I just really noticed that my car slightly understeers and I am lowered 1.5". It was there before I lowered it but never really noticed it til the other day.

I rented a crappy little Mazda Protoge in Atlanta on business. I noticed taking the onramps that that little sucker oversteered like mad compared to my Vette. Now that was other end of the extreme!

I want my vette to track a little more precisely! More than it does now and Less that that little sewing machine did :D

 

Just a guess but I think that you are mixing up the terms. I doubt that a fwd Mazda oversteers if probably understeers. Oversteer is when the car turns to much or when the back end tends to want to come around more that the frond. Understeer of push is probably what the fwd Mazda did, this is when you turn the front wheels and the car can not make the angle that the tires are pointed or the back is pushing and the car is not turning.

Most Corvettes oversteer because of peoples heavy foot, ie the back gets loose. Bad alignment can add to this problem to much positive camber.

I think you want to know how to induce Understeer. Get the alignment redone at Z06 specs this will add some negative caber to the front tires and make the car turn in better.

This is just the tip of the iceberg on alignments whole books have been written on the subject. I tried to make it very simple.

 

Hi Chuckster and all,

As memory serves some driver in NASCAR once said...

When you hit the wall with the Front of the car ... that's Under Steering,
& when you hit the wall with the Rear of the car ... that's Over Steering.

Also...may not be the best or proper way but increasing the air pressure in the rear tires makes them stick less and can induce Over Steering.

Kenny

 

Actually this thing Oversteered. Just the slighted flick of the wheel sent the nose flying in that direction. the nose turned faster than the steering wheel :eek:

My Vette has a slight delay before it starts to turn


[Modified by chuckster, 2:54 PM 11/5/2001]

 

That would be understeer.

Here at the skip barber definitions:

Understeer: If you were on the skidpad with a car which reached 100% of the tires cornering capabilities at the front tires before the rears, the front end of the car would slide first, leading your nose-fist away from the direction the front wheels weerre pointing.

Oversteer: This is the case where the rear tires reach the limit first and slide out wider than you intended. This tail out attitude is called "oversteer"

 

Ok what you are describing is neither oversteer or understeer. It is just a really responsive steering feel. It sounds like you are talking about a really responsive steering wheel. Many cars feel this way (surprising a Mazda protege does, but it might use the same steering rack as a miata which has very quick steering). Basically the C5 has a lot of slop through its power steering. It give the car a numb feeling when turning the wheel compared to say a BMW M3 or a Porsche 911 which reacts almost instantly to your inputs. This is a common complaint from folks who race about the Vette. I am not sure if a fix exists for this, but if I could put a Porsche steering rack in my Z06 I'd do it in an instant.

For the unitiated:

Understeer occurs when you turn the steering wheel and the car does not turn (it plows straight ahead... Try this in a parking lot: get up to a decent speed say 30 and jam the wheel to one side (keep on the gas). If the car plows or the front end hops or makes a lot of noise that's understeering

Neutral steer is when you have neither understeer nor oversteer. This makes the car very twitchy and responsive to any steering inputs. It also is great for a race car. Not so hot on the street. I had a car set up neutrally and it was a joy on the track and a nightmare on the street.

Oversteer is when you turn the wheel and the car's backend loses traction and comes around on you inducing a spin. This can be mimicked by going to full throttle in a high hp car through a turn. You lighten the front and load up the weight of the car in the rear and it wants to come around faster than the lighter front end of the car. Easy to do in a Vette. Most production cars won't oversteer unless you are turning and lift off the thottle completely or in high powered cars get on the throttle too quickly. An exception to this is a car with a lot of weight behind the rear axle (Porsche 911).

Almost all street car's understeer from the factory. Even the Vette. Some more than others. Understeering makes for a nice safe to drive car which doesn't hunt and seek over rough roads. A few cars come from the factory pretty close to neutral. Most dial in understeer by using staggered tire sizes wider in the rear and thinner in the front.

Hope this was informative.

 

To correct for over or understeer use these :

http://teamzr1.com/uosteer.html

 

if you want a quicker turn in just unbolt the front bar.

 

Try it out in a large parking lot, cause it will induce a profound change.

 

.

Also...may not be the best or proper way but increasing the air pressure in the rear tires makes them stick less and can induce Over Steering.


[/QUOTE]

Uh? I was taught the exact opposite.Maybe if you extremely overinflate it's true , but , lower air makes the sidewall flex and induces the rear to come around. :cheers:

 

Thanks for the replies.
Especially Mike and Team ZR1 :D

John, that's an awesome link!!

 

back in the sting ray days 63-67 i won a quite a few autoXs using this deal of removing the front bar.


