Speedometer reading and tire size?
03-11-2001, 08:01 PM
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About to get 18" wheels and need advice about tire diameter and speedometer reading. 215/40 245/35 tires are about the same diameter as the stock tires, but rare and hard to find in matching set. So I will probably go with 225/40 255/35 which are much more available, but are about 1/10 to 1/8 of an inch larger diameter. How much will this change the speedometer reading at say 70 mph? Is there a formula for figuring the exact difference?
William
William
03-12-2001, 04:28 AM
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03-12-2001, 06:41 AM
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Try this page it calculates the stock tire to the new tire.
http://www.miata.net/garage/tirecalc.html
http://www.miata.net/garage/tirecalc.html
03-12-2001, 07:00 AM
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Thanks Taimur,
Great little calculator. So the answer is for 225/40 255/35 is .681% to slow or 70 mph reading = 70.5 mph. 215/40 245/35 is .428% to fast or 70 mph reading = 69.6 mph. Not much difference either way.
William
Great little calculator. So the answer is for 225/40 255/35 is .681% to slow or 70 mph reading = 70.5 mph. 215/40 245/35 is .428% to fast or 70 mph reading = 69.6 mph. Not much difference either way.
William
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