Last week at this time I was in Nashville, TN, driving the Ford Edge I told you about here. Motor Trend managed to get a few different versions into their press fleet, and in extensive back-to-back testing found the low zoot SEL model to be quicker than the flashy Edge Sport, despite the Edge Sport’s horsepower advantage. Is this news? Does this re-write the pages of automotive history?
No, actually, but it does confirm that Sir Isaac Newton was right when he discovered that a larger, heavier body requires more force to move than a smaller, lighter one. Let’s take a look at the models Motor Trend compared:
Ford Edge SEL
This model comes with a 285 horsepower V6, and is available in either FWD or AWD. Wheels are 18”, fitted with 245/60 HR-18 all season radials. Motor Trend tested a FWD SEL, which has a curb weight of 4,082 pounds and horsepower to weight ratio of 14.32 pounds per horsepower.
Ford Edge Sport
This model ships with a 305 horsepower V6 (same as the one in the new Mustang), and is available in FWD or AWD. The Edge Sport has class exclusive 22” wheels, fitted with 265/40 WR-22 tires. Motor Trend tested an AWD Edge Sport, which has a curb weight of 4,428 pounds. The resulting horsepower to weight ratio is 14.52 pounds per horsepower.
So if we were comparing apples to apples (unlike Motor Trend), we’d have opted for a front wheel drive Edge Sport. The FWD version is significantly lighter, and would have given us a power to weight ratio of 13.98 pounds per horsepower. On paper, at least, an equivalent Ford Edge Sport would be quicker to sixty miles per hour.
There’s one more factor to consider, and that’s the added weight of the 22” wheels. Big wheels may look cool, but they add a significant weight and acceleration penalty to a vehicle. In an informal discussion, a Ford engineer told me that the Edge Sport’s wheels weight roughly 25 pounds more, per corner, than the wheels on the SEL or the limited. That amy not sound like much, but it has a huge impact on acceleration and braking.
In April of 2010, Car and Driver did a performance comparison of various wheel sizes on a VW Golf. Comparing smallest to largest showed that 15” wheels and tires were 14 pounds lighter per corner than 19” wheels and tires. Zero to sixty times were .3 seconds faster with the 15” wheels than with the 19” wheels. If 14 pounds is good for .3 seconds, then 25 pounds should translate to .5 seconds difference in speed (assuming a linear progression between weight and acceleration).
So what does that mean in the case of the Ford Edge? If you swapped wheels and used the 18” wheels on both the FWD Edge SEL and the AWD Edge Sport, I’d expect the acceleration times to be identical. I don’t know about you, but I’ll sleep much better now that I know this.