The science of tyre testing

No product review off the back of a tyre launch should ever be more conclusive than that. The thing is, there isn’t any context. There’s nothing against which to compare the new tyre. Unless your host has laid on several other comparable products for you to assess in strictly controlled back-to-back conditions – which has never happened in my experience – you’ll only be able to learn so much.

I know how pitifully uninformative tyre launches are only because I also know how enlightening and revelatory a thorough, in-depth multi-product tyre test can be. I’ve done a couple of these for Evo magazine. We’ll have 10 or so rival tyres from different manufacturers. We’ll be using a proving ground that’s specifically set up for the purposes of tyre testing. And we’ll assess these tyres in the most rigorous way we can.

Approached that way, you quickly learn how vastly different two apparently similar tyres can be. I have driven laps of a wet handling track with Pirelli rubber beneath me and felt the strong, consistent and confidence-inspiring grip and traction they generate. I’ve then switched to Hankooks and driven the same circuit in precisely the same way, but slithered off the track altogether because there’d been nothing like the lateral cornering bite I was expecting.

Same thing can happen on the dry handling course. One tyre will allow you to carry a certain amount of speed around a particular bend, but try the same thing on a lesser tyre and you’ll be off. It’s happened to me a couple of times. Go through that two- or three-day process even once and you’ll develop a very keen sense of how much variability there can be at the extremes between two tyres that you might assume would be indistinguishable. And you’ll never go for the cheaper set just to save a few quid ever again.

Whether we were using Pirelli’s Vizzola proving ground close to Milan Malpensa airport or Continental’s vast facility in Uvalde, Texas, the process is always the same. You begin with the least destructive tests, which means wet braking followed by wet handling. This ensures the tyres are in the best possible condition when you switch to the dry weather assessments – braking first, then the dry lap time. Certain assessments are purely objective. In the braking tests, for instance, it only matters how long the braking distances are for each tyre. (Interestingly, the car that’s used for these evaluations will be fitted with a sturdy arm that slots into a track running the length of the braking course. This fixes the car into position, meaning the very same piece of asphalt is used every single time, equalising the assessment as much as possible.)

However, other tests involve both a subjective and objective assessment, while others are subjective only. For instance, you’ll not only set a lap time around the dry and wet handling courses, but also record your own impressions regarding steering feel, confidence, the transparency of the grip available and so on. When assessing ride quality, though, the best-calibrated measuring device you’ll at have your disposal will be your own rear end.

Of course, it also matters which car you use. To assess performance tyres, you clearly need a performance car, one that has predictable and consistent handling traits at the limit of grip, communicative steering and brakes that do not fade substantially over time (because that would render the lap time data meaningless as the test went on). I’ve used a VW Golf GTI Mk7 and a previous generation Ford Focus ST and found both to be willing and faithful accomplices.

Having said that, we did have something of an issue with the Focus ST in Texas. The ambient temperatures were in the low 40-degrees Celsius and although the dry handling circuit at Continental’s R&D facility had been designed to be relatively gentle on brakes (for exactly this reason), the anchors did begin to wilt quite alarmingly. The trick is to let the brakes cool back in the garage, fit the non-competitive control tyre and set a lap time. That allows the clever engineers to do some maths that I’ve never understood to level out the playing field, so that those tyres that are assessed after the brakes have given their best are not unfairly penalised.

The control tyre is actually a fundamentally important aspect of a tyre test. You as the driver will inevitably become quicker around a dry or wet handling lap as the day goes on, for instance. There’s no way around it. The solution is to bolt the control tyres on at several points throughout the day so that the same equalising formula can be applied.

Those glamorous and lavish tyre launches tell you nothing whatsoever. Properly structured multi-tyre assessments, however, have been among the most revealing and informative assignments I’ve ever been tasked with. Tyres are all just black, round and full of air? Not even close.