Unstable at higher speeds

Higher tire pressures will somewhat improve stiffness, but the car still wanders more than others I've owned in wind and follows road grooves more. I expect changing tires eventually will change the tendency, but I also intend to do the brace and stiffening plate to reduce body roll of the narrow/tall design.

Ironically, other than the Prius, every new car I've ever bought needed an alignment when it was delivered. They either pulled a little or I noticed the thrust angle was off while following them with my wife driving.

Make sure they don't overfill the oil. This is one of the primary chronic issues in maintaining the Prius. Mine was shipped from Toyota with an extra 1/4" on the dipstick. Don't let them put in over 3.5 quarts (Toyota spec says 3.9, but is wrong, 3.5 will result in it being about 1/4" below overfull) and let them know you will check it before you leave the dealership. I'm not suggesting being confrontational about it, just specifying what you want so that they have adequate instructions.

 

Or maybe installing a strut tower braces can help you with the car's stability...

 

I had the same problem, my 2008 was unstable at highway speeds. Going 60 to 70 mph. Took into dealer and had it aligned, that took care of my problem. Didn't cost me anything. The car had about 6000 miles.

 

Just bought some snow tires from Tire Rack - was concerned that since snow tires frequesntly wonder more than regular tires, the Tire Rack Rep. pointed out that the Goodyear Integrity was very poorly rated for stability. Almost all tires were rated better.

 

Check alignment first.
W/o proper toe-in, the vehicle will wander.
If OK, check the tires.
My Prius is no BMW, but it does OK at high speed (before any mods I did to it).

 

I would check all tire pressures first.

 

Tires are hunting. Underinflated tires. Its tracking every little groove. Our OEM tires are the worst. If your still running at the tire pressure the dealer delivered the car to you (like 30/28) that's alot of it. Try inflating to 40 front 38 rear to start. There's alot of trial an error on tire pressure on these pos's for a give and take on liveable road noise, harsh ride, handling, and mpg gain.
Max tire pressure for good mpg gain is like 44/42 but ride is very harsh and road noise is high. At least imo. Alot of posters here pump much higher which you may get away with as these tires are Low Rolling Resistance tires which mean they have a much strengthened sidewall but extreme inflation way above sidewall warning level makes little sense to me just to gain 1 or 2 mpg.

Once you've had a side wall blow out at speed you will try real hard to avoid that in the future.

But at much higher inflation steering hunt is much improved. I'm at 38/38 and road noise is ok...mpg is not to bad at 46-47......and hunting is almost gone. Run lower psi and the tire is very quiet...poor mpg..and it will hunt bad.
I got 17k on my pos's. At about 30K I'll buy new. Can't wait.
Good luck.

 

Hi All,

I do not find any dead spot in the middle of my Prius steering. And that is probably part of the problem for some people used to the dead spot in the middle of hydraulic power steering. Without the BT Tech plate, a side gust will provide such a long time variation in required steering input, that PIO (Pilot Induced Oscillation) can be a problem.

I really liked the improvement the BT Tech plate provided in variable side load tracking performance and controllability of my Prius. Although, its no panacea for high speed understeer. It helps allot with side wind gusting tracking, and left turn oversteer over reverse camber surfaces. The difference was noticable and dramatic, even with the GY Integrity tires. I had the luck(?) of having nearly identical extreme conditions before and after installing the BT Tech plate, and made identical test before and after.

But, I agree that better tires are certainly worth it too! Hydroedges are great around here with the slick surfaces during rain after a dry spell.

I never had an calm weather straight line problems with my car even at 70 mph in dense air conditions with trucks flying by at 85.

 

Hi Shawn Clark,

At first I thought this too. And aerodynamic cars are notorious for side wind pressure induced tracking problems. But this is definately not the case with the Prius. The problem is almost for sure due to body flex induced steering. With the BT Tech plate on my car, at 65 mph, and a 40 mph side gust (0-40 mph in about a second), my car tracks nearly straight and is easy to counter steer to a straight course. And that evaluation was done with the stock Integrities. It does really roll a bunch though. That takes getting used too.

 

i have the same problem i changed tires and still have the same problem. i delt with it thinking it was just me. then i bought a second used prius and it has more miles on it and the same tires and it drives great no wander. is there anone that has fixed this problem.

 

One more data point:

Drove up to 70 MPH no problem when brand new fresh from the dealer. Checked tire pressure and found not even at all: LF 38.5, LR 37, RF 37, RR 34.5. Pumped up to 40.5/38.5. No problem up to 70 MPH. When weather got warmer tire pressure drifted up to 42/40. Still no problem up to 70 MPH.

 

Yes, on my car, the rear alignment was out of spec. When I corrected the rear toe in, the freeway speed handling was much improved. So, you should get an alignment check if you haven't done that already.

 

I have a Touring, 2500 miles. We are taking a road trip soon and I have to work out the cars wandering issues.

Tires are Bridgestone Turanza EL400 - 195/55 r16.

Oregon uses studded tires, so the grooves on the highway are pronounced. Our car is ALL OVER the highway. It feels very unsafe.

Before this we drove a jaguar and a HD pickup, both of which plowed dead on even down a dirt road - it could be me but I cant imagine Im that bad. The jaguar also has Turanzas, (Z rated tho) and they dont have that issue on that car, though its a much bigger tire and far heavier car) I can hold the Prius steering wheel dead straight and the car is so wobbly I would never ever let my wife drive it on the highway.

