Nearly wrecked my Prius on the highway

Maybe the winds were really bad that I drove in. When we got out of the car to change drivers, I could hardly stand up in the wind (and I weigh 220lbs). I drove my Suzuki Aerio SX (2600lbs) in some pretty windy areas and it never felt as bad as the Prius (2900lbs), though. Anyway, I still love the car I'll just have to think twice before I take it on any super long road trips...

 

See my front air dam mod (15 minutes, nothing to buy) at :
http://www.priuschat.com/forums/next-vt490...r=asc&&start=80
This made a bid difference in my 75mph crosswind stability.

Get front and REAR alignment checked. I had 40% extra toe OUT on right rear wheel (dealer can only adjust with a shim kit).

 

I could be wrong, but I thought (at least the '04/'05) Priuses had adjustable rear alignment, not shims. Not sure where, so maybe I'm full of it...

Regardless, it's worth having it checked and rectified! Toe-in/out controls directinal stability to a large extent, as cornering and/or crosswinds change the relative tire loads, which results in a change of direction if misadjusted.

Now I'll have to go back and check my rear specs when they aligned it--might get a little more improvement in freeway stability...

 

When I 1st bought the car in late 2003, I noticed the stability issues in high wind, but it has been less and less of an issue. After 18 months of driving the Prius, I guess getting used to the feel of the steeering wheel and my tendancy to generally drive slower has made a difference.

 

3,000 lbs. is light? What about the even smaller cars out there? The Prius is a midsize, are there other "light" cars to compare to in the midsize class? Just wondering. I think the "weight" issue doesn't work with a 3000 lb car. It really seems to be what we are used to "feeling" in our previous cars/trucks: more wander/freeplay of the steering mechanism. IMHO, it makes sense to slow down in adverse conditions, but we are all in a hurry. I for one like to enjoy my ride, not coming as close to the edge of control every trip out, fighting the weather or traffic, then wondering why the car doesn't seem to handle very well. Anyone else?

 

Is there a consensus that the low Cd, combined with the tall narrow profile, *may* contribute to high speed stability/tracking?

As some forum members have this problem and others don't, clearly there are many factors involved here and the individual contribution to the problem is variable.

I like the idea of modifying the front wheel spoiler or making your own. This is easy to do and may provide the most benefit.

At the moment I would have to characterize my Prius as being right on the edge of having the worst tracking in gusty conditions. My parents have a 2003 Buick LeSabre with very sloppy steering, but it also tracks straight as an arrow too.

You never have to fight it or get white knuckles at 110 km/h in gusty conditions.

 

think of it as a vector-problem: a car with a high Cd number (high wind resistance) has a large windvector directed along the car (say 3) at a certain speed and a certain cross windfactor (say 3) because of a certain very strong crosswind. The resulting powervector is directed 45 degrees sideways.
A car with a low Cd number has a little windvector along (say 1) at the same speed and the same cross windfactor (say 3) because of the same crosswind. The resulting powervector is directed -say- 80 degrees sideways (I don't have a table of tangens here).
So in the second example the car will be pushed by winds far more sideways again and again as the car in the first example.
This explains the problem of the Prius (and every car with a low wind resistance). It is inherent at cars with low wind resistance. The only possiblity is diminish the windvector along the car (slow down!), so the resulting vector goes more in the direction of the first example. That is exactly what some people did describe in this forum: slowing down helps very well.
Bye,
Jan

 

<div class='quotetop'>QUOTE(jhoogwegt\";p=\"79655)</div>

Jan:

Don't worry about tangent and vector tables. Your example is easy to understand if you have a good math background.

Jay

 

Has anyone else experimented with this mod? Looks interesting to me.

I'm a new Prius owner with several hundred miles of serious cross wind experence. I found it moderately annoying and am interested in improvement.

Harry

 

I live in El Paso and 30-60 MPH crosswinds are normal around here. When driving at 70 MPH there is a stability issue but when we have those winds I just slow down to 55-60 MPH and do not have a problem. I drive with both hands on the wheel anyways. I had an F250 here also with a camper shell and would have to slow down as well with the crosswinds here so not sure it is a car defect. There is not really a way to avoid this. Even a wider wheel base would cause the car to be pushed (just with less rocking).

