Brendon Hartley and Pierre Gasly are due to start the United States Grand Prix at the back of the grid as Honda fit modified Spec-3 engines in Austin, Texas.
However, after further analysis, the Japanese manufacturer have been forced to make some minor adjustments ahead of the United States Grand Prix and, with both drivers well above their penalty-free power unit allocations, more grid penalties will follow this weekend.
“On both cars, the new units will feature minor modifications to the specification when compared to that used in the Japanese Grand Prix,” said Honda chief Toyoharu Tanabe.
“After examining the power units used in Suzuka, we had some concerns and so we have decided to make these changes, which we believe is the best strategy for Toro Rosso for the remaining races.”
Gasly’s Toro Rosso has been fitted with a new internal combustion engine, turbocharger, MGU-H and MGU-K ahead of first practice, while Hartley will get his fresh components on Friday night following the conclusion of FP1 and FP2.