Attitude and Handling
 

I recently raised the front end of my 86 Carrera after trying out the settings recommended by Bruce Andersens book on 911 performance and have come to the conclusion that a level attitude handles much better than a nose down setting. Has anyone else had the same exprience? And if this rake is so important for handeling then why aren't all 996's set that way from the factory? The 959 looks pretty level to me too...so what am I missing here?

Joe Garcia
Redwood PCA since 1976

Joe, at the risk of sounding abrupt, I won't say whether you missed anything or not, but I don't think you have given anywhere near enough info about your car's setup, or what exactly you did when you tried lowering it. The basic info needed would be brand and age of shocks and struts, anti-roll bar sizes and type of linkage (fixed or adjustable) ... wheel and tire sizes/brands. What handling characteristic were you trying to achieve or change when you tried dropping the front?

And finally, have you ever competed in autocrosses or slaloms in any kind of car? The point of this question is to fins out if you have ever played around with handling characteristics of a car under somewhat controlled conditions, and really understood what different changes do to low speed and high speed handling characteristics. Personally, I think any 911 owner should do a lot of research before making ANY suspension changes! That said, I would state that I have significant autocross experience in my air-cooled VWs and Porsches, and a '68 340S Barracuda. My '73 911S is a street-driven car, but has been autocrossed, not towed to the events, but driven there, so it is not a race-only vehicle! At the same time, I have replaced every rubber bushing with polyurethane, every torsion bar and anti-roll bar on the vehicle, personally, with no outside assistance. It has 21mm/28mm t.b.'s, 19mm f. & r. anti-roll bars, Turbo tie rods, bump-steer spacer kit, fully adjustable links & sliders, Sway-a-way adj. trailing arms, and the factory Konis have been replaced, once. The tires are 225/50-15s on 8x15s in front, and 285/40-15s on 9x15s in back. The attitude I have the car set at is slightly nose low, at the minimums of the spec. range for factory settings for torsion bar adjustments. The basic settings of the anti-roll bars are softest in front, medium in the rear, for the street. A low speed corner taken hard on the street picks up the inside front tire about an inch, in a slalom setting, that increases to 3-4 inches.

For purposes of discussion, it would help to know EXACTLY what you changed, besides cranking down the front torsion bars, when you tried your experiment? Did you check/adjust the toe-in setting after adjusting the front tb's? What handling change were you trying to achieve with the change, and what did you experience after the change that made you think level was better? Was the front end twitchy or darty? Did any high-speed characteristics change?

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Warren Hall
1973 911S Targa

Warren,

When I dropped it down, the toe went out so I reset it to zero toe. I did the same when I cranked it back up, that is, I reset the toe back to zero again.

It feels a lot more stable now on the freeway and on the twisties.

Joe

Although there really is not much discussion about it, I suspect a plot of toe change versus vertical displacement when dropped, as you did, would explain the need for the rack spacer kits everyone seems to sell these days. There are some good books on handling and vehicle dynamics from the '70s by Mark Donohue and Paul Van Valkenburg that go somewhat into getting a handle on bump-steer changes and what a nightmare an uncontrolled situation can be. The Motorbooks International catalog still had them listed when I last time I checked. A toe-in setting of 1/16-1/8" can go a long way towards helping stability at highway speeds. But, all in all, most 911s are set-up from the factory for all-around good handling, so restoring yours to what it was may be the best idea. Remember, Bruce Anderson was race-team and track performance oriented for years, so his opinions on what is a good setup are probably a little different from the average 911 owner.

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Warren Hall
1973 911S Targa

So by raising my front end back to factory specs, I was able to improve handling significantly independant of the fact that my car no longer has a nose down attitude which is claimed to be so important.

Regarding the statement that a slight amount of toe-in will go a long way to highway stability, I found just the opposite to be true. In fact, that addition of toe actually erodeds straight line stability and makes the car feel rather darty.

Therefore, what is the purpose of a nose down attitude if it will not contribute to handling?

Joe

[This message has been edited by stlrj (edited 01-19-2000).]