Instability on highway

congrats, all the best!

 

Your saying the trip meter (and hence the odometer?) were off with the stock tires?

 

Cusco web site shows parts for Gen 3 Prius, not the Gen 4 chassis.
CUSCO USA

Expect any chassis or strut tower brace to stiffen the feel of the car. Some amount of chassis flex is expected and allowed for in the design.

 

I think that phenomenom you describe is called "hunting", it's when the car's tires grab for the grooves in the road.
My Honda Insight Coupe hybrid did that to a ridiculous extreme. It would seem that the car could change lanes by itself. It was particularly noticeable at higher speeds. I experimented with a different set of tires and got a complete fix of this problem, however, the fuel economy went way down. The problem tires were also Bridgestones. I've had no such problem when I switched to the Michelin low-rolling-resistance tires, and the fuel economy, noise level, durability, and ride quality were all excellent (2012 Prius Plug-in).

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What do you mean by over-sized tires? Bigger rim/tire combo or bigger diameter on the stock rim? Any recommendations for the Prime? Also, is it the increased mass or just the increased diameter that fixes it? Or stiffness/tire compound? Thanks for any help.

 

I used the "rev/mile" as the true diameter metric on the stock rims. Not as easy today, Tire Rack still lists the specifications on their web site on a tire/tire basis. I just cut-and-paste into a spreadsheet.

I no longer own a Prime so I'd prefer not to speculate. My own cars, no problem, but I'm over a year away from our Prime and it was traded-in with the OEM tires.

The goal is to seek a larger polar moment of inertia. Even slightly larger diameter (i.e., lower revs/mile) has a much greater effect than weight. BTW, I recommend doing a pair of new tires at a time. That way you can check clearance in the rear and dynamic effects by moving them to the front. If the first pair work, get the second pair and have a happy.

GOOD LUCK!
Bob Wilson

 

Toyota does sell a legitimate motion control beam for both the front and rear of the vehicle. I believe it will stiffen the body roll and thus stability on our vehicles.

Source:
Toyota TRD JP
PRIUS PHV -FEATURE- | TRD

Action:

I want to add something to the original discussion. Both my 2016 Toyota Prius and then 2017 Toyota Prius Prime drove straight and super stable on the freeways. Very rarely do they go off track on non windy days on a clear stretch of flat smooth road. This is because I very carefully avoid ALL potholes and generally try my best to route around broken roads. I have driven many cars and many new cars in the past and even sports cars with stiff suspensions. And they all had one thing in common. Stiff suspension + bad roads will equal drift or highway instabilities.

Anyway take my advice with a grain of salt! For certain if you upgrade the stock 195 mm tires to something say 205 or 225 mm, your vehicle should in theory be more stable and drive straight.

 

Just a reminder, when the cars are shipped from the factory the tires are inflated hard. This is to reduce the bounce while they're lashed to the deck inside the car carrier ship for the times the ship encounters rough weather. The generally worthless pre-delivery inspection by the dealership is supposed to correct the tire inflation pressures back to what is shown on the placard on the driver's door jam. Supposed to....

Groove wandering and tramlining, mentioned above, are real things. Different model tires will have different groove-wandering characteristics. While Bridgestone makes many fine tire models (I've heard very good things about the Bridgestone Turanza QuietTrack), is anyone pleased with the original equipment Bridgestone tires Toyota chose for the Prime?

 

I just noticed that this thread had been dead for the past 3 years....

Until user HPrimeAdvanced brought it back from the grave!!!

 

Cusco now does carry the rear sway bar for the 2022 prius prime. I am debating between this or the MEG stabilizer bars

• Solid 24mm +50% (2WD)

PRODUCT INFO
MSRP
$ 347.00
Part No.
1A1 311 B24

That is from Cusco's website