Unstability.... why?
Thread Starter
Intermediate
Joined: Jan 2003
Posts: 25
Likes: 0
From: Spain
Unstability.... why?
Guys,
My 86, 3.2 Carrera turbolook has become very unstable after you reach and surpass 160 km/h (I guess 100mph). Unstability was first noticed when I replaced my worn rear tires (Dunlop SP9000). Front tyres are OK in tread.
The problem happens in turns, right or left, but is worse on left-hand turns. The feeling I get is that the car will "wobble", and sometimes I feel as if rear tyres would lose grip, and then regain it, making the whole rear end shaky.
The car was absolutely perfect with this tyre setup last year, and I´ve waited some 600km, just in case it was a problem of having to run-in the tyres, but to no avail.
Obviously, the car STILL handles well, but I don´t have that "rock-stable" feeling of before, that made the car feel like on a railtrack... it would not budge.
I suspect 2 possible culprits: Wheel alignment or suspension. I don´t know how old my suspension is.
If you have any ideas, please let me know.
Carlos
My 86, 3.2 Carrera turbolook has become very unstable after you reach and surpass 160 km/h (I guess 100mph). Unstability was first noticed when I replaced my worn rear tires (Dunlop SP9000). Front tyres are OK in tread.
The problem happens in turns, right or left, but is worse on left-hand turns. The feeling I get is that the car will "wobble", and sometimes I feel as if rear tyres would lose grip, and then regain it, making the whole rear end shaky.
The car was absolutely perfect with this tyre setup last year, and I´ve waited some 600km, just in case it was a problem of having to run-in the tyres, but to no avail.
Obviously, the car STILL handles well, but I don´t have that "rock-stable" feeling of before, that made the car feel like on a railtrack... it would not budge.
I suspect 2 possible culprits: Wheel alignment or suspension. I don´t know how old my suspension is.
If you have any ideas, please let me know.
Carlos
Instructor
Joined: Aug 2002
Posts: 188
Likes: 0
From: Atlanta
I had the same feeling several weeks ago on a hard right turn (high speed), back end seemed to move in and out (wobble). I am looking at most of my suspension. I did find an strange drop link, you can see my message below regarding drop links. Take a look at yours.
Vince
Vince
Addict
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Lifetime Member
Rennlist
Lifetime Member
Joined: Jun 2001
Posts: 401
Likes: 9
From: Scotland
Carlos, have you had a look underneath the rear of the car yet? If not, it's possible that one of the mounting points of the rear anti-roll bar (sway bar), has sheared. It's a common failure and will cause the rear end to be all over the place through corners and over bumps.
It's not a bad idea to replace both mounts at the same time if one has gone.
It's not a bad idea to replace both mounts at the same time if one has gone.
Track Day
Joined: Dec 2002
Posts: 22
Likes: 0
From: Gilbert, Arizona
...WELL, Carlos...I HAVE The Answer!...Happened To ME A Month Ago On My '85 Carrera...Put New Dunlops On The Front Of My Auto...NO Problem...A Month Later Decided To Replace The Rear Ones Also (About 1/2 Worn)...ALL HELL BROKE LOOSE!!!...The Car Was ALL Over The Place!...On The Freeway It Almost Would Change Lanes!... <img border="0" alt="[crying]" title="" src="graemlins/crying.gif" /> I Was Freaked Out!...Well Thoughts Of $$$ Entered My Head...I EVEN Heard A Rubbing Noise As I Drove...Went Back To Discount Tire Removed Wheels...NOTHING!...Finally I Went To My Mechanic In Phoenix, STUTTGART...He Stated That I Was Experiencing "Squirm"...Caused By The Tread Flexing Under The Weight...He Said It Had Happened MUCHO Times With Dunlops, Explained It Had To Do With Tread Design, I Asked WHY My Exact SAME OLD Tire Did NOT Do That <img border="0" title="" alt="[Eek!]" src="eek.gif" /> He Stated The Tread Was Worn Down Enough To Not Flex From Side To Side, AND I COULD "Shave" Them Down OR Replace Them To Solve It...Sounded Valid!...SOOOOoo I Went Back, Changed To A Design With With Less Continuous Tread (Pirelli P Zero)...Discount Tire WAS Aware Of "Squirm" And Reluctantly Changed Them Out...GUESS WHAT?...NO "SQUIRM" <img border="0" alt="[jumper]" title="" src="graemlins/jumper.gif" /> ...Hope This Story Helps, I Was Surprised, BUT It Does Have A Happy Ending...THANK YOU Stuttgart!!!...
Instructor
Joined: Jan 2003
Posts: 232
Likes: 1
From: London.
Squirm sounds familiar to me too . I put new Kumhos all round on my 911 and it was about 200 miles before they started to give good grip and feel rleiable in corners . Now when 'run-in' they grip like leeches!
