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Join Date: Apr 2000
Location: Mid-life crisis, could be anywhere
Posts: 10,382
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Caveat: I used to race Formula Atlantics, but have never had my 911 on a track.
That said, I have new Dunlop 8000s on the car and took it up Ortega Highway this morning. Ortega is about 15 miles of 3rd gear, 80 mph twisties (YEAH!!!!). I swear, my car was pushing through most corners. No oversteer in evidence. What's going on here? Now, the car is lowered pretty far, and it even looks like the rear 'squats' a bit compared to the front. Would that be enough to cause understeer? ------------------ -Richard '84 Carrera Cabriolet '74 911 Widebody 3.6 Project |
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Yes... that could be the problem, check this out...
See how my car has a nose down slope. It puts more weight on the front for a little more traction there. I still understeer a bit but it's because I have 315 mm wide tires in the rear. Keith 79 930 |
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I've done a skill day, autocross, and a track event with my 911. I'm no expert by any means but all the instructors said the 911 will understeer all day until you let off the throttle. After you let off the throttle, you get major oversteer. We did this on a skid pad and you can throttle steer the car around in a circle all day long. Your car may be a little nose high but I don't think lowering the nose will solve your understeer. Also, I was told if you put 245's on the rear and have the std 205's on the front, the 911 will really push in the corners. You can easily check your ride hight. The front fender lip should be about a 1/2 inch higher than the rear fender lip.
Don 87 coupe |
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Yes, a 911 will push on entrance into corners in general, however I believe nose down really helps prevent completely gross understeer in that situation. It doesn't undo the push, however I know that a sagging rear will hurt. Anyway, my push is rather mild and turn in is almost excellent on the track. I've talked to people with a similar set up as me (245 front, 315 rear) and they have very neutral handling. I think the reason I've yet to find that is that I still have stock sway bars. They use 22mm adjustable ones with the rear on the firmest setting and the fronts the softest. Don is right about the front fender being a half inch higher than the rear (Bruce Anderson reccomends this), however some people go beyond and have both fenders about the same height. Many of the cars in the back of Bruce's book have a greater slope to them.
Keith 79 930 |
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Could be toe settings in front. If you have toe-out it will also cause more understeer
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There are lots of things that could be causing you to understeer. The following article has a great table that identifies the effects of tires and suspension changes on the car's tendency to over/understeer.
http://www.bmwclub.ca/ccrart3.htm You didn't provide any information about how your car is setup suspension and tire wise. Without that information it is really impossible to offer meaningful recommendations on what may be causing this condition. ------------------ ![]() |
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Registered
Join Date: Feb 2001
Location: Mill Valley, CA
Posts: 204
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I don't have the same car as you but, I HAD understeer on my 72. My car is very low. Lower in front than back which helped. I adjusted my 22mm front bar to almost the softest and adjusted the rear 22mm about 3\4 hard. Still a little understeer. Added 21 mm torsion in front and 28 rear. Got rid of almost all ubdersteer but it was still there. I started running 0 toe in the front-got even better.But, what did it for me and yes i know this not the way to really deal with this prob, but I went to kuhmo's in the front and yoko y032r's in the rear. My car handles great now. Next step when i get my car back from the shop will be corner balencing.
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Have you balanced the car? Check the corner weights! 911s will understeer under the right circumstances but that is easily remedied by lifting slightly . Of course, under normal conditions,lifting mid curve can provoke the tail and things can get real exciting in an awful hurry.
------------------ Bob 1982 911SC Targa PCA - Founders Region |
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