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Car unstable at High Speed

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Old 08-07-2006, 10:13 PM
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Originally Posted by DRKSYDE
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!
Well, your fears were justified. Good to see that they didn't come true--this time.
Old 08-08-2006, 06:54 AM
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I could be your shocks are getting old. Mine bounced a little more than I like when I exceeded 110, so I got new shocks, Tokico D-Specs. Now it's solid as a rock at high speeds.
Old 08-08-2006, 07:13 AM
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Originally Posted by MikeTyson8MyKids
Most street cars dont create any downforce.
Most street cars create lift (opposite of downforce) because if you look at the profile of a car it looks generally like an aerofoil or airplane wing.

On something like the audi TT the small lip spoiler removes something like 70% of the lift the car generates.
Old 08-08-2006, 07:46 AM
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I've had mine up to 143 mph w/o any problems with stability...
Old 08-08-2006, 08:06 AM
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Maybe I should find a place around me to try it out at 135 .... then I'll let you guys know how I feel
Old 08-08-2006, 08:14 AM
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Here's a good place...
www.scca.org
Old 08-08-2006, 08:45 AM
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Signed up. Looking at it.

Will try Lime Rock or Pocono.

WEEEeeeEEEEE !
Old 08-08-2006, 09:15 AM
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She could only see the speedo because she was practically in my lap...
Wearing a speedo? j/k
Old 08-08-2006, 09:34 AM
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LOL nice one... Won't EVER catch me in a speedo! Let's just say it was a GOOD night and the 142 was worth it in the end!
Old 08-08-2006, 09:43 AM
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I'm wondering if the euro lip spoiler would do anything to help. I was considering adding that and springs as my next mods. Hmm..
Old 08-08-2006, 10:05 AM
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The euro lip spoiler will help, since it breaks up (spoils) some of the airfoil effect. A larger spoiler would be better. I prefer spoilers to wings, though mostly for aesthetics.
Old 08-08-2006, 10:45 AM
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Exclamation Original tires

Hi there

Do you still have the original factory tires up front ?

The original tires on my RX 8 had a straight profile (parallel lines). Tires with such a profile have that downside.. bad choice Mazda...

I had to be very focussed driving at higher speeds with those tires; the car was all over the place..

I changed the front tires to Dunlops with another profile because of that issue, and now everything is ok.

Cheers

Steve
Old 08-08-2006, 10:51 AM
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Oh man, please don't do 135 just West of Austin. That road claims about 1 / month. Curvy, hilly, and full of recreational / tourist traffic...one of the most dangerous in the area.
Old 08-08-2006, 11:56 AM
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Originally Posted by DRKSYDE
LOL nice one... Won't EVER catch me in a speedo! Let's just say it was a GOOD night and the 142 was worth it in the end!
Heh, I do find that adrenaline has nothing but good effects in the bedroom

Back OT, I've been up to 140 indicated on a fairly rough highway. Car felt very stable, but this whas when I had less than 15k miles on it. How many miles are on yours? The car will feel a bit light, but generally not unstable. My guess is you might need new shocks, those will greatly enhance your track experiance as well. I run the Koni Sports and love them. I may go to the D-specs though for those rear external adjuster cables at some point.
Old 08-08-2006, 08:30 PM
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Most street cars create lift (opposite of downforce) because if you look at the profile of a car it looks generally like an aerofoil or airplane wing.
Right. There is more to it than that, but that is the main reason. Air does very strange things with moving bodies with irregular shapes (some of which move also). Its pretty much almost impossible to calculate, thats why everything is tunnel tested.

Many times the instability may only be partitially to blame from the amount of lift, but with the way the air just flows off the car. If there are corners or shapes that make the air vortex or buffet in an unusual way, that will deffinatly give you a wild ride.
Old 08-08-2006, 08:55 PM
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Originally Posted by Zoom510
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 Mustang(3400#s) over 150MPH and they felt way more in touch
Again Thanks
Not to sound condescending but if the Mustang with its ancient suspension design and aerodynamic lift at speed felt more in touch, you may want to take the Mazda to a good alignment shop and have it checked out.

Also I would highly recommend a Bondurant driving & suspension tuning school before driving triple digits. Obviously you could benefit from that quite a bit. It might even save your life.
Old 08-08-2006, 09:36 PM
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Originally Posted by musclecarconvrt
Here's a good place...
www.scca.org
Accually, in the SCCA (I'm a 30 yr member), without doing a lot of safety mods to the car you won't get on the racetrack. For anyone that wants to go fast on the public roads legally, enter the Silver State Classic road race. http://www.silverstateclassic.com/
They have hi-speed classes for unmodified cars.
Old 08-08-2006, 09:43 PM
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You could also start with track days, like the ones mazdadrivers.com does in Virginia. Check out tracks in your area - many of them do similar track days.
Old 08-08-2006, 10:32 PM
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Amazing, I ask a simple question and 1/2 the answers do nothing but preach how unsafe I was.


Yeah I could lose control but I was on a strech where I had a clear view of no traffic at all in either direction. For those who wanna know where I will be driving, Im currently working in Jonesboro,AR and Friday head back to San Antonio. I drive a 06 F350 with Lumber truck suspension and utility bed, Im also pulling a 20ft trailer with a 8ft Microwave dish that not only weighs over 1000# but creates a wind load of over 10,000#s. I drive from Jonesboro to just East of Dallas between 80-90MPH so just warning you, beware of IH40/30. If traffic would allow, I would drive the same speed from Dallas to SA but traffic makes it impossible.


To those who have not side tracked this post, I really appreciate the help and info


www.skittlesracing.com
Old 08-09-2006, 10:55 AM
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Thats probably why insurance companies raise their rates every year.
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