suspension tuning

[frosty]

So a month ago I installed a few new suspension components: springs (slightly lower and a lot stiffer), stiffer strut mounts, and koni sport inserts.

Now I'm faced with a new problem: how do a tune the adjustable inserts? Before, I only had tire pressure to adjust (and alignment, but not something a tested / tuned).

Does anyone have any suggestions on how to tune the shocks? Or how to tell when they are under or over dampening?

[chapmanr]

Koni has a suggested procedure on their website:

http://www.koniracing.com/autocrosstune.cfm

[froggy47]

Koni has a suggested procedure on their website:

http://www.koniracing.com/autocrosstune.cfm

Regarding this Koni procedure, they reference 3 "clicks" under bump and 3 "sweeps" under rebound.


Q1: does a click = a sweep?

Q2: If shock A has an adjustment of 6 sweeps & shock B has 16 clicks, then how do you use the Koni procedure in a sort of "standardized" way?

In other words is six sweeps = 16 clicks = one complete rotation of the adjuster (from min to max)?

Many thanks.

[Sebastian R.]

A set of camber plates will help your set up immediately, and will not affect your driveability.
WRXs NEED front camber and lots of it.

After you have camber it is much easier to fine tune with shocks.

[frosty]

That's for the tips. I need to pop the hood and check whether mine are single or double adjustable (yes, I should know this already... :thwack:). I'll be at the SCNAX practice in a week and will hopefully get a feel for what is firm enough.

Sebastian, I'll keep those camber plates in mind. When I was doing this and pricing it, it didn't work out this time around. I'm going to be doing those and sway bars at some point...

[Sebastian R.]

Koni sports are single adjustable, meaning you cannot adjust compression and rebound independent of each other; in most cases, the single adjustment changes compression way more than rebound.

If your budget only allows for camber plates or anti-sway bars, I would choose camber plates. Ideally, you want camber plates and a stiff rear bar. The camber plates will negate the need for an aftermarket front bar.

[jason]

Koni sports are single adjustable, meaning you cannot adjust compression and rebound independent of each other; in most cases, the single adjustment changes compression way more than rebound.


Actually, sports are rebound-adjustable only. :thwack:

[chapmanr]

Ultimately, the best way to determine what works for you is to use one of the practice days to test different shock settings. Or, a track day at streets of willow.

Lots of good advice preceding...here's how I'd suggest going about the adjustment.

If the car has historically understeered, start with 1/4 turn from full soft on the front and 1/4 turn from full stiff in the back. Try a couple of runs. If it still understeers, you don't really have any more shock adjustment to work with, so try making a large change in rear tire pressure (at least 5 psi). Take pressure out if you want a friendly car, put pressure in if you want a more nervous car. If its still pushy, try loosening the end links on the front sway bar a bit. If none of that works, definitely time to go shopping before the next practice.

Then, try one of the following:

go buy a big rear swaybar (cheaper and easier than camber plates)
get a smaller front one (often available off the base model of the car)
check the alignment. if the rear is toed in, have brought to zero toe
get the camber plates as Sebastien suggests

If the shock adjustment results in a car that's too loose, turn up the front 1/2turn, and try a couple more runs. This is actually a better outcome, as you still have lots of range in the the shock adjustment to work with.

Your goal is a balanced car which is easy to drive fast and generates consistent times.

It always a good idea to get someone who has developed the same car to try driving it, as you then can see if some of the issue is with driving style.

Or, ask an RCS to help you out.

[froggy47]

Actually, sports are rebound-adjustable only. :thwack:


Why is it that when a mfg makes a shock with one adjustment it is usually (always?) the rebound?

Bump less important or harder to engineer than rebound, or ?

:)

[ULLLOSE]

Why is it that when a mfg makes a shock with one adjustment it is usually (always?) the rebound?

Bump less important or harder to engineer than rebound, or ?

:)

Rebound controls body roll, and will effect how the car transitions, this is very important for Solo.

Compression effects the tires compliance with the track surface. It is really easy to dial in to much compression and take away grip. Typically you only need to change compression when you change spring rates, because the compression settings will work within a spring rate window - to much compression and the tires will chatter, to little and you can bottom out. Do not think for a second that compression is the same as, or a replacement for spring rate. The manufacturers are smart enough to get the compression settings to work with the OE springs +/- a certain range.
For instance, we have a set of "race" valved konis on Philips ITA Miata. These are a production shock from koni valved to work specifically with a certain range of springs, beyond what the "sport" koni will do.

If you get a compression setting you just have twice as much stuff to screw up. That is why I stay with singles. :confused:

[froggy47]

Thanks.

:)