The Shock-ing Truth

(By: Andy Fox)

If you have been following our journey so far you will have noticed we have had some challenges with the suspension. When we raced at Moyston we were being thrown onto 2 wheels after hitting bumps and a bunch of other handling issues.

During the off-season we removed the shocks and worked towards solving this issue once and for all.

There were a couple of key elements here we needed;

1. More compression damping.
2. Better control on the re-bound.

In terms of the compression stack, we already had the maximum shim stack. In terms of rebound, we had about 2/3 of the allowable stack.

The great thing about Fox Shocks is you can get so many bits for them. In our case a trip to the local Fox supplier, Racer Imports www.racerimports.com.au and we ordered some pistons from the US. The standard piston has a bleed hole in it and therefore we were losing the ability to force the oil through the shim stack. The new piston has no bleed hole and therefore will run all of the oil through the shim stack and the by-pass tube.

The theory goes like this;

The stack determines the dampening rate of the shock to get it into the zone, and then you use the by-pass tubes to fine tune the amount of oil that is allowed to by-pass the piston. The idea is the dampening characteristics can be changed through the stroke of the piston.

The key is to get the stack right and then fine tune with the tubes.

We fitted the same compression stack as we had before and upped the rebound by 20%, this put us straight into the zone. From there we needed another test session.

Accompanied by Cameron from Racer Imports we started testing at the local off-road track at Avalon Airport, approximately 40kms out of Melbourne.

The session started off by cutting some laps so I could dial myself into the Patrol and so Cam could get a handle on exactly what was happening externally to the car.

From here the process is pretty simple, cut some laps, make some changes and for each change, feedback from Cam and from myself determined the changes to the shocks. In some cases we made large radical changes to get a handle on where the sweet spot in the suspension would ultimately be…

After 2 hours of laps and tweaks we had successfully tuned the Patrol into and out of the zone a couple of times.

It’s a great experience to feel the vehicle dial in and then after a small change feel it go out again.

The settings are now recorded in the’ black book’ and from there we now have a ‘get out of jail’ setting that we know works.