MEXICO CITY (Reuters) - Mexican Grand Prix stewards have cleared world champions Mercedes to use a novel rear wheel rim design whose legality had been questioned by Formula One rivals concerned it might give an aerodynamic benefit.
The stewards gave their opinion in a statement issued after Mercedes made a written request for them to settle the matter ahead of Sunday's potentially title-deciding race.
Lewis Hamilton is poised to win his fifth championship in Mexico, needing only to finish seventh for Mercedes while Ferrari rival Sebastian Vettel must win to have any lingering chance.
Hamilton has won nine races this season, his run of four in succession ending at last weekend's U.S. Grand Prix in Austin, Texas, when Mercedes did not use that particular type of rim.
The wheel rim controversy concerns spacers, small holes and grooves that Mercedes say are for cooling purposes.
The technical regulations state that "any specific part of the car influencing its aerodynamic performance must remain immobile in relation to the sprung part of the car."
Some had felt that air passing through the holes and grooves was a breach of the rules, with media reports indicating Ferrari had sought a clarification after last month's Japanese Grand Prix.
Mercedes did not use the new rims in Austin to avoid any risk of a post-race protest, despite the FIA's technical department advising in writing that the configuration submitted to them complied with the regulations.
The FIA also advised that it was up to the Stewards, and ultimately the FIA International Court of Appeal, to offer a binding interpretation.
The Mexico stewards said that "should Mercedes run the part as described in the correspondence between Mercedes and the FIA's Technical Department, the Stewards would consider this part to be in conformity with the regulations."
The decision can still be appealed and it was not clear whether Mercedes would now feel confident enough to use the new rim in Mexico.
(Writing by Alan Baldwin in London, editing by Greg Stutchbury)