Handling issues - need adjustment advice Options

[Brian Fuerbach]

When driving large sweepers like freeway on ramps at high speed I experience what I can only describe as front end scrubbing. Not understeer, more like the front is just not planted and tracking. Things get better with a full tank of fuel. Is that just the nature of the 914, full tank factored into weight bias, or can the suspension be tuned to emulate the weight.

Here is what Im working with;
-19mm adjustable sway-bar set about 1” back from full soft.
-Koni yellow adjustable shocks
-Stock front torsions
-Rear springs are aftermarket (reddish orange color) but I do not know the poundage.

Any input would be appreciated.

[Superhawk996]

When driving large sweepers like freeway on ramps at high speed I experience what I can only describe as front end scrubbing. Not understeer, more like the front is just not planted and tracking.

(IMG:style_emoticons/default/confused24.gif) What you've described is the very essence of understeer.

19mm is a lot of front bar that can lead to understeer. Especially so without a lot of rear spring or rear bar behind it to balance it.

(IMG:style_emoticons/default/popcorn[1].gif)

[Brian Fuerbach]

When driving large sweepers like freeway on ramps at high speed I experience what I can only describe as front end scrubbing. Not understeer, more like the front is just not planted and tracking.

(IMG:style_emoticons/default/confused24.gif) What you've described is the very essence of understeer.

19mm is a lot of front bar that can lead to understeer. Especially so without a lot of rear spring or rear bar behind it to balance it.

(IMG:style_emoticons/default/popcorn[1].gif)

I guess it is possible that if I pushed it harder it could turn into noticeable oversteer but it just does not feel like understeer that I have experienced before.
Need find out what springs are in the rear now. Can you tell by diameter?

I used to drive this on the street, talk about oversteer. (IMG:style_emoticons/default/evilgrin.gif) (correction: "Understeer")

[Superhawk996]

I used to drive this on the street, talk about oversteer. (IMG:style_emoticons/default/evilgrin.gif)

Please don't take this the wrong way. I'm trying to help. Honestly. I've done chassis tuning as my day job for a decent part of my professional career as a chassis engineer.

That buggy by definition will have steady state understeer. Beam front axle without camber gain, wide rear tires, narrow font tires, lack of weight on the front tires.

I don't think we aren't talking the same terms.

I do agree the buggy could have massive lift throttle oversteer at initial turn-in due to the inherent rear weight bias. Likewise, it could develop on-throttle oversteer with enough horsepower. Both of those are transient conditions.

As I understood your original post, we are talking steady state condition, after you've entered the corner, steady state throttle, and the front end isn't tracking. You're putting in more and more steering input to the point that you feel the tires are scrubbing but yet it's not turning or following your steering input.

Do I understand correctly?

[Brian Fuerbach]

I used to drive this on the street, talk about oversteer. (IMG:style_emoticons/default/evilgrin.gif)

Please don't take this the wrong way. I'm trying to help. Honestly. I've done chassis tuning as my day job for a decent part of my professional career as a chassis engineer.

That buggy by definition will have steady state understeer. Beam front axle without camber gain, wide rear tires, narrow font tires, lack of weight on the front tires.

I don't think we aren't talking the same terms.

I do agree the buggy could have massive lift throttle oversteer at initial turn-in due to the inherent rear weight bias. Likewise, it could develop on-throttle oversteer with enough horsepower. Both of those are transient conditions.

As I understood your original post, we are talking steady state condition, after you've entered the corner, steady state throttle, and the front end isn't tracking. You're putting in more and more steering input to the point that you feel the tires are scrubbing but yet it's not turning or following your steering input.

Do I understand correctly?

No worries, your not going to hurt my feelings and I appreciate your tuning knowledge. You are totally correct, I meant to write "understeer" and we are talking the same terms. Your assessment of the power on power off are spot on. The car was almost not drivable in the twisties until a sway bar was added.

Now back to a car I still drive. In my original post I described it like a scrubbing but not over steer as I dont feel the front is going to wash. I drove the car today on my 60 mile commute which has opportunities to create the condition on four onramps and interchanges. I filled the tank completely and the extra weight up front made the front feel more planted like it should. I have to note that the scrubbing seems to come with some roughness that when weighted with extra fuel seems to lessen. More damping needed?

I have been working with the adjustments that I have to improve this. The two things that made the most improvement was adding the swaybar and then tightening the rear shock rebound.