FULLERTON, Calif.—Call him Yokohama Tire Corp.'s race tire maitre d'.
It rolls off the tongue easier than “senior technical engineer.” But Samuel Kwa, a four-year Yokohama Tire veteran, prefers to be thought of simply as the person who helps choose the right tire for American Le Mans Series teams from a “menu” of assorted flavors.
“Basically, it's very similar to your selection if you walk into a restaurant and you wanted to have a meal, the maitre d' or the wine person would suggest you pair this particular wine with this particular food item,” he said. “There's not much R&D done from my perspective. I supply all the data from the teams and from the particular event.”
It sounds simple, but the process of selecting the right tire is anything but, said Kwa, who is involved with ALMS GT and GTC class races along with the IMSA GT3 Cup Challenge by Yokohama and several grassroots-level motorsports events.
For GTC class and GT3 Challenge races, both of which feature Yokohama's Advan ENV-R2 as the spec tire, Kwa said his role is pretty straightforward.
“I'm there for technical support,” he said. “Whatever questions they may have come up in regards to the tire or in regards to setting up the car for working well with the tire. I try to give as much feedback and information to the teams, the drivers, to the mechanics, just so they have a better gauge of where the car needs to be to optimize the tire.”
Things get more complicated in the GT class, Kwa said, where there is a portfolio of tire compounds from which to choose. The crew will test a variety of these, often using a known compound from a previous race as a baseline.
“From there we'll run seven-lap sprints and we'll run through the various compound selections depending on the time during practice, and we'll try to maximize our testing time to figure out what's going to work and what's not for the weekend,” he said.
Kwa's role for GT events involves obtaining lap time data, taking tire pressures and temperatures, analyzing tire wear, getting feedback from drivers and looking at other information to select the optimum compound for qualifying and race day. “We also have to consider weather that may be approaching and amount of waterfall on the ground to choose the optimum wet tire, as well,” he said.
Kwa, who also is involved with Yokohama's off-the-road tire segment, said the two products—while very different from each other—share a common theme.
“They're very dissimilar, but one thing that is sort of an overlapping theme is that every tire that we produce or use in motorsports and every tire that we make in OTR, there's a tire that's built specifically for a certain application,” he said.
“With the mining side of it, the OTR side, we have different applications where we need to run certain compounds or certain constructions that will work best,” he said. “In motorsports, it's the same way. We have a tire that has a certain compound that will work with a track, a certain compound that will work with this amount of water … and we have to be able to make that judgment on the fly.”
Prepping for race day
A typical race weekend for Kwa lasts about four to five days, including a day for setup and two or three practice days. He usually shows up at the track a day before practice runs begin to perform a track characterization.
“That involves taking surface samples,” he said. “I use a quick-drying putty and I do surface impressions at various places around the track, and wherever I do a surface impression I also get a coefficient of friction measurement.”
Kwa said Yokohama utilizes an ASTM standard sample, and compares it to a sample of the compound it is using. “From there we can gain information about how much grip there is on the track, both mechanically and chemically. We can gauge how our compounds are going to run on the track and make a decision on what we plan to run for the track conditions that particular weekend.”
After practice days, Kwa spends more time back in his hotel room analyzing lap times and creating a report to compare the performance of each car.
Race day is often much more simple, with Kwa primarily serving in an advisory role. But in racing “nothing runs according to plan,” he said. Many factors—including changes in humidity lev- els, track temperature and the weather—can have an impact on how a tire will run in a race, and last-minute changes are not unheard of.
“Due to certain changes in weather, or any influences that can affect our plan, we have to be ready to account for those things and be able to make a decision with the information that is available to us,” he said. “This is where things may get difficult and rational thought and sound judgment are key. Sometimes a race can be won in making a crucial tire decision.”