I have been googling my ass off, but can't come across the reference chart for selecting the appropriate speedo gear by tire size and gear ratio. Somebody help a poor dude out here, I gotta get the speedo back into the ballpark.
Jerry
Speedo Correction Chart
Apr 20, 2004
7 Replies
Jerry Newton did pass the time by typing:
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Chris
Just a follow up to that chart. You can do it mathematically as well using the formula:
Gear Teeth = Axle ratio * 280 / Tire Diameter
Chris
Thanks to all, I have what I need.
Jerry
Raingler's chart is OK, and I've seen others, but none of them specify which year TJ/YJ they are talking about. I've seen references suggesting the older TJ's have a stock 27 tooth gear, but my 2004 TJ has/had a 29 tooth gear. When I timed it on the road and did the math, I needed a 35 tooth gear.
the math:
3600/mile time= miles per hour (mile time=time in seconds to cover a mile)Number of gear teeth=(old gear number)x Speedo reading/actual speed.
(ie--if the actual speed is lower than the speedo reading, you end up with a larger gear).
I usually average the times over 2-3 miles using mile markers on the highway.
tim
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