Stumbled upon a document that I put together for a school a few years ago. Feel free post up any tips you have.
Traction Circle
At any given point on course, you can only achieve 100% of the total available traction of any tire on the
vehicle. A tire’s grip is used in turning, acceleration, and braking. If you are braking at 100% of the tire’s
capability, the car will not turn very well. If you are using 100% of the tire’s capability to turn, then you
will not be able to accelerate.
Using precisely 100% of a tire’s total capability at any given time is nearly impossible on an autocross
course. However, you will often see many drivers use 110% or more of the tires capability, as evidenced
by painful-looking understeer, or high-horsepower rear-wheel-drive cars that just can’t seem to keep
the rear behind them.
Driving your car with the traction circle in mind should prevent you from making the most common
mistakes (overdriving the car into turns, using too much throttle) and going slower. However, as you
become a more advanced driver, the traction circle is not necessarily the best way to think about
negotiating an autocross course in the quickest fashion. A fast autocrosser in a fast autocross car is
constantly (and intentionally) losing and regaining grip, especially in transitional elements like slaloms.
This is something that takes plenty of seat time and car tuning to do correctly.
The Autocrossing Tips Thread
The Autocrossing Tips Thread
Chris Harp
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
Re: The Autocrossing Tips Thread
Important Autocross Tips by Andy Hollis
Position first, then speed. Positioning the car perfectly is more important than trying to attain the
highest potential speed. For example, you will drop more time by correctly positioning the car nearer to
slalom cones than you will by adding 1 or 2 MPH in speed. Same with sweepers (tight line). Same with
90-degree turns (use all of the track). Also, position is a prerequisite for speed. If you are not in the
correct place, you will not be able go faster. Or at least not for very long!
Turn earlier…and less. To go faster, the arc you are running must be bigger. A bigger arc requires less
steering. To make a bigger arc that is centered in the same place, the arc must start sooner (turn
earlier).
Brake earlier…and less. Waiting until the last possible second approaching a turn and then dropping
anchor at precisely the correct place so that the desired entry speed is reached exactly as you come to
the turn-in point is quite difficult to execute consistently. Especially when you consider that you get no
practice runs on the course, and the surface changes on every run, and you aren’t likely to be in exactly
the same position with the same approach speed on every run, etc. Better to start braking a little earlier
to give some margin of error. And by braking less you can either add or subtract braking effort as you
close in on the turn-in point. This will make you consistent and smooth.
Lift early instead of braking later. Continuing with the philosophy of #3, when you need to reduce
speed only a moderate amount, try an early lift of the throttle instead of a later push of the brake. This
is less upsetting to the car, is easier to do and thus more consistent, and allows for more precise
placement entering the maneuver (remember #1 above).
It is easier to add speed in a turn than to get rid of it. If you are under the limit, a slight push of the
right foot will get you more speed with no additional side effects. On the other hand, if you are too fast
and the tires have begun slipping, you can only reduce throttle and wait until the tires turn enough of
that excess energy into smoke and heat. Don’t use your tires as brakes!
Use your right foot to modulate car position in constant radius turns, not the steering wheel. In a
steady state turn, once you have established the correct steering input to maintain that arc, lifting the
throttle slightly will let the car tuck in closer to the inside cones. Conversely, slightly increasing the
throttle will push the car out a bit farther to avoid inside cones. It is much easier to make small
corrections in position with slight variations in the tires’ slip angle (that’s what you are doing with the
throttle) than with the steering wheel.
Unwind the wheel, then add power. If the car is using all of the tire’s tractive capacity to corner, there
is none left for additional acceleration. At corner exit, as you unwind the wheel, you make some
available. If you do not unwind the wheel, the tire will start to slide and the car will push out (see #6
above).
Attack the back. For slaloms (also applicable to most offsets), getting close to the cones is critical for
quick times (see #1). To get close, we must move the car less, which means bigger arcs. Bigger arcs come
from less steering and require earlier turning (see #2). Now for the fun part… When you go by a slalom
cone and start turning the steering wheel back the other way, when does the car start to actually
change direction? Answer: When the wheel crosses the center point (Not when you first start turning
back!) How long does that take? If you are smooth, it takes .25 - .5 seconds. Now, how long is a typical
person’s reaction time? Answer: about .5 seconds. Finally, how long does it take to go between slalom
cones? Answer: Typically on the order of 1 second. Given all of that, your brain must make the decision
to begin turning the steering wheel back the other way just *before* you go by the previous cone!!
