Recommended Tire Pressures
Use Ducati's recommended pressures.
This is from Bridgestone's Tire Tips
http://www.motorcycle-karttires.com/
Always keep the motorcycle manufacturer's recommended air pressure in both tires. This is an important requirement for tire safety and mileage. Your motorcycle owner’s manual will tell you the recommended cold inflation pressure. On some motorcycles, the recommended front and rear tire pressures will be different. The pressures stamped on the sidewall of the tire are only for maximum loads. On some occasions, these pressures will also be the manufacturers recommended settings as well.
Here's the word from Bridgestone UK Motorcycle Technical & Sales regarding a similar question about 999 tire pressures.
When bike manufacturers are developing a new model they have approximately 3 years during which time their test riders will be able to determine what pressures in their opinion, best suit solo and (if different) pillion riding. They are also generally only working with two tyre manufacturers who will become the original equipment (OE) suppliers. Bike manufacturers usually launch no more than three new models a year.
Bridgestone has approximately 4,000 different tyre approvals in our fitment guide so, as with all other tyre manufacturers, we obviously only have limited time to test each bike so we test for the one set of pressures that work well whether solo or with a pillion. It would be irresponsible of a tyre (or bike) manufacturer to recommend pressures that did not give optimum stability, and higher pressures lead to greater stability. If we were, due to the aforementioned time constrictions, to only recommend pressures for solo use and then a rider took a passenger along without increasing pressures, and suffered the consequent instability that may occur, it would be the tyre company that would be held to blame.
The higher pressures we recommend are perfect for commuting, touring, motorways, general riding and pillion use. The only area where you could possibly increase grip by reducing pressures is solo sport riding, and then not by a heck of a lot.
One other point - we are recommending pressures that our test riders have found best for our tyres on, in your case, a 999. Ducati have never tested BT010s on a 999 and because of the different way each type of tyre behaves, what's to say that Ducati's recommended pressures will work with our tyres?
By the way, we used a 999 as one of the bikes for our recent BT-014 launch and they suited the bike perfectly. The BT-014 is the tyre that will replace the BT-010.
Determining Best Tire Pressures
http://www.ducati.ms/forums/showthread.php?p=277556#post277556
Finally, Japanese sportbikes versus Ducati twins seem to have an extra 4-6 psi specified for their tyres, compared to the equivalent Ducati.
Here's why.
In-line fours heat up their tires more than a twin so a higher starting pressure is needed to prevent overheating the tires, particularly the rear tire.
Years ago, superbike racers discovered that it was easier to modulate the power to prevent wheelspin on the Ducati V-twins than it was to do the same on the Japanese inline-fours. This is because there is a longer interval (in terms of both time and crankshaft rotation) between cylinders firing, which gives the rear tire a "break" - time to recover traction and match its speed to that of the motorcycle.
More recently, more sophisticated traction control systems have been tried to reduce tire temperatures, improve tire life and lap times.
