I don't really do much highway driving, however this past weekend I went on a few longer trips and I started to notice that the car seems really unstable when doing like 65-70mph. I always noticed the steering's sensitivity on turns, but now even when the car is headed straight (on level ground) any correction w/ the steering wheel results in exaggerated motion. I thought it could be the alignment, but when my hand is off the wheel, the car tracks completely straight on a level surface. It's only when I have my hand on the wheel doing slight movements. I have a really hard time keeping the car going straight along its intended path. I know this extremely subjective, but I've never had a problem w/ this in any other car I've ever driven in. Does anyone have any suggestions on what it could be? I thought that maybe the wheel could be warped or maybe the tires aren't balanced, but those would cause more vibration, and the car doesnt vibrate at all...

One word: POStenzas.

They are not awe-inspiring. More like fear-instilling. Do away with them, and revel in the wonder of the tCs relatively neutral handling, even in stock kit.

See what's weird though is when I first got the car I never noticed the instability at all, I don't wanna throw down a few hundred bucks on new tires if the problem is still there... I know the tires aren't good, but could they really be causing the car to oversteer like crazy?

I can promise it is the tires... my car has yokohamas on it and it handles like it is on rails at any speed the car is capable of

Don't be too quick to rule out alignment. With enough castor, excessive toe out will not cause the car to pull side to side. I'm not sure what the tC's castor angle is but a little too much toe out will make a car very twitchy at higher speeds.

My car is rock solid by the way.

more insentive to get those pirellis :D

maybe it's the oversteer? i have seen several threads about tCs flipping off the highway.. :nails:

Why not start with the most basic problem of all? When did you last check your air pressure while the car was cold? If you are low on air pressure none of the rest of the stuff matters a whit. Any tire on any suspension will behave very badly if it doesn't have sufficient air pressure.

I doubt it's the 'POStenzas' although I plan on getting rid of mine ASAP.

i was just thinking the other day whilst on cruise control at 85mph how nice the TC handles at mid-high speeds.

It was a very relaxing drive down to Philly (apart from 192 where you have to drive at 60 or get a ticket.

i have logged to 400 mile trips in my TC no problems but i also do have the 18's w/ the perellis... really doubt its oversteer whilst going in a straight line

i used to think my car was unstable too... but that was before H&R and Koni came along...

Nah its not the tire pressure, to describe it best, it feels like a slight movement in the steering wheel results in exaggerrated movement in the actual direction of the car. i never noticed this until a few weeks ago, like lets say the road has maybe a 15 degree curve to it, normally keeping the wheel steady at a slight angle would keep the car travelling along the little curve. However now it seems like i constantly have to correct the angle because the car wants to veer too much in either direction when i turn the wheel ever so slightly.

There have been some reports of sidewall failure in the RE92. This might be an indication. Then again, it might just be incorrect toe.

yea I know what ur talking about Break...I feel it too when I'm going about 70-80 and it's like the car makes these weird movements side to side and it's kinda annoying. I also took my hands off the steering wheel and it didn't jerk at all when I had my hand on it.

its the re92

I have an '06 with Yokohamas on it, and do not notice any issues at high speeds. About a month ago I had the little mule up to 120mph with no problem. (Mostly straight line and lane changing on a long stretch of highway). Okay, that was a one time deal, but I drive 65-70mph to work nearly every day with no noticable problems. I've had five other Toyota's and three of those were Celica's. I think the tC handles a lot like my '92 Celica, and I love it. The only handling problem that I've noticed is when you corner and simultaneously accelerate at lower speeds. Under these circumstances, the tC tends to "hop" a little, causing you to lose traction.

I agree with the posts about air-pressure. Typically, front-wheel-drive cars will tend to understeer. (Which is normally NOT a desirable trait - most of us prefer oversteer, making it easier to "drift"). I have my front tires about 3-4 psi harder than the rears, this helps to reduce understeer. In your case, you may want to have higher pressure in the rear, if your are REALLY experiencing oversteer. There was an excellent article called "Making it Stick" in Sport Compact Car about three months ago. If you can't find it on the net, I can scan and email it to whoever wants it.

One last thought... are you running any aftermarket body kits? I have the standard Scion ground effects installed. I've heard varying arguments that a) gorund effects are for looks only, b) they help you aerodynamically, and c) they can hurt you aerodynamically. My only point is that when you install a 3rd party mod that actually changes the aerodynamics of your vehicle - you really DON'T know what you're going to get. (Okay, I am making the leap of faith that Scion/Toyota actually wind-tunnel tested their goods - or at least ran a computer simulation). Even at 70mph, your pushing a lot of air out of your way really fast. A modifed body may be lifting your front-end ever so slightly and causing the squirly steering.

