Instability at hwy speeds

I have accompanied this subject from the beginning. Some had said that their new Prius was unstable at highways speeds. I was one of those. The replies have gone something like this -- "Well my Prius is not unstable and if you think your's is, then you do not know as much as I know about electric steering, slab-sided cars, 3000 lb automobiles, wind speeds, tire pressure, lowering procedures, public transportation,alignment (including rear shims) etc, etc, etc."

Wow, I wish I could make such definite diagnosis from a distance.

 

Just know that "my car" is more stable now at highway speeds with the increased tire pressures.

 

With enough experience you will get there. For now, read the posts and add to your level of knowledge. There is a lot of expertise on this forum. It will take a bit to make sense of it all.

Much of the confusion on this thread revolves around one's definition of "unstable". Some of the more technical posters make a distinction between unstable and susceptible to cross winds. To avoid this confusion we should be more precise in our use of terminology. For example, one could say "unstable at high speed in cross winds", or "prone to driver induced steering oscillations".
Without qualification, one poster will say that the Prius is unstable, the other will say not, and both will be correct.

Part of the issue is subjective. What one driver finds to be responsive steering, another finds twitchy. Such is the nature of humans.

Setting aside subjective analysis, there are several characteristics that make the Prius feel unstable to some drivers:

1) Narrow, low rolling resistance tires.

2) Aerodynamic slab-sided shape.

3) "Dead" or low feedback steering.

4) Zero dead-band steering.

5) High profile.

6) Body flex.

7) Soft suspension.

How much any of these bothers one depends on the individual. Since we are dealing with subjective evaluations, there will be no consensus on this thread.

Tom

 

"With more experience, you will get there"??? Let's see, that would be more than 55+years and 40+ different cars of many, many, makes and models?? I just hear the same old story "my car doesn't do that so if you think your's does, then you just don't know as much about "subjectivity" (etc., etc.,) as I do".

Why not just instead of saying that someone is less astute than you, simply say "here are some things that have helped others". Trust me, that goes down a lot better than having someone say my car is not unstable. BTW, that approach will serve well in other areas of life.

I will not post again to this subject until some new owner comes on lamenting instability. That does happen on a fairly regular basis.

In case someone is thinking my 2011 Four might be up for sale. Tough luck! I love my car since it does 90% of it's miles in town.

 

That was your statement, to which I made a proper reply. I pretended to not understand your sarcasm. You obviously *didn't* understand mine. Oh well. Danny really needs to add those [SARCASM][/SARCASM] flags.

Tom

 

2011 Prius III here. Apple Valley Kalifornia. High winds constantly. Handles great. Tracks well.

 

Concur.

Maybe a disclaimer would work:

"WARNING" This comment is based in whole or in part as "sarcasm."
In case you're a product of the United States Public Education System the following definition is herewith provided:
sar·casm/ˈsärˌkazəm/
Noun: The use of irony to mock or convey contempt, or express humor.

In the unlikely event that you are seeking sincere advice to solve a for-real problem, the preceding comment may offend you if you were picked on excessively as a child and/or you've otherwise failed to develop a fully functional sense of humor. The author shall be held blameless for any damage to your already fragile self-esteem, along with the owners and employees of this forum, your ISPs, and Albert Arnold ("Al") Gore, Jr...inventor of the internet.

 

Almost all cars sold today and in past 50 years have an amount of understeer built into them. This allows the car to push when the wheel is turned. This is comfortable/ controlable. A few high performance sports cars are designed to oversteer and it is a VERY uncomfortable feeling. Porshe Spyder, Honda S-2000, Lotus Elise, Toyota Spyder, and other rear engined cars(read Italian). Our car will over steer (snap-over steer)under following conditions. Heavy luggage load on top of/or behind rear axle. Car already has heavy batteries in rear so the extra weight will cause this issue. When you turn quickly the rear end can come around and have a mind of its own due to the weight. This is due to more weight in rear of car. This is why cornor weight balancing is so important to race cars. Too much weight in wrong place and your into the fences. All light weight cars are subject to being blown around by wind, unless they are race cars with stablity wings on front and rear causing downforce at speeds above 20mph.

 

BMW it is not but most of what you describe is attributed to Yokohama S33 tires. They will get better after a few thousands miles.

Had the same experience with Avids in good handling car, it is just the way they make them.