Since this is a mental issue, a good visualization technique to get used to this is to think about trying to
run over the back side of each slalom cone with the inside rear tire of the car. To hit it with the rear tire
(and not the front), the car must be arcing well before the cone and the arc must be shallow. Attack the
back!
Hands follow the eyes, car follows the hands. Look where you want the car to go and your hands and
feet will take you there.
Scan ahead, don’t stare. Keep the eyes moving. Looking ahead does not mean staring ahead. Your eyes
must be constantly moving forward and back, and sometimes left and right. Glance forward, glance
back. Your brain can only operate on the information you give it.
Don’t forget the stuff in between the marked maneuvers! Too often we think of a course as series of
discrete maneuvers. There is typically more to be gained or lost in the areas that are in between. Pay
special attention to the places where there are no cones
Position first, then speed. Positioning the car perfectly is more important than trying to attain the
highest potential speed. For example, you will drop more time by correctly positioning the car nearer to
slalom cones than you will by adding 1 or 2 MPH in speed. Same with sweepers (tight line). Same with
90-degree turns (use all of the track). Also, position is a prerequisite for speed. If you are not in the
correct place, you will not be able go faster. Or at least not for very long!
Turn earlier…and less. To go faster, the arc you are running must be bigger. A bigger arc requires less
steering. To make a bigger arc that is centered in the same place, the arc must start sooner (turn
earlier).
Brake earlier…and less. Waiting until the last possible second approaching a turn and then dropping
anchor at precisely the correct place so that the desired entry speed is reached exactly as you come to
the turn-in point is quite difficult to execute consistently. Especially when you consider that you get no
practice runs on the course, and the surface changes on every run, and you aren’t likely to be in exactly
the same position with the same approach speed on every run, etc. Better to start braking a little earlier
to give some margin of error. And by braking less you can either add or subtract braking effort as you
close in on the turn-in point. This will make you consistent and smooth.
Lift early instead of braking later. Continuing with the philosophy of #3, when you need to reduce
speed only a moderate amount, try an early lift of the throttle instead of a later push of the brake. This
is less upsetting to the car, is easier to do and thus more consistent, and allows for more precise
placement entering the maneuver (remember #1 above).
It is easier to add speed in a turn than to get rid of it. If you are under the limit, a slight push of the
right foot will get you more speed with no additional side effects. On the other hand, if you are too fast
and the tires have begun slipping, you can only reduce throttle and wait until the tires turn enough of
that excess energy into smoke and heat. Don’t use your tires as brakes!
Use your right foot to modulate car position in constant radius turns, not the steering wheel. In a
steady state turn, once you have established the correct steering input to maintain that arc, lifting the
throttle slightly will let the car tuck in closer to the inside cones. Conversely, slightly increasing the
throttle will push the car out a bit farther to avoid inside cones. It is much easier to make small
corrections in position with slight variations in the tires’ slip angle (that’s what you are doing with the
throttle) than with the steering wheel.
Unwind the wheel, then add power. If the car is using all of the tire’s tractive capacity to corner, there
is none left for additional acceleration. At corner exit, as you unwind the wheel, you make some
available. If you do not unwind the wheel, the tire will start to slide and the car will push out (see #6
above).
Attack the back. For slaloms (also applicable to most offsets), getting close to the cones is critical for
quick times (see #1). To get close, we must move the car less, which means bigger arcs. Bigger arcs come
from less steering and require earlier turning (see #2). Now for the fun part… When you go by a slalom
cone and start turning the steering wheel back the other way, when does the car start to actually
change direction? Answer: When the wheel crosses the center point (Not when you first start turning
back!) How long does that take? If you are smooth, it takes .25 - .5 seconds. Now, how long is a typical
person’s reaction time? Answer: about .5 seconds. Finally, how long does it take to go between slalom
cones? Answer: Typically on the order of 1 second. Given all of that, your brain must make the decision
to begin turning the steering wheel back the other way just *before* you go by the previous cone!!
Since this is a mental issue, a good visualization technique to get used to this is to think about trying to
run over the back side of each slalom cone with the inside rear tire of the car. To hit it with the rear tire
(and not the front), the car must be arcing well before the cone and the arc must be shallow. Attack the
back!
Hands follow the eyes, car follows the hands. Look where you want the car to go and your hands and
feet will take you there.
