On Tuesday, Chip Ganassi Racing-Chevrolet’s Tony Kanaan and Rahal Letterman Lanigan Racing-Honda’s Graham Rahal tested at Phoenix International Raceway. The Verizon IndyCar Series will return to the hallowed one-mile oval in 2016 with a race on the evening of April 2, some 11 years after the last Indy car race at PIR.

The test was hosted by Firestone, so Motorsport.com spoke to Dale Harrigle, Bridgestone Americas chief engineer and manager of race tire development, to gain insight on the challenges Firestone faces as it encounters new (and ‘new old’) tracks, and the adjustments the company plans for next season.

What kind of things are you looking for from a test such as the one at PIR, and what conclusions did you come to?

The main focus was to see how much Phoenix had changed since we last raced there in terms of the banking adjustments and track surface. We started with the Milwaukee tire and we found that was a pretty good compound for Phoenix. We are going to alter the left-side tire compound to be a little harder than at Milwaukee but not a lot different than our standard one-mile oval tire.

We know about the tweaks Firestone makes to the red and black [alternate and primary] compounds that you take to all road and street course races. But it’s quite a common misconception that you only have one or two oval compounds – superspeedway and one-mile oval. Can you clarify the situation?

The left and right side on each of the ovals has a different compound. But loosely speaking, we have an Indianapolis setup, a one-mile oval setup, a Texas setup, Pocono setup and Iowa setup. There are eight different oval compounds, but arranged ten different ways.

Is it right to assume that somewhere like Iowa, you have to take into consideration vertical loads as well as lateral, because it’s so bumpy?

Absolutely, Iowa you’d think would be a one-mile oval tire, but the right side tires have to be our superspeedway tires because that track creates such a high load because of the combination of banking – therefore speed – and its bumps.

At a test like Phoenix where you’re stepping somewhat into the unknown, does IndyCar set its downforce levels according to how much grip you’re predicting, or is it the other way around – do they tell you what they’re running and you decide on compounds accordingly?

Well yes, they’re quite related. I’d say IndyCar first decide how much downforce they plan to run and then we make our decision, working closely with Will Phillips [IndyCar vp of technology] and Tino Belli [director of aerodynamic development]. At Phoenix, like I say, we’ll pretty much go with the Milwaukee tire setup, but over the years there have been occasions – for example at Pocono – where IndyCar have made a change to the downforce and we’ve adapted our tires to suit.

"We want to help IndyCar get away from pack racing but obviously the reaction to that is all over the map"

When you had tire degradation, such as we saw at Texas Motor Speedway especially 2012-’14, and the top talents loved the fact that pit strategy was defined by tire life rather than refueling needs, does Firestone like that kind of publicity in that at least people are talking about the tire? Or would you rather the tires were more durable?

Well that’s a tough one to answer. In that situation we’re working from the standpoint of being a good supplier to IndyCar by giving them the tire that delivers their objective. So we want to help them get away from pack racing and obviously the reaction to that event is all over the map. Some drivers love it, some drivers hate it, some fans love it, some fans hate it. But we’re trying to walk the fine line between not having so much grip that the cars are packed up, but not having so little grip that the cars are excessively difficult to drive fast. We want IndyCar putting on a good show for the fans.

And I think Fontana this year was a good example of how small a target we’re trying to hit. The track temperatures were cooler than anyone expected, the cars had more grip and so the cars were running much closer together than IndyCar would have preferred.

Companies that have a monopoly often have a hard time getting the credit they deserve, in that often they only get noticed if something goes wrong; if everything goes well, that’s no more than everyone expected. Is Firestone satisfied it gets recognition for its efforts?

I think so, in that we do take pride in our safety standards, durability, consistency and I do think the drivers and teams pay tribute, yeah. I think we’re trusted partners, and I think it’s fair to say also that we have been pretty conservative over the past couple of years. There haven’t been that many major changes to compounds, so that means IndyCar has a solid baseline to work to when deciding their aero levels. If they decided to take a lot of downforce away from an aero package at a race where we’d come along with a tire that gives a lot more grip, then we could end up canceling out their intentions. So we try to be as consistent as possible.

How about new events, such as Boston? Do you send a representative beforehand to study the track surface, or do you just err on the side of caution and take a tire that you know works at somewhere like Toronto where there are about five different surface changes to deal with?

A bit of both, actually. We will send someone in advance to check the surface textures at new events and assess what would be best, but for a first event, we probably will go a bit conservative and get a read of both types of tire [primary and alternate] on that track. Then we may change in subsequent years.

