Posted: June 10, 2016
Publication: Total Magazine Article 2009
Over previous issues we have been focusing on driving technique - relating our driving inputs to the dynamic loading of the vehicles platform as we drive on a circuit. Let’s take a more polarised look at the tyres we use and how we can optimise their grip with the tarmac.
As we drive a circuit at speed, our tyres will increase in pressure. The increased cornering forces generate friction with the consequence being that tyre temperature rises and the air expands inside. We will be asking the brakes for maximum retardation which generates further heat to soak throughout the mechanical components and in to the wheel, further increasing the heat generation in the tyre carcass. Radiator and cooler venting can have an adverse effect on tyre pressure if the venting is not central to the vehicle, as one tyre may experience more heat soak than its counterpart.
If you have arrived at a circuit on road tyres you may find you can leave your tyres at road pressure. The subsequent high speed laps will raise the pressure to a more suitable pressure for circuit driving. After your first 5 to 10 laps return to the pit lane and check the pressure. How much you run them over the standard manufacturers pressure settings is largely down to the vehicle you drive and the tyres you use. As rule of thumb 4 to 6 PSI is safe guide for road tyres. If you are in any doubt please seek advice from your tyre supplier or race shop.
You will need to monitor the pressures throughout the day. If you have swapped your road tyres for track day tyres the advice is to set the pressure cold and monitor and adjust after your first short session. As a rule you will experience a 4 to 6 PSI differential between a cold and a hot tyre. It is essential to take a basic tool kit with you to track days which includes a tyre pressure gauge and tread depth indicator. If you are driving home on the tyres you arrived with, you need to make sure you have enough tread left at the end of the day to drive home legally. The legal minimum requirement for a tyre is 1.6mm across the central three-quarters of the breadth of the tread and around the entire circumference.
Let’s go back to basics to answer the question. In previous articles we have discussed Slip Angles – let’s explore the subject in more depth. To generate a side or lateral force, a tyre has to be rotating and running at a slip angle. Slip Angle is defined as the angle of the plane of the wheel and the direction of motion of the contact patch across the road. In short, the tyre and the wheel through a corner, travel by a few degrees in a different direction to each other. As the cornering forces acting on the tyre build through a corner, the tyre will flex on the rim. The difference in the travelling direction of the wheel and the tyre generates friction and grip.
There is an optimum amount of flex (Slip) the tyre will accept before it will no longer be able to support the weight of the cornering vehicle and the tyre will roll onto its side wall and start to slide. Typically the optimum slip angle for a road or track day tyre is 6 to 10 degrees. It is worth considering at this point in the discussion a modern saloon car will generate in the region of 0.8g to 0.9g of grip between the tyre on the road. A modern supercar, for example the new GTR, will achieve a staggering 1.5g on its road tyres. Modern vehicles offer high levels of lateral acceleration through a corner and consequently our tyre pressures are a major part of the equation.
Choosing the correct tyre pressure is fundamental to maintaining the optimum contact patch on the road and tyre sidewall rigidity. A road tyre pressure may not support the increased cornering forces and increased weight experienced by the tyre on circuit. Through a corner a tyre has to experience slip as the inner and outer edges have to travel different distances. For the very same reason our vehicle has a differential in the transmission. The challenge is to adjust our tyre pressure to the correct pressure for the conditions.
Subtle adjustments to tyre pressures will increase and reduce understeer and oversteer as we moderate the characteristics of the tyre sidewall flex(Slip) on the rim. A development in tyre pressure consistency is to fill your tyres with Nitrogen. Compressed air contains water molecules and will affect the tyres ability to maintain a consistent pressure once heated. Dry Nitrogen offers a moisture free alternative offering lower tyre running temperatures and consistent pressure maintenance.
Keep safe and enjoy the longer summer days and evening bargain track sessions.
CAT Driver Training Ltd.
Tel: 01234 757633
COPYRIGHT CAT DRIVER TRAINING LTD. APRIL 2009
"Performance Driver Track Day Course I participated in the course arranged by Porsche Club GB and very happy to give 5 stars all round. The team has put a huge amount of thought and effort into making the facilities and training Covid-secure, which is indicative of their professionalism. I found the whole day both fascinating and a lot of fun, in briefings, on the various driving segments, and chatting with the team and other participants. I was genuinely in awe of how much Colin moved my theoretical and practical driving on, and what he got me to get the car to do in the space of one day - always building confidence, encouraging me to explore my limits, while not pushing me beyond them. Can't wait to return!"
"I have had a reasonable degree of driving training over the years as am ex police officer and advanced police driver. I took the performance driver driver training to learn about track driving, and found it excellent. My instructor was Paul who was fantastic. The training built up during the day and I learnt so much about the capabilities of my own car and although I was nervous about using my own car realised afterwards it was the best thing for me to do. The instruction was extremely informative from an engineering perspective coupled with driving, friendly and tailored to your individual needs and abilities. At no time was I encouraged or pushed to do anything I wasn’t comfortable with. It was extremely professional throughout. I would thoroughly recommend this to anyone whatever your standard of driving."
