Tyres
For 2009 F1 returns to slick tyres after 10 years of grooved tyres. This will improve mechanical grip, however this will be offset by changes to the aerodynamic rules. Two dry weather compound tyres will be avaialable for each race and both will have to be used during each race.
Engines
These will now be limited to a maximum of 18000 rpm an dwill have to last 3 races instead of 2 races.
Aerodynamics
A selection of changes that will produce a car with cleaner lines through removing various additional add-ons to the body work.
Changes to the front and rear wings are designed to reduce turbulance when following another car and hence increase overtaking. The front wing is lower and wider and also can be adjusted by the driver by upto 6 degrees twice a lap. The rear wing and diffuser are also changed to reduce down force.
KERS (Kinetic Energy Recovery System)
Teams have the option of using a system that stors energy from the braking process to use at other sections of the lap. This storage can be electrical or mechanical. Potentially this could add 80hp per lap but has a weight penalty. How well this will work will depend on the technological development of these systems.