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Car unstable at High Speed

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Old 08-07-2006, 10:41 AM
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Car unstable at High Speed

Ok so this weekend I was traveling and had a chance to open it up. I got to 135MPH and to my suprise the car felt very unstable. It felt like it was barely floating over the road. The car is bone stock but does have a rear spoiler and front facia, is this normal ? There were no winds that could have had any effect on how the car was driving.
Old 08-07-2006, 10:55 AM
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Was it being pushed around or was there wheel vibration?
Old 08-07-2006, 11:21 AM
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IS your car stock ?

and I mean, 135 is really fast, dont expect it to have the same feeling as you're going 35Mph

Last edited by nycgps; 08-07-2006 at 11:25 AM.
Old 08-07-2006, 12:06 PM
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how many stock cars DO feel stable at 135?

that's really f'n fast
Old 08-07-2006, 12:09 PM
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I, for one, was pleased by how stable the car was at an indicated 133mph, practically one-hand-on-the-wheel kind of stable... Bone stock with the "appearance package".

Maybe that last two mph gets it all squirrelly.
Old 08-07-2006, 12:20 PM
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I've done this once before too. I don't think the car creates enough downforce to really keep us stable at those kind of speeds. 135 mph is pretty fast and I don't know any car that is going to be sticking to the road and feeling like it is a rock.

It also could have been the road. The barely perceptable grooves from the traffic that start to form over time are hitting your car a lot faster and more often at that speed as opposed to 60.
Old 08-07-2006, 12:58 PM
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Check your alignment.
Old 08-07-2006, 01:19 PM
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... and tire pressures
Old 08-07-2006, 03:48 PM
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Ok lemme answer a few of the replies but please keep them coming. Im going to be at a open track event next month, while I know I wont be running 135 in the straights, I do want to know if something is wrong.



My tire pressures were all set at 37PSI(Hot Tire Pressure) before I left on the trip. As for what I expect a car to feel like at 135MPH, I had my Ford Lightning (5200#s)over 140MPH, my Mustang(3400#s) over 150MPH and they felt way more in touch with the ground than the RX8 did. In comparision to the Mustang and Lightning, this car is way lower, should have more downforce and way lighter. I actually got out of the throttle because it felt like the car was too unstable. The road I was on wasnt a interstate but was a very wide and smooth road(HWY 71 for those in Texas) Its almost like the car was Dancing over every bump I hit on the road, All Im asking is if this is a normal characteristic of the car. Ive been impressed with every aspect of this car vs previous mentioned. However I was disapointed and scared when I hit 130-133(This is where I actually backed off) this weekend.

Perhaps I will take it in to have the alignment varified even though it doesnt pull and has never met a pothole or curb.


Again Thanks
Old 08-07-2006, 03:58 PM
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I spent several hours at 125 MPH and at least dozens of minutes over 130 on my move to Phoenix. There was a spot in Oklahoma where we sat at 140+ for a bunch of miles.
The car does lighten at 115 to 120, even when severely lowered as mine is.
I have the MS stuff all the way around the body.

I suspect that it is simply too smooth and causing the air to speed up too much over the top, which makes lift.

Since a Cessna 152 can leave the ground at 50 MPH, don't underestimate the power of a virtual airfoil.
Old 08-07-2006, 04:04 PM
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Originally Posted by Zoom510
The road I was on wasnt a interstate but was a very wide and smooth road(HWY 71 for those in Texas) Its almost like the car was Dancing over every bump I hit on the road, All Im asking is if this is a normal characteristic of the car. Ive been impressed with every aspect of this car vs previous mentioned. However I was disapointed and scared when I hit 130-133(This is where I actually backed off) this weekend.
LOL, I live off of highway 71. It is one of the most dangerous roads going west in Texas.... prolly because of people going 135!

Anyway, I have cruised at 120-130 in short bursts and it felt a bit light, but not unstable.

Last edited by SOVINE; 08-07-2006 at 04:07 PM.
Old 08-07-2006, 06:47 PM
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I agree when I went a little over 130 it felt very light to me too.
Old 08-07-2006, 07:07 PM
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wonder what the euro lip spoiler would do... looks very similar to the audi TT spoiler that prevents those cars from flying off the road
Old 08-07-2006, 07:19 PM
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Most street cars dont create any downforce.
Old 08-07-2006, 07:48 PM
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Might need to ad some body work like this to hold it down.

But seriously I have not been over about 120 and it felt pretty good up to that point. I know that drag (air resistance) increases with speed.
Maybe you just found the limit with stock on a highway.
Is this a Base model or a Sport or GT package?
Sport and GT have stiffer springs than the Base model.
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Old 08-07-2006, 07:58 PM
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How often have your driven that speed? Mine feels very stable at that speed... for a car going that speed. 135 is not going to feel like 70. I've had mine to 150 (took a loooong time to get there even slightly downhill) It's not a speed for public roads and will feel light without functional chin and rear spoilers if the road (read track) isn't pancake flat. At that kind of speed steering input, tire design, tire pressure, and of coarse alignment get very important very quickly.
Old 08-07-2006, 07:59 PM
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The 8 is pretty light even stock(already) so as you go faster, it will feel lighter.

