Suspension Set Up

[Lotusjps]

Trying to figure out what I need to do to improve the handling of my Europa.  Currently it's lifting the inside front wheel mid corner, and sometimes snaps oversteers at corner entry.  It has damping adjustable AVO shocks and adjustable front and rear sway bars (though I currently have the rear disconnected since it made the rear really quick to oversteer.  There's about -2 degrees camber front and -1.5 rear.

Any thoughts what adjustments to make?  I'm sure I'd be faster using 4 wheels rather than 3.  LOL

[BDA]

I am NOT the guy to set up your suspension so maybe someone who knows more than I can set both of us straight.


It seems to me that your springs may be too soft. The front rolls and the anti roll bar picks up the front wheel. What spring rates are you using? I would guess that stiffer front springs would reduce the roll and so the anti roll bar wouldn't raise the inside wheel so high. Richard suggests 250# front and 130 or 140# rear for a street car. In spite of the fact that it's about twice the stock spring rates, it's not a harsh ride. I don't know what he suggests for autocrossing. It might be worth a call to him to see what he things.


I'm completely at a loss for your oversteer going into the turns. That may be related.

[EuropaTC]

 

That's an impressive amount of grip for a 3 wheeled car.... 

I guess the first thing to ask is what you'recurrently running with in terms of spring rates. As BDA says, looking at the rates sounds a reasonable start,there looks a lot of compression on the rear and one front wheel that's in contact with the black stuff.

The wheels also look chunky, are they standard or larger tyres ?

Given that you're doing autoX, I think I'd post a request on the Yahoo Group as there's a guy there (Jay Mitchell) who has done a lot of suspension development on his S2 for autoX. It's true that the spring rates and roll bars won't be directly transferable to your car, but the principles will.

Impressive photo though....

[Rosco5000]

From my little bit of knowledge I know the sway bar does a lot to change grip on its opposite end.  E.g. you want more rear grip dial in more front anti roll bar and vice versa.  You can have too much antiroll bar though have you tried softening up the front anti roll bar?  Might not reduce roll as much but as Chapman has proved soft is sometimes better for handling especially if the car isn't dedicated so a smooth race track.  Now that might not mean you get more absolute grip but you might get more feel near the limit and be able to drive the car at the limit with more confidence and therefore better lap times.

Otherwise I would agree with BDA you may need more spring up front as the stock rate will not provide as flat a cornering attitude.

Droop is a big thing for getting good traction as well and right now it seems like your sway bar may just be too stiff for the front spring rates and not working in harmony and causing a premature lift of the inside wheel.

But if your not pushing through the corners, Jim Clark proved that was the fastest way around a track in a Lotus Cortina.

[Lotusjps]

Thanks for the feedback!!

Unfortunately I'm not sure what the sprint rates are (though I know they're quite a bit stiffer than stock).  I purchased the springs and shocks from Richard with the intent of track use.  The front sway bar is a modified stock one to use rose joints and shorter vertical lings (needed for ground clearance).  The wheels are Revolutions running 185/60/13 Hoosier R7 tires.  This is pretty much the maximum rubber I can use without flaring the fenders.  As it is the fronts just barely rub at full lock, and the rears I can barely get a finger between the tire and fender.

I agree with you that changes on one end definitely effect the other end.  When I had the rear sway bar connected it still lifted the inside front wheel, though not nearly as much as it currently does.  What do you think about stiffing the bump adjustment on the front shocks?  Thinking that it compresses less that it might not cause the sway bar to pick up the other wheel.

One side note I might mention the picture is at mid corner, and even though only one front wheel was on the ground, there was power on oversteer.

[Clifton]

Stiffen the front of soften the rear. If you are new to pushing it and going to a track, softer cars are more forgiving and easier to drive at the limit. You can measure the spring rate with a bathroom scale, press and calipers.

Lifting a tire on the non powered in is common, more common in autocross than road racing.  Front wheel drive cars lift the inside rear.
 My 240z (track only car) would lift the front inside a few inches. It was very stiff and a wicked fast car.

[Lotusjps]

FYI, just in case it helps anyone else.  I was able to improve/reduce the front wheel lifting by stiffening the bump on the front shocks 2 clicks and the rears by one click.  Made a noticeable improvement, though still occasionally lifts, but just barely. 

[Bainford]

Thanks for coming back with this info. I was curious about this issue, and I'm always eager to learn more about the black art of suspension tuning and troubleshooting of handling problems.