Reading the sawtooth chart
Each gear is a straight line of speed against RPM — steeper gears (lower gears, higher ratios) reach redline at lower speed. Follow one gear up to the redline, shift, and the engine drops to a lower RPM at the same road speed: that vertical fall is your rev-drop. String them together and you get the sawtooth. Speed at redline in any gear is:
speed = (RPM ÷ (gear × final)) × π × tire diameter
A well-spaced box keeps each shift landing back in the meat of the powerband — big gaps between the low gears drop you out of boost or off-cam, while a tightly-stacked top end holds revs high for overtakes. The rev-drop column is where you judge that.
FAQ
What's a good rev-drop between gears?
It depends on how wide your powerband is. Peaky engines (small turbos, high-cam NA) want small drops — maybe 1500–2500 rpm — to stay on song. Torquey, wide-band engines tolerate bigger gaps. The chart makes an uneven set of ratios obvious at a glance.
Where do I get my tire diameter?
Use the tire size calculator — it gives overall diameter in mm from width, aspect and wheel size. A 225/45 R17 is about 632 mm; a 245/40 R18 about 653 mm.