a typical air compressor.

 

Yes it's nitrogen. I believe hydrogen would give our tires way too much pep.

 

With over 5K miles on mine, I'm also feeling less of what I call "wandering" due to the grooves cut into the pavement on some of our L.A. area freeways. I don't notice anything unusual when changing lanes. I started out running my tires at 40/38, but am gradually letting them drop naturally to find the most comfortable and stable pressure. My usual practice is to check and air them up twice a month, so now they are down a couple of pounds and that may be helping. On smooth pavement without the grooves, the car has a very comfortable and smooth ride, without any wandering at all.