Scan ahead, don’t stare. Keep the eyes moving. Looking ahead does not mean staring ahead. Your eyes
must be constantly moving forward and back, and sometimes left and right. Glance forward, glance
back. Your brain can only operate on the information you give it.
Don’t forget the stuff in between the marked maneuvers! Too often we think of a course as series of
discrete maneuvers. There is typically more to be gained or lost in the areas that are in between. Pay
special attention to the places where there are no cones
Chris Harp
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
Re: The Autocrossing Tips Thread
The Mental Aspect of Autocross by Chris Harp
Being one of the fast folks at an autocross, especially on the National Level, takes a lot of seat time, car
preparation, and dedication. But there is one aspect of autocrossing effectively that needs to be
practiced, but is often overlooked – the mental aspect.
Before you even make your first run, we often begin to impose limits on ourselves without even
knowing it. How many times have you said to yourself “I could beat that guy if….”? With thoughts like
this, you are already admitting defeat.
Preparation
Before you can really begin to focus on the mental aspect of autocross and transcend those selfimposed
limits that you’ve created, you have to be prepared. Put yourself in the best position possible.
Being “prepared” for the even doesn’t mean having the most expensive shocks, the lightest wheels, or
the stickiest tires (although all of this helps). Preparation means that everything you do related to the
participating in the autocross is done the best way you know how to do it.
Perhaps the most important part of preparing is walking the course. Do this several times, and without
distraction. While walking, make a plan for driving the course. Take notes if you need to. Try to
emphasize the areas of the course that will allow you to be on throttle for the longest period of time and
try to make them count. I’ve included some basic course walking tips in the following pages.
With this said, you must understand that your plan needs to be flexible. If you execute your plan
perfectly, but the plan is incorrect, then you have gained nothing. Pushing the limits of yourself and the
car will always be more important than sticking to your plan perfectly.
Execution
All of the preparation that you have applied to the car is already done when you pull up to the starter
for your run – there’s nothing you can change about it until later, so don’t think about it. There will be a
time to reflect on your car setup, the run that you are about to make, or mistakes made on previous
runs - but that time is not now.
Don’t think about the result. Focus on executing your plan and driving the elements of the course
correctly.
“The great mistake is to anticipate the outcome of the engagement; you ought not to be
thinking of whether it ends in victory or in defeat. Let nature take its course, and your tools will
strike at the right moment..” –Bruce Lee
Confidence
Once you have learned to prepare and execute effectively, you will build confidence in what you are
doing. Confidence will exponentially increase the effectiveness of your preparation and execution
Being one of the fast folks at an autocross, especially on the National Level, takes a lot of seat time, car
preparation, and dedication. But there is one aspect of autocrossing effectively that needs to be
practiced, but is often overlooked – the mental aspect.
Before you even make your first run, we often begin to impose limits on ourselves without even
knowing it. How many times have you said to yourself “I could beat that guy if….”? With thoughts like
this, you are already admitting defeat.
Preparation
Before you can really begin to focus on the mental aspect of autocross and transcend those selfimposed
limits that you’ve created, you have to be prepared. Put yourself in the best position possible.
Being “prepared” for the even doesn’t mean having the most expensive shocks, the lightest wheels, or
the stickiest tires (although all of this helps). Preparation means that everything you do related to the
participating in the autocross is done the best way you know how to do it.
Perhaps the most important part of preparing is walking the course. Do this several times, and without
distraction. While walking, make a plan for driving the course. Take notes if you need to. Try to
emphasize the areas of the course that will allow you to be on throttle for the longest period of time and
try to make them count. I’ve included some basic course walking tips in the following pages.
With this said, you must understand that your plan needs to be flexible. If you execute your plan
perfectly, but the plan is incorrect, then you have gained nothing. Pushing the limits of yourself and the
car will always be more important than sticking to your plan perfectly.
Execution
All of the preparation that you have applied to the car is already done when you pull up to the starter
for your run – there’s nothing you can change about it until later, so don’t think about it. There will be a
time to reflect on your car setup, the run that you are about to make, or mistakes made on previous
runs - but that time is not now.
Don’t think about the result. Focus on executing your plan and driving the elements of the course
correctly.