"Truly exceptional In my experience, driving instruction has generally consisted of being repeatedly told that you are 'doing it wrong' accordingly to some unknown standard or principle that you had hoped to learn about by taking said instruction. Then there is Colin. It is not that common to find an individual who genuinely understands both people and engineering. It is incredibly rare to find one who can actively apply both to deliver a sustained behavioural change. Colin adapts his teaching style to the way you learn. For me, he lead with the WHY of the learning point, grounded in physics and engineering. We'd then put it in to practice, often doing several variants of an excercise to explore how the car reacts to differing inputs, providing valuable context for what good feels like and reinforcing the learning point. Each point built on the previous ones, layering up and coming together in to a whole, one far greater than the sum of it's parts. Subtle changes to huge effect. I was concerned on the day that the learnings would rapidly fade, but I have found that because Colin has taught me an understanding the lessons have persisted, even if I do still need some more practice (48 laps of the Silverstone GP circuit last Thursday definitely helped!). Add to this the fact that Colin is great company and an absolute pleasure to spend time with, and you have one of the most positive learning experiences I've ever known. Truly exceptional. I could not recommend more highly. Thank you!"
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"Far better than any track day you can imagine! There is a massive difference between a typical driver experience or track day events and CAT driver training. The main difference is that you drive your own car to the full extent of it's capabilities, and your own, while being given expert one to one tuition by brilliant trainers Colin and Paul, who come from a Motorsport and auto engineering background. Their combined domain knowledge of engineering and competitive Motorsport allows them to explain the physics of why the car behaves as it does and how you can exploit the cars characteristics for maximum performance., in a safe fun environment. The frankly brilliant experience on the track is matched by the quality hospitality hosted by Jo, and classroom training, which prepares you for what you will experience on the next stage. These stages include such delights as the ring, where you will drive with no hands on the wheel at 100MPH, providing you with a clear understanding of the fact the car finds its own balance , and my personal favourite the alpine stage, with hairpins a plenty and 'character building' drops and rock faces. I have to admit to being slightly 'corner shy' before the training, however after some brilliant coaching from Collin urging me to 'stay on the gas, stay on the gas!' I am now far more confident and safe in the twisty stuff!"
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"First class performance car training day. Many thanks to Paul & your great team for a really enjoyable training day at Millbrook on Friday. I learnt a lot more about the capabilities of my F430 and found many new limits! The attention to detail in the delivery of the training was exceptional. I would recommend this to anyone with a performance car who wants to fully understand and enjoy their vehicle."
"An amazing day. If you drive you should go to CAT. If you have a performance car you MUST go to CAT. A day with CAT will transform your driving, you it be safer on the road in any situation and it will be the biggest performance upgrade your car will ever get. I learned so much in one day without any pressure, effort or stress. Colin's coaching is world class, he makes it simple / interesting to understand and easy to absorb / remember. The whole day and and everything leading up to it are well organised by the team. They REALLY care that you have a great day and TOTALLY deliver. You owe it to yourself to go."
"Absolutely Brilliant! The best advice I can give: believe every one of the glowing reviews on CAT! I approached CAT because I wanted to feel more comfortable with my newly-purchased BMW, the first rear-wheel drive car to be used for every-day driving after decades of FWD cars. I wanted to find out what the car's capabilities are, what it would feel like in extreme conditions, understand what it was telling me at the limits and, generally to get advice on my own technique. I wasn't a novice, having done plenty of track days and laps of the Nordschleife but I just knew that there's always plenty more to learn... A day's Performance Driver session met every one of my targets, and then more! Paul was a patient, logical and technical instructor who took time to explain what would happen in each manoeuvre and then fully debriefed that stage so that I not only knew what the car was doing but also understood what effect on the car my own actions were having. The proof of the pudding was in the final stage - setting consistent timed laps of the handling circuit. I'd worried a little about this all day as I'd have described my driving as enthusiastic but perhaps not consistent. The results were close to unbelievable to me! By remembering all that Paul had demonstrated and explained to me I surpassed my wildest dreams. Fantastic! As a result of this day, I now have more belief in my ability to read what my car's saying to me which brings confidence and relaxation. The car and I are now a team, rather than me just sitting there making it go down the road. I can highly recommend the whole CAT experience. Professional, friendly, patient, technical when required and not afraid to challenge when necessary. Oh, and the lunch is good too! I wish I could afford to go back every month..."
"Achieve your driving goals here! Can't ask for more than that! The entire experience was a positive and pleasant one. Everyone I met at CAT Driver Training contributed positively to the day, regardless of the role, so thank you to Jo, Lynne and of course, Colin! CAT have existing programmes for teaching anyone the fundamentals and advanced techniques of how to drive fast, but Colin can identify really quickly what you can and cannot do, and is quick to understand how to best use your time. I went in with my own unique set of requirements which slightly 'broke' the programme, but it was no problem at all and the most impressive thing was that I achieved my goals by the end of the day! I wanted to understand my car, be able to find and drive at the grip limit, and also understand how to be a faster and better driver. A lot to fit into a day, but Colin managed it in the most efficient way possible, and we achieved them all! Colin has great insights into vehicle dynamics, as well as the human machine behind the wheel. He understands why we sometimes don't function as optimally as we would like! His ability to listen to you, translate your input and isolate what is not working with your current technique helps focus the day on exactly what needs attention. This focus, along with Colin's 'feeling' of how the package of car and driver is behaving, makes him uniquely qualified to provide great direction and input to help you become the best driver possible. A lot of people talk about it, but very few can translate the inputs to a specific process for you to follow as a driver. The process is all about starting with foundations and building on them. It doesn't always seem to make sense, but trust the system - it all comes together in the end! The time is not cheap, but it will help you achieve your goals, so how do you put a price on that!? Thank you CAT Driver Training!!
"Best In Class Driver Training The training provided by Colin at CAT Driver training is superb. I am lucky enough to attended training days with Porsche, Lotus, Aston Martin and the day with a Colin at Millbrook has topped them all being informative, challenging, practical and above all delivered by a true Petrol Head. Thanks again and I will be back with the 911."
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