Ill get the alignment check first thing. Could it be the tires for the touring model?

Do the plate and brace recommended earlier in the thread work for the touring as well?

 

Shapechanger,

I've got an '08 Touring wjth both BT brace and strut tower mods
installed. And I like the dead straight tracking. But... that's just
my perception.

Even without these two mods, I never had any tracking problems. I
run the OEM Turanzas at 42f/40r and now have ~23K miles on them,
rotated every 5K miles, no signs of uneven tread wear. Then again, I
haven't yet experienced any really strong cross winds.

So, why'd I put on the extra stuff? Well, just to see what all the fuss
was about; some say Yea! some say Nay! Both sides feel they
are correct about their experience.

I put the brace on first. On a section of wash board surface on one of
my daily commute routes (~2 - 3 in. ripples) I felt that the car
was quieter noise-wise and less jumpy and shivery in the back end.
This I liked very much.

The car still leaned into the turn and if I pushed too hard the back end
would slide a little. But these are most likely tire/suspension/torsion
bar issues.

Then I put on the steering tower brace. WOW! The steering seemed
to tighten right up. Very solid and secure if I have to do a quick right-
left-right (or the other way 'round) to miss pot hole, road debris, or
get out of the way of someone encroaching on my lane, let's say
through inattention.

So I have always felt good about my Amapola's tracking. Now, I feel
even better. But I can't prove in any way that my car handles any
better than when it was stock.

YMMV (Your Mileage May Vary)

You pays your money, and you takes your chances.

I'm afraid this doesn't help very much, but it's one happy Prius driver's
story. Dollar-wise I'm a little poorer, but satisfaction-wise I'm very
much better off. Go figure!

All the words in bold above are purely subjective, no objective
proof whatsoever that the brace and strut support actually do
anything!

 

Thank you Rokeby. It looks like if you were doing pretty well from the start, I need to address alignment.

I just ordered the plate. I will see how it goes. Ive read two reviews that havent seen as much from the plate on the Touring as people are getting on the standard. If I get some benefit from the plate Ill try the more expensive strut tower brace.

Im glad to hear it isnt the tires, that really helps to narrow it down.

I know part of the problem are the deep grooves left in the pavement from the studded tire wear, and the very windy Columbia Gorge. The shiftyness in the lane however, is really excessive atm - so it must be the alignment.

 

I have this issue. Thank god I have been running 42f/40r from the beginning. If you get into a big skid it might save your life like it saved mine. Extra battery weight adds to turn sway like a having 3 NFL linemen in the last row of a 15 pass van which adds to the over steer. Then to top it off the ECU adds more power to steering durring the skid so you over correct. Oversteer is very rare in any passenger car and uncomfortable/dangerous to the untrained. Higher tire presure in front helps with this issue run at least 2lbs to 4lbs more in front tires. Next stiffen the front suspension with stiffer springs or a stiff front sway bar (stiffer than the TRD one offered on the touring modle) Alignment and higher presure in front are 1st mods. Then think about eliminating body roll.

 

Hi greenrepbub, you get a bit of wind out there in Bakersfield sometimes, right? Seems like I noticed that while passing through there in 2004 on my OEM tires ... the cross wind DID buffet me a bit. But as mentioned, the stock integrities are NOT the best tread in the world. The symptoms went away when I switched to our hydroedges ... and they're wearing MORE than 500% better! Others have added the stiffening plate listed on the PC store. You might want to add that. It only takes a few minutes for a do-it-yourself'er. Good luck!

 

Shapechanger I have a yaris 2006 model. Factory tires were "rain" Bridgestone B250 185/65R15. After 3 years I changed them to all-weather Turanza ER300 asymetric (350 euros). Bridgestone B250 came to a price of 200 euros.

After 10k miles on new tires, I assure you that the factory eco B250 are LIGHT YEARS BETTER than the more expensive and sportive Turanzas in handling, comfort, noise and economy no matter the season (Summer,Winter).

While my yaris on B250 was very steady at 70 mph, now on ER300 it just frightens me. Not to mention that my MPG reduced dramatically from high 30s to high 20's. I am going to change them as soon as possible. Turanzas are not so soft and they seem not to wear so fast. Other than that i think that I made the HELL choice. If I were you I would certainly drive a prius on different tire to make up my mind.

 

Believe it or not, I've NEVER had a wheel alignment on my 2004 Prius. I have the BT stiffening plate (LOVE IT) and Goodyear Tripletreds (195/60/15). The car tracks straight and crosswinds are negligible. The only thing that I feel is the wake turbulence from big rigs. I'd imagine that most cars would be effected by that too. Bottom line is that for a few bucks you can dramatically improve the Prius' highway manners just by making the mods I made. You'll be amazed what a difference it makes. As to the alignment, I use a crude method to determine if mine is ok. I drive in the center lane of a three lane highway (minimal crown effect) and let go of the steering wheel. If it tracks straight, I assume that the alignment is acceptable. I'd appreciate if someone would chime in and let me know if this is adequate. Oooh... I have 63k miles.

 

Sorry to rain on your parade, but steering straight is not the only indicator. A tire could be causing the vehicle to pull with the alignment being ok. Uneven front tire wear, especially on the edges is a better indicator! At 63k, an alignment check would be a good idea.