Straight line stability fixes

I know there are lots of posts on this subject so I won't get into the debate over if some of us imagine our cars don't handle well, we own lemons, all the Prius are like this, they all handle great, etc. I just want to address some issues with my car finally after too exhausting drives from san diego to vegas with cross-winds. So here's my plan:

Since March 2005 all Prius have used the Touring Edition frt struts. So I ordered mine today.

In 2006 there was a change to the front underbody baffling/dam but that's about $150 and I'm going to hold off on changing that for now.

I also ordered the TE front anti-sway bar-15% stiffer and the rear TE anti-sway bar-about 48% stiffer.

I also moved the frt tire air dams right up to the front bumper (again). Another early adopter did this back in 2004 and I tried it then too. The theory is that while this isn't what you want to do for aero economy, the effect is to reduce the lift. I think there's too much lift making the tires and front end "light" and then any side force makes it move sideways easily. I'm pretty sure I feel a big difference now. Another early adopter found a way to hang 100-200 lbs out front to fix the lift issue.

The tires I'm running 195X60-15 really suck when it comes to gas mileage and catching those crappy wavey road grooves. I've tired Scion 17" wheels and tires, michelin hydroedge (both the std and slightly larger sizes) and now Falken 912's. I'm running 42/40 psig with them that too increased the stability a noticeable amount but these tires rival the stock tire in lack of stability with grooves. I just don't like them and will either go back to Hydroedge or X-Radial from Costco.

I have experiemented with stiffening the frt springs with those large rubber spring wedges. That worked really well. And I think it's because the side movements and wheel corrections did not exaggerate the nose dives like they do with the very soft front end. I've considered the B&G springs but I think the car is so low now that I'll do more damage than I have in parking lots and over speed bumps if it's another inch lower. So I plan to go back to the those wedges on the front once I evaluate the struts and anti-sway bars.

I've done some work with the alignment. I'm at max toe in now but once I do the suspension mods I'll back off just a bit. The camber is even on both frt wheels at -1.5 deg and will not go less than that per recommendations receive from others. I have not really looked at the back toe in yet.

Oh can't forget BT Technologies mid brace. I have that and I'm thinking I'll go with that frt strut tower brace too very soon, maybe even when I change the struts in a week or so.

So any thoughts suggestions or ideas. I'm also experimenting with a full air dam up front. I made a weak looking one back in 2004 that seemed to help too but it was too thin and weak and air just folded it back. The "Autospeed" site did some front end work with the gen I prius that looks promising and there's an article there that shows how to improve the underside. I can see an area in the frt middle of my car, underneath that acts like an air dam about a foot back and could be producing a lot of extra lift. Maybe that's what the 2006 change addressed.

 

Ok so let's talk specifics on the rear toe in then. I can't find my latest alignment report, but assuming this older one is right, I have 0.23 deg on the left rear and 0.19 deg toe on the right rear. The spec was listed as 0.05 to 0.55 deg and nominal is 0.30 deg. So I'm close. I know the front is right at the max toe in of 0.2 deg. I'd really like to reduce the amt of toe in on the front but the car was pretty wild then. when the tire dealer set it to zero. I now have a friend that has a modern alignment system so I try lots of thing.

And please, I'll try to set the record straight on this. I'm not causing this. I can use a death grip or barely touch the steering wheel or anything in between and the car will literally jump to where I feel it and my wife, who really doesn't notice much when driving, feels it too. I think I've mastered the art of slight correction with this car and if you're doing that constantly it can really wear you out on long trips.

I've been driving since my I got my first car, a '55 chevy back in 1967 and have owned anything from a 65 corvair, 64 GTO, Fiat X-19, 2003 RSX, 94 RX-7, vans, mini-pickups etc. I'm not new driving a car and had a few that exhibited characteristics similar to my Prius, but not as bad. The Fiat X-19 did it when I put new Michelin tires on it and it badly needed a rear alignment. The RX-7 did it with some brand new Yokahama tires that were on it when I bought the car new. That one, because it was so quick and fast, scared the crap out of me but new bridgestone tires on it were like night and day.

Sadly the Prius has been that easy to fix. I have driven a few others and while they share similar characteristics, they all were noticeably more stable.

I'm going to have to disagree on the aero lift not being an issue for a couple of reasons. Some of you will remember the real spoiler that Brian from BT tech made a few yrs ago (I just learned he died and still trying to assimilate thas). It was made for a BMW and Brian in talking with an Aero engineer came up with using it on the Prius. As small as it was, it did work and everyone that tried it noticed a difference. But we could not make it stick to the back glass. I kept mine on for overa year by usingan glass etching adhesive but it finally popped loose. And I know the front end under treatment I just did has made the car more stable (but probably hurts gas mileage). So I'll probably try tweaking that some more today.

