How to Set-Up Your Track Car & Become a Driving Legend
Just bought yourself a nice powerful car
for some track day action or invested in a race car? Whether it's a single seater or
saloon car you're going to need to know how to 'set it up' to get the most out of it. A well driven and well set up car has the potential to run rings around much more expensive, powerful and exotic machinery and will make you look like a driving god in the process!
The article below is courtesy of Sheane Cars in Co Wicklow, chances are you haven't heard of them but they have been designing and manufacturing race and championship winning single seater racing cars for over 30 years. They currently run the fastest one-make single seater championship in Ireland - Formula Sheane. So they know a thing or 2 about setup!
This simple, beginners guide will walk you through most of the basics of car set-up and will also touch on driving technique. It's designed to get you thinking in the right way and asking the right questions more than an outright technical 'How To' guide.
A Beginners Guide To Car Set-Up.
'Set-up' means adjusting all the variables on the car to
make it go around the track as fast as it can. It means getting the car to
'feel' right for the driver and making it behave properly around the corners. Car
setup is part science, part art, part luck. The really annoying bit of it is
the amount of variables in play make it very difficult, if not impossible to
define exactly what is the solution to any particular handling problem.
You’re trying to balance driving technique, damper rates, spring rates, camber
angles, caster angles, toe angles, Ackerman (or anti-Ackerman) angles,
anti-roll bar rates, brake balance, roll-centre position and height, king-pin
inclination, tyre pressures and innumerable other variables to find a handling
package that works. Each of them is interconnected with the others and changing
one has an impact on the others.
At this point many people give up and go for the Jeremy Clarkson approach of “POWER!” Don’t despair. There are a few principles that can make life much
easier. The first thing you need to be clear on is what you are trying to make
a car do. If your car over-steers horribly in the pit-lane, who cares? It is
not going to affect your lap time. Drivers regularly try to find a set-up that
feels great in every corner. In reality that is as unnecessary as it is
difficult. The first thing you must do when setting up a race car is figure out
which corners are most important. Here’s the priority list:
- A medium to fast corner leading onto a
long straight.
- A slow corner leading to a fast straight.
- A medium to fast corner leading to a
short straight.
- A slow corner leading to a short
straight.
Why this order? Well, your exit speed out of a corner is
like saving money; the more you have at the start and the longer you can save
it the richer you’ll be. Same with racing; a fast exit onto a long straight
gives you a long time to build your speed. It doesn’t matter as much if you
come out of a corner like a rocket and almost immediately have to hit the
brakes for another corner; you’ve had very little time to let your investment
grow. So the most important part of any circuit is fast corners exiting onto
long straights. If you carry a high exit speed onto the straight, you make
bigger and bigger speed gains all the way to the next corner.
So why are slow corners leading to long straights not so
important? Primarily because there’s less opportunity to make gains in a
slow corner. A 5% difference in speed through a 100mph corner means a 5mph
difference. A 5% difference in a 30 mph corner means a difference of less than
2mph. Also, there’s less handling required in a ‘point-and-squirt’ corner than
in a fast sweeping one.
Medium-to-fast corners leading to short straights give
gains for less time; you have no long straight to build speed so your gain
through the corner cannot be built as much. But you can still squeeze out some
time if you can carry speed through the corner.
Lastly you have slow corners onto short straights. Any
gain made in the corner is small because it’s slow (even if you drive it like
Senna) and you have no straight to build on the gain. Think of your driveway,
you don’t go flat out at the start of it because you know you are going to have
to slow down at the end of it to pull out onto the road.
What this means for the driver is after each test session
you should assess the car’s behaviour in each corner according to priority.
Take Mondello (National Circuit) as an example:
1) How well is the
car coming out of the turn 2? (Fast corner leading to long straight)
2) How well is the
car coming out of the turn 6? (Medium corner leading to long straight)
3) How well is the
car handling in turn 3? (Medium corner leading to short straight)
4) How well is the
car handling in turn 4 and 5? (Slow corner leading to short straight)
If your car handles perfectly through the turns 2, 6, and 3
but is a dog through 4 and 5, be happy. The losses through 4 and 5 will be
vastly outweighed by the gains round the rest of the circuit.
