JACKSON JUMPS FROM ONE TO ANOTHER FOR FIVE VICTORIES
Carl Faux, MN’S technical editor, gives us an idiot’s guide to ironing out some rough spots
Five wins in three cars was a massive haul for
Cam Jackson as the historic season started on the
Brands Hatch GP track.
After a Formula Junior double, Jackson also took both Classic FF1600 races in his
Van Diemen RF80 and then fended off a determined Linton Stutley to win the Historic FF race in the unfashionable March 709. It could have been six, but the second Historic FF race was lost to the curfew after earlier incidents.
Michael Lyons starred in two of Saturday’s best races, including a storming Aurora Trophy victory from the back of the grid. He took over the Eagle
FA74 of mum Judy for the race after a qualifying tangle eliminated his Lola T400.
While James Hagan rocketed his F1 Hesketh 308 into the lead, Lyons carved his way up the order and deposed the ex-james Hunt car to take a resounding win. Hagan won the second race, with Lyons sitting out.
The Guards Trophy race was a cracker as a safety car set up a charge to the finish. Initially, Andy Newall (Chevron B6) and Anthony Reid (Lenham P69) battled mightily but both lost ground when the safety car emerged as the pit window opened.
Once the race went green
Sam Mitchell, in the Chevron
B8 started by dad Westie, had a narrow lead but was being hunted by Newall, Greg Caton (in Richard Piper’s Brahma) and Lyons, who took over the Lenham. Pursued by three hard chargers, Mitchell held on superbly as a second and a half split four cars after 40 minutes.
Saturday delivered resounding double wins for two aces of historic racing.
Ben Stiles bounced back from a qualifying tangle to dominate the FF2000 races while Jackson was peerless in Formula Junior despite a spirited chase by
Mark Shaw.
Andrew Smith’s prodigious pace in his Formula Atlantic March 79B ensured the opening
Historic F2 spoils despite a trip over the Paddock gravel during an early battle with Mark Hazell’s March 782. On Sunday Smith held off the attack of
Miles Griffiths (Ralt RT1) until a misfire hobbled the March and Griffiths swept ahead.
Dean Forward aced the first Thundersports race in the awesome Mclaren M8F despite a persistent misfire as Tony Sinclair headed the chase in his Lola T292. A fuel leak sidelined the Mclaren on Sunday but that set up a stunning contest between Sinclair and Jonathan Mitchell (Chevron B19). After a safety car, Mitchell’s relentless pressure was rewarded when he dived ahead of his rival.
In a new series of features, our engineer in the know, Carl Faux, aims to demystify some of the more common problems experienced by competitors. Faux is one of the senior engineers with the Walkinshaw United Andretti team in Australia working on its Supercar programme. The former short oval racer has a strong background in the British Touring Car Championship series too, working with Triple Eight Racing and with BMR Racing, helping the latter win the title with Ash Sutton in 2017 in the Subaru Levorg which Faux had designed before plying his trade abroad.
We are going to ask him to debunk some of the tricky topics with affect a number of race and rally drivers, and give us his advice. We start with the plight of understeer.
MN: What are the main causes of understeer?
Carl Faux: “In simple terms, the tyre is an elastic band that is connected to both the rigid wheel and the ground. When forces are put through the car, longitudinal or lateral, this elastic band changes shape. In cornering this shape change causes the tyre belt that is in contact with the road to travel in a direction different to the direction the wheel is pointing; this is called slip angle. When the slip angle of the front tyres is greater than that of the rears the car will be in an understeer condition.
“This condition can be because of many parameters of the car, especially when driven on the limit of grip. The main contributors are vertical load on the tyre, camber angle and toe.”
MN: Why does it cost a driver so much time?
CF: “To drive a circuit in the most efficient manner and hence fastest time it is incredibly important to make the compromise of the shortest distance travelled and the fastest minimum speeds achievable. This can only be achieved if the driver can position the car where this driving line is. A car with too much understeer will require the driver to over-slow the car to get the car to follow the optimal line if it can be achieved at all and therefore is slow.”
MN: Is it ever beneficial to have understeer in a competition car?
CF: “In general, a very minor amount of understeer is fast as it is predictable to drive. A driver can be proactive with their inputs rather than reactive that gives confidence to drive to the grip level available. In a rear-wheel-drive car this trait also encourages throttle application on corner exits…however if too much understeer is present midcorner the application of throttle with too much steering input results in snap oversteer on power.”
MN: Do some drivers prefer it?
CF: “Yes, some drivers do prefer an understeer-limited car. The style of all drivers and their requirements to extract their personal best performance are different. Obviously we are talking about small margins, any car with lots of understeer will not be able to go quickly but this also applies to cars with lots of oversteer.
“It is difficult to explain why this is the case, it is in their psyche. Certainly in lowgrip conditions, like the wet, it can be seen the fastest and the quickest to get to the limit are those cars that give confidence to the driver with the feel of grip coming through the steering wheel much more than the inner ear and lower back sensors.”
MN: What if your car starts fine and then promotes understeer?
CF: “Over a stint there is only one reason for this and that is the tyre, either temperature or wear. The usual factor is where the surface temperature of the rubber gets hotter the front tyre will go over the optimal grip temperature. If the car and tyre combination is well balanced, the rear tyre will also present with the same characteristics. If, and as is usual, the tyres do not behave the same, the issue of a front going out of the temperature window whilst the rears are coming into the window understeer increases exponentially.”
MN: How can you mitigate against that? CF: “In these situations, it is extremely common and necessarily requires to set a car up with the knowledge that the balance will change through a stint. This means that initially the car will be set up to be quite nervous and oversteer-balanced with the aim that halfway through the stint the balance is neutral and ends the stint with understeer. The best compromise for a car, for example a front-wheel-drive touring car, is to make the fastest stint time even if the car is not ideal for one-lap pace.”
MN: What are the simple fixes? Is it as much to do with the rear of the car as it is to do with what’s happening at the front? CF: “For different cars different tools are used. As discussed earlier the main things that affect the balance outside of the tyre are vertical load on the tyre, camber angle and toe.
“To increase the vertical load in the tyre, this could be by adding downforce with front wing however this is an addition rather than an optimisation of the mechanical grip. In a corner there is naturally a lateral load transfer occurring that takes the vehicle weight and puts more of this on the outside tyres. The distribution between the front and rear axles of this load transfer can be, and is, adjusted by springs, dampers, anti rollbars and geometry.
“To reduce understeer mechanically the prime objective is to reduce the lateral load transfer on the front axle, ie: keep more vertical load on the inside front tyre and also conversely reducing load on the inside rear, this can be achieved by reducing the stiffness of the front anti-roll bar or increasing the rear rollcentre height amongst others.
“It is also important to consider the contact patch of the tyre so reducing this effectiveness by using too little or too much camber angle for the part of the corner where understeer is its worst needs to be considered.
“Finally the mechanical method that has a very big influence on the direction the tyre is travelling on the road and the slip angle of the tyre is the toe angle of the wheel. Either static or dynamic toeout on the rear of a car will naturally steer the rear of the car away for the corner and produce an oversteer moment to counter any inherent understeer issue.”
MN: Do tyre pressures affect the situation?
CF: “This is a whole area for discussion. The tyre pressure, camber, vertical load, temperature are all things that need to be matched to achieve the optimum grip level. On a typical circuit race car we see pressures rise at around three pounds per square inch until stable. On an oval car, this can be as much as 15psi over a stint. In both these examples the track surface is fairly consistent, rallying on the other hand… that is a whole different topic again.”