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jluetjen jluetjen is offline
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Join Date: Oct 2001
Location: Westford, MA USA
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The symptom I'm having is the front end doesn't steer as well relative to the amount I'm turning the wheel. For example, If I lay the hammer down in a transition ramp the front end wants to keep going to the outside of the turn, so I have to turn in more to keep the car turning.
I think that Kevin's on the right track. From your description above, you are not necessarily describing "understeer". Keep in mind that there are different kinds of understeer also; Corner entry, mid-corner and corner exit. Each one has to be addressed differently. Gross understeer is when all 3 are occurring. In your case it sounds like Corner Exit Understeer.

30 lbs can make a difference, but not if your definition of throttle control is to "lay the hammer down". Below the car's limit, 911's tend to understeer. Applying the throttle in a 911 will often make it worse. Conversely breathing the throttle in a corner will often induce some oversteer (aka Trailing Throttle Oversteer) to help rotate the car. Insensitive use of the brakes or throttle will have a drastic affect on a cars handling and cause understeer, oversteer or a combination of them. It's also common for a driver to come in describing that a car is loose if they are unaware that they are trying to drive around a push (or vice versa).

It's happened to me and the description is the exact opposite of what you described. I was racing a rented Spec Racer that was set-up with a pretty strong push. In trying to drive around the problem I was pitching the car into corners and then applying a lot of throttle. The result was that I was often getting sideways on the exit and complaining of corner exit oversteer. So, the driver can often have the biggest impact on the car's handling. Have you tried changing your line so that you are taking a later apex? That alone may fix your problem.

Anyhow, mechanically loosening the front sway bar or tightening the rear sway bar should help some. Reducing the rear toe-in (small changes can make a big difference btw!) or increasing the rear tire pressures can also help. Softer front shocks in low speed droop or stiffer rear shocks in low speed bump can also help. Increasing the rear spring rate (thicker T-Bars) could also help. You might also find that lowering the front a little may help. Finally, if you don't mind moving your suspension mounting points around, raising the rear roll center while adding anti-squat (via Smart Racings slotted trailing arm mounts or a Turbo Trailing Arm update) will address the fundimental problem if your car has really sticky tires and a lot of HP.*

In general, with the exception of the front shocks, I suspect that the "fix" will be either in the driver's seat or in the back since the situation that you are describing sounds like the front end is being picked-up (unweighed) under hard acceleration. The front tires just don't work very well if they are off the ground or lightly loaded.

*Small print: Please note that all of the mechanical changes described WILL affect other portions of your car's handling and as such may have unwanted side affects in some other area of your car's handling!
__________________
John
'69 911E

"It's a poor craftsman who blames their tools" -- Unknown
"Any suspension -- no matter how poorly designed -- can be made to work reasonably well if you just stop it from moving." -- Colin Chapman

Last edited by jluetjen; 02-03-2004 at 06:13 AM..
Old 02-03-2004, 06:09 AM
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