“Impossible” to build mule cars to test tyres for new 2026 F1 rules

Formula 1’s official tyre supplier has warned it will be “impossible” to build mule cars to test the sport’s new rules for 2026.

Pirelli needs to develop a new range for the season after next, when F1 will switch to narrower front and rear wheels. It is part of a drastic overhaul of the technical regulations in which new power units will be introduced and F1 will allow great use of active aerodynamics.

Previously Pirelli has been able to prepare for changes in tyre size using ‘mule cars’ adapted by the teams (pictured above) to simulate the forthcoming new rules. However Pirelli’s motorsport director Mario Isola told RaceFans the nature of F1’s 2026 regulations will largely prevent that.

“It’s impossible, I would say, to create a mule car with similar characteristics,” said Isola. “We will not have smaller cars. We can save some weight – instead of doing long runs with full tanks you can, reduce the level of fuel just to simulate the weight. But for the rest, it’s impossible because you don’t have the active aerodynamics.”

Under the 2026 rules, drivers will be able to switch to a low-downforce mode on straights, then switch back to maximum downforce when cornering.

The 2026 rules will be the third time in 10 years F1 has changed its tyre format. Wider rubber was introduced in 2017, and two years ago F1 switched from 13-inch wheels to 18 inches.

On those occasions teams were able to produce mule cars which approximated the accompanying rules changes. Isola said Pirelli will have to rely heavily on simulation data to develop its 2026 tyres until the first cars arrive at the beginning of the season.

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“This is a similar situation we faced with the mule cars when we were developing the 18-inch tyre, for example, or during 2016 when we were developing the wider tyre for 2017, also in that case we had mule cars that were not fully representative.

“So what is important for us is to work in parallel with the virtual model and the physical model. We try to understand that which is the correlation between the two in order to have tests on-track that are as much as possible representative of what we will find in 2026, knowing that it will never be 100% representative.”

“For the moment, we have simulations that are coming from the FIA, not yet from the teams,” he added. “But in the in the usual process of development we will receive also simulations from the 10 teams and we can understand which is the general idea of the performance estimated for 2026.”

Another change Pirelli has to cope with is the increased electrical power output of the hybrid engines. The FIA estimates total power will increase by around 10% to 1,100bhp. As more of this is being generated electrically, the torque demand on the rear axle is expected to rise significantly.

“We still don’t have numbers for that, we are working to get simulations that are telling us all these numbers,” said Isola. “We need these numbers to characterise the stress on tyres and then design the tyre.”

Pirelli did not join the discussions around F1’s new regulations until October last year, after it agreed an extension to its current tyre supply contract. It pushed against a move to smaller, 16-inch wheels, which the FIA desired to help reduce car weight, as Pirelli feared that would harm car performance too much.

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“The 16-inch tyre that was estimated at the beginning of the process was not the right size, in our opinion, if we want to keep it the performance of the car similar to what we have now,” Isola said.

“If you want to slow down the cars, reduce the loads, reduce the speed, you can go down with the size. But if we want to keep a similar level of performance, we cannot go in this direction, it’s too much. Small tyres like this don’t have the loading capacity that is required for these fast cars and heavy vertical load that you put into the tyres at a high speed.

“We have also the active aerodynamics that is changing the configuration, with the low downforce and the high downforce. So in cornering we have high downforce and you push a lot the tyres on the ground. On the straight, you have lower downforce but much higher speed. That has a different impact on the integrity of the tyre.

“So considering all these elements we came back to the FIA with a proposal of a size that is an 18-inch, slightly smaller, but with the characteristics we believe are guaranteeing that the performance is in line with the expectations.”

He pointed out that the projections of how much downforce cars would create under the new rules changed significantly while the regulations were being crafted.

“In the meanwhile, when we were discussing that, also the estimation changed. So from an initial estimation where the loss of downforce was quite important, we got simulations where the loss of downforce is not so big.

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“So this is another element that we considered and we decided to go with this proposal, knowing that the final target is to have lighter cars to save weight. So we want to do our part in that, but not with a tyre that then is not able to cope with the level of stress that is predicted for 2026.”

Pirelli plans to conduct its first test of the narrower prototype tyres for 2026 in September, with Aston Martin.

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