Petty Charger body to chassis rake - Speedway & short track comparision

[odcics2]

Note the extra metal over the rear tire on the speedway car!

It was found that the airflow over the backlight would stay attached with more rake, giving
a lower drag number for the speedways. Lower drag = faster lap times.  With long sweeping turns, the higher back end didn't matter for dynamic handling.

Short tracks need more weight in the rear, so those cars have no body to chassis rake.
For the short turns, lower in the back helped a lot.

The spoiler seen on the front cuts lift in half, at any speed.  45 degree angle, located at the leading edge of the front valance.  Width was from frame rail to frame rail centerlines.  (per Nascar rules)

[Mike DC]

Interesting stuff.

I'm surprised there was such a dramatic difference in the ideal rake angle between the Daytonas vs Birds.  That back window really made a huge difference.  I guess the stock front window was already close enough to ideal that they didn't have to cater the setup to it as much.



It also surprises me that the short-track thing was worthwhile.  I wouldn't have expected a 1-2 degree change in the stance to move the F/R weight balance enough.  It needed to outweigh the negative aero effect of lowering the back end.  Aero makes a difference at pretty much anything over 50-60mph.  

[tan top]

interesting sruff 

[odcics2]

Glad you appreciate this stuff...

Petty was putting the speedway body on a flat chassis, instead of just jacking the entire car up in back.
Best of both worlds...