Car handling (oversteer/understeer) in the real world

[SvenDriver]

(And so it begins)

 

After playing around on a track 😬 I cannot help but notice that the car understeers and oversteers in different places. Oversteer generally being the response to over-enthusiastic go-juice on apex exit.

 

My feel is that the car understeers if I hold too much power on the corner. It is controllable

but could perhaps be less.

 

How can you tell when the behaviour is due to the driver or due to the car?

 

Will improving handling on the track be to the detriment of handling on the road?

 

Changing the car it is easy, it wont argue that it is all the fault of the driver. Changing the driver requires more thought since the driver will tend to blame the car.

 

I remember a certain Mr Clarkson bitching about chronic understeer in the new Elise and then being totally miffed when the Lotus technician power slid merrily through corners.

[wackydo]

OK, but understeer and oversteer is also dependent on how setup (ie prepared) the car is before you enter the corner. It also depends on what lines you take through the corner as to how well the car performs.

 

As yours is a road car, it is probably better setup for road use, so might not do as well on track as something that is more dedicated to track work.

 

Taking some tution is always beneficial, they had some good tutors there on Friday. I had a tution session and managed to loose a lot of understeer as a direct result of their teaching.

 

Tony

[Julian Thompson]

When you exit a corner, weight is shifted to the rear because you are accelerating. Additionally, since you are still cornering there is also weight transfer from the inside tyres to the outside tyres. It is clear that this overloads the outside rear tyre and causes oversteer.

 

You can, of course, minimise the effects as a driver by being smoother with your application of power or changing your line to minimise the time when you are cornering and accelerating at the same time, and remember that with 400 or 500bhp per ton or whatever you have you WILL have to be judicious with the throttle - there aren't really any "magic Blue-Tak" tyres !!

 

But. You could try going a bit softer on your rear ARB which will reduce the load on that outside tyre.

 

With regard to the car behaving differently in different places - yes - this is normal! Try and set the car up to feel neutrally balanced mid corner - ie away from the entry and exit phases.

[SvenDriver]

We don't have a rear ARB so I'm told! so softening it up is not an option. Therefore we can fiddle with tyre pressures. However, listening here I think that I am tempted to leave things as they are (17psi all round on Pilots) and just get the driver uprated.

 

Since the car seems quite sensitive to tyre pressures I might try a +/-1 differential front to rear and see how that changes things just for reference and then change it back for the driver upgrade.

 

All things being said, that Chapman bloke new what he was doing. There is something deeply satisfying about getting it right and flicking the car through a chicane at high speed. 😬

 

I've only got 122bhp so snap oversteer needs some foolishness on my part.

 

I don't have a rear ARB. From what I can see I think it fits onto the chassis above the div. On each side there is a steel plate with 3 or (ISTR) 4 holes in it pointing to the rear of the car. That looks to me like where the ARB might go.

 

Edited by - SvenDriver on 9 Feb 2003 10:10:05

 

Edited by - SvenDriver on 9 Feb 2003 10:30:52

[EFA]

On the subject of the Lotus engineer who took Clarkson out and miffed him, this guy was deliberately upsetting the balance of the car before turning into the corner, by actually turning very breify in the wrong direction!

 

This is also Tiff Needell's technique for those massive power slides......

 

Arnie Webb

The Fat Bloke back @ 512k

 

Edited by - fast arnie on 9 Feb 2003 17:50:56

[puremalt]

You may be entering the corner too fast and not accelerating through it, to keep neutral/oversteer on the exit. That's all my handling knowledge expressed now so I'm off for a lie down.

Slow in, fast out (That should be the signature surely)

 

Mine Farts and Belches

[SvenDriver]

Probably you are right.

 

On the corner where understeer was worst I was trying to brake right into the apex and then accelerate out very gently. Balance was on reflection all off so acceleration had to be left quite late to prevent a snap oversteer.

