Go Back   DIY Go Kart Forum > Announcements & Suggestions > FAQ & Articles

Notices

Reply
 
Thread Tools Display Modes
  #1  
Old 01-05-2020, 09:56 AM
JTSpeedDemon's Avatar
JTSpeedDemon JTSpeedDemon is offline
2019 Build Off Winner!
 
Join Date: Jan 2019
Location: Texas
Posts: 2,973
Thanks: 717
Thanked 425 Times in 391 Posts
Default Racing Lines: A Basic Tutorial

I wrote up a mini article for gegcorp2012 about this a little while ago, and I figured I should post it here in the FAQ where more people will see it.

I DO know what I'm talking about here, so if you want to criticize it, you'd be criticizing Memo Gidley(pro racecar/kart driver), Jeff Grist(kart driver), and my personal applied experience.

Now that that's out of the way, on to the tutorial!

Important terms are in bold.


Firs off I'll lay down a few basic terms regarding racing lines:

Apex: The "peak" of the corner, it is pointed out in the illustration.
Turn in: The portion of the track immediately before the apex, where you begin to go around the turn. You want to be braking on this portion of the corner. This part of the turn is indicated by the red arrow in the first illustration.
Exit: The exact opposite of the turn in, where you leave the apex of the corner. You want to be on the gas on this portion of the corner. This part of the turn is indicated by the orange arrow in the first illustration.


The concept of racing lines is to draw the straightest line possible around the track, thus maximizing traction and minimizing lap times.

Theoretically, the fastest line around a track is to always hug the inside of the track, thus minimizing the distance traveled. But current tires and chassis setups simply are not up to the task, so racing lines are the accepted convention.

To understand some of the content here, it's essential to understand a concept called chassis flex. A racecar has a differential to allow the two rear wheels to go around the corner at different speeds. Race karts have live axles, with no slip to allow that. So to avoid "scrubbing the tires", which kills speed, race kart chassis are designed to flex in a certain controlled way.
The flex allows the inside rear wheel to be lifted up off the track(see the second pic), thus making no tire scrub and maximizing speed through the corner.


The racing line is pretty well represented in the first illustration.

The green line is usually what you want, but there are a few variations I am about to cover.
The dark blue line is the overtaking line, for when you want to overtake someone in a corner. You need to be on the inside of your opponent to do this. There are a few other ways to pass, but I won't bother covering them here.
The cyan line is due to the aforementioned tire scrub. It is for a wet track. Because traction is lessened with a moist track, the kart driver must turn in more aggressively to get the tires to bite and the chassis to flex.


In "esses", with multiple corners leading into one another, one must make use of a compound racing line. You want the exit of the first turn to be very mild, as it is when you set up your turn in for the next turn. Find a happy medium.


This stuff really does work, I was once on identical concession karts with other people, and I passed about 4 or 5 people using nothing but racing lines!

I hope this helps y'all go fast, and happy karting!!
Attached Thumbnails
external-content.duckduckgo.com.png   ChassisFlex.jpg  

__________________
King of Controversy
Reply With Quote
  #2  
Old 01-05-2020, 12:23 PM
itsid's Avatar
itsid itsid is online now
Moderator
 
Join Date: Jul 2013
Location: Ruhrpott [Germany]
Posts: 10,519
Thanks: 1,428
Thanked 4,422 Times in 3,325 Posts
Default

Sorry, but you are generalizing things that cannot and should not be generalized

If you mention road track race karts.. then for the sake of this write-up,
STICK with road track race karts!
and don't wash out the info with yard kart habbits
or dirt track racing (which is a different fruit)

Frankly.. that is a three sentence basic idea,
one of which sentences you clearly misunderstood...
or was explained to you halfheartedly.

Quote:
Originally Posted by JTSpeedDemon View Post
Theoretically, the fastest line around a track is to always hug the inside of the track, thus minimizing the distance traveled.
Not entirely true,
especially on fast double S corners
the inside of any indicidual corner isn't even the shortest distance.
The truth is,
the FASTEST way to get through a corner is a carefully balanced spot
somewhere between the shortest distance and the highest speed.

And it's not even always the same line for each kart.
geared higher the very same kart and driver might want to carry more speed through a corner since the setup lacks a bit of acceleration and thus it should take a wider line..
it might be a hair slower than when geared lower and taking a tighter corner alright, but it has the potential to make use of that speed benefit on the very next stretch (faster top speed)
That's why racers carry several different sprockets to tweak gearing during training on a specific track.
Making the best compromise for the track at hand and their individual style and preference!
(tweaking includes, jetting for weather, gearing and picking the perfect rubber hardness for the track, fuel mix and exhaust length on two strokes.. flex of the chassis etc.etc.etc.)