EZ~G

I've tracked the tC on stock tires. The car will handle on those tires when properly inflated at higher speed(95+). The car does get really unstable under high speed moderate braking. When I say unstable, I don't mean a predictable movement like the back end coming out or sliding... it just gets really wiggly, the backend kinda jacks around from side to side. There's no steering wheel inputs going on when this happens either. It scared the crap out of my instructor and me the first few times it happened. I've had a discussion with a guy on this forum who has tracked his tC on the same track with DIFFERENT tires and noticed the same problem. It's not the track either. We decided it must be a suspension issue.

Could it be related to this some how?

-Tide

I've noticed the back trying to seperate itself from the car under moderate-heavy braking. If anyone knows what this is, please by all means enlighten us! I ahve Potenzas for the record, and in response to the first post, I haven't noticed any increase in sensitivity. My Saturn used to become really light up front and basically not respond at all at around 55 and up, but the tC seems to stay planted pretty well. Plus steering sensitivity to me isn't really a bad thing at all, if anything at higher speeds it would be an advantage. And a random quesiton to put out there, does the tC have a variable ratio power steering system? If so that may be the answer to the problem.

I noticed (really noticed) last night that it has some issues in Heavy braking like the back end doesn't want to slow down. I saw an accident in front of me and had no where to go left or right so I laid on the brakes and it stopped very effectively but I had to make several adjustments to keep the back end planted... and I do not believe (don't flame me if I'm wrong) the tC has variable ratio power steering

I've noticed the back trying to seperate itself from the car under moderate-heavy braking. If anyone knows what this is, please by all means enlighten us! I ahve Potenzas for the record, and in response to the first post, I haven't noticed any increase in sensitivity. My Saturn used to become really light up front and basically not respond at all at around 55 and up, but the tC seems to stay planted pretty well. Plus steering sensitivity to me isn't really a bad thing at all, if anything at higher speeds it would be an advantage. And a random quesiton to put out there, does the tC have a variable ratio power steering system? If so that may be the answer to the problem.

Ive got the Potenzas too and never had a problem like that. Low air pressure or uneven pressures can make the car handle weird though.
Those Saturns can get scary like that. High speed going over a large bump and you can do whatever you want to the wheel and it wont respond at all for a second. At least my SC1 did that. Not fun in the snow. :nails:

potenzas are nice tires.... they're soft... but wear easily... I kinda...know what you mean when @ higher speeds... i just hold on to the wheel tighter... but most def... tires would make a difference

potenzas are nice tires.... they're soft... but wear easily... I kinda...know what you mean when @ higher speeds... i just hold on to the wheel tighter... but most def... tires would make a difference

Man... Idk ... they don't stick worth a crap.

What Potenzas are you talking about? The S-03s on my Supra? Yeah, they're pretty good. The RE92's on the tC? They're crap, even Tire Rack customers agree on that. They are rated second to LAST in their category for good reason.

While I don't like the EBFD system, and I think the ABS on the car is too aggressive kicking in, especially over bumps, if you are still on RE92s, you really haven't experienced what a stock tC will do with just better tires. I'd spend money on tires before springs, shocks, strut bar, swaybars, or any other suspension mod. None of those mods will yield as large an improvement as better tires will. Even all of them together with the RE92s will not beat a bone stock tC on any decent tire. Really. Spend money where it makes the biggest difference first.

I've tracked the tC on stock tires. The car will handle on those tires when properly inflated at higher speed(95+). The car does get really unstable under high speed moderate braking. When I say unstable, I don't mean a predictable movement like the back end coming out or sliding... it just gets really wiggly, the backend kinda jacks around from side to side. There's no steering wheel inputs going on when this happens either. It scared the crap out of my instructor and me the first few times it happened. I've had a discussion with a guy on this forum who has tracked his tC on the same track with DIFFERENT tires and noticed the same problem. It's not the track either. We decided it must be a suspension issue.

Could it be related to this some how?

-Tide

With 245/40/17 Proxes T1S on 8.5" rims, I've had ABS working on all four wheels from a 75 mph roll and the car was stable with the stock suspension. It's really the tires. They suck.

its a combo of everything that everyone is saying. after i put my kit on and springs, this little problem is gone. i need some canards and a gt wing now. i think that problem is more noticable when the car is stock, but then again my wife's tc is basicly stock and there r no problems with hers. u might have a lemon. :doh:

I drive 30 mins to and from work every day, all highway, at a constant up and down from 85-95 mph simply because my tC handles like a dream. It's just so fun to drive. Especially weaving in and out of traffic. All the dirty looks are hillarious. People are so uptight.

