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Law and Order Tests Police Tires, Part 8 of 10

Written by Law and Order Staff

Objective V. Subjective Testing

Like so many tests, these tire tests raised some questions as they provided answers to others. Why did one objectively superior tire get relatively low subjective driver impressions in the wet? Why did another objectively inferior tire get relatively high driver subjective ratings in the wet? How important is it for the objective measurements and the subjective driver impressions to match, as in the case of the Firehawk GT Pursuit?

What feels good may not be fast. What is fast may not feel good. This was certainly the case in the wet testing. The Continental ContiProContact had three 1st-ties and 2nd in the various aspects of measured wet testing. Yet in wet driving, the driver assessment rated in 3rd out of five, in the middle of the pack. On the other hand, the ContiProContact was clearly the 1st Place dry performance tire, objectively, and was arguably rated as such by the drivers, subjectively.

The Goodyear Eagle RS-A was a solid 4th Place wet performance tire as measured by the instruments. Yet it was a 2nd Place or better wet performance tire according to the drivers’ subjective ratings. The RS-A is slippery when wet but was progressive and predictable enough to instill confidence. A police tire should provide confidence to the driver, or else the driver will mistrust the vehicle and slow down. Again, like the ContiProContact, during dry testing of the Eagle RS-A, the objective and subjective results matched.

The wet results for the Firestone Firehawk GT Pursuit made a little more sense. It measured either 1st or 1st-tie in every wet event, and the drivers rated it 2nd overall. The dry results also made more sense in matching timed performance to driving impressions.

Tires that feel good to the driver are not always the fastest around the course. Tires that are the fastest around the course don’t always feel good. We found clearly that one driver may prefer the feel of one tire, while another driver may prefer the feel of another tire. Since police officers are all different, and tires are different, this difference in what “feels right” or “feels good” or “is confidence inspiring” is to be expected.

The tires with higher driver subjective ratings would be driven closer to the limit of that tire, whatever the objective limit may be. However, the driver favoring the tire does not make the tire stick any better. On the tires with lower driver subjective ratings, the drivers would back off sooner, not push them as hard, and be well below the tire’s objective limit, as high as it might be.

For all these reasons, selecting a tire based only on subjective feel is not the best answer, even at the hands of a qualified EVOC driver. The subjective opinion is a part of reality of driving, but the objective, actual performance is the ultimate measure. On some tires, in some aspects of performance, the three drivers had the same subjective impression of the tire. On others, the drivers had separate and different opinions. On others, a majority and minority report. Clearly, more consensus is better than less consensus.

The objectively superior ContiProContact drew some lower driver impressions in some areas. The objectively inferior Eagle RS-A produced some higher driver ratings in some areas. The “best” overall tire, the Firehawk GT Pursuit, was the one with both consistently high objective results and where the subjective driving impressions are in close agreement with the objective results.

This helps us sort out the four possible outcomes, 1) the tire feels good, and is good, 2) the tire feels good, but is not, 3) the tire does not feel good, but it is, and 4) the tire does not feel good and it is not. In the final analysis, the top two tires (Firehawk GT Pursuit, ContiProContact) turned out to be the ones with the highest objective performance, even though driver impressions had an equal weight in the calculations.

Published in Law and Order, Aug 2009

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