speedometer changes???
#1
06-10-2005, 06:50 PM
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#2
06-10-2005, 07:43 PM
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http://www.miata.net/garage/tirecalc.html
Multiply the speed on your speedo by 5.3% (.053) and then add that to the speed and that is how fast you are actually going.
Example, 75MPH. 75 * .053 = 3.9 ... 75+4 = 79, so youre about 5 MPH off at 75 MPH.
Multiply the speed on your speedo by 5.3% (.053) and then add that to the speed and that is how fast you are actually going.
Example, 75MPH. 75 * .053 = 3.9 ... 75+4 = 79, so youre about 5 MPH off at 75 MPH.
#3
06-10-2005, 07:47 PM
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It's a percentage, so as speeds rise the MPH difference grows but the percentage remains the same.
Using this this online tool:
http://www.miata.net/cgi-bin/tirescgi
...shows a 5% difference in rotations per mile.
That is, the new tires are turning 5% slower, so your speedometer will show 5% slower than your actual speed.
Using this this online tool:
http://www.miata.net/cgi-bin/tirescgi
...shows a 5% difference in rotations per mile.
That is, the new tires are turning 5% slower, so your speedometer will show 5% slower than your actual speed.
#4
06-10-2005, 07:52 PM
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Great minds think alike, evidently... 
Please correct me if I'm mistaken, but I think that your speedo will show a slower speed than actual.
Imagine a 10-foot tall tire. It will turn very slowly at high vehicle speeds, so your speedometer will be much slower than the vehicle's speed.
Since your new tires are taller than the old ones, the same thing applies - the tires/speedometer will show a slower speed than actual. In your case, 5% slower.
Please correct me if I'm mistaken, but I think that your speedo will show a slower speed than actual.
Imagine a 10-foot tall tire. It will turn very slowly at high vehicle speeds, so your speedometer will be much slower than the vehicle's speed.
Since your new tires are taller than the old ones, the same thing applies - the tires/speedometer will show a slower speed than actual. In your case, 5% slower.
#7
06-13-2005, 01:14 PM
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Go to http://www.tyres1.com/calculators.html . It is an interactive calculator where you can enter in all of your tire information and it will tell you what your speedo will tell you at what speed you are really going. It will also tell you what the bigger tires have changed your gear ratio to and what gears you need to make up for the size change.