The departure of Bridgestone and the arrival of Michelin as the official tire supplier to MotoGP is an extremely delicate operation, in terms of marketing, tire development, and motorcycle set up.
Bridgestone have paid a lot of money for the exclusive rights to MotoGP branding with their tires for 2015; Michelin have done the same for the rights from 2016 onwards.
Neither company wants to tarnish their brand or see the value of their investment diminished, either by rider comments expressing a preference one way or another, or by lap time comparisons showing either firm up.
This posed problems for the Michelin test, held on the fourth day of the Sepang MotoGP test. After the factory test riders had tried the Michelins at the first Sepang test, it was the turn of the MotoGP regulars.
To avoid any comments which might favor one factory or another, Bridgestone imposed a blanket ban on riders or team members speaking to the media after the test.
All Bridgestone branding was removed from bikes and leathers, and no visible Michelin branding was allowed, even down to the manufacturer’s logo on the tire sidewalls.
With major money on the line, the PR gag-order was enforced rigidly, and observed religiously. No official times were released, nor made unofficially available by the teams.
A range of times have seeped out from journalists present, but given that only a few laps were timed by a few people out of practice with using a stopwatch (or its modern equivalent, the smartphone), those times can be taken as guidelines only.