Cornering Confidence

[jwawhite]

I had the great opportunity to drive Hwy 18 from San Bernardino to Running Springs yesterday to attend my niece's high school graduation. (My BLW is doing a great job with his family!) Anyway I wrote some time ago my concerns about the front end feel while aggressively cornering be it on/off camber right or left turns. I feel a bit like Tom Cruise in that movie "Days of Thunder" where it comes to light that Tom, the Professional Driver does not know how to discuss driving with his Crew Chief, Robert Duvall. Well, anyway the front end feels like it's sliding away towards the momentum of the turn--especially if something on the road affects tire adhesion just for a moment like a bump, tire snake, gravel, etc. It seems that my Dodge sways more but holds the road better. I have this fear of a front end wash out. I admit I don't know this road (Hwy 18) but coming home in the dark, downhill, small foreign vehicles were on my tail until I could get out of the way and eventually ended up about a block behind at the end of this long and varied mountain road.

QUESTION: Is it just that I don't know the capabilities/limits of my vehicle or is there some sort of slide out problem with the front end? Tires are stock with about 11k on them.

I have a fear that if I'm cornering side by side/overtaking another car that my car will drift and cause a serious problem. I know the limits of my BMW motorcyle and really enjoy overtaking --squids at times--- who speed through the straight-a-ways and come back down in speed because they do not know how to steer. I want to have that confidence while driving my car.

 

[Patrick]

JWA,
Since you posted this twice, I'm going to merge the two threads and leave it as one thread in the C5 General Discussion Forum.

As to answering your question about cornering, I'll be interested to hear other's experiences- particularly those who autocross with their C5s. It's been my experience that the C5's cornering abilities are second to none in performance sports cars. Of course, if you're comparing it to a BMW bike, the feel will be obviously quite different.


-Patrick

 

[DRTH VTR]

I am no pro at autocross, but I have done it maybe 80-100 runs. The car WILL push, especially if you are trying to brake and turn at the same time. You can also get power oversteer and throttle lift oversteer.

I would suggest three things. First, make sure that there is not something mechanically wrong with the car. That should be ruled out as a cause first. Then find a big parking lot, a deserted road, or some safe place to practice a little bit. Maybe SCCA offers an autocross school in your area. There is one in Boise every year for example. I drive a Z06, and it is a very robust car with great handling right out of the box. But I had to learn how to drive it. I had some experienced Z06 drivers go on some autocross runs with me to offer tips, and I rode a few runs in their cars with them. The limit is further out than most people ever drive. You won't break your car. The last suggestion has to do with tires. Tire selection can make a HUGE difference in cornering capability. If the tires are old or worn, it might be good to replace them. There are many opinions about what tires are the best. I suppose it depends on the conditions that you drive in.

 

[jwawhite]

Some input

Thanks for the response DRTH VTR.

Here is what I do: I try to enter the corner at a reasonable speed. I try to accelerate smoothly through the curve with a smooth input on the steering wheel. If i encounter a bump or steel grate it seems the front end slides about the same width of the object I travel over. The front end steps out towards the outside.

I believe the car is in excellent conditon, the tires are stock run flats inflated to 30 psi all around and I have the car generally in Touring Position.

My insurance compay, Farmers, will not cover me if I have an accident while on a track.

Is this the nature of the car? How do you work around this?

 

[DRTH VTR]

Thanks for the response DRTH VTR.

Here is what I do: I try to enter the corner at a reasonable speed. I try to accelerate smoothly through the curve with a smooth input on the steering wheel. If i encounter a bump or steel grate it seems the front end slides about the same width of the object I travel over. The front end steps out towards the outside.

I believe the car is in excellent conditon, the tires are stock run flats inflated to 30 psi all around and I have the car generally in Touring Position.

My insurance compay, Farmers, will not cover me if I have an accident while on a track.

Is this the nature of the car? How do you work around this?

The term "bumpsteer" applies what you describe. When a wheel looses some traction for a brief moment due to a weight change at one corner, it will not turn as well until it recovers from the bump. It can happen to a front wheel with a little understeer (or "push") or to a rear wheel with a little oversteer (or "loose"). The wheel sort of steps out.

