20 percent water clearance depending on the number of cuts and the depth. Dunlop does slick testing at several locations and wet testing where they can. “At the end of this year, we went back to Sebring in Florida – we have lots of experience from Sebring, especially with BMW – we did a few 12 hour tests there before last year’s season,” says Meenan. “We did other tests with the cars that went on to win Sebring 1 and 2. We had one of the best performing cars at that race in the GT class.” Dunlop went back there this year because Sebring is one of the tracks where they see the smoothest and the bumpiest surfaces. It’s an old airfield with concrete sections that are offset and quite bumpy and they are hard on the cars – Audi go there for weeks, just to do endurance testing on the chassis. From a tyre point of view you are looking for something that gives a reasonable balance on the smooth and bumpy parts. Sebring has fast and slow corners and some high speed sections so you can test in all sorts of track conditions. Also the weather can be a little bit unpredictable so it has a bit of everything. “We 8 April 2016 think Sebring is the best all round circuit for testing,” says Meenan. “In Europe you have to go the southern Spain or Portugal to get anything close. Estoril, Jerez or Portimao at testing time (ie. the off season) can be wet or foggy whereas Florida is bound to give you dry days. We went to Sebring with all our development partners to prepare for ELMS (European Lemans Series) and WEC- (World Endurance Series).” All the development work is done on CAD. “We use some element of CAD to design the tyres,” says Meenan. “We would start off with a construction we may already have. Make some modifications and put it through Abaqus. We compare different designs this way. And from that we can get the delta stiffness – the difference between the tyres. Because our process is so well honed the percentage difference we see with the FEA simulation we also see on the track.” It’s quite difficult to get absolute correlation with track testing because lots of things are going on with lots of variables that you can’t control absolutely. “Things like the actual construction and lay-up, the way the tyres shape in the mould, the way the tyre fits on the rim are more predictable than how it performs with the car,” says Meenan. “Our biggest challenge is trying to optimise performance for a specific car. From previous tests we would decide on the area that we would like to explore from a car performance point of view, improve the front or balance the rear etc. So we would have a weight distribution or stiffness balance that we would want to target, so we would take a few options (different tyres) in that area to test. Options one through five either side of a baseline. (Baseline is another variable term – when describing a test, baseline is a term that describes a tyre that is a known quantity. This is a tyre that has a given construction and compound that the team and driver know well and how it reacts with the car. In a given test the tyre variants will be compared and contrasted to the baseline tyre – in the above, the baseline would generally be in the middle with 2 softer and 2 harder compounds either side. After a test the baseline is usually the optimum compound combination for the car and the circuit – this is the combination that goes into the race set-up process where dampers, aero and Because our process is so well honed the percentage difference we see with the FEA simulation we also see on the track
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