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Regear Comparison Calculator
Your current setup on the left, the setup you're dreaming about on the right — crawl, cruise RPM and speedo error, side by side.
A regear comparison puts your current axle ratio and tires next to a candidate setup and shows what changes: crawl ratio, highway RPM, crawl speed and speedometer error — before you spend anything.
Formula: crawl = 1st × low × axle · rpm = mph × 336.135 × (gear × axle) ÷ tire (in)
What this number means
A regear decision is four numbers wearing a trench coat: crawl ratio (trail control), RPM at highway speed (daily manners and fuel), crawl speed at idle (can you actually idle over it?), and speedometer error (the ticket and the fix). This page puts current and candidate next to each other so the trade is visible in one look instead of four separate calculators.
What to change next
Work the candidate column. One ratio step deeper (4.10 → 4.56) buys roughly 11% more crawl and costs roughly 11% more cruise RPM. Two steps (4.10 → 4.88) is the classic '35s now, 37s later' move — check the crawl speed row: if idle crawl is still under your comfort speed, the gears are doing their job.
Worked example
JL Rubicon, 850RE, 4.10s on 33s today; candidate 4.88s on 37s. Crawl goes 77.2 → 82.9 even on the bigger tire, cruise RPM at 70 rises from ~1,940 to ~2,070, and the speedometer needs a programmer because both tire and gears moved. That is the whole decision, on one screen.