This is why you see mechanics despair when a driver gets out of a race car and
says ‘it’s over-steering’. It’s the equivalent of going to a doctor and saying
‘I’m sick, you figure it out, I’m off to the pub.’ The least you can do is tell
the mechanic where it’s over-steering and where it’s not.
The next thing is to narrow the geography even more. And
that means breaking each corner into phases for further diagnosis. Each corner
can be broken into a number of phases. Different drivers, engineers and
telemetry systems do this different ways, but let’s take a simple, repeatable
method:
Each corner can be broken into three sections:
1) Corner entry
2) Transition
3) Corner exit
Let’s look at what
happens in each one:
Corner entry
This is the part of the corner from brake-point until apex.
When you hit the brakes the rear tyres lighten and the front tyres gain
download as the weight transfers to the front. This happens regardless of what
settings you have on springs and dampers. Even if you make your suspension out
of solid box-section, you still get weight transfer when you hit the brakes. As
you begin to turn in (you may or may not still be on the brakes) the weight
begins its transfer from inside to outside as the lateral g-loading increases.
Transition
This is the point at which the car ‘takes its set’. This is
an easy way to put something that is a complex interrelation of slip angles and
weight transfer. It is basically the point at which the car assumes the
attitude it will remain at until the exit phase starts. The transition phase is
when the driver is not adding any more turning to the steering wheel and
(usually) is transitioning from brakes to throttle. At this point the car will
be at maximum lateral g and will be transferring weight from front to back as
the brakes are released and the throttle applied.
Corner exit
This is the phase where the driver will move to full
throttle and start to unwind the wheel (ideally at the same time). At this
point the final weight transfer to the rear is completed as full throttle is
reached. The reason it’s important to analyse corners in these phases is
because you’ll find totally different things causing similar car behaviour in
each of the phases. Let’s take it from the engineer’s perspective; you’re
waiting in the garage as the driver comes in. He gets out of the car and tells
you the car ‘has too much over-steer’. That’s essentially useless unless he can
understand where and thereby why...
If it is corner-entry over-steer, the cause could be brake
balance or poor gear-shifting. If it is transition over-steer it could be
overly hard dampers, bump-steer, roll-bars, spring rates or a simple ‘pop-off’
the brakes by the driver. If it is corner-exit over-steer it could be
over-heavy spring rates or roll-bars or a leaden right foot.
So if you’re the engineer any changes you make will be as likely to make things
worse as better if you don’t know where the car is doing what it is doing.
All of this looks very daunting and complicated if you don’t
know one end of a spanner from the other, but it isn’t that tricky. A lot of
variables are taken out of the equation if you get Sheane Cars in Co. Wicklow
to do a basic set-up on the car. They’ll set camber, caster, toe, Ackermann,
bump-steer, roll-centres and spring rates. That leaves the less
mechanically-minded driver to play with dampers, roll-bars and brake balance.
And here’s how…
When you get to the circuit to set up a new car, the first
thing you want to do is get a baseline set-up. Here are the steps…
1) Set the roll-bars to full soft.
2) Set
the dampers to full soft.
3) Set the brake balance to the centre.
Go out and drive the car. It should feel horrible, like a
pogo-stick. It is worth doing this to familiarise yourself with how an
under-damped car feels. (This knowledge will come in handy the first time you
blow-out a damper and spend weeks chasing the handling problem because you
don’t know what a blown damper feels like).
Come in and set the dampers to full hard. Then go back out.
The car should feel like a brick. You should notice wheel patter. The tyres
should skip over any significant bumps and you are likely to get the wheels
‘skipping’ over the surface under braking. (On cars with separate rebound
damping the car will jack-down when the damping is too hard, not usually a
problem on cars with combined bump and rebound. If you don’t know what bump and
re-bound are, don’t worry about it, its way too much effort to explain and it
doesn’t apply to most cars). You will get away with harder damping on smoother
surfaces.
Now you know what full-hard and full-soft feels like. Now
you’re going to find a middle-distance. Take the shocks about four clicks
softer all-round (write down any changes you make) and drive it again. You’re
looking for the point where you no longer get wheel patter over bumps or
skipping under braking. (You should also notice it putting down its power
better with less wheel-spin). Once the wheel patter stops, it is soft enough.
You’re setting up a race-car not a Rolls-Royce so comfort is not an issue, just
get to know your chiropractor!
Now you can set the brake balance.
