The Ultimate Guide to Suspension and Handling Part III: Balance the chassis
by Mike Kojima
Check out part one of the series here!
Check out part two of the series here!
Now that you have reduced body motion and improved steering response, we can work on the next major area of improvement, improving chassis balance. The goal for most of us is to have a car with neutral balance. Neutral balance, where all four tires slide the same amount, is the fastest way around a corner most of the time. This way the total maximum grip of each tire is being used. It might seem odd but experienced drifters prefer a neutrally balanced car because it allows them to have many control options for setting the car sideways. For example I set up Dai Yoshihara's Team Falken S13 in about the same way I would if it was a Time Attack car.
Unfortunately for the enthusiast, most cars are tuned to understeer from the factory. Understeer occurs when the front tires slide before the rears at the limit of grip. Manufacturers do this because it is the easiest handling mode for the average driver to control. Understeer is not efficient for extracting maximum lateral acceleration because the car will use the front tires excessively while the traction contribution of the rear tires is wasted. It’s also the slowest and most boring way around a corner. Bottom line? Understeer sucks.
If we go too far in the quest to eliminate understeer through chassis tuning we will inevitably create oversteer. Oversteer occurs when, at the limit, the rear tires slide before the fronts. Drifters work at controlling and driving in a state of continuous oversteer, raising it into an artform. A fast autocross car is often set to oversteer as are most rally cars. Any sort of race car that is driven mostly in very tight corners will probably be faster if it tends to have a bit of oversteer. Due to consumer advocate Ralph Nader's highly publicized campaign against General Motors and the rear engined Corvair in the 60's which resulted in huge lawsuits against automakers, the entire automotive industry is adverse to producing a car with anything close to oversteer. When an oversteering car exceeds its limits, it “spins out” which lawyers like to make sound especially heinous. However this simply means that an understeeing car will plow off the road nose first and an oversteering car will go tail first. You are gonna crash either way!
3 comments
You blown my mind when stated that slightly more pressure in tires will gain traction in the respectively axle (due less slip angle). Huge fan here, Mike!
Greetings from Brazil.
Can you help explain a bit more on the physical phenomenon involved with more pressure = less slip angle? The way I am imagining keeps involving tire carcass twisting deflection between the contact patch and wheel angle, but am not sure that’s right since slip angle doesn’t specify whether it’s the carcass or wheel angle that is compared to the car’s heading.
Great series, thanks Mike!
You guessed correctly, it’s both. More pressure makes the carcass stiffer.