Yeah all of this is a bit subjective but having almost hit an SUV recently, that drifteded into my lane at 75 mph at the same time the Prius chose to "jump" that way has motivated to improve my car in the interest of self-preservation. And yes it will never "feel" as stable as my wife's RSX but I think there are some additional improvements to be had. The trick is to not buy and try everything that's available but try to sort thru all the opinions, beliefs, experiments, etc. of others. My tire dealer swears the P4 Pirelli is what I need for instance but my experience was that the Hydroedge was pretty good. Is the P4 enough better to risk $4-500? Thanks for the feedback everyone.

 

I did some work today with the front dam and I confess it's so windy that I can't tell the difference. So I did some searching on a term you may be familar with, tramlining. That's really what I'm feeling exaggerated by soft suspension, tall narrow car with lots of side area, numb electronic steering with no real centering feel, and from what I've read directional tires (wider is worse, I have 195's and directional).

Here's a good article of a guy on the cadilac site that took 2 yrs until he fixed his tramlined and then it was ALL about the tires.

Severe Tramlining Follow-up—Problem Resolved - Cadillac Owners Group

And his orginal reports of tramlining (sounds like me, lol)
Tramlining, aka The (Un)Happy Wanderer - Cadillac Owners Group

And here's a pretty good description of the why:

http://homepage.ntlworld.com/robert.smith19/How-to-tramlining.pdf

So maybe if I really want to effect a change I should try the x-radials and not the hydroedge tires again.

 

Yes castor angle is a key element in how different motorcyles are adapted to different sports. A trails bike for instance has a very step angle because it has to turn on a dime and doesn't need the high caster angle for stability. And so a trials bike is extremely twitchy in top gear, where a motocros bike isn't. Trail is the term used for bikes (probably appropriate for cars too but not used much) and it relates strongly to castor angle, triple clamp offset, and somewhat related to tire circumference and fork length. It really easy to feel the difference in various bikes but more difficult to feel in a car.

I have heard of few brave souls that know what they're doing modifying caster but that's pretty extreme. I think once I get the suspense just a bit tighter and less mushy I'm going to focus on these Falkens. At 20 lbs they are a bit heavy too but it's the tread pattern that's the biggest issue along with not being a symetric type and being a bit wider. I don't think they have a very low rolling resistance either based on my mileage.

 

Yes it is a combination of things of course but the general agreement is that the asymetrical tires are worse as are low profile and wider tires. Oh and higher pressures too. That's not my experience with the Falkens but it is with the hydroedge. And I'd be rich if I had a dollar for everyone here telling me that extremely high pressure cures the wandering. Not necessarily.

Also, tires with sharp side wall to tread transitions are more prone to this and that's why something like the Triple tred seems to be very good until it's very worn out and then I read about the owners complaining. Those edges get sharper....maybe??

The hydroedge tires are not very rounded off on the corners and obviously are directional. But they were far better than stock (just a better tire overall). Evans tire even let me try the 195X60-15 versions for 1000 miles and I lost a couple of Mpg and they were not better handling so I went with the stock size.

Yeah it's a bit frustrating finding a consensus on anything on the internet. Lots of opinions and few facts sometimes. It's expensive but you sometimes just have to experiment on your own until you find something that works. What I do know is that my car really doesnt go well in a straight line right now and any other Prius owner that's driven my car has agreed with me execpt for the factory reps..."normal" was their summary.

 

I got my car back after my friend installed the touring edition struts (std after March 2005) and the touring edition anti-sway bars. And there is a big difference. I can feel the Falken twitching at the back, but I can virtually let go of the wheel and not have to constantly correct. Big difference and I think Toyota could have helped me enjoy my car more years ago. I'm not sure which change made the biggest difference but this is really motivating me to do more now. And I'm a little bit disappointed in Toyota for not offering us early adopters some deal on upgrading. I almost like my car again, lol. The Falkens are really bad with grooves but I bet with the Michelin Energy tires and maybe that new 2006 frt spoiler and underside shield my car might be decent. Toyota I really am disappointed in you now the more I think of the times your dealer and regional rep said my car was normal....NOT!

My gas tank is still only an 8 gal gas tank and the piece of *&*^% dash rattles like there's no tomorrow because the dealer has tried to fix the rattles so many times (with black putty mostly) and worn the snap fits out and made it worse to boot.

But I think there's some hope for my car. I think Toyota also did something to improve the dash rigidity too but I'll have to pay thru the nose for that too I bet. This is probably my last Toyota because of this but I guess I'm stuck with this car so I'm going to make the best of my $28K investment.

Moral, there's sometimes a steep price to pay for being an early adopter.