[Modified by clem zahrobsky, 9:57 PM 11/5/2001]

 

Well Chuck as we say on the team :
We don't no zip about wax,
but we do know how to go Fast :)

Next time you'll know to search the team website or forum for techie stuff.
Glad I could be of help.

John

 

Kenny,

I think that quote is property of Fireball Roberts. :D

Mark

 

My favorite saying is:

Oversteer makes the passenger scared.
Understeer makes the driver scared.

So you want oversteer without any suspension changes. Try more throttle (power induced over steer) in a turn. Or go in way too hot and do a complete lift off the throttle (be ready to get back on to catch it as it comes around).

Want more responsive steering. Add a little toe out to the front (be careful at high speeds). My Rx7 was real slow on turn-in. About 3/16" toe out and it would just dive into a turn. Was scary as hell with snow tires (on a dry road) when the speeds approached 100mph.

 

Hi,

You all have some great explainations for oversteer, and understeed. You are correct.
At LG Motorsports, we know a little bit about handling and how to make a car do what you want. Three World Challenge Championships and wins in the Trans Am series qualifies us to respond on this subject.

Dialing in a suspension is like tuning a radio in. When the chassis is right, it is like listening to a creamy FM radio, but when it is wrong it is like listening to a static laiden AM radio on a rainy night.

If a car "pushes" or is "Loose", you should always try to work on the end of the car that is not sticking. So just adding spring rate to the rear will only reduce the push by taking traction away from the rear. It is better to try to work on the front to make it stick better. Now this only works if there is some unused traction available at the front. Someone said,"add camber to the front" Well on the production Corvette, that will help, because the factory sets the front for best tire wear, and to insure that these cars understeer. This is the safest from the factory view point. The natural driver reaction when a car is over the limit is to slow down, and hit the brake. This will make an understeering car come back to you, by loading the front tires, and giving you traction on the front of the car. On the flip side of that if the car is oversteering when it goes over the limit, the same natural driver reaction would still give more traction to the front, and thus add to your troubles. It takes a better driver to control a car that is over the limit if the car has oversteer characteristics.

That said, now to tuning the car. The basic rule of thumb, says that when you add spring rate to either end of the car, you take traction away from that end. If you add "bump" to the shocks, you will also take traction away from that end of the car, but with shocks, it is only temporary until the shock compresses, then it goes back to the spring rate.

On a track car, you always need rear traction to get off the corners, so just adding spring rate to the rear might reduce the rear grip enough to hurt the car coming off the slow corners, and that will hurt lap times. So we start out by going softer at the front, to reduce a push. Then comes the hard part. When is softer, too soft?
Without changing springs and shocks, you are very limited. You only have tire presssure and alignment. Every tire has a spring rate. The side wall stiffness determines most of it but so does air pressure. More air pressure equals more spring rate, and vice versa. And you must be mindful of the footprint of the tire. For example, a tire that has too low pressure will gain grip when you reach the optimum prressure. There is a pressure window where the tire will put down a good footprint. Once you find that point, then you can add or subtract pressure to modify your handling

GM usually sets their cars up on the test track "Neutral" and then reduces the rear anti roll bar size or the rear springs, to make it understeer. It is uaually a safe bet that if you add aftermarket sway bars that are biased toward the rear, you will regain the Neutral handling that is so close on a C5.

So tuning the car with what you have is more complex than one would think. You have so many tuning tools at your disposal that it can be overwhelming. Just have at it and try things. It beats playing golf.

Sorry for the long winded response, that only scratched the surface. Next time we will get into roll centers anti squat, and anti dive :)

Thanks,

Lou Gigliotti http://www.lgmotorspots.com

 

So if I want the car to act more neutral. Can I just add Urethane bushings to my sway bars front and back? I have Z51 suspension

 

On a Z51 package, I would just add a little negative camber to the front, and check the alignment to make sure that it is what it is supposed to be.

Adding the urethane bushings to the swaybars, will reduce the compliance of them but will not add roll rate to them.

Make the front stick better.

LG


[Modified by LG Motorsports, 3:51 PM 11/6/2001]

 

Chuckster, are you trying to get better turn in or is your car pushing mid-corner?

One thing you do NOT want to do if you are trying for less understeer mid corner is to switch to a ZO6 front sway bar. This will increase front roll stiffness and cause more understeer. Also, to add to what LG Motorsports mentioned, just as a general rule of thumb, softer gives more grip but reduces transient response. Also, weight distribution: more weight in the front usually causes quicker turn-in but increases mid corner push. Stiffer bushings will likely help your transient response.

You can also help the car by being less abrupt with your inputs. Smooth driving can make as big a difference as any suspension mods. As was mentioned a few times before though, the best bet in this case is probably some good alignment specs. You could pick up both transient response and grip.