Stability/Drifting Issues With Added Weight?

[tbird77]

I've had my 2005 Prius and been driving it for over 50k miles. I've noticed some slight issues in the wind before, but nothing bothersome.

This weekend I went on a camping trip with friends. I was one of the drivers because of the great gas mileage and long drive.

One friend met at my house with gear and we drove 1+ hours to meet person #2. The car handled fine during the first leg of the journey. We added the 3rd person and gear to the mix, then started driving.

The handling of the Prius on the highway seemed to be severely compromised. At low speeds something was off, but it was drive-able. Anything over 60 seemed to make the car have a boat like drifting feeling. A passing semi(truck) might cause the car to jerk. Wind also caused the car to be rather unpredictable. It was about 3 highway hours of this. The last hour of the trip was on side roads under 50mph and the car was ok, though not normal.

At the campground, we unloaded gear. During the 3+ days there the car was fine under 50mph around town or at the park.

On the way home (with all the gear), the handling was horrendous. There were some winds, but I'd say under 15mph. I checked the book which states weight capacity is a little over 800 pounds. With 3 people and gear, we couldn't have been more than 600.

When I dropped off person #2 and gear, the car seemed ok for the 1 hour ride back.

Has anyone experienced anything like this? The car seriously seemed like a safety hazard with added weight and then the handling was fine as soon as there was less weight. I've driven the car for 3 years and loved it. This is the first time, it has ever been packed with a decent amount of weight other than people.

[Patrick Wong]

I'm wondering what tire pressure you are running, and what is the tread depth of your tires? I also am wondering whether you carried any of your camping load on the roof?

I recently traveled ~700 miles through Nevada during Memorial Day weekend, group of four plus the hatch was filled with luggage. Highway speed around 75 mph, and I did not notice any handling issues.

[Sufferin' Prius Envy]

I would guess tire inflation, worn tires, alignment out of whack are where you will find a problem.

I've had my 2005 fully loaded on long trips . . . never felt a difference, except the added weight makes acceleration a bit slower.

[windstrings]

I ran as high as 60psi with the integrity tires and seemed to do fine ... possibly because the tread was not deep.... but then I went to pirelli tires and I drifted all over the place with those tire pressures.... especially going around corners and high speeds... almost like I was tip toeing on the tops of the puckered threads.
I dropped to 40psi and now they do great now.... I haven't really noticed any difference in mileage... maybe 2mpg or so.. but thats from the old tires.

I think drifting all over the place is less efficient anyway and possibly raises gas mileage.... as well as increases the risk for a blow-out with the higher pressures... especially in the summer.

What made me a believer was when I simply drove off the edge of the road slightly going about 40mph and the edge of the asphalt was broken just a bit on a country road and my right rear tire blew... thats when I upgraded to better tires and was thankful it wasn't my front that blew.

[qbee42]

We have taken several trips with four adults and climbing gear. We were packed in like a fraternity stunt, but the Prius handled fine on the highway. I'd look at the tires and tire pressure.

Tom

[tbird77]

thanks. Will check out tire pressure. I recently got new tires ---within the past 6 weeks. Maybe the pressure is up higher than it should be.

ETA - No load on roof. Everything was in the hatch and backseat.

[Porsche998]

I would suggest that you may want to also look at the weight distribution. If there was significantly more weight towards the rear - this would make the front end light and it would tend to be unstable with the degree dependant on the amount of weight.

[windstrings]

I wonder if you underestimated your weight?.. unless you guys are teenagers or very thin, most adults alone would add up to 600lbs for 3 people if not allot.... but assuming your right... gear can add up too if you have several bags.

I noticed your car was about 3 years old.. have you recently gotten brand new tires?
if so, check the pressures as already discussed.

This has been a long debated topic, but the BT stiffening plate did help my car for side winds and cornering.. I would think added weight would only cause one to appreciate its benefits even more.

[hyo silver]

I'd agree with Porsche998. Too much junk in the trunk. I've done that before, and found the headlights gave me a great view of the treetops, but not so good of the road. (Now that was an adventure, driving 1000km of mountain roads in the dark.) Next time, if you can manage it, try to put more of the weight up front and less in the back. Passengers, too, if you can find a delicate way to suggest the "full figured girls" sit in front.

[windstrings]

Its about time I'm not the one who said something like that!!!