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Speedometer Discrepancy

Loe

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It's more prevalent on 21" wheel cars with 265/305 F/R tires, they are shorter in OD than the 20" -or- the J1.2 21" wheels/tires with 245/285 F/R all-season tires with higher sidewalls and similar OD to the 20" wheels.

In other words, you get spot on or near spot on speedo readings with the 20" or 21" with 245/285 cross section tires, or be 1-3mph off with the 21" 265/305 cross section tires (the higher the speed, the higher the error).
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SoccerMan94043

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I passed one of those speed monitor signs yesterday and it read exactly 3 MPH lower than what I was going. Now I need to speed more.
 
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gnr3312

gnr3312

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I passed one of those speed monitor signs yesterday and it read exactly 3 MPH lower than what I was going. Now I need to speed more.
lol exactly my thoughts, like now that I know I want my extra 3 mph 🤣
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