Q: “I’ve really been enjoying the No Dumb Questions podcasts and I finally have a dumb question that seems interesting enough to ask. Is there a big difference between driving an IRS (independent rear suspension) car versus a solid-axle car other than the lack of adjustability? Do you have any general car setup or driving tips?”
A: Jeff and I have put the No Dumb Questions podcast on hold for a bit, while we focus on the new podcast that we’ve just launched called It’s Not the Car. Sam Smith – the auto writer, club racer, and all-round brilliant storyteller – is kinda the leader of the band with this podcast, and it gives Jeff, Sam, and me the opportunity to tell some stories behind the cars, the races, and what we’ve learned about driving, car setup, and all things gearhead. Not to toot our own horn too much, but you really need to listen to this new podcast because it’s fun, entertaining, and I think you’ll learn a few things from it.
Since Jeff is not here right now, let me take a stab at answering your questions. And it’s going to be a relatively simple one in terms of driving.
No.
See, that was short and simple, wasn’t it?! You asked if there was a difference between driving a car with an IRS versus solid-axle, and really there isn’t in terms of changing one’s technique. You’re going to drive both the same way, and then adapt to it.
Now, will these two cars handle differently? Likely. But you could have two IRS cars, or two solid-axle cars, and there’d likely be as much difference in the way they handle as there would be when comparing the IRS and solid-axle cars.
Your job as a driver is to adapt to the car, no matter what, managing the strengths and weaknesses of the handling of it.
IRS is used because it most often results in better handling. Why? Because both rear wheels/tires are operating independently (mostly, as they’re usually linked in some way by an anti-roll bar), enabling them to travel up and down, following the track surface without upsetting the other side of the car. A solid rear axle is more of a compromise than an IRS setup is.
A common weakness with a solid-axle car is rear tire wheelspin, or not being able to put the power down exiting corners (particularly tighter corners, especially if there are bumps). So, you may want to adapt to this weakness by doing what you can to “open up” the exit of the corner. That may mean a later turn-in and apex so you can begin unwinding the steering early in the corner – the car will be pointing straighter as you accelerate out of the corners.
This is the same way of adapting to the solid-axle car as you’d use if driving an IRS car that didn’t put the power down well.
I’m not going to imitate and stand in for Jeff here (because I couldn’t do him justice) and try to answer your question about setup, but I believe he’d say something along the lines of you have to tune both cars using the same type of process: start by identifying the weak point in the car’s handling; then use the tools (setup adjustments) that you have; make one change at a time; make notes of everything you do and what the result was; and go back to the baseline setup every now and then for a A-B-A test.
NOTE: If you don’t want to wait for me to answer your question(s) here (which can take months, since I have so many!), you can always use my new SpeedSecrets.ai by signing up at SpeedSecrets.ai. The real beauty of using this app is that you can get out of your car after a session on track, and immediately ask it questions and get your answers, as well as what you should work on for the next on-track session. Since it’s “trained” only with my content, it really is like having me with you at the track.