rear shock setting

[Todd Geisler]

Originally Posted by Bill Harris

A shock that is easily extended will present a softer resistance to the axle housing than a shock that is hard to extend. The body will separate more with the soft setting and more energy will be stored in the chassis than a stiff extension setting. The more energy stored, and the longer it takes to store it, the less power is applied to the tires. This is often referred to as the amount of "hit" on the tires. A very rigid rear suspension with a stiff shock extension will result in a harder "hit", since more of the torque is getting to the tires and less is being used to power the chassis movement.

I mean no disrespect, but that statement contradicts what I've understood about suspension function/reaction. What I feel is contradictory is the fact that a stiff rebound setting is a harder hit to the tire and a softer rebound setting is a softer hit to the tire. Now granted, I run a GM tringulated 4 link style suspension (G-body), but I think many of the same theories still apply.

Here's my thinking on the subject.

The first reaction of the suspension at WOT is the rear suspension separates to some degree. It's this separation that pushes the tire away from the body and down to the track. The rear shock compression and rebound settings control the velocity of this movement to control the "hit" to the tire.

Now it's my understanding that a stiff rebound setting creates less hit to the tire and is used most often on days when the track is real good and less "bite" is needed out of the chassis to maintain traction. Less "hit" to the tire means your using more energy to go forward and less driving the tire into the ground. My own car I've got a real good baseline shock setting for real good track days, but the car won't go down the track when it's hot/greasy out as the shock settings are pretty firm.

On days when it's really hot out, 130-140 degree track temps, and just goey/greasy, you loosen up the rebound softer to allow the chassis separation to hit the tire harder and plant the tire harder. This may give up some ET as your putting more energy into planting the tire and less into moving the car forward.

I mean no disrespect, just wanted to hear more on differing opinions on this subject.

I run a DOT D/R tire which is similar to a D/R slick, but is shorter at 27 3/4" tall and thus a slightly stiffer sidewall due to less height of the sidewall. As I said, the car hooks very well on good track days, but had problems in the heat. I wound up buying a second set of rims and put a pair of Hoosier 10.5 x 28 stiff sidewall slicks (CO7 compound) on to use till I am able to dial in a shock tune for the hot/greasy track days for the DOT D/R tires.