“The great mistake is to anticipate the outcome of the engagement; you ought not to be
thinking of whether it ends in victory or in defeat. Let nature take its course, and your tools will
strike at the right moment..” –Bruce Lee
Confidence
Once you have learned to prepare and execute effectively, you will build confidence in what you are
doing. Confidence will exponentially increase the effectiveness of your preparation and execution
Chris Harp
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
Re: The Autocrossing Tips Thread
Course Walking Tips from The SOLO Novice handbook
"You must be able to keep track of the course in your head. If you can't, then you can't drive it to its
fullest potential" --Josh Sirota
That quote is worth five seconds to a novice. Knowing how to walk the course is the most important
step in being competitive and staying "ahead" of the course. Usually, you'll want to walk the course at
least three times.
Walk the course. Your first walk will be to get the general layout, and is often a social walk. Now get
away from friends and walk the course alone, concentrating on memorizing the layout. Think of it in
sections, with key cones marking the turns, such as:
start straight
slalom (enter on right)
decreasing sweeper to the left
"little snake" then "big snake"
right-hand curve (look for three pointers)
"thread the needle section"
tight right, then tight left
finish
Stop every now and then and run through the course in your head, from the beginning to where you are
now. Get down - the course looks different from a seated position. This will give you a better picture of
what the course will look like at speed.
Pace off the distance between cones in a slalom. Some course designers vary the distance, and it's good
to know before you arrive whether you will have to vary your speed in a slalom. Take a note-pad if you
like, and make notes such as pavement changes, camber change, bumps, sand, etc.
Make a mental note to yourself (or write it down) as to how far ahead you will be looking. When I walk
the course, I say to myself, "OK, when I am here I will be looking there" This will help you to remember
to look ahead while you are driving.
"Repeat this step over and over until the picture is perfect."
--Andy Hollis - Four-time Pro Solo and Solo II National Champ
How do you know if the picture is perfect? Sit down by your car and try to draw the course on a blank
piece of paper. Include the key cones you want to recognize while you drive. If you can't draw the
course, you will want to walk it again. Once you leave the start line in your car, you should not be
spending any time figuring out where the course is.
Plan the course. (Do this while walking the course again) Now decide exactly how you want to drive the
course. Driving the course perfectly involves two things; coming up with the correct plan, and executing
the plan correctly. If you don't have a plan, you can't possibly know where you didn't execute it
correctly. It's hard to know if you did this step correctly, but step 4 is something you can work on.
The plan involves the line you will take through the cones - the quickest way through. Note, I didn't say
shortest. Think about the characteristics of your car; does it corner better than it accelerates, or the
other way around? That will tell you whether to slow down so you can get through the corner in control
and get on the throttle as soon as possible, or try to carry speed through to keep up the revs.
Don't forget to plan where you will be looking. There is no need to memorize every cone on the course,
only the ones you plan to be near, the "key cones”. Look from one key cone to the next in your plan.
In Grid. Before you run, while you are in grid, go over the course again several times in your head,
executing the plan you made before.
After the run. Sit in your car and go over your run. Figure out where you didn't execute the plan. If the
plan was to be near a particular cone, and you were five feet from it, then you didn't execute the plan
correctly, and a red light should have gone off in your head. Maybe you need to adjust the plan because
you were going too fast in the slow parts. Decide at this point whether your next run needs to be a
better execution of the plan, or a modification of the plan.
Basically, don't use the car as an excuse, you will see a big difference in your times when you drive a
course that never surprised you.
"You must be able to keep track of the course in your head. If you can't, then you can't drive it to its
fullest potential" --Josh Sirota
That quote is worth five seconds to a novice. Knowing how to walk the course is the most important
step in being competitive and staying "ahead" of the course. Usually, you'll want to walk the course at
least three times.
Walk the course. Your first walk will be to get the general layout, and is often a social walk. Now get
away from friends and walk the course alone, concentrating on memorizing the layout. Think of it in
sections, with key cones marking the turns, such as:
start straight
slalom (enter on right)
decreasing sweeper to the left
"little snake" then "big snake"
right-hand curve (look for three pointers)
"thread the needle section"
tight right, then tight left
finish
Stop every now and then and run through the course in your head, from the beginning to where you are
now. Get down - the course looks different from a seated position. This will give you a better picture of
what the course will look like at speed.
Pace off the distance between cones in a slalom. Some course designers vary the distance, and it's good
to know before you arrive whether you will have to vary your speed in a slalom. Take a note-pad if you
like, and make notes such as pavement changes, camber change, bumps, sand, etc.
