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jbwthree · 11-10-2020, 01:16 PM

Hello. Divide the 2 ratios: 1.78/1.54 = 1.07. That number can be used to scale the speedometer reading, so 40 mph reading on the speedometer is 1.07*40 = 42.8 MPH. Your error will increase as the speed increases and vice versa. This of course assumes that the speedometer was right in the first place and some of the prior responses will help you verify that. Hope that helps !

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11-10-2020, 01:16 PM	#5
jbwthree Member Join Date: Oct 2020 Location: East Sandwich, MA Posts: 62	Re: Rear axle ratio and car speed Hello. Divide the 2 ratios: 1.78/1.54 = 1.07. That number can be used to scale the speedometer reading, so 40 mph reading on the speedometer is 1.07*40 = 42.8 MPH. Your error will increase as the speed increases and vice versa. This of course assumes that the speedometer was right in the first place and some of the prior responses will help you verify that. Hope that helps ! Sent from my iPhone using Tapatalk