Christian Horner thinks Red Bull's participation in last year's Pirelli tyre tests has had a detrimental effect on its 2017 car because the tyres developed differently than expected.
Red Bull, Mercedes and Ferrari provided "mule cars" to F1 tyre manufacturer Pirelli last year so it could extensively test the wider tyres introduced as part of the 2017 rule change. Tyre testing was blind, with Pirelli sharing data among the teams equally, though many have suggested Ferrari's big step forward this year shows there was an advantage in taking part in the test programme.
However, Red Bull has failed to live up to pre-2017 expectations and finds itself a distant third in the pecking order, something team boss Horner says can be traced back to those mule car tests.