Pick a long straight where you do most of your braking in a
straight line (not when you’re doing a tip-toe trail brake all the way to the
apex). When you apply the brakes, keep squeezing them until a wheel locks up.
(As soon as it does, come back out of the brakes or you’ll be investing in a
new set of tyres). Do not jump on the brakes. A ‘panic’ or snatch brake will
almost always lock the front tyres because the snatch causes the wheel to lock
before enough weight has downloaded onto the front tyre to get full braking
performance out of it. This will teach you nothing. You get on the brakes fast,
but smoothly, squeezing up to the lock-up. Not going at the pedal like a bull.
You then take note of which wheel locks up. If it is a front
wheel it is easy to diagnose; you see it happen. If it is a rear you diagnose
it two ways; first you can see it in the mirror (tricky to do, because the last
thing you want to be doing is gazing in the mirror at 120MPH) second, you’ll
feel the back of the car get ‘skittish’; snapping erratically from side to
side.
When you have diagnosed which end is locking up first,
change the brake balance until the front locks up just before the rear. Having
the rear lock up first is a good way to introduce yourself to a Marshall, by
way of a gravel trap!
Now you have a car that will ride over the surface properly
and will stop properly. Now you can make it handle.
As we’ve said before, there is a very complex series of
interrelationships happening with race-car/track day-car suspension, so in some
instances things that really should do one thing end up doing another and
improvements make things worse. But we’ll ignore all that. Call Sheane Cars if
you want to discuss the nuances of suspension geometry. This is the quick and
dirty version.
Before you take on the onerous task of setting up a car, a
few words on how roll bars and dampers work. Dampers live their lives for two
purposes; first to stop your wheels jumping around like happy poodles, second
to control the speed at which your car transfers from weight from front to back
and side to side.
We’ve already looked at the first; now let’s look at the
second.
The stiffer your dampers are, the faster the weight will
transfer when you brake, accelerate and turn.
At this point you will say ‘no’ ‘it’s a misprint’ ‘how
can that be?’ ‘that’s backwards’.
No it’s not.
Soft dampers allow weight to transfer slowly. Stiff dampers
allow weight to transfer quickly. Don’t believe us? Buy a book. (Or call Sheane
Cars and annoy us in person).
Let’s be clear; the same weight transfer will occur
regardless of your damper settings. Even if you throw them away and just use
bare springs the weight transfer will happen. Even if you take the springs out
and replace them with box-section, the weight transfer will happen. All dampers
can do is control the speed at which it happens. And, once again; the stiffer they
are, the faster it happens.
Now, let’s look at
their partners in crime; the anti-roll bars.
Anti-roll bars control where the transferred weight goes.
Let’s imagine your car has no front anti-roll bar and a rear anti-roll bar made
from inch thick Titanium bar. When your car turns into a corner it is going to
transfer weight from the inside to the outside. The titanium girder is going to
resist that transfer. In doing so, it is going to put all the weight onto the
outside rear tyre. That tyre is a) going to hate you, and b) it is very quickly
going to have more force applied to it than it has grip to cling on and it is
going to slide and you will have an over-steering car. (You’re also going to
have a disproportionately light inside rear tyre, but that gets very technical
and needs a calculator, so let’s ignore it. It doesn’t matter much anyway if
the relationship between anti-roll bars and springs is well planned. Remember
when we said everything is connected earlier?? You need to take into account
what your upgrade will affect on the other areas on the car; simply upgrading
something like your springs is not going to make a huge difference if the roll
bar is too soft or too hard. Sure it might feel quicker but you’re not getting
the full potential out of your springs (and more to the point your money!).
Now let’s say you unbolt the titanium girder and attach it
to the front. Now all the weight will be transferred onto the outside front
tyre and it will get quickly overwhelmed and your car will slide at the front.
And you have under-steer.
So here’s the summary. A stiffer bar will make the end it’s
on slide. A softer bar will let it grip better. (At this point engineers are
getting dizzy with all the assumptions that makes, but it’s accurate enough the
purpose of this.)
So now let’s put it all together. You have a car that can
behave on the straights and can brake well. Now you need to do some analysis;
Figure out what are the most important corners on the
circuit (see above) and assess what the car is doing in each phase of them. You
need to be pushing to do this. Driving like Miss Daisy will tell you nothing.
