Car Handling

when i was looking at chassis rigidity, i found this very informative video, as well as some other helpful facts


What is understeering and oversteering?

UNDERSTEER :

Front wheels lose their traction and cause the car to go wide. Understeer can be corrected by stiffening the vehicle's rear chassis.

OVERSTEER :

Rear tires lose grip and causing the rear end of the vehicle slides out. Oversteer can be corrected by stiffening the vehicle's front chassis.

It should be noted that understeer and oversteer are not binary functions. It's not a 'all of a sudden I'm understeering,' it's a gradual (if sometimes very rapid) increase in the tires' "slip angle."

The slip angle of a wheel is the angle between where the tire is pointed and the direction it is moving.
Understeer is any time the slip angle of the front tires is higher than the rear, oversteer is any time the slip angle is higher in the rear tires.

Every time you take a corner in a car at least one tire will slip. In fact, turning the steering wheel causes the front tires to slip and then the front of the car will attempt to negate their slip angle, which is what ultimately causes the turn. In this sense, every time you steer your car it understeers at least a tiny bit.

In the same respect, every time you accelerate your tires spin and every time you brake your tires skid.




I could go on for pages and pages and pages and pages if I'm not careful... Knowing this crap was my job for a long time. I'm much happier with the practical application of it

More helpful info:

For a given road surface, a tire on a car has an 'optimum' slip angle -- this is the slip angle where the tire has the best coefficient of friction, allowing for the highest inertial load (cornering speed ; ). The optimum slip angle is higher if the road surface has less friction, which is why you slide a bit more to go fast on dirt and snow.

Cornering speed for a given corner radius increases and decreases on a bell curve from the optimum slip angle -- As you increase your speed in a corner (ignoring for the traction used by the drive wheels) the tires must increase their slip angle to maintain a radius, but once they are past the optimum slip angle you will not gain any more corner speed. This is what causes that part of the car to "go wide."

[For anyone who knows chemistry, the relationship between corner speed, slip angle, and radius of the car's travel is a lot like the relationship between pressure, temperature and volume]

If you go into a corner and accelerate gently through it until the front end slides and steer more you increase the slip angle even more than the understeer event, causing the car to go even wider. The best way to correct understeer is to reduce the steering angle then gently steer back in. You'll see good drivers 'sawing' the wheel rapidly when they understeer accidentally... it's like letting the tires have a short break then try to push the front end of the car through the curve again.

I hope that made sense :/

Dani, if you really want to learn about chassis dynamics, read "Drive to Win" by Carroll smith. I would let you borrow mine but it's like a bible to me so I read it a lot.

dogbreath wrote:

For a given road surface, a tire on a car has an 'optimum' slip angle -- this is the slip angle where the tire has the best coefficient of friction, allowing for the highest inertial load (cornering speed ; ). The optimum slip angle is higher if the road surface has less friction, which is why you slide a bit more to go fast on dirt and snow.

Cornering speed for a given corner radius increases and decreases on a bell curve from the optimum slip angle -- As you increase your speed in a corner (ignoring for the traction used by the drive wheels) the tires must increase their slip angle to maintain a radius, but once they are past the optimum slip angle you will not gain any more corner speed. This is what causes that part of the car to "go wide."

This ^^^ is the most important thing one should know.

I have found that a lot of people have a hard time understanding that there is an area between going slow and sliding off of the road. In any car, the fastest and most desirable way to apex a corner is by achieving the optimum slip angle with all four wheels. While very few cars can be 100% neutral, we try to achieve neutrality by increasing the slip angle of the end of the car that has the most grip. In addition very rarely in a 2wd car is the end with the most grip the drive wheels.

needs vids to illustrate.

Nick what about "Tune to Win" have you read that book? im thinking about getting both of those books, they seem fairly interesting and informational

I haven't read tune to win, I probably should but from what I understand it goes a little more in depth with the engineering side of vehicle dynamics. The thing I like about drive to win is that it was written for drivers. He even says in the book, this book is not written to tell you why things work, it is written to tell you how things work. I am really just interested in how to make my car faster around the track, as far as why things work the way they do, I already struggle enough with the first part haha.

these books sound pretty interesting, you should put these in the store on the Fendego site

Not a bad idea, I'll look into how many I have to buy to do so.

you also need to get the TRF interview up their, as well as the shirts and stickers

*there

Thanks for the correction, even though i posted this at 2 in the morning

Just got Drive to Win in the mail today, can't wait to start reading!

you bastard bring it to school tomorrow, i would like to see this book, that nick calls his bible

It's amazing and very confusing haha

acedeuce802 wrote:

Just got Drive to Win in the mail today, can't wait to start reading!

I ordered Speed Secrets, perhaps when we are done we can trade.

http://www.amazon.com/Speed-Secrets-Professional-Driving-Techniques/dp/0760305188

Sweet! Amazon ftw, ordered Friday night, received Monday afternoon

It's cool seeing all these people getting into driving.

hard parker sell outs.

stfu hArdprkr

Also, I started reading this last night, it's very interesting! I think it's going to be a great read. I flipped through the suspension section, and from what I could tell it's very detailed and informative!

xcoldricex wrote:

hard parker sell outs.

Man it's like I can't decide whether to prk hArd or to drive! Is there some middle ground somewhere that might let me accomplish both?!?! We may never know.

haha i probably drive my car more than any of you. over 70k now

Maybe. I'm at 44k in about 2.5 years.

halo0 wrote:

xcoldricex wrote:

hard parker sell outs.

Man it's like I can't decide whether to prk hArd or to drive! Is there some middle ground somewhere that might let me accomplish both?!?! We may never know.

I went through the same thing. I just asked myself what I was going to use more. Have my car setup where I can drive it hard for maybe 10 minutes a week, or have it sitting really nice and low, so that everyday I drive/look at it, I enjoy it. You can definitely have a in-between also, It just takes time to get everything just right.