Q: How do I adjust my suspension & driving to reduce understeer?

Q: “How does the Bump/Rebound/Spring Ratio settings in the rear suspension affect a cars handling? I’m driving a FVee with zero roll suspension. So I don’t know how the suspension basics differs from a more conventional suspension. Anyway, my main struggle with this car is that it turns in well, but mid-corner when I try to get back on the throttle it understeers a lot, so I end up having to release/accelerate a few times during the corner to get the car to the line I want. A few times I managed to get the car in the perfect mini-drift that rotated the car just enough to be able to get on throttle and exit cleanly. But it wasn’t easy to replicate. So how much of this can I improve with my driving and how? And what can I do with the setting to help out?”

A: It sounds like stiffening the rear (shocks, springs, bars) would be the right direction to go. Or softening the front. I don’t know what adjustments you have available to you, but that’s the direction. What you’re trying to do with these adjustments is to control the rear of the car so it doesn’t roll over so much, keep more load on the front two tires. Or, by softening the front, you’re allowing both front tires to stay on the track surface longer, giving them more grip.

If you want more information about tuning shock absorbers (dampers), I have an eBook called Shocks for Drivers, and it’s available here.

But how about the driving side? Supposing you can’t change anything on the setup, how would you overcome this by adjusting your driving?

To clarify, it sounds like the understeer only begins after turn-in, in the mid-corner. So it turns in well (nicely balanced with no oversteer or understeer), and as you begin to accelerate the understeer starts.

One thing to consider is to minimize the amount of time you spend turning the car. In other words, reducing the amount of mid-corner. To do that you would turn in slightly later, allowing you to begin unwinding the steering sooner. Another way of looking at that is to “square off the corner” with a later turn-in and apex. That means the first part of the corner will be a little tighter radius, but as soon as you’re finished with the entry part of the corner you can begin to straighten the wheel – just at the point where the understeer would have begun. This might work in some corners (but probably not in all corners); it will depend on the radius and speed of the corner.

What you’re currently doing is the right throttle approach. By easing up on the throttle you load the front of the car more, giving it grip.

5 Comments

  1. In my experience racing Formula Vee the key to the handling of a properly aligned and maintained car is the droop setting of the rear suspension. A common rule of thumb is to raise the rear tires off the ground and set the rear camber to half of the camber as it sits on the ground with the drivers weight. An example would be 6 degrees negative camber (-3 per side) with driver and 3 degrees total negative camber raised with suspension in full droop. The stiffness of the droop rubber is another critical tuning tool. I would suggest experimenting with different droop settings, for my particular car I settled on 1 negative degree of rear droop Measured with one wheel set at 0 degrees of camber and the other at -1 with 4.5 degrees total of negative camber (-2.25 per side). I also would suggest experimenting with different droop rubber duro settings as this can also change the mid corner feel drastically. These are my findings with my particular car I hope my experience is a help to your situation.

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  2. A very common thing with some of my drivers is that they put in much too much steering lock to start with.IE,they tend to load the front end rather than obtain a nice equal balance front to rear.

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  3. Can you adjust tear spring rates? It sounds to me like the culprit (when you boil it down) is weight transfer from front to rear under throttle application being too quick (weight transfers off the front to the rear suddenly resulting in understeer). Options off the top of my head: stiffer rebound front shocks, stiffer compression rear shocks, stiffer rear springs, more rake. An idea for driving style change is very slow application of throttle or even some low percentage maintenance to throttle heading to the apex (the goal being to slow down the transfer of weight from from to rear). Just some thoughts. Good luck!!!

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    • Ugh, phone typing. Multiple mistakes in there, apologies. Hope it’s clear.

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  4. When I read these my practice is to ask myself what would I do and why? Since the car is fundamentally ok I would not be inclined to change the roll and would instead first go to more front shock rebound; the front is the end with the observable problem and that is the end you drive. If I liked that then I would add some rear bump, if I didn’t like it then I would return the front rebound and still try the rear bump. I’m thinking these would be minimal changes not likely to cause significant changes to the entry. That great entry allows great flexibility in “race craft”, fixing the understeer without compromise to the entry then really adds flexibility to choose the exit line and thus the ability to really “race” the exit.

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