My insurance will not cover competitive driving, either. A well controlled autocross is very unlikely to result in any collision. The course is set up on a large parking lot, an airfield, or some other smooth empty surface. You drive around a course for time, and no other cars run at the same time. The course is marked with orange traffic cones. You can push the car as much or as little as you like. You are absolutly right about being smooth. I have never seen any body damage at any event that I have gone to. It is a safe way to test the limits of the car and your driving ability.

It is a little tough on the tires!

 

[IH2LOSE]

How much faster are you pushing the car thru the turns?

I have an 02 vert with about 12,000 miles on it with original tires and I have yet to push this car to the point of feeling insecure with it in very spirited driving.

Are you braking while in a twisty

best of luck with it

 

[DRTH VTR]

How much faster are you pushing the car thru the turns?

I have an 02 vert with about 12,000 miles on it with original tires and I have yet to push this car to the point of feeling insecure with it in very spirited driving.

Are you braking while in a twisty

best of luck with it

I push the car through the turns as fast as I can accomplish. If you enter the turn to fast, it will tend to push. If you are in the turn and lift the throttle or push the throttle, you can produce oversteer. So it becomes a case of finding the right balance. Jerky mores and skids are slow, in general. Smooth is fast, in general.

I do brake in the turns, but common wisdom is to do the braking before the turns. The tire only has so much grip, and grip that is used for braking is subtracted from the grip that is available to turn.

 

[DRTH VTR]

Here is a nice article about autocross:

http://www.corvetteactioncenter.com/racing/autox.html

 

[ToolGuy]

You may want to upgrade your sway bars to FE4 Z06 sway bars, links and bushings... My next mod and the bars are on order, $260 shipped from GM...

 

[semperfih2o]

You may want to upgrade your sway bars to FE4 Z06 sway bars, links and bushings... My next mod and the bars are on order, $260 shipped from GM...

As an old SCCA guy i discovered trailbraking a long time back.
Both the Bonderant and Jim Russel schools teach this technique.
In a nutshell it keeps the chassis set when entering a turn so there is less transition to the outside and you maintain a better tire contact patch.
That being said use a little descretion as it is a little hard on pads and rotors; how fast do you want to go?
Semper Fi

 

[gmjunkie]

QUESTION: Is it just that I don't know the capabilities/limits of my vehicle or is there some sort of slide out problem with the front end? Tires are stock with about 11k on them.

I have a fear that if I'm cornering side by side/overtaking another car that my car will drift and cause a serious problem.

My car did all that you mention,Plus would Swap end's on ya in a Heartbeat on wet pavement!!!!!!!!! Bump steer was Terrible and Scary at different times!! I took it to 2 or 3 places to have the alignment checked and they said it was with in spec's. and set the Toe!! They got to Twist something they want there $89.95!! :eyerole Still did not drive like a $50,000 car!! :eyerole So for the next 6,000 miles I played with it on my Antique Alignment equipment that I think came here on the Mayflower!!!! I also have some other specialized Equipment called Strings and Thumb Tack's!!

After measuring out chassis I came to the conclusion that the wheel base was 5 millimeter short on the left side!! 4 mm is about top's before a vehicle will pull in the direction of the short side!

And now this is something that most Computer Whiz Alignment men won't Do!! I loosened the rear suspension cradle and shifted it back on left side and forward on right till I had the W/B dead even!! and then set up alignment to GM's spec.'s!! It drove allot better but was hard on the Inside of the front tires. Still had some bump steer but not near as bad,Still pushed in the corners a little but was tolerable!! But still a handful on wet pavement!! So I played with it some more and came up with the settings I use now and I have no bump steer and my tires are doing fine!! About 11,000 miles ago I put a set of Kumho Ecsta ASX all season and now the handling on wet pavement is Perfect!! They are smooth and I can hear my Radio!!
The settings I use are ::
LR 0 cam. RR 0 cam. 0-1/32 toe in ::
Lt F 0 cam. 6 deg+ caster Rt F 0 cam. 6 1/4 deg.+ caster 1/32 toe in
If it feels a little loose you can take the front toe in up to 1/8 MAX!!
But remember the more you take it in the harder it will be on the outside of the front tires!! I have mine at 1/32,It Feels good there!! And I'm gonna get 40,000 + out of this set of Tires!!

