March 30, 2022 3 min read
The second generation Subaru BRZ and Toyota GR86 are a step forward in handling over the previous model. Looking at the new car in comparison to the first generation, there are couple of differences beyond just the new factory springs and dampers, which were revised frequently during the 2013 to 2020 model years of the first generation.
Overall vehicle weight and individual corner weights of the new generation are similar to the previous. These numbers vary more from driver to driver than car to car.
The largest difference going from first to second generation is the option of Michelin Pilot Sport 4 tires on the top-range models. This tire is much stickier than the standard Michelin Primacy of the current base models and all 1st gen models (other than the Subaru tS special edition). And while the BRZ and GR86 have different spring rates from each other, each model uses the same spring rates regardless of the tire equipped from the factory.
A suspension system should be chosen or designed with the tire in mind, and that Subaru and Toyota use the same spring rates for their cars regardless of tire choice is surprising. There is a much larger difference in overall handling behavior between these two tires than there is from first generation to second generation.
The 2022 BRZ has two small changes that are not seen on the 2022 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 car are as follows:
Each of these are important. Interestingly, the first two have counteracting effects on how the car behaves through a corner.
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.
So to put it too simply, one of these is increasing oversteer and the other is reducing oversteer. Do they balance out?
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. More overall grip and cornering force would be expected on the second generation car, but handling balance is very similar.
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. Furthermore, suspension adjustments from a baseline will have a more noticeable effect, requiring more attention to make the right changes for the desired impact on ride and handling.
In brief, a properly designed suspension for the first generation BRZ/FRS/GT86 is a great fit for the second generation BRZ/GR86. The latest models are better handling cars overall, but even more attention should be paid to suspension set up to maximize performance and ride quality.