Lotus Europa Forums > The Paddock

1st Autocross

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BDA:
Ok, I'm a bit out of my depth, since it's been an age since I last autocrossed and I knew even less than I do now about shocks and springs but here are my thoughts (I welcome comments from those more knowledgeable):

Because you seem unsure about exactly what springs you have: How does your car handle now? Does handling on the highway seem vague or unstable? Do you have to intently watch steering inputs on the highway for fear of ending up in the next lane or even a ditch? That's likely a sign that your shocks are not stiff enough for your springs.

Is your ride rough or even bouncy where the car seems to follow every undulation of the road and absorbs none of them not enough of them? Then your shocks are likely too stiff for your springs.

Considering that you mentioned you might have 110# springs (probably on the rear since the stock front spring rate is 116#) and your shocks are set full soft, I'm guessing that you probably have your shocks, at the rear in that case, set too soft.

Assuming that your shocks are in a comfortable setting where steering and handling is precise in fast turns and the car is stable on the highway, you might turn your shocks up two clicks for your autocross. If that works well, you could experiment with a couple of more clicks.

Shocks can affect the balance, too. since they affect the roll resistance. Increasing the roll resistance in the front will give tend to give you more understeer and more roll resistance in the rear will tend to give you more oversteer. Tire pressures also affect roll resistance. I've attached some information about that.

If you plan on doing more autocrossing, it would be good to know what springs you have. Quite often springs are marked with their rate. Sometimes with paint, or engraving on the end of the spring (the flat part). Sometimes there is a band that is heat shrunk on the coils with the rate. Who knows how it might be noted on the spring (or not). Look all over the spring for some identifying marks and if you can't find any, you can use a bathroom scale, some 2x4s, threaded rod and a ruler to determine the number of pounds force is required to compress the spring one inch. It's linear so you don't have to start at 0 and go to 1 inch, you could start at 3/4" and go to 1 3/4 inch for example. Knowing how your spring rates compare with the stock rates would be helpful.

Because I only know a little about this (and because I already have more springs than I need), I would try to stay close to the same multiple for spring stiffness. For example, you mentioned you might have 110# springs. If those were on the rear, they are 46% stiffer than the stock 75# springs. I would want a similar increase in stiffness in the front springs to maintain the balance that Lotus designed into the car. Of course, if you are an experienced performance driver you might have a different idea of how you want your car to behave and thus might want a relatively stiffer rear spring for more oversteer or a relatively stiffer front for more understeer, but I think most of us "amateurs" just want what Lotus designed or maybe "a bit more" of what Lotus designed.

A lot of this is personal taste. I've made my suggestions based on my experience with new shocks and not actual racing or autocrossing experience. I'm still experimenting and I readily admit that I am walking in the dark to some degree. I hope if someone more knowledgeable thinks I've steered you in the wrong direction, he will set me straight.

rjbaren:
I checked my pressures this morning and the fronts are at 14psi and the rears are at 24 psi.  I also added 8 clicks to the firmer side on the rear shocks.  I read if you adjust all four shocks equally than you haven't really made a change.  So I will leave the fronts alone and then maybe even drop back on the rear.
The car felt fine in a straight line.  Then I made a couple of quicker turns and the tires were squealing quite a bit.  I am thinking of adding more air to the fronts, like 2 lbs., and trying it again.   

BDA:
Tires squealing just means they’re working hard. Two more pounds in the front might be good. Use Clifton’s trick about the chalk (when I was autocrossing an age ago, we used white shoe polish - can you still get that?) to see if your tires are rolling over to help decide if you need more or less air in your tires.

I think what you read about adjusting all your shocks the same amount is about the balance. If you have too much or too little damping, it will make a difference.

I seem to remember that the SPAX folks told me that the adjustments are not linear - i.e. the difference between click one and click two is less than the difference between click two and three. I also seem to remember they suggested increments of two clicks.

Just some thoughts…

Have you run your autocross? Let us know how it went!

rjbaren:
Autocross is the 26th, unless its rains.  Then I will take my BMW wagon instead.  I don't think the Europa is water tight.  I bought some chalk and I want to find a cheap 12 volt compressor with cables to connect at the battery because the car doesn't have a cigarette lighter.

Clifton:
Bike pumps work good. I cut the end off a female cig plug and stick the wires in a 18v Makita battery for portability. Pumps fast with more volts.

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