I was confused by the new regulations: I had an old version for 2008 that was published in March, 2007 and the tyres had the same dimensions as in the 2009 regulations I have. Then I discovered that the
new 2008 regulations, published this year, in February, do not increase the size they had in 2007. My conclusion: tyres
were to be larger in 2008, but that change was delayed to 2009.
The maximum sizes are:
Rear: In 2009, 46 cm wide by 71 cm high (right now is 38 x 66, that is, they will be
8 cm wider and 5 cm taller)
Front: In 2009, 36,5 cm wide by 67 cm high (right now is 35,5 x 66, that is
1 cm wider and 1 cm taller, not much. Actually you can use 1 cm wider wet tyres, in 2009 wet tyres are the same size, so the 2009 tyres are as wide as wet tyres).
The wheel bead is also taller, it goes from 33,2 cm right now to 35,8 cm in 2009, that is,
the rim should be 2.6 cm taller.
About the body, well, I tried to read quickly section 3.
The car is wider: it goes from 1,8 meters to 2 meters. That's
a 20 cm wider car for lateral stability and mechanical grip. As I read it, this maximum dimension applies to the wheels, not for the entire bodywork, which has its own maximum width.
The bodywork behind the rear wheel center line (I'd say the
engine cover and diffusser assembly) goes from
1 meter wide to 2 meters. That's huge.
The car is slightly taller:
from 95 to 97 cm tall. This applies (I imagine) to the rear wing and maybe the air intake.
The bodywork forward of the front wheel center line (well, "a point lying 33.5 cm behind the front wheel center line"), that is, the front wing, can be as low as 10 cm, while right now you cannot go lower than 15 cm, so the
front wing is 5 cm lower.
The "depth" of the wing is increased only in 5 cm, because the maximum height of it goes from 35 cm in 2008 to 30 in 2009, so the wing "rides lower".
The back of the engine cover is "raised", I think. The regulations are too confuse for me to dillucidate this without a drawing, but
you can have an engine cover that is 20 cm taller than this year.
From 1.3 m forward of the rear wheel centerline (most of the bodywork, I think) you have to have "continuous lines". I think this is the part that
forbids ailerons and aero-gadgets, but I'm not sure if this applies to the entire car, I'm not sure about bargeboards, for example.
I throw up my arms in despair when I tried to compare regulations for the rear wing bodywork. It seems you cannot make wings wider than 1.4 meters, but beyond that I did not get the wording. Can someone help me here?
Just in case, here you have
the link to 2008 and 2009 regulations.
EDIT: The 2009 regulations are the ones published in December 2006, the PDF hasn't changed since then.