 

On the corner where understeer was absent on exit I had braked hard on entry, dropped two cogs after braking and then started accelerating from the apex onwards with maybe little drift happening. Entry was I felt too slow Didn't break hard eneough for heel-n-toe. Car must have been nicely balanced.

 

On the gentle corners I could just accelerate right through them.

 

Hmmm, maybe the driver has something to do with all of this after all.

 

I have a sneaking suspicion that the car really has been properly setup in the past and that anything odd is down to the driver.

 

[Julian Thompson]

Could you change the spring rates?

 

 

[Tony C]

SvenDriver - there goes an honest man 😬

 

After I was shown how to corner in my tintop by Hugh Noblett, the difference is amazing.

I'm sure there are more modern books on the subject, but try to get hold of a copy of Piero Taruffi's book "The Technique of Motor Racing". I got mine through Amazon, so it's still in print. The ISBN is: 0-8376-0228-9, it is the biz 😬 he goes into the complete dynamics of cornering in language even I could understand.

 

IMHO, if the car is set-up neutral, the driver is THE biggest variable. It's possible to fiddle with anything and everything on the car and you still won't go round corners any faster if you are not applying the welly in the right place.

 

Cheers,

Tony

 

Still waiting for my BRG SV kit. 😬

[SvenDriver]

We could change Spring rates, roll bar, tyres, driver. I think we change the driver first, tyres second, everything else last.

[Alias]

Turning the opposite way first is a well established way of getting a car to do a respectable powerslide. It is called the "scandinavian flick" and I believe was first introduced by Stig Blomquist as a very effective rally technique to go round corners.

 

 

 

One car - 1400 Supersport with 6 gears and clamshell wings.

[Slipper man]

What wheels do you have? If they are 16" jobbies, you are experiencing the handling you would expect, and there isn't much you can do about it. At the handling test day we did for Low Flying a couple of years ago, the car on 16" wheels/tyres was spun by almost everyone because it was so un predictable. You would not believe the difference more suitable wheel/tyres make. That is why most people go for 13" wheels - they are much more forgiving.

 

 

[SvenDriver]

I have 15 inches. With the pilots run slightly low (16-17psi) they handle in a predictable way without sudden shear. At 18psi they will shear without warning and quickly. At 20psi they become quite nervous. These are all COLD pressures.

 

Don't let size fool you it is a somewhat misleading thing. There is lots you can do with tyre tech.

 

CR500's on 15" work because Avon have engineered a thin sidewall giving the tyre more flex. ISTR that Yoko's et al. on 13" have tall thicker sidewalls that flex because they are taller. Both have the same effect. Running tyres softer has the same effect as thinning the sidewall or increasing the height.

 

My experiments with tyre pressure seems to indicate that 7s are sensitive to it. This is consistent with their low weight.

 

Edited by - SvenDriver on 9 Feb 2003 22:12:07

[Jam Mad]

if someone has mentioned this, and i've missed it in my haste, then sorry... but the caterham is a very light car, so easily understeers.. it's best to think about it, as someone above is doing, in terms of the forces on the wheels.

 

with little weight over the front of the car, if you turn in too fast, or with too much gas, the front wheels won't necessarily grip. why should they ? set-up can of course ensure a fiercer turn-in, but so can trail braking. that is braking until you just after you have turned in. braking transfers weight to the front wheels, giving them more grip. this won't stop a badly set up car from understeering, but it will sharpen turn-in on a neutral car.

 

the best thing to do is get instruction. that way you will soon be overtaking people who spend a lot more money on the cars, and a lot less money ( often none ) on improving their driving ability. it's fun to see their faces !

[puremalt]

Good call. How is the Land of the Long White Cloud. Best roads in the world you lucky man.

 

Mine Farts and Belches

[Peter Carmichael]

On top of the suggestion of tuition, which is a good idea regardless, I would advise you to believe your gut reaction to the car.

 

Do you like driving it round corners. Does the car "play" with you, or fight against you. Are there moments when you drive on tiptoe because it feels unpredictable. Are there moments when there is an aching, yawning pause where you can't get on the power because the nose will scrub wide.

