rec.autos.simulators

Handling question.

Chris Shearbur

Handling question.

by Chris Shearbur » Sat, 13 Jul 2002 01:39:56

Rear: Wider = more lift. Narrower = less lift.

You were right the first time.

Front Wider = More inside rear lift
Rear Wider = more inside rear lift.

However, you are not counting the lateral G-forces.  The wider you move the
wheels out the wider your stance.  When the kart enters the turn all the
weight shifts to the outside bringing up the inside.  The wider the kart the
less it can bring up the inside, sometimes also creating hopping if you get
too wide because it tries to lift it up but then breaks the outsides loose.



> x-no-archive: yes

> ***! I made a typo!!!!

> Front: Wider = LESS lift. Narrower = MORE lift.
> Rear: Wider = more lift. Narrower = less lift.

> Sorry about that. I've corrected it below, so you can read it in context
if
> you like.


in

> > x-no-archive: yes

> > Guys,

> > As you know I'm now looking at kart handling, and trying to get my head
> > around that.

> > I think I've come up with a _really_ simple theory. So simple it's
scary.
> It
> > _must_ be wrong! :-D

> > Basics:

> > When you turn the front wheels on a kart, the effect is to cause the
> inside
> > rear wheel to lift. You can ONLY adjust the front toe angle, and the
front
> > and rear track widths. I am going to leave the toe angle at parallel.

> > Simple geometry says that the closer together the front wheels are, the
> > greater the angle caused, which lifts the rear wheels, and the further
> apart
> > the rear wheels are, the more one will lift. I.e.

> > Front: Wider = LESS lift. Narrower = MORE lift
> > Rear: Wider = more lift. Narrower = less lift.

> > This can also be observed, so it must be right.

> > The next statement I'm going to make is this: (Forgetting about the
> > peculiarities of solid rear axles.)

> > A wider track is better. I can't state exactly why, but ferraris are
wider
> > than my golf, F1 teams make the cars as wide as the regs allow, etc. I'm
> > confident this is right, even though I can't prove it ;-)

> > Now, if the inside rear doesn't lift enough, then the kart is going to
get
> > understeer. This is because the outside rear won't be turning fast
enough,
> > (braking it) and the inside rear will be too fast (accelerating it). The
> > effect will be to pust the front out.

> > If, on the other hand, the inside rear lifts too much, then the outside
> rear
> > will reach a point where it can't grip any more, so it will slide out,
> > causing skipping, and oversteer.

> > So, when trying to setup my kart, surely I should set the front and rear
> > track as wide as possible, then go and drive it. I will get one of 3
> things
> > as a result.

> > 1. The track record!!
> > 2. Understeer.
> > 3. Oversteer.

> > If, then...
> > 1. Leave everything alone! :-D
> > 2. Not enough inside rear lift. Can't widen the rear any more, so narrow
> the
> > front to compensate.
> > 3. Too much rear lift. Can't widen the front, so narrow the rear to
> > compensate.

> > See what I mean? There _must_ be some trade offs or something that I'm
> > missing!

> > Any help will make me very grapefruit!

> > R.

Jonny Hodgso

Handling question.

by Jonny Hodgso » Sat, 13 Jul 2002 02:00:55


> >Front: Wider = LESS lift. Narrower = MORE lift.
> Rear: Wider = more lift. Narrower = less lift.

> You were right the first time.

> Front Wider = More inside rear lift
> Rear Wider = more inside rear lift.

Yup. Geometrically, Richard was right - but it's forces we're
interested in.  I think I can explain it nicely by pointing
out that if you reduce the front track to zero, you get *no*
rear weight transfer.

Actually, I think that means that a narrower rear track will
*increase* the weight transfer...

Jonny

bengal2

Handling question.

by bengal2 » Sat, 13 Jul 2002 12:46:19

Interesting theory...I race 4 cycle but have also driven Rotax. I have a
coyote chassis and its amazing how many factors contribute to setup.
Humidity and track temp are also a big factor.

If the back end of my Kart is too loose, meaning excessive oversteer, I
actually narrow the width. This results in more grip and unloads the
inside rear tire slightly which is what you want.
Too narrow and the kart will skip or bicycle in the corner...NOT GOOD.
For a less drastic rear adjustment, tire pressures will also effect rear
grip but one must be carefull because as you ad pressure to one side in
the rear, you transfer weight to the opposit front corner.
With a solid axle, stagger is also important. I tend to run a slightly
larger circumference tire on the right since most of our turns are left.
I think one of the reasons norower in the back means more  rear grip is
it raises the centre of gravity over the rear tires.
Stiffening the chassis in the rear also has a big effect

As far as the front end, I think the width mainly effects the response
of the front end which can appear to effect grip. In a left turn it is
the inside tire that bites first and starts the turn, the chassis then
twists and weight is transfered to the rear through acceleration as the
outside rear grips and hopefully unloads the inside rear. For me, this
is perfect.

Birel, MBA, or other chassis may be different. Italian built chassis
will respond different than an American built chassis.
I am by no means an expert, Just my 2 cents :)


> x-no-archive: yes

> ***! I made a typo!!!!

> Front: Wider = LESS lift. Narrower = MORE lift.
> Rear: Wider = more lift. Narrower = less lift.

> Sorry about that. I've corrected it below, so you can read it in context if
> you like.



> > x-no-archive: yes

> > Guys,

> > As you know I'm now looking at kart handling, and trying to get my head
> > around that.

> > I think I've come up with a _really_ simple theory. So simple it's scary.
> It
> > _must_ be wrong! :-D

> > Basics:

> > When you turn the front wheels on a kart, the effect is to cause the
> inside
> > rear wheel to lift. You can ONLY adjust the front toe angle, and the front
> > and rear track widths. I am going to leave the toe angle at parallel.

> > Simple geometry says that the closer together the front wheels are, the
> > greater the angle caused, which lifts the rear wheels, and the further
> apart
> > the rear wheels are, the more one will lift. I.e.

> > Front: Wider = LESS lift. Narrower = MORE lift
> > Rear: Wider = more lift. Narrower = less lift.

> > This can also be observed, so it must be right.

> > The next statement I'm going to make is this: (Forgetting about the
> > peculiarities of solid rear axles.)

> > A wider track is better. I can't state exactly why, but ferraris are wider
> > than my golf, F1 teams make the cars as wide as the regs allow, etc. I'm
> > confident this is right, even though I can't prove it ;-)

> > Now, if the inside rear doesn't lift enough, then the kart is going to get
> > understeer. This is because the outside rear won't be turning fast enough,
> > (braking it) and the inside rear will be too fast (accelerating it). The
> > effect will be to pust the front out.

> > If, on the other hand, the inside rear lifts too much, then the outside
> rear
> > will reach a point where it can't grip any more, so it will slide out,
> > causing skipping, and oversteer.

> > So, when trying to setup my kart, surely I should set the front and rear
> > track as wide as possible, then go and drive it. I will get one of 3
> things
> > as a result.

> > 1. The track record!!
> > 2. Understeer.
> > 3. Oversteer.

> > If, then...
> > 1. Leave everything alone! :-D
> > 2. Not enough inside rear lift. Can't widen the rear any more, so narrow
> the
> > front to compensate.
> > 3. Too much rear lift. Can't widen the front, so narrow the rear to
> > compensate.

> > See what I mean? There _must_ be some trade offs or something that I'm
> > missing!

> > Any help will make me very grapefruit!

> > R.


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