Engineering Tip #8: Spec Miata – Fine Tuning at the Track

If you’ve followed the steps in our last post about getting a baseline setup for your Spec Miata, then you’re ready for those small adjustments at the track.

When I go out in the first session, my first goal is always to find a balanced platform. You want to ensure the car is working equally in all parts of the corner. To achieve this balance, I start with ride height and corner weight adjustments in mind.

Ask yourself two questions: Is the car turning equally left and right? Is it predictable into and out of the corners? It should be pretty close if you’ve done your baseline setup properly. Keep in mind, not all tracks are the same, nor are the track conditions. For this reason, we spend the first few on track sessions fine tuning our set-up to both the track and the track conditions.

I like to begin by achieving a left-right balance. For example, sometimes you will have a car that seems to be loose because it oversteers in a few corners. This can lead you to believe the car is loose across the board. Before you make changes or tell the crew, “The car is loose,” make sure it is happening when you turn in both directions, not just one. It is important to determine whether your car is indeed loose or maybe the cross weight is just a little off, therefore handling poorly in a certain direction. Same goes for the car understeering in certain directions.

If the car is turning better in one direction, we want to make a cross weight change. I try to keep it simple and adjust either of the rear corners accordingly. You always want to make one change at a time to keep testing and tuning consistent, allowing you to determine exactly which change solved the handling issue. Raising the left rear of the car or dropping the right rear can correct an understeer in right-hand corners and/or an oversteer in left-hand corners. If you have an understeer in left-hand corners and/or an oversteer in right-hand corners, do the opposite and raise the right rear or drop the left rear.

My usual adjustment is a half turn to an entire turn up or down on the spring perch. You don’t want to go beyond two to three turns in any direction on either side as you may begin to cause the sway bar to bind. If you can’t find the balance with a couple of turns, you will have to go back to the scales and adjust your crossweight accordingly by adjusting all four corners.

Once the car is turning equally left and right, I begin to evaluate how the chassis behaves on the way into and out of the corner. If the car is loose (oversteering) on the way into the corner (corner entry), you’ll want to lower the rear ride height on both sides. Usually one or two turns down on the spring perch will get you there. This will help stabilize the chassis on corner entry and through the rest of the corner, as well. On the opposite side, if you are having problems getting down to the apex at turn in because the car is understeering, you might want to raise the rear of the car on both sides. This change will make the chassis more prone to oversteer, especially when on the brakes at turn-in.

Once you have a nearly-perfect platform, it’s time to do some more fine-tuning to make the car just right for the particular track and conditions. Remember, in a Spec Miata, your sway bars, ride height and tire pressures are your primary tools for those minute adjustments.

When you’re thinking of what’s working on your suspension in a corner, consider the entry, middle and exit. What’s working on the entry and exit is your shocks and springs, and the sway bars are at work in the middle of the corner, once the car is maintaining its static load. So when you evaluate your car’s performance, consider where in the corner your car needs improvement, and what pieces need to be adjusted accordingly.

On most Spec Miatas, the only sway bar to adjust is the rear one which has three holes/settings per side. The NA (first generation Miata) Spec Miata is the only one that runs with an adjustable front sway bar, which is usually set to full soft (hole closest to the end). There are two holes/settings on each side of this bar. If you feel the need to take away front grip, you have the option of changing this to the full stiff setting (hole furthest from the end). When it comes to the rear sway bar, if the car cannot maintain its “set” and is loose in the middle of the corner, you want to soften the sway bar. To do this, work your way towards the holes closest to the end of the sway bar, one setting at a time. On the other hand, if the car is tight/understeers when it loads in the middle of the corner, you want to stiffen the rear sway bar by working towards the holes furthest from the end of the sway bar. If you want to get real technical with it, you can find a middle ground in the settings by moving just one side at a time. Ex. Right side setting of the sway bar on full stiff (hole furthest from the end) and left side setting on the middle hole. I consider this a “half change” and think of it as being half a setting softer than “full stiff”.

When it comes to your shocks in Spec Miata, the spring rate is fixed and non-adjustable, but you can use tire pressure to get the feel of different spring rates. Less tire pressure equals less spring rate (softer – more grip), and more tire pressure equals more spring rate (stiffer – less grip). If adjustments for how your Spec Miata handles into or out of the corner are still needed, then you can make them with tire pressure, but only after you’ve finished your sway bar and ride height adjustments.

Remember, make only small changes to your tire pressure – just half a pound or a pound at a time. When your setup is close to perfect, you want to make only slight changes and only one change at a time.

Everything up to this point is a change you can make on pit lane. But maybe you hit a curb, ran off track, or even had something happen during transport. That means you want to reevaluate the alignment.

Camber and caster will be something you adjust a bit depending on the track characteristics; expect to adjust those from track to track as mentioned in our previous article.

For a typical Spec Miata driver, you will make most of your changes when you first arrive at the track. Within the first couple of practice sessions, you should be pretty set for your weekend. Keep in mind, though, that when you return to that track in the future, you may be making small adjustments based on that day’s track conditions.

Get the car to a level that’s comfortable for you, then go out and drive it! It’s easy to start over-thinking these things and wind up wasting time making adjustments that don’t really need to be made. If the car is performing predictably, then you can get on track. These tips are meant to help you, not take control of your weekend!