Unstable at higher speeds

[richard schumacher]

Don't be surprised if alignment is not the cause. Mine felt the same way when it was new and the alignment was spot-on. Not wanting to bother with new tires, after a few weeks I got used to the feel of it.

[jdenenberg]

When I upped the air pressure to 42/40, the instability was reduced. When I bought GOOD tires to replace the Goodyear Integrity tires the instability disappeared completely (with no realignment, although that could hep as well). My first replacement tires were Michelin MXV4+ "energy saving" tires which were very good, but my present Nokian WR tires are great. Both improved MPG with the Michelin tires giving a small improvement (about 0.5 MPG) and the Nokian tires getting a 2 MPG improvement (averaged over a 12 month period) compared to the original tires.

JeffD

[hyo silver]

There are several possible causes for this. First, get the alignment checked, if for no other reason than to rule that one out. Apparently many Prius are delivered out of spec. Better tires are a good idea even if you're not having handling issues - the improvements in stability, braking, and traction make the car much safer. Chassis braces also help, though more with cornering. Another thing is to 'get used to it'. Not the wandering, I mean, but the car. When I first got mine, it was all over the place. After awhile, I realised it was my fault. I was used to a larger car with a fair bit of play in the steering, and was in the habit of gently moving the steering wheel back and forth. The Prius's steering lacks feel, but not precison. Every little movement of the steering wheel translates into movement of the front wheels.

[kn6vv]

I too had this on my new 2006 until this week. I replaced the OEMs with same size Michelin MXV4s. With new tires I decided to also have the front wheels aligned and checked as I never checked it since new. I think I just got use to the higher speed wandering in the freeway lanes.

Well I'm glad I checked the front alignment as the guy told me they were toed out 3 degrees! Our speed limits on the interstates are 75mph and the difference is night and day. The Prius is VERY stable with a proper alignment and good tires.

[bedrock8x]

Incorrect toe in or toe out does not cause stability issue absolutely. It may cause over steer or under steer problem on high speed turns and of cause excessive tire wear.
Stability is usually caused by insufficient traction from the tires, light weight vehicles reduce the traction and tall vehicles aggravate the traction requirements.
A good tire with good traction will improve the stability.

[GreenRepublican09]

The car is only about 2 months old and has roughly 1300 miles on it. I thought about the tires, I'll probably do that sometime soon. It may also be the comparison... I drove a 2000 Mustang for 6 years. The car was wide for its size and hardly moved on the freeway. All other cars I've driven for significant amounts of time have been larger and heavier. Could it really be the alignment this soon after I got it? Normally I notice that kind of thing even at lower speeds, and the car does move one way more, it just seems to get knocked all over the place when my hands aren't moving.
I'm also not great on the technical terms. I appreciate all the input, but can you guys use laymans terms?

[richard schumacher]

In some of them the alignment is bad from Day 1, caused by the way the car was tied down on the ship.

[qbee42]

Also note that the electrically assisted steering in the Prius has little dead band or feedback. It's very easy to over control until you get used to it.

Tom

[bwilson4web]

Originally Posted by GreenRepublican09

. . . Could it really be the alignment this soon after I got it?

Yes. Assume nothing about the alignment until it has been measured.

Originally Posted by GreenRepublican09

. . . Normally I notice that kind of thing even at lower speeds, and the car does move one way more, it just seems to get knocked all over the place when my hands aren't moving.
I'm also not great on the technical terms. I appreciate all the input, but can you guys use laymans terms?

Let me suggest:

• early tire rotation - this gets them in front of a technician who can
• measure tread depth - normally they do just center and edges for each tire. If there has been an alignment problem, this will be 'the smoking gun.'
• wheel alignment - get a hard copy listing with all of the values:
  • toe - how much the tires try to roll towards each other. More toe, more stability but higher drag. Unequal toe tends to pull. Outside toe, the car becomes unstable and tries to dart to either side.
  • camber - how much the tops of the tires lean towards the car body. More camber, the better to take sharp turns at high speed. Less camber, less drag and more even wear.
• caster - how the steering linkages work so turns are smooth and the tires don't 'make smoke' in a turn. More of a linkages and suspension issue, it tends to go bad only after a bad accident or bad road hazard event ... very bad event ... like an accident type event.

I would recommend asking Mr.Google about wheel alignment but if you'll get your tires rotated, tread depth measured, and the alignment report brought here, we have a number of folks who can make practical recommendations.

GOOD LUCK!
Bob Wilson

[GreenRepublican09]

Thanks for all the input. I think when I have the oil changed I'll ask them to check the alignment.