Tire & Staging Rollout Calculator

Calculate tire circumference per revolution and estimate front-tire staging rollout distance and time to 0.001 second using your measured 60-foot ET. These are separate distances: circumference is used for gearing; staging rollout is forward travel before the front tire uncovers the stage beam.

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Enter the time-slip 60-foot ET, such as 1.300. Estimated rollout is shown to 0.001 second; this is display resolution, not guaranteed accuracy.
Results update as you type.

Results

Measure tire circumference at race pressure when accuracy matters. The staging estimate treats the front tire as a rigid circle on a flat track and the stage beam as an infinitely thin horizontal line; loaded tire shape, beam width, wheel lift and track equipment can change actual rollout. The 1.5-inch beam height is an example, not a guaranteed track specification. Depth is forward travel after the tire first breaks the stage beam, not the distance between pre-stage and stage beams. The stage beam must still be blocked at the entered depth. The time model assumes a start from rest and constant acceleration through rollout and the first 60 feet. The 60-foot ET begins when the stage beam clears; the model also accounts for the leading tire edge breaking the 60-foot beam, assuming the same beam height and a 60-foot beam separation. Real launch acceleration, wheel lift, tire deformation, clutch behavior and timing equipment can substantially change the answer. A 60-foot time alone cannot establish actual rollout time. This is an estimate, not measured reaction time or a guaranteed ET change. Switching units converts existing length entries.
Formula and assumptions

Circumference = π × tire diameter. Revolutions per mile = 63,360 ÷ circumference in inches. Full shallow staging distance = 2 × √[2 × front-tire radius × beam height − beam height²]. Remaining staging rollout = full shallow distance − staging depth. Time model: let r = remaining rollout in inches and D = 720 − full shallow distance in inches. With constant acceleration from rest, rollout time = 60-foot ET × √r ÷ [√(r + D) − √r]. The stage timer starts after rollout; the matched-height 60-foot beam is triggered by the leading tire edge.