The car has to be on the limit before you get a decent assessment. Now come in
off the circuit and address what the car was doing in those corners and in
which phase it was doing it.
Okay, this is the tricky bit. But here are some decent rules
of thumb.
Over-steer:
1) If you have
corner-entry over-steer on the brakes, you either have too much rear brake
balance or you’re a driving legend who’s backing it in
like Valentino Rossi. If it’s the former, adjust the brake balance. If it’s the
latter, call Ron Dennis. If you are getting corner-entry over-steer and your
foot is nowhere near the brake then the problem is the organic, meaty bit in
the seat, not the mechanicals. One of the best investments you will ever make is some professional driver tuition
2) If you have
transitional over-steer, in other words as you come off the brake and move to
the throttle, you either have too stiff rear dampers or you are popping off the
brake. If the former, change ‘em. If the latter, repeat the mantra ‘a smooth
driver is a fast driver’ 500 times and take a cold shower.
3) If you have corner exit over-steer, in other words, the car has taken a set, you’re feeding it throttle and the back is coming around on you then the rear anti-roll bar is too hard or the front is too soft.
Under-steer:
1) Corner
entry under-steer usually means front dampers are too stiff. But it’s a complex
one. And it’s also very unusual. Drivers mouth on all the time about ‘turn-in’
but in reality it’s unusual to find any car with a Sheane Cars set up on it
that has its front tyres fully loaded going into a turn and wants to wash out
away from the apex. It likely means a bad combination of toe, caster, camber
and Ackermann angles.
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2) Transitional under-steer is either of two things; either the driver is leaping on the throttle in the middle of a horrible line and trying to drive the car like a snow-plough or it means the car is not rotating at transition. (Rotation is a fascinating thing that results from the overlap of weight transfer, vehicle yaw angle and tyre slip angle. All very interesting. And technical. And not for here, engineers put away your calculators. Suffice it to say it feels lovely and is what all race cars live to do.) The quick and dirty version of a car ‘not rotating’ means the driver comes off the brakes onto the throttle and the car responds like a blancmange. If that’s what you are feeling, then your dampers are too soft all around.
3) Corner exit under-steer is a terrible thing that brings shame on your family. It is the result of a front anti-roll bar that is too stiff or a rear that is too soft. It is terrible. Rid your car of it at all costs. A car that is exiting a corner should (in general) reach the outside curb with its rear outside wheel, not its front outside wheel. Not like the Dukes of Hazzard, but rotated enough that the rear is making it to the curb. (And yes, we know you don’t see it in F1. But you also don’t see a thousand kilos of downforce, and the resulting aerodynamic implications in most racing classes or track day cars.)
A few words on putting all this together…
Look at your tyres.
If your front tyres’ surfaces are wrinkled like hippo-skin
and your rears are smooth as glass then your car is under-steering. It doesn’t
matter what you think its doing. If it is overworking its front tyres and
underworking its rears; that’s under-steer and you need to re-calibrate your
internal definitions of what under-steer feels like. Same the other way around;
if the rears are wrinkled and cooked and the fronts are smooth then you have
over-steer and you need to re-calibrate the seat of your pants to feel it.
Most new drivers set up their cars with too much
under-steer. That’s how all road cars are set up and it feels ‘normal’. If in
doubt, set up with too much over-steer. (At worst it’ll be good training in car
control and the spectators will love you.)
If you have under-steer, don’t turn-in more…
New drivers often think cranking on the lock will wring some
extra turning out of the front wheels. It won’t if they are under-steering they
have no grip left. You make them turn more, you rob grip from them, the exact
opposite of what you want. Then when they finally do grip again, they’re
pointed into the inside of the turn and they tuck the nose in, snapping the
tail out and introducing you to a man in an orange suit with a fire
extinguisher.
Lastly. A small
dose if realism.
If you are more than two seconds off the pace of a similar
car like yours it is not the set-up. It’s you. Don’t spend your time getting
covered in oil trying to find that magical 2.5 seconds. It’s in your driving,
not the car. Any of the top drivers will put any car (as long as the wheels are
vaguely in the right direction) within 2 seconds of pole. If you can’t,
concentrate on improving you’re driving. Then worry about the car.
For more information about car Set-Up for track days or Race Cars contact David Sheane at Sheane Cars on:
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