Note : If you drive your car at speeds in excess of 135-140 mph these settings are not for You!! (add 3 deg + caster with 1/16- 3/32th's toe in) There will be a noticeable difference in tire ware!!

 

[Patrick]

As an old SCCA guy i discovered trailbraking a long time back.
Both the Bonderant and Jim Russel schools teach this technique.
In a nutshell it keeps the chassis set when entering a turn so there is less transition to the outside and you maintain a better tire contact patch.
That being said use a little descretion as it is a little hard on pads and rotors; how fast do you want to go?
Semper Fi

Now, this is one of the things I absolutely love about the CAC- the knowledge our members have, and their willingness to share it with someone who has a legitimate, thoughtful question about Corvettes.

Thanks, Semper Fi! You made my "Drive Your Corvette To Work Day" day.


-Patrick

 

[wishuwerehere82]

I am using the same combination as the GMjunkie on my 98. Thanks for the dial in numbers the Junk provided, I am driving effortlessly and with more control than previously with the old tires and alignment specs.
I had been flinching and twitching with every bump and crack in the road with the old setup.

Since I did the change to both tires and alignment at the same time, I can't say which change made the most difference. I will say the combination is great and feels nothing like the factory alignment and Run-flats. The road feel is solid, tire grip amazing, and absolutely no bump steer.

Try it, you'll like it!

 

[jwawhite]

gmjunkie: Thanks for responding with the analysis and recommendation for improvements. What I don't understand is why isn't the Corvette ready to go? After-all, this is "America's Sportscar" then why don't I have confidence in cornering? Why isn't the car setup correctly in the first place? I have yet to drive the car in a real rain and now I'm concerned about "swapping ends". Perhaps I should increase my liability coverage limits and let GM know I'm really not happy with the way the car handles. It's all stock and was in perfect condition until recently--now have a small scratch on the rear cover from a slow speed rear-ender.

 

[jwawhite]

What the?

After measuring out chassis I came to the conclusion that the wheel base was 5 millimeter short on the left side!! 4 mm is about top's before a vehicle will pull in the direction of the short side!


quote]

gmjunkie:
Thanks for responding with the analysis and recommendation for improvements. What I don't understand is why isn't the Corvette ready to go? After-all, this is "America's Sportscar" then why don't I have confidence in cornering? Why isn't the car setup correctly in the first place?
I have yet to drive the car in a real rain and now I'm concerned about "swapping ends". Perhaps I should increase my liability coverage limits and let GM know I'm really not happy with the way the car handles.
It's all stock and was in perfect condition until recently--now have a small scratch on the rear cover from a slow speed rear-ender.

 

[6 Shooter]

Keep da shiney side up...

Tires are stock with about 11k on them.

I've heard from more that a few C5 owners that stock run-flats tires are not what ya want to push real hard in corners.

Later - D

 

[gmjunkie]

gmjunkie:
Thanks for responding with the analysis and recommendation for improvements. What I don't understand is why isn't the Corvette ready to go? After-all, this is "America's Sportscar" then why don't I have confidence in cornering? Why isn't the car setup correctly in the first place?
I have yet to drive the car in a real rain and now I'm concerned about "swapping ends". Perhaps I should increase my liability coverage limits and let GM know I'm really not happy with the way the car handles.
It's all stock and was in perfect condition until recently--now have a small scratch on the rear cover from a slow speed rear-ender.

In the first 2-3000 miles a vehicle will settle down!! Bushings will seat in shocks will break in springs will settle down chassis will relax!!! They just will need to be realigned!! These cars are capable of running 170+ so the high caster and neg camber makes them easier to control at that speed!! But also makes them hard on the front tires and follow the groves in the road at slower speeds!!They have to set them this way,Do you want to meet some Idiot trying to see if it will do 170 mph coming at ya and can't control it!! I don't!! I drive my car below 100 mph so I'll take the better handling and tire ware at slower speeds!!