Make a mental note to yourself (or write it down) as to how far ahead you will be looking. When I walk
the course, I say to myself, "OK, when I am here I will be looking there" This will help you to remember
to look ahead while you are driving.
"Repeat this step over and over until the picture is perfect."
--Andy Hollis - Four-time Pro Solo and Solo II National Champ
How do you know if the picture is perfect? Sit down by your car and try to draw the course on a blank
piece of paper. Include the key cones you want to recognize while you drive. If you can't draw the
course, you will want to walk it again. Once you leave the start line in your car, you should not be
spending any time figuring out where the course is.
Plan the course. (Do this while walking the course again) Now decide exactly how you want to drive the
course. Driving the course perfectly involves two things; coming up with the correct plan, and executing
the plan correctly. If you don't have a plan, you can't possibly know where you didn't execute it
correctly. It's hard to know if you did this step correctly, but step 4 is something you can work on.
The plan involves the line you will take through the cones - the quickest way through. Note, I didn't say
shortest. Think about the characteristics of your car; does it corner better than it accelerates, or the
other way around? That will tell you whether to slow down so you can get through the corner in control
and get on the throttle as soon as possible, or try to carry speed through to keep up the revs.
Don't forget to plan where you will be looking. There is no need to memorize every cone on the course,
only the ones you plan to be near, the "key cones”. Look from one key cone to the next in your plan.
In Grid. Before you run, while you are in grid, go over the course again several times in your head,
executing the plan you made before.
After the run. Sit in your car and go over your run. Figure out where you didn't execute the plan. If the
plan was to be near a particular cone, and you were five feet from it, then you didn't execute the plan
correctly, and a red light should have gone off in your head. Maybe you need to adjust the plan because
you were going too fast in the slow parts. Decide at this point whether your next run needs to be a
better execution of the plan, or a modification of the plan.
Basically, don't use the car as an excuse, you will see a big difference in your times when you drive a
course that never surprised you.
Chris Harp
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
-
dewittpayne
- Posts: 1503
- Joined: Wed Nov 02, 2011 4:19 pm
- Location: Kingsport, TN
Re: The Autocrossing Tips Thread
On Attack the Back: When a car is turning, the rear wheels track inside the front. If you almost hit a cone in a turn with the front tire, the rear tire will run over it. There are exceptions to this, one being if the rear tire slip angles being higher than the front. But that's probably not going to happen with a front engine car and certainly not with a front wheel drive car.
One can also make the argument that driving at the limit should come first and correct line second. That's at the limit, not past it. For some types of turns, you can't even take the correct line unless you're driving close to the limit, i.e. at high tire slip angle. But not everyone agrees. Still, if you've never spun, you probably aren't trying hard enough.
One can also make the argument that driving at the limit should come first and correct line second. That's at the limit, not past it. For some types of turns, you can't even take the correct line unless you're driving close to the limit, i.e. at high tire slip angle. But not everyone agrees. Still, if you've never spun, you probably aren't trying hard enough.
DeWitt Payne
2011 Mustang GT CAM-C
"Tires are meant to die young." Heyward Wagner
2011 Mustang GT CAM-C
"Tires are meant to die young." Heyward Wagner
-
John Brown
- Posts: 8798
- Joined: Fri Dec 05, 2003 11:05 am
Re: The Autocrossing Tips Thread
dewittpayne wrote:On Attack the Back: When a car is turning, the rear wheels track inside the front. If you almost hit a cone in a turn with the front tire, the rear tire will run over it. There are exceptions to this, one being if the rear tire slip angles being higher than the front. But that's probably not going to happen with a front engine car and certainly not with a front wheel drive car.
..is this from an article? or what?
ETR Pro Class Champion-2002-03-10-11-12-13-14-15
BMW/CCA D-Mod National Road Racing Champion-2011
Pro-Solo Prepared National Champ-2004
Pro-Solo Prepared National Champ-2005
2016 Dodge Challenger SRT 6.4L CAM-C
BMW/CCA D-Mod National Road Racing Champion-2011
Pro-Solo Prepared National Champ-2004
Pro-Solo Prepared National Champ-2005
2016 Dodge Challenger SRT 6.4L CAM-C
Re: The Autocrossing Tips Thread
Yeah. Generally when this happens to me, it is a result of me not turning the wheel enough and not attacking the back.John Brown wrote:dewittpayne wrote:On Attack the Back: When a car is turning, the rear wheels track inside the front. If you almost hit a cone in a turn with the front tire, the rear tire will run over it. There are exceptions to this, one being if the rear tire slip angles being higher than the front. But that's probably not going to happen with a front engine car and certainly not with a front wheel drive car.
