The new Toyota Supra has arrived, sharing a platform with the BMW. There has been a lot of discussion regarding how much they share and whether the Supra is just a Z4 with Toyota sheet metal draped over it. Toyota’s engineers state that the car is completely unique and that they even cut off communication with the BMW teams at one point to keep the development independent, but the parts diagrams appear to tell a different story.
The Z4 and Supra both pull some parts from current BMW models ranging from the X5 to the i8, but the key here is how much is shared between the two and what parts Toyota changed in order to give the Supra a unique feeling. Toyota specifically worked on the suspension and steering to fit their image of what the Supra should drive like, so we’ll focus on those.
The steering system in the Z4 and the Supra pulls the column from the X3 but the rest of it is unique. From a hardware standpoint, both vehicles appear to use the same rack that shares a 15:1 ratio with the M2 but likely have slightly different programming.The Z4 steering rack part number does not appear to interchange with the Supra. The rest of the hardware, such as the tie rod ends, is identical between the two cars.
Bushings, an often-overlooked component of how a vehicle handles, appear to be identical from Supra to Z4. According to the diagrams, the subframes and their corresponding bushings are all shared between the Supra and the Z4. Most of the bushings are universal across both lines but the front differential bushings on the Supra are likely of a performance variant, as they are only shared with the Z4 M40i trim.
Moving on to the front suspension, we see that the Supra is almost identical to the Z4 3.0i with common parts on everything aside from a lower control arm. This is a key distinction that affects suspension tuning as the unique part on the Supra allows Toyota to get different camber and caster settings. BMW has made a similar change to its own cars in the past, as it has installed longer, lower control arms on the M versions of the 1 Series and 3 Series in order to provide around 0.75 degrees of negative camber compared to the non-M vehicles. This allowed for a reduction in understeer and better response at turn in, which is likely what Toyota was going for with the Supra, as well.
A difference in part numbers alone doesn’t tell us that the control arm lengths are different. The proof actually comes from the headlight aim sensors. If we compare the parts between the Z4 and the Supra, we see that they receive different rods for the rear aim sensors. This translates to a difference in length of the lower control arm as they have to compensate for the new angle of the suspension. The Z4 M40i shares most of its front suspension components with the Supra and Z4 3.0i, but it does have a different anti-roll bar. Depending on how that influences the Z4’s character, it could possibly be a popular upgrade component for the Supra.
The parts catalog for the Supra shows that its adaptive dampers interchange with the units on the M40i, but each set likely has customized programming. Overall, the front suspension on the Supra appears to be a mix of Z4 3.0i and M40i components with the lower control arm being the only unique part that impacts the chassis configuration.
Moving to the rear of the car, we find that the anti-roll bar comes from the Z4 M40i while the rest of the rear suspension is much more common. Upper control arms, trailing arms, and track arms are all shared with the entire Z4 line as well as the new G20-generation 3 Series. The only component that is not shared with the 3 Series is the aluminum upright that holds the wheel hub assembly.
Much like in the front, the VDC dampers are shown to be shared with the Z4 while the VDC control module is shared with a variety of BMW models ranging from the 3 Series to the Z4. Although the hardware is the same, these dampers and modules are all likely run by custom mappings created by Toyota.
Springs were not listed in the parts catalog for the Z4 or the Supra, so we could not compare those at this time, but it is likely that there will be multiple spring variants for each vehicle depending on the trim and market for the vehicle.
The wheels and tires between the two vehicles are the last part of the handling equation, and they actually have the same specs despite different designs. The 19-inch versions of the wheels on both vehicles are exactly the same size. The front wheels are nine inches wide wheels with a 32mm offset, while the rears are 19x10 inches with a 40mm offset. This also explains how both vehicles have the same track widths.
Considering the parts that are used on both vehicles and the fact that the rear suspension of the Supra not only shares almost all of it components with the Z4 but also shares them with the 3 Series, I find the claims of solitary development to be a bit inflated. It appears that most of the suspension was created by BMW, and Toyota went in and picked things from the various trims of the Z4, with the only unique component being the front lower control arms. Once those pieces were put together, all that was left was the mapping for the dampers, which is the area where Toyota likely did do something unique.