Quote:
Originally Posted by JTSpeedDemon View Post
The dark blue line is the overtaking line, for when you want to overtake someone in a corner. You need to be on the inside of your opponent to do this. There are a few other ways to pass, but I won't bother covering them here.
If you ever cared enough to just watch a few kart races
(and by that I mean professionals) you certainly know,
that while the inside might be shorter.. it's not always faster..
and overtaking on the outside happens just as frequently as on the inside (okay.. maybe 60:40)
with open wheel racing, you try to not wedge yourself in too often,
that can hurt very quickly... so corner exit is where most battles take place anyways as far as I can tell

Quote:
Originally Posted by JTSpeedDemon View Post
...The cyan line is due to the aforementioned tire scrub. It is for a wet track. Because traction is lessened with a moist track, the kart driver must turn in more aggressively to get the tires to bite and the chassis to flex.
wet track karts are differently setup than dry track karts
(pro racers at least.. hobbyists might not)

most noteworthy and visible rain tyres..
also softer (usually skinnier) axles
crossbar is either removed or at least loosened up,
sometimes set up with different gearing too. (to adjust for the rubber reduction ).

they flex just as good as a dry track kart if done properly
Absolutely no need to get more aggressive in corners.
In fact the opposite is true...
too aggressive cornering on a wet track usually results in a spin out.
thanks to the effective rubber patch being smaller than with slicks
So.. that part is maybe what you think you remember, but you might be mistaking or what was explained to you carelessly!

And don't get me started on concession karts..
I raced my cousin twins.. 5years of weekly kart racing on their backs btw.
They certainly know how to drop a pubertarian jaw when they show up with their high heels and fashion bags just to whip some behinds on the track.. too funny)

on the first race they both could overtake on the outside in every corner no matter what.
on the second race (got a different kart) one suddenly was unable to.
So "all identical karts" is not always true some are just worn out a bit more and my additional buttsize made it very obvious (we talk ~50lbs weight difference)

And no, I'm sure I haven't learned a thing during the first 20laps,
and neither did she forget anything.
I just got a low mileage kart.. she didn't (lucky me!)
(still only came in third )
aaaanyways...

Considering a fixed setup kart... (us being hobbyists)
no regearing no nothing...
MY fastest line through a corner doesn't need to be your fastest line through a corner (our karts not being identical)
So generalization is a double edged blade and while it may be good advice for some it might also be bad advice for others.

I'll leave it at that, but your theory above isn't exactly sound..
the basic concept isn't incorrect, the conclusions you seem to have drawn are

'sid
__________________
Jokes about german sausage are the wurst.
Reply With Quote
The Following User Says Thank You to itsid For This Useful Post:
Kartorbust (01-05-2020)
  #3  
Old 01-05-2020, 04:07 PM
JTSpeedDemon's Avatar
JTSpeedDemon JTSpeedDemon is offline
2019 Build Off Winner!
 
Join Date: Jan 2019
Location: Texas
Posts: 2,973
Thanks: 717
Thanked 425 Times in 391 Posts
Default

I never said that this is for dirt track karts or anything.......
Of COURSE there will be variations!

The cyan "wet" line is explained exactly how it was written by Memo Gidley and Jeff Grist, if you want to debate, feel free to contact them. Same for the dark blue line.
I am simply sharing what I have read from reputable sources and applied.

And what I've written up already is far more specific than other racing line tutorials I've seen. I'm not the only one to generalize this subject. I'm just trying to be helpful. Besides, the title says that it's a basic tutorial.

---------- Post added at 04:07 PM ---------- Previous post was at 03:47 PM ----------

And believe it or not, I have applied these same principles to dirt oval RC racing, and it really made a night and day difference.

I ask: How much experience do YOU have with these things?
__________________
King of Controversy
Reply With Quote
  #4  
Old 01-05-2020, 08:13 PM
itsid's Avatar
itsid itsid is online now
Moderator
 
Join Date: Jul 2013
Location: Ruhrpott [Germany]
Posts: 10,519
Thanks: 1,428
Thanked 4,422 Times in 3,325 Posts
Default

Quote:
Originally Posted by JTSpeedDemon View Post
The cyan "wet" line is explained exactly how it was written by Memo Gidley and Jeff Grist
And not even THAT is true!

you are referring to the book "Karting: Everything You Need to Know"
are you not?
Page 144 if I'm not mistaking..
and that isn't by any of the two it's a quote from Todd McCall
Quote:
Originally Posted by Todd McCall
When racing in the rain,
drivers need to be very aggresive while turning the kart to
ensure the inside rear wheel lifts off the ground.
Finding enough grip is always a challenge when racing in wet conditions.
And the finding enough grip is explained in the flow text
not to quote the entire book I'll try to keep it short..
Quote:
Originally Posted by from the book on page 143/144
The easiest way to think about this is in wet conditions,
drive the track in a completely opposite line from wherever you drive in dry conditions.
As extreme as it may sound, this is a really good place to start.
If you brake on the left side of the track when it's dry, brake on the right when it's wet.
If you apex on the inside of the turn in dry conditions, try to apex on the outside of the turn in wet ones.
If you exit on the outside, try exiting on the inside. In effect what you are doing is crisscrossing the racing line

