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How-To Section: Race-tune your handling



Understeer – Front of car heads towards outside of turn. Can be less dramatic than oversteer, so therefore easier to not notice.

Oversteer – Opposite of understeer. Rear of car heads towards outside of turn. Usually dramatic therefore gets your attention more!

Camber – negative :- viewing car from front on, wheel attitude has them outwards at the bottom. Measured in degrees.

Esky Standard = buggerall to 1.25 degrees neg

Castor – positive :- Viewing car from side, the angle in degrees , that the strut is away from the vertical. Standard has the top of the strut towards the rear of the car.

Esky Standard = 1 to 2 degrees

Toe-in : Viewing car from above, the distance from one wheel to the other, with the dimension at front, less than behind wheel centreline ( wheels pointing in at front ), measured in mm.

Standard = 3mm

With the nature of front engined rear wheel drive cars, they are prone to understeer, either by manufacturers design or the fact that the engine is over these two wheels- read heavy lump.

Because of this it is important to reduce understeer, although it is a balancing act, front to rear. The front is the most tortured due to the weight imbalance.

For anyone in competition it is a matter of finding what works best for your vehicle/driver style, which means testing various setups.

Remembering that the stop watch is the ultimate gauge.

With this in mind I jotted these notes, collected from various publications to help pinpoint things to reduce understeer :-

better tyres e.g. wider, softer, lower profile and slick

braking too hard and too late ~ driving style

tyre pressures front to rear

not enough negative camber ~ outside of tyre will be hot and wearing

front roll stiffness too high

too much front toe-in

too much front spring

front track width too narrow

insufficient front shock absorber bump resistance

front roll centre too low or rear too high

too much toe-out in bump steer

too much toe-in in bump steer ~ rear


So, where to start…..with an Esky?

Re-drill track control arm mounts in crossmember to give increased negative camber this will be from 6mm out and up, approx. 1.5 degrees to 8mm out and up, 2 degrees approx., or purchase adjustable track control arms ( T.C.A. ) Too much negative camber will affect the braking performance of the front tyres, but I feel this is when you use much more camber than as above.

Using other strut tops, other than Esky, can give you a means of adjustment, but this is less dramatic than modifying TCA. However, these can be used to adjust castor. Castor is there to provide stability, mainly in a straight line, adding more than the standard setting will produce ~ better initial turn-in, more negative camber in turn and higher input from you to turn the steering wheel! The best way to understand this is to grab a spare tyre /wheel and strap on ( tape ) a tube or wooden stake to it to simulate the strut . Then hold upright and turn left/right while watching tyre contact patch on the ground. Repeat with tube/stake angled back toward you.

Corty MKII GT strut tops have a smaller outside diameter, therefore these can be moved around in standard body strut top hole. New holes in body inner fender will have to be drilled, for the mounting bolts

K-Mac sell a 24 and 27mm sway bar with threaded ends to allow for castor adjustment. I guess a street car could have a 24 and a race car a 27mm. A cheaper way is to obtain a MK I and MK II bar ( they should be different diameters ) and cut the ends off, then make up some clamps to clamp on the extra bar below the existing one, then try out the two.

Front toe in, is there to allow for flex in all the front end, including the bushes. Therefore a good start is to replace all the bushes with urethane type. The standard toe setting is 3mm in at the front. With the new bushes , you will need something closer to straight ahead. While we are on the subject, you might want to experiment with toe-out, as this can give you better initial turn-in, into the corners. This should only be done on a race car as it will become " darty " e.g. will be difficult to hold in a straight line…..just hold on.

Start with 30% stiffer front springs and go from there. Standard is front 95 – 135lb per inch, depending on model and accessories etc. I noticed in a magazine recently that they used 600lb per inch front and 450lb per inch springs on the rear of a MK II race car. Therefore that gives the two extremes, I guess. Spring rates are fairly easy to calculate, especially when comparing one to another, unfortunately they need to be off of the car. Have your moderately sized friend stand on the spring and measure compressed and free length, then weigh person. Calculate:- spring travel ( free – compressed length ) , then person weight divided by travel. Same for leaf springs, stand on diff mount area only whilst spring is inverted. Best to do this on some nice hard ground e.g. concrete. This is as accurate as you and I can get without expensive equipment.

Front track should be as wide as possible. Purchase wheels with widest offset or try wheel spacers. Front track needs to be wider than rear.

Shocker resistance can only be checked via testing, however count on resistance improvement being in line with percent stiffer springing

Roll center changes usually require suspension redesigning, however the easiest way to change this is to raise/lower the relative ends of the car. This can have a big influence on car characteristics

Toe-out in bump, when the suspension moves up/down the steering rack arms act to change toe settings. Relatively simple jig needs to be built to check this, spacers for rack mount and/or tierod – strut connectors need to be bent.

As rear axle moves up/down, especially in roll ( going around a corner ) one of the wheels will move forward more than the other, effectively steering the rear of the car, especially if you have de-arched springs. Difficult to adjust, however maybe better to use lowering blocks than de-arcing springs.

One of the better ways to see what’s happening is to take a picture of your car cornering. A lot can be revealed from this. With this in mind lets look at this famous esky .

One of the first things I notice is how fashion just goes around and around [sunglasses]

Next is that car is in understeer mode. Front left wheel is off of the ground , no weight on it, so car is three wheelin, would corner better with 4 wheels on ground.

Right front tyre, closest to you, has the majority of weight on it, the tyre wall is buckling under, therefore would seem to need more negative camber to corner faster. This is the reason for negative camber , to keep the tyre tread flat on the track surface, however it is always a compromise. The rear is doing a fine job. He’s probably about to bury the throttle pedal and bring the back round anyway!

There is probably lots of things that I have missed , therefore I suggest you read the following publications :-

Escort Performance – Dennis Foy

Escort Rally preparation – Charles Reynolds

Race and Rally Car Source Book – Allen Stanifoth

Engineer to Win – Carroll Smith

Tune to Win – Carroll Smith

Drive to Win – Carroll Smith

Race Car Engineering and Mechanics – Paul van Valkenburgh

Advanced Race Car Suspension Development - Steve Smith

I don’t profess to know everything, just passing on my experiences.

Hope it helps…..where’s my next beer!

Roger Miller




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