Instruction Manual for ST96050ZM000 on ZD8/ZN8 chassis

Subaru STI BRZ Dry Carbon Fiber Rear Swan Neck Spoiler Installation and Instruction Manual


The second generation of the Subaru BRZ/Toyota GR86 platform was introduced in the 2022 model year.

The 2022 ZD8 Subaru BRZ has two small changes that are not seen on the 2022 ZN8 Toyota GR86. That is the front aluminum
uprights (which reduce unsprung weight) and the rear swaybar mounting method. Both of these changes are good, but fairly
minor overall.

Three other changes to the second generation are as follows:
* Increased rear motion ratio
* Increased rear track width
* Chassis stiffening

An increase in rear motion ratio on the second generation cars (due to a slight change in rear spring/shock mounting points)
means that with identical springs, the newer car will have a slightly stiffer wheel rate, or spring rate at the wheels,
compared to the first generation.

For example, a 300 lbs/in rear spring on the first generation car equates to about 173 lbs/in in wheel rate. On the second
generation car, that same spring would mean about 183 lbs/in in wheel rate. A small difference that means a slight increase
in the tendency to oversteer.

Meanwhile, the slight increase in rear track width reduces rear weight transfer in a corner and reduces overall weight
transfer. This means slightly more rear grip and less oversteer. An analysis of the total lateral load transfer distribution
(TLLTD) of each car indicates that _these two changes do essentially balance out_ in terms of oversteer and understeer.

A key change to the second generation car is the stiffer chassis structure itself. This can be felt from the driver’s
seat but is difficult to quantify. Reducing chassis flex has the effect of an overall increase in spring rate and the
car will feel slightly firmer with the same spring rates.

An important consideration is that a car with a stiffer chassis structure (second generation) will be more sensitive to
suspension changes than one a softer chassis structure (first generation). This means that while poorly chosen spring
rates on an earlier car is not a complete disaster, a properly designed suspension is necessary for the later cars to
maintain a good handling balance and performance.


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Subaru STI BRZ Dry Carbon Fiber Rear Swan Neck Spoiler Installation and Instruction Manual

Changes In the 2022 Subaru BRZ Toyota GR86 ZC8/ZN8 Chassis and Suspension