How much you avoid the dry racing line really depends on how slippery that line is in the wet.
If it's not too slick, you just need to change your line a little.
If it's extremely slick, you need to change your line a lot.
going on in the very next paragraph about wet-prepping the kart

So, you want to debate? learn to concentrate on the things being said in the book you are referring to.
And it helps if you really let it soak in what they say...
While calling an italian restaurant was a good idea for Ferrari back in the days (I even know the reason, do you?),
the rest shows that this book is fairly old, every smartphone has a well working rain radar app available these days.
And while I don't know if chassis prepping and axle swapping is legal in US karting rules (or regional rules) it is for professional races on this side of the pond.
In case you cannot soften the chassis, yes.. an insistent turning of the steering is required.. everything else (especially brakes) are to be handled more carefully however.

And what I really have a problem with is exactly that:
"there is no simple" in racing or finding your ideal line
it all depends on you and the vehicle you're in.
Sure there is a shortest line;
and if you try to follow that you are as likely to come in last as the one taking the longest line on the track.
And finding the fastest line is an artform and cannot be boiled down to
three misinterpreted quotes from a book..
That's why it fills a book in the first place

BTW on dirt tracks you don't have to lift the inner rear, the soil you're on takes care of the slip for you.. you should only avoid excessive drift (looks cool is terribly slow though)

I personally never enjoyed competetive racing too much, no.
it has immense downsides for my wellbeing
Back in the days I had the very same car at my front door as in the NFS racing game on my computer (car editor ..best thing ever!);
an hour or two of gaming and suddenly I went 70mph in the city the next occasion in my real car... I'm somewhat susceptible to those kinds of mistakes.

In the wet I spun out my moms 65k BMW and totaled it (cornering a bit too aggressive) crashed my motorbike about 30 to 40 times in the winter times (cornering just a bit too hasty)
Spend a total of an estimated 20000 km (roughly 12500 miles) on a kart
about 80000 km on a motorbike and at least 120000 km in a car
Short: I'm motorized for almost twice as long as you are alive and I like to be propelled!

I spend a significant time in learning to race-control a vehicle
(from staying on the throttle while braking into corners, to not countersteer when the tail comes swinging by by accident; as a result of the totaled car I felt I could use some additional lessons for the "edge cases", repeated that with the motorbike as the power became significant)

Karting instructor .. never had one myself, only sat with one when my cousins raced listening to him bark into the void of the noisy track;
does that count?

'sid

PS Also Memo crashed badly in a corner in Daytona in 2014, no?
I mean if he wouldn't have been hurt so badly it'd be almost funny taking his cornering advice ... just saying
__________________
Jokes about german sausage are the wurst.
Reply With Quote
The Following User Says Thank You to itsid For This Useful Post:
Kartorbust (01-05-2020)
  #5  
Old 01-05-2020, 08:48 PM
JTSpeedDemon's Avatar
JTSpeedDemon JTSpeedDemon is offline
2019 Build Off Winner!
 
Join Date: Jan 2019
Location: Texas
Posts: 2,973
Thanks: 717
Thanked 425 Times in 391 Posts
Default

Fine then. Go ahead and take this thread down if I'm so wrong! If it's gonna cause this much controversy it might as well be taken down.
__________________
King of Controversy
Reply With Quote
  #6  
Old 01-05-2020, 10:19 PM
itsid's Avatar
itsid itsid is online now
Moderator
 
Join Date: Jul 2013
Location: Ruhrpott [Germany]
Posts: 10,519
Thanks: 1,428
Thanked 4,422 Times in 3,325 Posts
Default

I don't feel the need to take it down tbh..
but I want to make sure that you (as well as the bypassing reader) understands
that none you said is set in stone,
close to nothing about kart racing is really.

There are good theories and bad ones,
seldom occasions where the bad ones become great advice and vice versa,
and absolutely everything in between.
Knowing what's what is a matter of experience and training.

And the reason I'm poking at you is this (as if you didn't know):
Quote:
Originally Posted by JTSpeedDemon View Post
I DO know what I'm talking about here, so if you want to criticize it, you'd be criticizing Memo Gidley(pro racecar/kart driver), Jeff Grist(kart driver), and my personal applied experience.
Since obviously you DO NOT entirely, and more obviously THEY DID NOT put it that way.
So no, you may have misunderstood, misread, or just flew over the pages in a hurry..
nothing wrong with that, but such a bold claim (literally bold!) with what followed afterwards..
needed to be "commented"

The book is a good recommendation,
they do explain WHY you want to (try to) do some things and WHEN.
And that simply cannot be shortened down to just a "do this and you'll be faster!"

'sid
__________________
Jokes about german sausage are the wurst.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 02:47 AM.