Instability at hwy speeds

My Gen2 with the bt stiffening plate handled great. The stock Gen3 now handles just as good as the modded gen2 imo

 

More like, why should Toyota make a vehicle that is unstable at 70-80mph speeds?

FYI: Recently Texas raised their speed limit to 85mph in some areas.

 

The car is perfectly stable at those speeds and higher. If yours is not then please have it checked out for your safety and those around you. Have you tried running higher tire pressure? It helps make any car handle better.

In my experience over the last 131,000 miles of driving a Genii (which handles worse than a geniii) I have never experienced this unstability you speak of except in high wind situations.

 

Based on this thread, I don't think the issue is just my car.

 

Any reasonable person will not doubt that a slab sided car with skinny tires and relatively tall body like the Prius will be less stable at hiway speeds on windy days. But this is PC.

 

Last weekend I drove from north to south of Switzerland and back, what is 90% highway with top speeds of 130km/h (80.8mph). When passing a truck or larger bus I have experienced some noticeable travelling of the car to one or the other side due to sidewinds. No instability at all but I had to correct the situation with the steering wheel. In fact the traveling to one side is as much as with my previous car the 08 Cadillac CTS4 or our 07 RAV4 but much more than my 94 Z28 Camaro or Mitsubishi 3000GT. This is definitely due to the non-curved side shape of the car that makes it more sensible to sidewinds compared to the somewhat "flat" sports cars. I run the 17" 215 tires what help to increase the stability of the car.

 

I think the people in this thread complaining are having the issue in windy conditions or their tires are not properly inflated. That is different than saying the car is unstable in all conditions.

 

I have driven the Prius up to 190km/h on German highways and it is not more unstable than other cars I have driven. Actually it is pretty good. I have driven other cars, and it doesn't feel in other way inferior or problematic.

Side winds are a problem for all cars, unless they are flat as a pancake. The Prius is not going to be a side-wind champion, but it will not be any worse than many other similarly sized cars.

If you have 15" tires, I would suspect it to be "wobbly" - this is why I bought the mid-trim option package to get the 17" alloy wheels (which look *really* good ). I want to be able to drive fast here if I want to, and 15" small tires are not what I would go for.

I have also driven it fast with 16" winter tires and I don't think it is in any way unstable. Sure the tarmak place a big role - if the road is not flat it will be unstable, like with all cars, I would say.

You can read more about it here.

 

I didn't say my car is unstable in ALL conditions, only at higher speeds (maybe this is what you meant?).

I can say with confidence that this instability is related to wind conditions, but quite frankly it's disturbing how easily a small wind can move this car. Something as simple as passing a truck can require steering input to correct lane position. This is the worst car I've driven in terms of this issue.

 

F8L is pointing out the difference between a car being unstable at speed, and unstable in cross winds. His point is that the Prius is not unstable at high speed, but that it is susceptible to cross winds.

Some cars, particularly some older designs, become squirrelly at high speeds, even without a cross wind.

Tom

 

That is exactly what I was trying to say. I just wasn't clear. Sorry.

J,worms what size tires are you running and at what pressure?

 

Not sure, whatever factory specs are. The car only has 1500 miles on it.

 

You should check them to ensure they are at factory recommend pressure. Then you might want to consider running them higher. The higher pressure makes the car easier to control and helps the tires wear more evenly and you'll get a boost in mpg. Up to you though. I'm just trying to help you enjoy the car a little more.

 

I am amazed at this car's stability at 80. I do have high-performance tires on it, however.

 

Did you actually measure them? Or just assume that they are fresh enough to not have deviated from the factory setting?

Don't assume. My delivery pressures, as measured the morning after buying the car, were 5-7 psi different than the door placard and owner's manual specs.

Other readers here have posted their delivery pressures, and the spread has exceeded 10 psi.

 

Tire pressures are kept high during the transport to prevent flat spots from developing. But do higher pressures help or hurt stability ?

 

Not everyone who has reported non-spec pressure has had high pressure. A significant minority found the pressure too low.

 

Somewhat higher pressures help.

The balance between front and rear is important too. The factory 2 psi higher in the front works for most people.

 

I have had mine over 100 mph with no problems. In fact I recall it being very stable. Much more stable than my mind for going that fast in the first place.

 

As fuzzy wrote. The majority of reports from PC members showed that their pressures were lower than manufacture's suggested pressure and they also tend to be different at each corner (beyond the 2psi split front/rear).

I agree. Higher pressure makes the car feel more solid and connected to the road. Steering response is improved as is overall handling. The car sways from side to side less and the tire is less prone to rolling over during hard cornering. At very high pressures the car can feel a bit more twitchy at high speed. I reduced my pressure to 50/52 and the car drives fine. In fact it feels like a Cadillac compared to a 17" tire at max psi.