Toyota 86 set up

Hello,

I just finished the Motorsport Suspension course which was really interesting.

I noted on your set up sheet that you are running 98NM springs on your car, which equate to 10kg.

I also race a Toyota 86 in a sprint series with 7F/6R springs and have been told that this is too stiff.

MCA sell their red springs with 6F/5R for the Toyota 86 series, and Josh Coutte uses 7F/6R on his time attack car.

Just wondering how you ended up with this ‘stiff’ spring? Are you using slick tyres? Did you have to revalve the dampers? Does it compromise the ride over bumps?

Would you be willing to share any set up data or tips you came across that might help me with my car.

My Toyota 86 is track only and is tuned on E85, with MCA reds, roll cage and running Nankang CRS 245/40/17 tyres with 4.3 diff.

Hi Dwight, our own 86 race car is pretty much in a constant evolution and hence we've moved through quite a range of spring rates to test the effect on ride, balance and lap times. In your case with the same vehicle we can obviously directly compare spring rates but the more important (and usually overlooked or misunderstood) aspect is the suspension frequency. In general we want to target a specific suspension frequency and the spring rate is tuned to achieve this. You can refresh your memory on the topic here - https://www.hpacademy.com/dashboard/courses/suspension-tuning-and-optimization/foundation-concepts-suspension-frequency/

You can also use this spreadsheet to convert between a target frequency and spring rate - https://docs.google.com/spreadsheets/d/1TkOHlhC5ThV-E5WF7rWl079_U3HMoHjjydbLN5wxv7o/copy

As usual with a race car, spring rate and hence suspension frequency, is a compromise. Particularly with a high downforce setup it can be an advantage to run the car stiffer in order to control the ride height and prevent bottoming at high speed. The compromise here is that an overly stiff spring rate can reduce mechanical grip in low speed corners, particularly if the track is bumpy. And that leads me to the other consideration - You can get away with a stiffer spring rate on a smooth track but this would compromise grip on bumpy surfaces.

So to specifically answer your question, since this course was filmed we have moved back to a softer spring rate which is currently 8/7 kg/mm (F/R). I would not suggest running spring rates this stiff though if you have little or no aero on the car. Ultimately you're best to start with a baseline setup (your current 7/6 kg rates for example) and then test a softer and a stiffer setup (I'd move in 1 kg increments) to actually understand how this affects your car. In the end it's the lap times and driver confidence that will tell you what is optimal for your application but this course is designed to at least get you in the ball park with no guess work.

As Andre said, the specification of the vehicle will make a big difference to the spring rates that you can run, having effective aerodynamic download on the car usually requires a stiffer spring to support the aerodynamic platform, but going too stiff can lead to porpoising or chattering if the aero stalls or is disturbed over bumps and curbs. A car running on a slick tyre can also (usually) use a stiffer spring more effectively than a car running on R Spec or road tyres.

The other area to look at when it comes to spring rates is the compliance in the remainder of the suspension and mounting areas. Depending on the design of the suspension, it is possible for the initial movement of the suspension to be taken up by compliance in the bushes, before the spring even moves. This will lead to a notch in the spring rate that can unsettle the vehicle over bumps. An example of this is with a multi link suspension where the spring is mounted onto a spring platform on the lower arm. If the spring rate is greater than the stiffness of the inner bushing, the arm will pivot around the spring base until the inner mount bushing is fully compressed, and then start compressing the spring.