This past Sunday, drifting savant and rally driver Rhys Millen charged up 12.42 miles of tarmac — and 4,720 feet of elevation gain, up to 14,110 feet — in his all-electric, 1,595-horsepower eO PP100, sponsored by Hankook Tire, during the centennial of the Pikes Peak International Hill Climb.
And he crushed it. Millen demolished the previous electric-vehicle record of 9:07.222 — set by him last year, naturally — with a time of 8:57.118. Though he wasn’t able to secure a first-place finish, he came in second overall, and achieved his “number-one goal” of breaking nine minutes.
Before the event, we spoke to Millen about the race, the car, his goals, and the all-important rubber that would eventually carry him to victory. (You can check out part one of the interview here.) Read on below for his expert analysis of how tires can make or break a race like Pikes Peak:
Hunter Slaton: What kind of tires do you need for this race and setting?
Rhys Millen: When you plan to maximize a set-up on a vehicle in a road-racing environment, you want the maximum amount of rubber contact patch. So for off-road and dirt, you [want] a grooved tire that has lots of biting little edges to give you traction. When you go to a road race, you want the biggest contact patch ever, so you run a full slip. And then those edges are not gonna wear away and you’ve got more rubber contact patch.
Go take that slipped tire and put it in the environment of a mountain, where there is rain and debris run-off over the road, [where] the road temperature might be 30 degrees not 100 degrees like a standard race track, [and] the tire is going to react completely different and be very inconsistent as you run different sections of the road. Braking force can be different, turning force can be different, corner exit can be different.
HS: Do you use just one kind of tire, or do you evaluate the conditions on race day and make a decision?
RM: Hankook’s been a credible partner of mine now for five years. This year they’ve developed this multiple compound to run up the mountain, and we’ve been testing on them all. For morning practices, you’re practicing from 5:45 to 8:45, whereas on race day you’ll run around 11:00. That road surface completely changes when the sun comes up. So we’ve been running softer compounds in the mornings to compensate for the lower surface temperature. And then on race day we’ll run a slightly harder compound to balance that higher surface temperature, to keep the vehicle balance and driver confidence up.
HS: How much of a role do the tires play in terms of keeping things balanced?
RM: A tremendous amount. We’ve given the car a lot more torque, so we’re having to compliment the tire grip with the amount of torque force, and actually make the tires slower [in order] to make the car faster. For this amount of torque on a vehicle, you can quite easily overheat and destroy the tire if you don’t have that balance right.
HS: Is Hankook innovating new tires each year, specifically for this race and for you?
RM: The tire size and structure [that we use for Pikes Peak] is the same as Hankook’s circuit-racing spec tire. The only thing they’ve done uniquely for this particular event is to bring a special compound. In years past, we’ve run their softest off-the-shelf compound, but after last year, running the electric car with increased torque force, we gave them the tires back after the event to evaluate them.
We pushed them far beyond their comfort zone. If you ran this tire at a regular race track at sea level, [with] regular ambient air and track-surface temperatures, the tire would only last about three laps or miles. We are in a completely different environment. This race is so specific to its own nature. And now we can make that tire last triple its life expectancy from if you ran it at a regular race track.
HS: It sounds like this race in particular really pushes the boundaries of what Hankook does.
RM: As an individual team, we are leading the charge of pushing their engineers to develop a formula that they have never applied before. It will give them feedback, and I think this is why manufacturers go racing. It enhances their products and makes them better overall.
We have even taken the tire and given it a heat cycle. We’ve gone and run the tire prior to going up on the mountain, to take it from its ambient cold temperature to up to 180 degrees, scuff it a little bit, and then let it sizzle overnight. And [this] actually stabilizes the compound to maybe one to two grades harder, to actually get a little bit more performance out of the tire.
HS: Oh, really?
All of that is feedback we provide to the engineers. And then if the program continues and the development continues, then we can just better our baseline for following years.
Hunter Slaton is the Content Director for Studio@Gawker.