"Road America in 2016 will have its own unique tire. The track has held true to form, because it is quite severe for us"

Going back to Road America, the more experienced drivers were remarking on how they reached the same sort of lap speeds as they did in Champ Car but by very different means – slower in a straight line because of drag, but faster cornering speeds due to all the downforce. Did your data from eight years ago guide which compound you brought, or did you just bring something like your Mid-Ohio tire?

Well again, I’d have to say ‘both’. We went to Road America with the GP of Indy tire, because that track is our fastest road course. But then we found that similar to what we did in Champ Car, we still need to make some changes to that tire to make it last at Road America. So Road America in 2016 will have its own unique tire. The track has held true to form, you could say, because it is quite severe for us but the drivers love it and it should be a great event for the fans.

Regarding the red alternate tires and black primaries, how often do you alter the difference between them? Some drivers, especially those who start mid-grid, like it if there’s a big difference between them so their team can maybe pull a great strategy on race day.

We do alter the difference quite a bit, although on the street courses, you’ll probably see that difference remain the same over the course of one season. On the road courses, we have worked on altering the differences, not only from year to year at the same venue, but from venue to venue over one season. For example, at Sonoma this year, we had quite a big split between primary and alternate.

So we try and collate as much driver and team feedback, because as you’d imagine, this issue creates lots of different opinions. But if the reds offer more grip but wear faster than the blacks, then we feel we’ve pretty much done our jobs. But you’re never going to match up with everyone’s wishes if their wishes are all different! I’d say it’s a process that’s undergoing constant refinement throughout a year and from year to year.

"You’re never going to match up with everyone’s wishes if their wishes are all different!"

Do you change the compounds a lot from front to rear? I remember when everyone first got to test the DW12, the drivers who like a positive front end to their cars were hoping Firestone could put reds on the front and blacks on the rear to neutralize the Dallara’s natural push…

Ha! No, we don’t do that. We do change the tire structure between front and rear, but not the compound.

This time last year, as you started to get data through from Honda and Chevrolet testing their aero kits, how quick did you get data on revised downforce levels and how quick can you change compound as a result?

We had to work closely with not only IndyCar but also the manufacturers, who are both great partners, to understand how much the loads would increase and therefore how much the performance would increase. I’d say that we can respond in a three-month window, roughly.

How strict are Firestone and IndyCar when it sets parameters for tire pressures? Quite often an engineer will respond to his driver’s description of the handling by having the pressures altered, rather than – or as well as – adding front or rear wing. Considering speeds on ovals, that always spooks me…

We do supply the teams with a pressure range for every tire on the car, and also supply a single number that we believe is the optimum pressure for that tire. Most of the time when you hear them changing pressures, they’re changing within the range that we’ve specified, although there aren’t direct rules about it like in Formula 1. But in all honesty, the teams have always been very good at following our guidelines for safety and durability purposes, because they trust us.

When the aero kits debuted last year, our recommended tire pressure figures rose, but whenever IndyCar, Chevrolet and Honda reported back that the increase in loadings weren’t quite what was expected, we quickly readjusted them down. The teams basically want to lower their pressures as much as they can and we try and construct tires that fulfill our objectives along with theirs.

And once the definitive 2016 aero kit revisions are set in stone, we will be working with IndyCar and the manufacturers again to reset anything we perceive needs adjusting.

"In 2016 we’ll have two wet compounds…As soon as we get some wet running, we’ll compare them and we’ll probably use one for street courses, one for road courses"

Finally, on the subject of wet tires – how often do you change those compounds and is there a difference between a road course wet and a street course wet?

The intention is to use only one compound and that is more about being cost effective. It minimizes the number of changes a team needs to make and the number of tires that needs to be hauled from track to track. Having said that, in 2016 we’ll have two wet compounds. We actually were going to debut a new compound at Mid-Ohio, but it didn’t rain! So we’ve yet to use it in anger, but as soon as we do get some wet running, we’ll compare the two compounds. We’ll probably use one for street courses, one for road courses, with the ultimate objective of using just the one from 2017 onward.

What’s the purpose of this new wet tire? To come up to temperature quicker in cold wet conditions? To be more durable as it hits a drying track? Or what?

The motivation was finding more grip in the wet as that’s what the drivers say they want. It will also have a gray sidewall, so that the fans trackside and watching TV can tell who’s on what compound as track conditions change, dry to wet or wet to dry. I think those kinds of races with changing track conditions highlight the skill level of IndyCar drivers – driving a 700hp racecar on slick tires on a damp track surface can’t be easy…