“I only stayed with her as long as I did because of the kids”. It was the stock phrase from Tyrone, who spoke of little else than how unhappy his marriage had been and who he was chasing at the moment. The latter part hadn`t changed since I first got to know him, despite the fact he was married then. Tyrone was always chasing women - someone from one of the offices, maybe, or from the factory floor, or someone he`d met on a sales conference or training day. Tyrone may not have been happy at home; but he sure made up for it elsewhere. “Hang on, I`m a victim here”, he would joke when I showed any sign of sympathy for his ex-wife or suggested that he should have worked harder on his marriage. He was younger than me by about ten years and definitely, by comparison, someone who dedicated himself to women as opposed to a woman. I had been out with a couple of girls, met the one I would marry, had children, concentrated on family and career, and been happy. To Tyrone women and career were one and the same thing. A new car and smart suite, combined with nights away, meant sponsored, serial womanising - and I suppose some part of me envied him.
To Tyrone, impressing was everything. He always wore modern, designer suits and shoes. Brand names were his bible and he displayed them whenever possible. His complexion matched his dark hair, which was always lightly oiled and shaped in a distinct pattern. Tyrone always made sure that he was flexible enough to be the one to help or advise a female colleague or customer, usually gleaning as much information as he thought necessary from an appropriate source before bearing down on his target with assured expertise. If it was paint, he`d spend hours on the internet researching the correct terminology or procedures. Driving and training, he knew it all. And it wasn`t just trucks, Tyrone made sure he knew about cars as well, confident that he could impress any women with his knowledge. He made sure he could identify what a problem might be, who could fix it – locally, quickly and who was the cheapest – and, above all, how he could help the lady to the garage and then home. Tyrone worked hard for every new liaison.
I didn`t really see much of him except during breaks, when we were part of a small group that would gather in the canteen – the rest of us usually ending up being entertained by Tyrone`s tales of conquest. But one day he did venture down to my small office, poking his head round the door as if unsure that he was in the right place and looking somehow out of place. “Err, TW, can I have quick word”. “Sure, come in”, I said. “What can I do for you”. Tyrone sat down on a comfortable chair close to the door and rubbed his hands together between his knees, which were tight on his hands, as if he was cold. All the while he looked about the office, at the photographs of old trucks, at the graphs and the memorabilia collected over a lifetime in the business.
I knew when I first saw him in the doorway that whatever he wanted his visit would ultimately be about women, or more specifically, a woman. And I was right. Apparently, at a recent trade show in Europe, Tyrone had met a woman who he had singled out for attention. Stunning is the word he used, slim and dark she was a real beauty, literally. She had been married but this was now dissolved and her children were all approaching late teenage years. “She`s French”, Tyrone said, “and her eldest is a girl of eighteen. And she`s the problem”. “Good God”, I said, “there`s absolutely no stopping you, is there”. “No, TW, you don`t understand”, Tyrone protested, with a grin on his face. “She`s had an accident in her car and the police are saying it was her fault. Her mum asked me to comment and I didn`t know where to start. I`m speaking with mum later and I need a heads up on it. You`re an engineer; you think about this sort of thing all the time”. “Not accidents, I don`t”, I said. “She lost control of the car”, Tyrone said, “it`s right up your Champs-Elysees.”
Tyrone soon became animated as he related the story and although he remained firmly fixed in his seat, his body bent this way and that, as if absorbing the energy of the course he had found himself on. According to Tyrone, the girl had been travelling through a rural area near her home with a few friends in the car, a small Peugeot hatchback. As she rounded a bend it seems that part of the car drifted across the centre white line, clumping an oncoming small truck. No one was seriously hurt, but as a new driver the little French girl is in for some grief. The police say she was going too fast for the bend – she and her friends insist she wasn`t. The truck driver, an elderly man who lived locally, isn’t able to comment either way. Apparently, it was a narrow road even for a small truck. “If she`d lost grip, she would have heard skidding, surely”, Tyrone said. “There`s a lot to consider”, I told him, “road surface and weather; tyres are particularly important; you need more information before you, I mean I, can comment accurately. Just gather as much as you can, ask about the scene, impress her with your investigative thoroughness and we`ll speak next week”. With that he was gone, repeating the word `tyres` over and over as he hurried out the door.
