questions about tires and speedo
10-15-2002, 01:03 PM
#1
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Thread Starter
Join Date: Sep 2002
Posts: 37
questions about tires and speedo
hi guys,
i have read that the recommended tire size for th 17 oem se rims is 225-50-17. my questions is, aside from the issue of the tire being to wide for the rim ( which has been hammered to death in previous posts)
what harm does going to a size 235-45-17 have on the speedo?
will this also mess up the tranny in the long run?
thank for the input?
i have read that the recommended tire size for th 17 oem se rims is 225-50-17. my questions is, aside from the issue of the tire being to wide for the rim ( which has been hammered to death in previous posts)
what harm does going to a size 235-45-17 have on the speedo?
will this also mess up the tranny in the long run?
thank for the input?
10-15-2002, 01:23 PM
#2
Senior Member
Join Date: Jun 2002
Posts: 412
Re: questions about tires and speedo
Originally posted by cyberg21
hi guys,
i have read that the recommended tire size for th 17 oem se rims is 225-50-17. my questions is, aside from the issue of the tire being to wide for the rim ( which has been hammered to death in previous posts)
what harm does going to a size 235-45-17 have on the speedo?
will this also mess up the tranny in the long run?
thank for the input?
hi guys,
i have read that the recommended tire size for th 17 oem se rims is 225-50-17. my questions is, aside from the issue of the tire being to wide for the rim ( which has been hammered to death in previous posts)
what harm does going to a size 235-45-17 have on the speedo?
will this also mess up the tranny in the long run?
thank for the input?
225 is the width of the tread in millimeters
50 is the percentage of that tread that the sidewall is high
225x.50x2(upper and lower sidewall)/25.4+17=Total diameter of 25.858"
235x.45x2/25.4+17=25.327"
25.858/25.327 = 1.021 or the 225 is +2.1% more in diameter. So the 235 will take more rotations to complete the same mile. Therefore, if you're going 60mph by the speedo (assuming it was correct in the first place), you'd really be going 58.77 mph.
It won't mess up your tranny unless you had drastically different sizes on your front wheels. And if you went 100,000 miles on the odometer, you'd really have gone 102,098.5.
Hope that helps.
10-15-2002, 03:49 PM
#4
Senior Member
Join Date: Dec 2001
Posts: 239
Re: Re: questions about tires and speedo
Originally posted by 2002Maxxxima
Strictly by the numbers your speedo will read 2% faster than it would with 225-50-17.
Therefore, if you're going 60mph by the speedo (assuming it was correct in the first place), you'd really be going 58.77 mph.
And if you went 100,000 miles on the odometer, you'd really have gone 102,098.5.
Strictly by the numbers your speedo will read 2% faster than it would with 225-50-17.
Therefore, if you're going 60mph by the speedo (assuming it was correct in the first place), you'd really be going 58.77 mph.
And if you went 100,000 miles on the odometer, you'd really have gone 102,098.5.
The reason I say this (and I could be wrong) is that if the SPEEDO reads 60 MPH and you're ACTUALLY traveling 58.77 mph (as you said), then wouldn't that mean that you have ACTUALLY traveled LESS miles?
10-15-2002, 04:16 PM
#5
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Join Date: Jun 2002
Posts: 412
Re: Re: Re: questions about tires and speedo
Originally posted by CHAZMAX
Hey, I'm absolutely not trying to flame, but wouldn't it be the other way around? The odometer would read 102,098.5 and the actual miles would be 100,000. Meaning that you're odometer will show MORE miles than what you've actually traveled.
The reason I say this (and I could be wrong) is that if the SPEEDO reads 60 MPH and you're ACTUALLY traveling 58.77 mph (as you said), then wouldn't that mean that you have ACTUALLY traveled LESS miles?
Hey, I'm absolutely not trying to flame, but wouldn't it be the other way around? The odometer would read 102,098.5 and the actual miles would be 100,000. Meaning that you're odometer will show MORE miles than what you've actually traveled.
The reason I say this (and I could be wrong) is that if the SPEEDO reads 60 MPH and you're ACTUALLY traveling 58.77 mph (as you said), then wouldn't that mean that you have ACTUALLY traveled LESS miles?
10-15-2002, 05:12 PM
#6
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Join Date: Apr 2002
Posts: 702
Re: Re: questions about tires and speedo
Actually the speedo w/ the 235 45 17s would be 2.1% too fast. When the speedo reads 60, you're doing 58.8mph.
I figured this out by doing several complex calculations. However, you can just click here. http://www.miata.net/garage/tirecalc.html
I figured this out by doing several complex calculations. However, you can just click here. http://www.miata.net/garage/tirecalc.html
Originally posted by 2002Maxxxima
Strictly by the numbers your speedo will read 2% faster than it would with 225-50-17. Here's how to calculate:
225 is the width of the tread in millimeters
50 is the percentage of that tread that the sidewall is high
225x.50x2(upper and lower sidewall)/25.4+17=Total diameter of 25.858"
235x.45x2/25.4+17=25.327"
25.858/25.327 = 1.021 or the 225 is +2.1% more in diameter. So the 235 will take more rotations to complete the same mile. Therefore, if you're going 60mph by the speedo (assuming it was correct in the first place), you'd really be going 58.77 mph.
It won't mess up your tranny unless you had drastically different sizes on your front wheels. And if you went 100,000 miles on the odometer, you'd really have gone 102,098.5.
Hope that helps.
Strictly by the numbers your speedo will read 2% faster than it would with 225-50-17. Here's how to calculate:
225 is the width of the tread in millimeters
50 is the percentage of that tread that the sidewall is high
225x.50x2(upper and lower sidewall)/25.4+17=Total diameter of 25.858"
235x.45x2/25.4+17=25.327"
25.858/25.327 = 1.021 or the 225 is +2.1% more in diameter. So the 235 will take more rotations to complete the same mile. Therefore, if you're going 60mph by the speedo (assuming it was correct in the first place), you'd really be going 58.77 mph.
It won't mess up your tranny unless you had drastically different sizes on your front wheels. And if you went 100,000 miles on the odometer, you'd really have gone 102,098.5.
Hope that helps.
10-15-2002, 05:36 PM
#7
Senior Member
Join Date: Jun 2002
Posts: 412
Re: Re: Re: questions about tires and speedo
Originally posted by jjames
Actually the speedo w/ the 235 45 17s would be 2.1% too fast. When the speedo reads 60, you're doing 58.8mph.
I figured this out by doing several complex calculations. However, you can just click here. http://www.miata.net/garage/tirecalc.html
Actually the speedo w/ the 235 45 17s would be 2.1% too fast. When the speedo reads 60, you're doing 58.8mph.
I figured this out by doing several complex calculations. However, you can just click here. http://www.miata.net/garage/tirecalc.html
10-15-2002, 06:29 PM
#8
Senior Member
Join Date: Apr 2002
Posts: 702
Re: Re: Re: Re: questions about tires and speedo
Au contraire mon ami. You said 2% ,I said 2.1% j/k. I just wanted to give the guy the link to that page. I know I pretty much echoed what you said.
j/k. I just wanted to give the guy the link to that page. I know I pretty much echoed what you said.
Originally posted by 2002Maxxxima
We've said the same thing.
We've said the same thing.
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