Charles Pic reckons Formula 1 won't find it easy swapping from 13-inch to 18-inch tyres should the move go-ahead.
The Lotus driver completed 14 laps on the Pirelli 18-inch tyres during Wednesday's in-season test at Silverstone.
Asked how he felt about the tyres, Pic told Autosport: "If we go with this type of tyre one day, it will be a big challenge.
"For the teams, because they will have to build a completely new car around it because the philosophy is completely different, and also for the drivers because they are completely different.
"And on the looks side, it is different and some people will like it, others not.
"Honestly, I thought they were a bit too big, but then maybe it is because it was the first time I saw them on the car."
The Lotus E22 had to be adjusted on Wednesday to accommodate the larger tyres with changes made to give the car greater ground clearance.
Added to that, Pic was limited on how hard he could push while, according to Autosport, he also had to stay off the kerbs.
The Frenchman revealed that that car felt nervous on the 18-inch tyres but expects Pirelli will make huge improvements before the tyre is raced - if it ever is.
"The goal was to try and run them and see how they react.
"The overall grip was very low, I think it was five or six seconds off the pace, mainly for the reason that the rest of the car was made for the normal tyre, not the prototype.
"It is true that they are more reactive and nervous, and then on top of that you lose a lot of aero.
"It is not even like you are in Monza configuration, it is even less because of this type of tyre.
"If you look at handling, of course it is not good - but that was not the point of the test.
"This was really the beginning with this type of tyre and for sure they will improve it.
"I think in the philosophy it will be a type of tyre that will react quickly, and the reaction you get in the steering wheel is more nervous. Each time you get the snap it is quicker [than with the standard tyres]."