..is this from an article? or what?
'16 FRS - PSTX 97
-
dewittpayne
- Posts: 1503
- Joined: Wed Nov 02, 2011 4:19 pm
- Location: Kingsport, TN
Re: The Autocrossing Tips Thread
JB,
It's simple geometry. The extreme example is a tractor/trailer. In a right turn from the inside lane of a four lane highway to a two lane road, the tractor will use the wrong lane of the two lane road and the right side wheels on the trailer will still likely run over the curb on the right. That's why they have the 'wide right turns' sign on the back of the trailer. But it's also true for cars. See these images from this article:http://what-when-how.com/forensic-scien ... asurement/
Note that in this case every tire leaves a separate track.
It's simple geometry. The extreme example is a tractor/trailer. In a right turn from the inside lane of a four lane highway to a two lane road, the tractor will use the wrong lane of the two lane road and the right side wheels on the trailer will still likely run over the curb on the right. That's why they have the 'wide right turns' sign on the back of the trailer. But it's also true for cars. See these images from this article:http://what-when-how.com/forensic-scien ... asurement/
Note that in this case every tire leaves a separate track.
DeWitt Payne
2011 Mustang GT CAM-C
"Tires are meant to die young." Heyward Wagner
2011 Mustang GT CAM-C
"Tires are meant to die young." Heyward Wagner
Re: The Autocrossing Tips Thread
Good, you should pin this thread and put a link on the web site.
Old men can still dream!
Scott Gibson
Scott Gibson
-
John Brown
- Posts: 8798
- Joined: Fri Dec 05, 2003 11:05 am
Re: The Autocrossing Tips Thread
If my car ever tracks like any of those diagrams on course or the race track... Ill be waaay down there at the bottom of the time sheets taking up last place.. lol
ETR Pro Class Champion-2002-03-10-11-12-13-14-15
BMW/CCA D-Mod National Road Racing Champion-2011
Pro-Solo Prepared National Champ-2004
Pro-Solo Prepared National Champ-2005
2016 Dodge Challenger SRT 6.4L CAM-C
BMW/CCA D-Mod National Road Racing Champion-2011
Pro-Solo Prepared National Champ-2004
Pro-Solo Prepared National Champ-2005
2016 Dodge Challenger SRT 6.4L CAM-C
Re: The Autocrossing Tips Thread
X2John Brown wrote:If my car ever tracks like any of those diagrams on course or the race track... Ill be waaay down there at the bottom of the time sheets taking up last place.. lol
Ted V.
don't make me list all my VW's
don't make me list all my VW's
Re: The Autocrossing Tips Thread
There's a webinar tomorrow that you might find useful
Learn to Autocross, FASTER!
https://www.motorsportreg.com/events/fr ... SwXRPnF8n4
Learn to Autocross, FASTER!
https://www.motorsportreg.com/events/fr ... SwXRPnF8n4
Chris Harp
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
Re: The Autocrossing Tips Thread
This might be accurate if the tire is never breaking traction. But while autocrossing, you're going to have all kinds of slipping going on in the rear....or at least you should!dewittpayne wrote:JB,
It's simple geometry. The extreme example is a tractor/trailer. In a right turn from the inside lane of a four lane highway to a two lane road, the tractor will use the wrong lane of the two lane road and the right side wheels on the trailer will still likely run over the curb on the right. That's why they have the 'wide right turns' sign on the back of the trailer. But it's also true for cars. See these images from this article:http://what-when-how.com/forensic-scien ... asurement/
Note that in this case every tire leaves a separate track.
If you're just driving in a circle at low speed and the rear is following the front, then yes. But at speed this should almost never be the case.
In fact, if you look at a lot of pictures of autocross cars with good drivers behind the wheel, you'll often see shots where you think - wow, he must have plowed that cone with the front - when in fact, they didn't.
There is another universal rule here that applies to every car despite their tendency to understeer/oversteer The more throttle you add, the wider the arc of travel, the less throttle, the narrower the arc.
Chris Harp
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3
2009 Mazda RX-8 | 2018 Toyota Tundra | 2011 BMW M3