pitroad01
join:2006-07-10
Raleigh, NC
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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 Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| 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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pitroad01
join:2006-07-10
Raleigh, NC
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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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markwp2001
Spreadhead
Premium
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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pitroad01
join:2006-07-10
Raleigh, NC
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·RoadRunner Cable
| 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 Olds
I Need A Remedy For What's Ailing Me.
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join:2001-04-19
1970 442 W30
clubs:
| reply to markwp2001
said by markwp2001 :I believe he got the 7% figure 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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pitroad01
join:2006-07-10
Raleigh, NC
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·RoadRunner Cable
| said by Doctor Olds :said by markwp2001 :I believe he got the 7% figure The difference value is seen in the post directly above yours which was determined by » www.tiresizecalculator.info/ after the tire sizes were posted. 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 Olds
I Need A Remedy For What's Ailing Me.
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join:2001-04-19
1970 442 W30
clubs:
| 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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pitroad01
join:2006-07-10
Raleigh, NC | 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 Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| 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
The second choice 225/60-14
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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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pitroad01
join:2006-07-10
Raleigh, NC | yea maybe the P185/70/R14
It would probably look a lot better then a really wide tire (225) |
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