Definitely try better tires!

i need new tires and a sway bar, i got outhandled and out accelerated by a v6 accord on the highway through the twisties.....i knew i couldnt beat him in straight line speed but he walked even harder in the turns, the accord looked like it has stock suspnsion too :nope:

Not sure unless it is alignment...

The potenzas arent great, but have no issue at high speed. I have run mine a lot faster through tight corners as well as flat and straight, and feel it is VERY stable. There is way too much panic regarding them causing a wreck. If not so grippy tires causes it, then what happens when people drive on streets just getting wet from rain.. or even snow???? If you can get better tires, do it, but I dont see it being that, as mine does very well at high speed. I have gotten it to 115 (on a straight, flat KS road that I could see for miles down.. .so no mothers griping at me please) and it felt as good as would be expected at that speed. I was actually pretty impressed.

And as far as "the oversteer" causing it.... the tC needs MORE oversteer as does most all FWD cars, which is the main reason I want a rear sway only. The flipping off the highway posts I have seen were due to poor driving 100%. And then there is the "fishtailing wildly taking off from a stop light" which was either poor recognition of torque steer or the story was not completely told. Even with BALD tires on rain a fwd is not going to start fishtailing from a dead stop no matter what you do unless the e-brake is on. Sorry if I am referring to anyones experience that is here, but sorry , the fishtail from stop just goes against physics in this case.


So bottom line, go get it checked.

Interesting comments. I ditched the RE92s after I got power understeer on a wet on-ramp at 30 mph. I've taken the same turn at 45 on my T1Ss in the wet, so I know it was the tires. Glad you are OK with them. I still think they are crap and should not be on any car sold as a "sporty" model.

^^ I do agree they arent great tires... but so many people try to blame them for the dumbest things. THAT is what I was refferring to.

Well, took my car in today... They checked the alignment and nothing was off, so I went out driving on the highway with them and they simply said that's the way that the car handled. I think that's BS cause I've had my car for like 5 months so far, and I only started noticing this like 2 weeks ago. Maybe I'll get some better tires, and do some suspension mods to keep it cornering better...

That's an unfortunately frequent answer. The truth is, they don't want to troubleshoot something for very long because it doesn't get covered by warranty if it takes a long time. The dealership just eats troubleshooting, so they do what they need to do: check alignment to be sure it isn't bad, check the tires and the pressures, look for obvious problems like bent wheels or suspension, leaking shocks, etc, and call it good. Anything more is going to really hurt them financially, and they've addressed all the safety issues by doing those things, so they know you aren't going to die from the problem. That's part of why I didn't want to be a line mechanic for a car dealership. Too much emphasis on speed, and if you get a reputation for being really good, you end up with a lot of diagnostics that don't pay very well.

I hope tires sort out your problem. I know for sure you'll like the car a LOT better with quality rubber under it. I know there's nothing I've done that made as big a difference.

while I do know about how crappy the stock tires are. I have had no problems with them like you have described.

eventually I will get better tires, but not until the current ones are near death.

i think that the it could only be that it was windy that day you were drivin at that highway, coz yesterday i was on 680 north and i kept noticing that my car wanders, i thought my car was messed up, but as i got to highway 80, the unstability disappeared, and my friend that was in the car too said that it was only the wind, coz he was drivin at the same highway with a tc and he said it was so windy outside that he had a hard time keeping the car straight too...

altho im pretty sure that it's just the wind, it could be that it's the tires too...

Nah, it was a beautiful day no wind. And besides, I've taken it out on the parkway at least 5 more times to try and pinpoint what it does exactly and it has done it every single time.

Potenzas are the worst tire I have ever had on a car. My '02 Mazda Protege also came with Potenzas. I am also concerned about how my car feels in turns and corners. I am sure it's not just the tire, because I could really hang in corners with my protege (handling did improve when i switched tires). I can't wait to get new tires for my TC. I have changed the stock sway bar to the TRD sway bar on race setting and I noticed that the handling improved but it is still lacking.
I can take cars on straight aways but when it comes to windy roads I dont even try.

I think it's either you are too sensitive or there is something wrong with your car. I drive three times a week 65 miles averaging 85mph and my 2005 with 19,000 miles on the Potenzas is as stable as any car ive driven. In fact I hit triple digit speeds a lot of those days and the tC is still stable. Only around 115mph-127 mph on conrners does it feel flighty at all but it is stock. I imagine some springs would fix that right up

yo, where are you at that ur hitting triple digits!!! with corners no less!

Highway through the cornfields of Illinois

neatness!