Well, To keep it stable, I guess u need to get some really good bodykit, yes it does help alot. (stock ones dont do ****, its for the looks ONLY)

I tried the highest and lowest setting on my MS spoiler, and there is a noticeable differents when its at the lowest setting. The rear is way more stable. but if you want max speed, put it to the highest.
Old 08-07-2006, 08:10 PM
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Ever watch nascar even at shortr tracks? One car close to another can cause a car to spin out, and those cars are built to be perfect at high speed. Do you expect any stock car to feel very stable at 135mph?
Old 08-07-2006, 08:38 PM
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Solvine- It sounds like you know the exact area I was driving. It was a strech between 281 and LLano.


Thank you all for the replies based on all your posts, Im going to just chalk it up and say the car isnt that stable at those speeds. Now to all those who wanna say the car shouldnt handle at those speeds, maybe the RX8 shouldnt but Ive driven at least a dozen vehicles at or above 135 and none have given me the uneasy feeling I felt in this car. Im not ******* the car one bit, it is incredible the way it brakes and goes into corners. It is by far no where near the fastest(1/4 mile) but it is the fastest corner carver Ive ever had.


Thanks again to all
Old 08-07-2006, 08:56 PM
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Originally Posted by Zoom510

I actually got out of the throttle because it felt like the car was too unstable. The road I was on wasnt a interstate but was a very wide and smooth road(HWY 71 for those in Texas)
Texas 71 is a very nice road, but if you were doing 135 (twice the legal speed) you were way too fast for safety (yours and mine) and you should thank your lucky stars the car cautioned you to back off.

Save the high speed driving for the track, or let me know the next time you plan a stunt like this, so I can be sure to be out of the State.

P.S.: Yes, I have driven this road (Brady to Austin, Austin to Houston) many times.
Old 08-07-2006, 09:35 PM
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PS everytime someone posts something like this someone comes out and says this exact thing. I don't think he really is going to suddenly say "boy I'm reckless and foolish" and never speed again, so just save it.

Sorry to be so blunt and its nothing personal it just gets on my nerves. It's like telling someone who smokes that smoking is bad for them and second hand smoke kills.
Old 08-07-2006, 09:49 PM
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Originally Posted by terretsboy
PS everytime someone posts something like this someone comes out and says this exact thing. I don't think he really is going to suddenly say "boy I'm reckless and foolish" and never speed again, so just save it.

Sorry to be so blunt and its nothing personal it just gets on my nerves. It's like telling someone who smokes that smoking is bad for them and second hand smoke kills.
It is something personal--my family uses these roads, too; and it really gets on my nerves whenever I read about some horrendous wreck taking innocent lives. I speed, too--all the time. (Thank God for Valentine). But recklessness pisses me off. (Of course, no one ever judges themselves to be reckless.)
Old 08-07-2006, 09:51 PM
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Soo funny...

I just had my 8 the fastest I have ever been Saturday night. 142. That was pretty fun. Prolly a lil stupid too, 2am, high beams on. Oh did I mention I live in NH/VT where there is no more than 1 1/2 miles of STRAIGHT road and lots of deer and moose? I was extremely impressed with how well the car handled any type of turning at that speed. Very slight turns of course!

It did feel a lil light but the interstate I was on was freshly paved a couple months ago.

I have a stock GT.

Oh and the reason for this stupid maneuver? The same reason men do most stupid things. A very attractive woman turned on by speed!
Old 08-07-2006, 09:55 PM
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Originally Posted by DRKSYDE
Soo funny...

I just had my 8 the fastest I have ever been Saturday night. 142. That was pretty fun. Prolly a lil stupid too, 2am, high beams on. Oh did I mention I live in NH/VT where there is no more than 1 1/2 miles of STRAIGHT road and lots of deer and moose? I was extremely impressed with how well the car handled any type of turning at that speed. Very slight turns of course!

It did feel a lil light but the interstate I was on was freshly paved a couple months ago.

I have a stock GT.

Oh and the reason for this stupid maneuver? The same reason men do most stupid things. A very attractive woman turned on by speed!
Your lucky to have such a woman. I'm thankful that mine can't see the speedometer from her seat; or I'd be nagged viciously.
Old 08-07-2006, 10:02 PM
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She could only see the speedo because she was practically in my lap... Believe it or not she kept saying FASTER! I told her she was crazy and we were either going to die or I was going to get pulled over and lose my car and my license!


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