I had almost forgotten our conversation when I met up with Tyrone at a test day the following week. I could see he was anxious to speak and as soon as the opportunity arose he had me cornered. The story of the French daughter had developed and the conquest of her mother was at a critical stage. He had, thanks to me apparently, impressed with his questions but now he needed more. Tyrone wanted to be the expert who would show the Gendarme for what they were – idiots when it came to vehicle dynamics and, therefore, completely wrong about Madam`s daughter`s accident. He told me a little of what I wanted to know: the car had suffered damage to the rear wing, as if it had been side swiped, and the rear bumper had been ripped off. The road was damp. There were no visible marks on the road. The tyre tread was good. “And tyre pressures”? I said. “Didn`t ask”, he said. “Well do”, I told him.
The next day Tyrone told me he`d emailed his French lady and been informed that the tyre pressures were never checked. She also suggested that the truck had come on to her daughter`s side of the road, as the Peugeot had been hit on the rear wing and not the front. “Where was the debris”? I said, “And where did the vehicles end up”? “I`ll ask”, Tyrone said. The reply came during a visit to the canteen later in the day. “It`s a text”, Tyrone announced. “`Car spun round quarter circle`. `Truck almost straight in his lane`. `Glass and stuff behind truck in his lane`. What does that lot mean”? Tyrone looked confused. “The truck didn`t enter her side of the road”, I told him. Tyrone looked disappointed. “What now, I need to help her out if I`m going to get anywhere TW, come on, what next”? I thought for a moment. “Ask what the girl`s actions were as she drove through the bend. Did she brake or steer differently when she saw the truck”?
It wasn`t until the next morning that Tyrone was able to bring me a reply to this last question. “She didn`t sound too impressed”, he said. “Thought I was trying to suggest her girl was in the wrong. Anyway, I`m hoping for an invite, hoping to fly out this weekend, in fact, and then it`ll all be worth it TW; oh you should see her”. Tyrone made a slight whistling sound and closed his eyes for a second, no doubt dreaming of impending delight. “And? I said. “Oh, sorry”, Tyrone was back with me. “She says she saw the truck and took her foot off the gas, steering away from it. After that, it`s all a blank. Now, I need help TW, I need this weekend but I can feel it slipping away from me”. “Lift off over steer”, I said. “What?” Came the reply.
I sat Tyrone down in a quiet corner of the canteen and told him about tyres. "Tyres", I said, "are all there is between the vehicle and the road, as everyone knows. But we sometimes forget that no matter what devices the vehicle has to modify its handling, the whole shooting match relies on something quite small: patches of rubber in contact with the road that are often no bigger than a human hand. And when it comes to contact with the road it`s these patches that deal with all the forces acting on the vehicle. Tyres are not keyed into the road like train wheels are to a track; they do it differently - tyres work on the road in their effort to get grip. To change a vehicle`s course, tyres have to travel in a slightly different path to the one they are pointing. This is a tyre`s slip angle - and it is everything. Slip angle controls handling and grip and, therefore, stability. It is determined by the tyre`s characteristics: construction, tread, materials, profile, pressure; as well as, side force, load and road surface. Too much slip and the tyre drifts, too little and sufficient cornering forces may not be generated. Geater slip angle at the front and the car under steers; too greater at the back and it`ll over steer. "So", I told Tyrone, there`s a balance". “But the French girl”? He said.
"Tyres", I went on, "have a finite amount of friction available to them. Use it all for cornering and there`s nothing left for braking or traction. There`s always a balance, as I have said. The French girl`s accident can probably be summed up as: Bit quick into the bend; car drifts out on wet surface; lifting off gas shifts weight forward and increases cornering ability at the front. With traction demand stopping at the front, the front tyres are given more friction for cornering. With a steering angle that has increased from the driver, and is now too big, the car steps in at the front. The result – lift off over steer on a car already on the white line. Add to this any extra weight due to passengers, without any compensating increase in tyre pressure, and the car has higher than expected slip angles, especially at the back. It was asking to yaw".
When I had finished Tyrone looked at me, thoughtfully. “Tyres then are not really following the path you think but they mustn`t drift too far off if they are to stay on an acceptable course”, he said. “That`s about it”, I said. A week later I saw Tyrone and I asked how the French weekend had gone. “I didn`t go”, he said, “She went really strange when I suggested the daughter might be at fault, despite all that slip angle stuff”. “I`m sorry”, I said. “Don`t be. I think I`ll stick to familiar ground from now on”, Tyrone said, “travel a few roads I already know for a change; slow down a bit, maybe. Fewer disappointments that way”.
