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Rollins_2241 · 04-12-2012, 08:46 AM

Talking about the first 60' only, not downtrack aerodynamics or rolling resistance, 2" from say, 24" to 26", is worth about .012. This is not exact due to tire "squat" and depends on the air pressure you run in both sets (hopefully apples to apples of course).

But the math is pretty simple and has been done here before. Draw a circle with radius R, and a "beam" with height H. Then draw two right triangles using R and the chord made by a horizonal line through H, and use the Pythagorean Theorem. H is specified by NHRA but actually varies from track to track and depends also on where you stage (where the groove is) relative to the crown of the racetrack. The differential in rollout can be calculated when R changes. Then more difference equations can be used to turn it into ET. I spared you all that stuff.

04-12-2012, 08:46 AM	#5
Rollins_2241 Member Join Date: Nov 2007 Location: Tallahassee, FL Posts: 170 Likes: 0 Liked 0 Times in 0 Posts	Re: Front tire size vs. ET in a Stocker.... Talking about the first 60' only, not downtrack aerodynamics or rolling resistance, 2" from say, 24" to 26", is worth about .012. This is not exact due to tire "squat" and depends on the air pressure you run in both sets (hopefully apples to apples of course). But the math is pretty simple and has been done here before. Draw a circle with radius R, and a "beam" with height H. Then draw two right triangles using R and the chord made by a horizonal line through H, and use the Pythagorean Theorem. H is specified by NHRA but actually varies from track to track and depends also on where you stage (where the groove is) relative to the crown of the racetrack. The differential in rollout can be calculated when R changes. Then more difference equations can be used to turn it into ET. I spared you all that stuff.