 

The observations I am talking about are not specific, measured or conscious but are rather the subtle subconscious things. Try driving a road, sending your focus of attention further ahead than the next 10 yards and see if the car looks after itself "in the moment". These are all good tests of whether your car handles.

 

Another good test is to see if the car can be driven at a range of effort, with equal reward. If the car feels good at 10/10 and can give a relaxing drive at 4/10 but can't do anything consistent anywhere in between, the chances are you have a handling issue. If the car can do 7/10, 8/10, 9/10 with equal elan then the next thing to improve is the driver.

[SvenDriver]

Gut feel:

 

Tyre pressure is critical. If the tyres are too hard then it will lose grip too fast. If set right it is nice and progressive. The car never feels unpredictable.

 

If I want to drive like Grandma then I can just forget about the car and enjoy the scenery. If I want to drive it hard I can. On a rough road the car will still keep on track at speed. On a track it behaves well (I think), it can brake from 100 to 30 in not much space without either end getting nasty.

 

On one chicane on the track it was just beautiful. Accelerate in, Flick, Flick out. Sorted.

 

I think it is the driver. The car is consistent and predictable.

 

I keep looking on "For Sale" but no-one has an airfield to sell.

[Tony C]

I don't know about the effect of the Se7en being lighter.

It has lower mass so less kinetic energy, but

less down force on the tyre contact patches and therefore less friction.

Don't the two characteristics cancel each other?

 

The car is going in a straight line, therefore wants to continue in a straight line - good ol' Newton

 

The force to make it change direction comes from friction at the tyre contact patches - Newton again

 

Taruffi explains all this far better than I ever could, but it's all in the physics. If you have a given car, using the correct line, speed, brake point and acceleration point during an EXTREMELY dynamic manoeuvre, your car will retain its maximum kinetic energy, which is always easier to shed than generate. Ergo, sh*t off the proverbial

 

Still waiting for my BRG SV kit. 😬

[F355GTS]

Sven

 

Don't forget track conditions when considering understeer/oversteer on a particular day, surface condition/type, temperature, how wet/ dry will all factor.

 

At the 'track' in question there are several changes of surface resulting in different grip characteristics. for example the first fast right hander (after the chicane and slow right) is slippery on the apex and like ice on the exit, it was last year and still is, the next right which takes you across the white lines on the runway gives inconsistent grip depending on whether you are on paint or tarmac.

 

In addition it was wet in the morning and dried throughout the day, whilst not visible it's possible there was retained moisture at certain points on the circuit eg exit of the bottom hairpin. well moisture and about 1/2 ton of grass and mud where a few had gone wayward and brought it back onto circuit

 

I would agree with all the suggestions to take some instruction, you'll find your lines will improve dramatically and you'll be more prepared to deal with variables such as grip or a lack of.

 

Mark

[SvenDriver]

Mark.

 

Yes, I was very aware of the grip changes on various parts of the 'track'. However, I didn't know that one or two of the exit points were greasy - I thought it was me!!

 

OK, so stick with plan a. Car is fine for now, driver needs upgrading. We've got two 7 sessions booked to do this.

 

Only thing now is if I can get time off on the 21st to go back on track. 😬 😬

[F355GTS]

Sven

 

I think the 21st date may be 'moved'! keep an eye on their site

 

Mark

[wackydo]

Talking about dates moving, Motorsport Events were talking about having a new location, but now the events at this new location seem to have disappeared.

 

Have I got this wrong, what's happend ??

 

Tony

[F355GTS]

Tony

 

info I have suggests they've had problems as the venue has told them they can't run Fridays therefore they're having to re-arrange the calendar, details coming shortly

 

Mark

[Jan T]

Does anyone know where Motorsports' new venue is?

Jan

PS ...and is Hullavington worth a visit?

[F355GTS]

Jan

 

Don't know the new venue but Hullavington is definitely worth the effort

 

Mark