Soft Does Not Equal Grip – Part One

A pretty common statement at the race track is:

“Lets soften it up so it will work better”

Sometimes this refers to the front, sometimes to the rear, other times to the whole car. A common strategy to find traction is to reduce stiffness in some way. This can be effective (which is why it is common), however pursuing it to the ends will result in a pretty poorly handling race car. We’ve seen many a racer go down this path. Let’s keep you off of it.

We’ll touch a few key points in this email about general suspension stiffness, and move on to more in depth discussion as time goes on.

1. What softening an end of suspension does in roll
2. How much damping do you need?
3. Where do I start?

1) Softening an end of suspension in roll

Putting things simply, when a race car is fully loaded in the middle of the corner, we can consider it to be “in roll”. During roll, the vertical load transfers from the inside wheels to the outside wheels, as they hold the car up against the forces of cornering. The various suspension components (springs, anti roll bars, shocks, roll centers, etc) resist this roll, and the ratio of the front to the rear determines the balance (understeer/oversteer).

Softening an end of the suspension changes this balance, but also changes the overall roll resistance. If you keep softening the end that isn’t working as well, the total roll resistance may go low enough that overall traction and handling is adversely effected. Keep an eye on the primary goal; making the most traction. Make sure you are going faster through the slowest point of the corner as you make changes.

2) How much damper force do you need?

Keeping things simple – between all the stuff you have going on in your chassis like; weight, spring rates, track surface, driver preference – there’s going to be a certain amount of damping that’s going to work. Clearly, the blue line which goes up and down the most, is going to feel bouncy. The main issue for car setup is that “bouncy” can also be because the car has more than the correct amount of damping – like the green line. This sends the chassis over the track surfaces and knocks the driver around. The driver simply tells you “bouncy.”

Often times we’ll come across situations where people have thought they had the green line, and softened shocks up to the blue line. Then they ask for a revalve, when in actuality, it was time to get back to basics.

3) Where do I start?

If you feel that your spring rates are close, set your shocks to a soft, baseline adjustment. Compression 4, rebound 5 for example. Go out with sway bars on a soft adjustment and increase them until the car doesn’t handle the track well or your corner speeds go down. Then move on to the dampers.

Here, we’ll go back to our procedure from our discussion on 3 ways, but simplified for 2 ways:

With the shocks at the baseline adjustment; increase the compression damping 2 clicks at a time until the car skips a little bit or feels stiff. Reduce the compression one click. Perform the same exercise with the rebound.

Next time we’ll talk about getting a starting point for springs.

– The Olsen Motorsports Team