Just wait until they goto composites and cut the car's weight in half.

 

Checked repair manual, rear suspension is not adjustable.

 

is this a problem with the prius in europe and japan? I know they have larger wheels more grip better tires mabye? different suspension?

 

I read that the Euro Prius has stiffer bushings (don't know which ones) in the suspension. The "racing" Prius used for a SCCA demo used them and they adjusted the back end geometry for more consistent tire angles.(???).

 

ummm.. around here we have several areas of extreme crosswinds and i mean extreme. only difference is that we dont drive 70 mph because we cant.
the Tacoma Narrows bridge speed limit is 50 mph and has been as low as 25 mph if the wind speed is over 55 mph and its always a perpendicular breeze. the I-520 floating bridge is completely exposed and its speed limit is 55 mph but drops to 35 mph 9very common occurance) if the wind speed exceeds 35 mph i think (its also a narrower than normal bridge with no shoulders to speak of)

i have been over both several times and once it was "interesting" in the Prius. but i have had several "moments" in my truck. in fact, the truck, if empty, is much worse imho.

a few times going across I-90 at 70-75 i never noticed much of anything and to be honest with ya, its famous for wind (there is nothing to stop the wind across the "moonscape" east of the Cascades.) cant say if it was windy because never bothered to notice. there is no trees so hard to tell when driving.

 

<div class='quotetop'>QUOTE(finman\";p=\"79627)</div>

actually, the Prius is very light for a midsize car. and that does make a difference because wind resistance will still hinge on weight and area for the wind to work on. yes there are lighter cars but they are also smaller.

 

<div class='quotetop'>QUOTE(Erick\";p=\"79438)</div>

Clearly you have not had a chance to drive a proper training car. I had years of experience with a 20+-year-old VW bug with bad ball joints. That thing would try to change lanes on the freeway no matter what the weather conditions. Kept me alert (and probably caused others behind me to think I had been drinking).

I have not noticed any stability problems with my Prius, and I've driven through some extremely windy mountain passes during Santa Ana periods this spring. I have, however, heard from others besides you who have complained bitterly about poor tracking on the freeway. So perhaps you ought to have the alignment checked (I wonder, would tire balance affect this at all?).

 

I regulary drive from San Diego to Barstow/Las Vegas and the winds can get pretty hairy. I just did it this weekend and though not epic conditions, I definitely knew I was in some wind. I've also driven the SD-El Centro route in bad winds. Both those routes will shut down on occaision and its wise to keep one eye on the big rigs in your vicinity. Although the prius can be busy in cross winds, I've not had any white knuckle rides. Toyota does know how to build stable cars. My corolla ('92) and corona ('78) handled exceptionally well. My 1st generation Voyager ('87) was an E ticket, however. Talk about a rolling billboard. In short (too late), the design is unquestionably made to reduce forward drag and won't win any slalom races, but I've found it to be acceptable.

But I also think that those whose experience is otherwise should keep speaking up. There may well be a design flaw which manifests itself in only some percentage of the product. But its a bitch when its yours.

 

After a few hundred miles and experimentation with different tire pressures, I decided that that the OEM Integrities had to go. I bought Goodyear Assurance ComfortTreads in the same size for a net price of about $245 from a Discount Tire store.

These tires are not made for handling, so they feel a little resistant to sudden course changes, but on the positive side, they also seem to resist the sudden direction changes that are making you nervous.

As an added benefit, they significantly reduce the jolts and vibrations the car experiences on bad roads (which are just about all of them here). Think fewer mechanical problems, squeeks and rattles in the future.

I would also recommend lower tire pressures for improved stability. I use the ones listed on the sticker on the inside rear of the driver's door. No doubt this lowers MPG a little, but it significantly improves stability on rough roads.

 

Has anyone tested oversize tires on the Prius. If so, what size and any difference in handling, especially in windy conditions?

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