| reply to pitroad01
Re: Tire size question Well I found out that running 14" tires on a car that was built for 15" causes the speedometer and odometer to error. The tire size is programed into the cars processors. So my speed and mileage are off by about 7%. I took a 400 mile trip and used my GPS to monitor speed and distance against the cars speedometer and odometer. I really don't care about the speedometer being off but I do about the odometer. I am logging 7% more miles then are actually being driven. Sucks .... expensive to correct and put 15" wheels and tires on at this point. Best I can find are 15" used Honda aluminum wheels for $150.00 each and then I have to buy tires. |
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 Doctor OldsI Need A Remedy For What's Ailing Me.Premium,VIP
join:2001-04-19
1970 442 W30
kudos:17 | said by pitroad01:Well I found out that running 14" tires on a car that was built for 15" causes the speedometer and odometer to error. The tire size is programed into the cars processors. So my speed and mileage are off by about 7%. You are leaving out what size the Tire is that is installed on the 14" rim. Without knowing that and without knowing a few other factors you are possibly incorrect about the 7% difference.
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What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
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| said by Doctor Olds:said by pitroad01:Well I found out that running 14" tires on a car that was built for 15" causes the speedometer and odometer to error. The tire size is programed into the cars processors. So my speed and mileage are off by about 7%. You are leaving out what size the Tire is that is installed on the 14" rim. Without knowing that and without knowing a few other factors you are possibly incorrect about the 7% difference. The tires are P185 60 R14 .... 14" tires |
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 markwp2001SpreadheadPremium
join:2002-05-25
Long Beach, MS | reply to Doctor Olds
said by Doctor Olds:said by pitroad01:Well I found out that running 14" tires on a car that was built for 15" causes the speedometer and odometer to error. The tire size is programed into the cars processors. So my speed and mileage are off by about 7%. You are leaving out what size the Tire is that is installed on the 14" rim. Without knowing that and without knowing a few other factors you are possibly incorrect about the 7% difference. I believe he got the 7% figure by comparing his odometer reading to the GPS reading of miles driven.
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Into music? tealeafgreen.com |
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| said by markwp2001:said by Doctor Olds:said by pitroad01:Well I found out that running 14" tires on a car that was built for 15" causes the speedometer and odometer to error. The tire size is programed into the cars processors. So my speed and mileage are off by about 7%. You are leaving out what size the Tire is that is installed on the 14" rim. Without knowing that and without knowing a few other factors you are possibly incorrect about the 7% difference. I believe he got the 7% figure by comparing his odometer reading to the GPS reading of miles driven. I threw out the figures I had recorded for the trip but it came to like 93% .... + or - a little. |
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Doctor OldsI Need A Remedy For What's Ailing Me.Premium,VIP
join:2001-04-19
1970 442 W30
kudos:17 | reply to markwp2001
The difference value is seen in the post directly above yours which was determined by »www.tiresizecalculator.info/ after the tire sizes were posted.
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What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
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| That's a neat site. I'm sure their numbers are correct. I guess I'm stuck. I was hoping they could make a change in the car processor to calculate speed and distance with a 14" tire but evidently they can't. I wonder if there is a certain size 14" that would work ? |
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Doctor OldsI Need A Remedy For What's Ailing Me.Premium,VIP
join:2001-04-19
1970 442 W30
kudos:17 | If you want the same width tire then:
Original tire [195/60-15]
Sidewall: 4.61 in
Radius: 12.11 in
Diameter: 24.21 in
Circumf: 76.07 in
Revs/mile: 832.96
New Tire [215/60-14]
Sidewall: 5.08 in
Radius: 12.08 in
Diameter: 24.16 in
Circumf: 75.89 in
Revs/mile: 834.86
Speedometer reading with new tire is 0.23% too fast.
When your speedometer is reading 60mph you are actually traveling 59.86mph.
or
Original tire [195/60-15]
Sidewall: 4.61 in
Radius: 12.11 in
Diameter: 24.21 in
Circumf: 76.07 in
Revs/mile: 832.96
New Tire [225/60-14]
Sidewall: 5.31 in
Radius: 12.31 in
Diameter: 24.63 in
Circumf: 77.38 in
Revs/mile: 818.85
Speedometer reading with new tire is 1.72% too slow.
When your speedometer is reading 60mph you are actually traveling 61.02mph.
or 65 series (not as wide)
Original tire [195/60-15]
Sidewall: 4.61 in
Radius: 12.11 in
Diameter: 24.21 in
Circumf: 76.07 in
Revs/mile: 832.96
New Tire [205/65-14]
Sidewall: 5.25 in
Radius: 12.25 in
Diameter: 24.49 in
Circumf: 76.94 in
Revs/mile: 823.45
Speedometer reading with new tire is 1.15% too slow.
When your speedometer is reading 60mph you are actually traveling 60.68mph.
or 70 series
Original tire [195/60-15]
Sidewall: 4.61 in
Radius: 12.11 in
Diameter: 24.21 in
Circumf: 76.07 in
Revs/mile: 832.96
New Tire [185/70-14]
Sidewall: 5.10 in
Radius: 12.10 in
Diameter: 24.20 in
Circumf: 76.02 in
Revs/mile: 833.50
Speedometer reading with new tire is 0.07% too fast.
When your speedometer is reading 60mph you are actually traveling 59.96mph.
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What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
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| So what you are saying is that I could correct my problem with a 225/60/14 ...... I wonder if that tire would fit on my current 14" rim ? |
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Doctor OldsI Need A Remedy For What's Ailing Me.Premium,VIP
join:2001-04-19
1970 442 W30
kudos:17 | said by pitroad01:So what you are saying is that I could correct my problem with a 225/60/14 ...... I wonder if that tire would fit on my current 14" rim ? Actually the 70 Series fits better with the closest to the original revolutions per mile.
This helps visually:
»www.miata.net/garage/tirecalc.html
Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
195/60-15 4.6in 12.1in 24.2in 76.1in 833 0.0%
185/70-14 5.1in 12.1in 24.2in 76.0in 834 -0.1%
The second choice 225/60-14
Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
195/60-15 4.6in 12.1in 24.2in 76.1in 833 0.0%
225/60-14 5.3in 12.3in 24.6in 77.4in 819 1.7%
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What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
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| yea maybe the P185/70/R14
It would probably look a lot better then a really wide tire (225) |
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