Toyota explains how it made the wrong tire choice

Technical director Tom Fowler walks DirtFish through the decision-making process and what it could've done differently


Toyota technical director Tom Fowler doesn’t feel taking no hard compound tires for Saturday morning’s loop of Rally Chile was a mistake, because that would have meant deviating from its usual data-driven process.

All three Toyota drivers ran into trouble on SS9, the final stage of Saturday morning, with Elfyn Evans and Takamoto Katsuta picking up rear punctures and Kalle Rovanperä backing off significantly so he didn’t suffer the same fate.

None of the GR Yaris Rally1s headed out for the three stages with any hard compound tires fitted or in the trunk, which proved to be a bad decision.

Fowler explained how Toyota made that choice on Friday evening.


“Our tire choice that we made here was made in exactly the same way that we make all our tire choices, so we have a process by which we calculate which tires will be the best option,” he told DirtFish.

“Of course the calculation comes out with normally various options which we discuss with the drivers and then decide what we’re going to do for that loop.

“This calculation is obviously a relatively complicated one, it takes into account the tires which are available, takes into account the road surface, the temperature and the conditions on the ground on the day. And of course calculations can be wrong.

“We went with what our usual process tells us to do, we put that process to the drivers last night. We went with the solution that came out, and it turned out to be the wrong one.

“So I would say the good news is that we know how we chose that tire, we know what data was used to choose that tire and we know that data is not correct. So we can adjust that for the future.

“The takeaway from this is we’re data driven, we’ll always be data driven, but that we need to always take into consideration that our data can be better.

“Fundamentally what we need to improve is being able to characterise the road that we had, that we saw during recce, that the drivers saw during recce, and how we characterise that in comparison to every single other tire we’ve ever driven on a different type of road,” Fowler added.

“What we’re doing is collecting data from test roads, from previous rallies and comparing that to the performance and the wear degradation of the tire in characterising what that will do on different roads in the future.

“So of course we do this by using a lot of data to try to make sure we have as much information as possible, but in the end it is still a calculation using averages and it can be wrong.”

Fowler didn’t feel Toyota made a mistake, but confessed “the calculation was off”.

He argued: “Our other choice was to ignore our normal process, our normal calculation, and that would be a mistake.

“The way we need to look at this is in one season we’re making, I don’t know I’m going to quickly say 70/80 tire choices in one season perhaps.

“This one’s obviously not gone how we want it to but 70-something-else other ones have gone pretty well.

“We’re not going to change our process, we’re just going to make sure the data that’s behind our process is more accurate.”


Asked how much the drivers feed into the decision making process, Fowler explained that they are the final link in the chain but still ultimately have the final call.

“The driver is obviously the final part of the tire choice,” Fowler said. “We will never send a driver out on a tire he doesn’t want to use.

“We had the discussion last night in the service about what are the options. The drivers agreed with us and the situation as it is today is that the whole team together understands that we could have done better, so that comes from the engineers, from the drivers, from the support staff, from the whole team, that we could have done better and someone could have picked up on it.

“But we all made the mistake together.”