Tires: Revolutions per mile
06-19-2003, 08:07 AM
#1
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Tires: Revolutions per mile
Does anyone know the outer diameter of the factory tire or the revolutions per mile as Honda has them spec'd? If so, please share.
TIA,
TIA,
06-19-2003, 08:40 AM
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Just go on http://www.tirerack.com and look at the specs of the tire you want to look at.
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06-19-2003, 09:39 AM
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You're totally missing my point. The OEM tire diameter is not the same as different brands of the exact same size tire. I'm trying to calculate X (revs per mile) which is a standard spec that should ALWAYS be considered in ANY tire purchase if you don't feel like losing fuel economy, changing your final gear ratio, or having to recalibrate your speedometer. Honda has a spec for it.
_1_ = __X___
2<pi>r 63,360".
63,360 is the number of inches in a mile. 2<pi>r is the diameter. I don't care to see any numbers like xxx/xx/xx. None of those numbers have anything to do with calculating tire diameter.
_1_ = __X___
2<pi>r 63,360".
63,360 is the number of inches in a mile. 2<pi>r is the diameter. I don't care to see any numbers like xxx/xx/xx. None of those numbers have anything to do with calculating tire diameter.
06-19-2003, 12:28 PM
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Well then go find the tire that came originally on your car and it will tell you 
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06-19-2003, 12:58 PM
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:doh:
I wasn't bent, I just re-read that and it didn't sound right. I didn't specify that info before, and I wasn't trying to blast anyone if it was read like that. I don't like tirerack.com because they don't sell NITTO, their website isn't the most accurate, nor is it always up. I've had a few friends that have bought packages that were supposed to fit for non-Hondas, and they didn't fit.
:dunno:
Harumph! I guess I need to get back to work on that time machine. I don't know what brand tires a 92 Honda civic came with because they all have a tenth of a million miles (or more) on them and those tires are long gone. I wasn't the original owner of mine, either. If anyone knows what a 92-95 CX tire brand and size was, I could find out the rest. I don't know where to look.
If I find out, I'll post the revs-per-mile so anyone can run any wheel width and size they want (that fits) without losing any gear. It would probably help solve a lot of wheel/tire questions, and help people calculate how far off their speedometer is at different speeds after slapping 18's on their civic.
I wasn't bent, I just re-read that and it didn't sound right. I didn't specify that info before, and I wasn't trying to blast anyone if it was read like that. I don't like tirerack.com because they don't sell NITTO, their website isn't the most accurate, nor is it always up. I've had a few friends that have bought packages that were supposed to fit for non-Hondas, and they didn't fit.
:dunno:
Harumph! I guess I need to get back to work on that time machine. I don't know what brand tires a 92 Honda civic came with because they all have a tenth of a million miles (or more) on them and those tires are long gone. I wasn't the original owner of mine, either. If anyone knows what a 92-95 CX tire brand and size was, I could find out the rest. I don't know where to look.
If I find out, I'll post the revs-per-mile so anyone can run any wheel width and size they want (that fits) without losing any gear. It would probably help solve a lot of wheel/tire questions, and help people calculate how far off their speedometer is at different speeds after slapping 18's on their civic.
06-19-2003, 01:26 PM
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Originally posted by Jafro
I don't care to see any numbers like xxx/xx/xx. None of those numbers have anything to do with calculating tire diameter.
I don't care to see any numbers like xxx/xx/xx. None of those numbers have anything to do with calculating tire diameter.
06-19-2003, 01:40 PM
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It doesn't take tread depth into account, and those measurements are at the belts inside the tire, under the rubber. You can see how that would affect the measurement. The gears in the car and the odometer/speedometer turn a specific number of revolutions to make it count 1 mile. That's what I'm looking for. With that information, you can reference ANY tire for proper fit regardless of your wheel dimensions.
Really, I'm not a lunatic. :screwy:
Really, I'm not a lunatic. :screwy:
06-19-2003, 08:06 PM
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One tire manufacturer to another of lets say 205/50x15" is not going to change DRAMATICALLY. Maybe .5mm or so.
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06-20-2003, 07:59 AM
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Maybe I am getting a bit carried away. BUT I FOUND OUT!!! 
The tires that came on my civic were 22.1" 943 Revolutions per mile Michelins with 9/32" tread depth. Michelin is a FRENCH company that doesn't like putting any of their product specifications on-line. I had to go to a tire store to find out their specs. :angry:
If you can't get the tire's rev's per mile, but you can get the diameter...
Take the overall tire diameter and SUBTRACT twice the tread depth. Multipy the adjusted diameter by pi (3.14). Divide the number of inches per mile by the circumference. The answer is the number of rev's per mile.
(D - 2(tread depth))3.14 ÷ 63360 = revolutions per mile.
That size is difficult to match outside of low-end econo-radials. You're supposed to stay within 3% of the OEM diameter or you'll throw off your speedo and cause the geometry of your suspension to change, hurting its performance.
Here's how you find out how far off your speedo/odo will be per mile...
Take the larger tires' rev's per mile, divide it by the smaller tire's rev's per mile. The answer is a percentage that you can multiply by what your speedomoeter reads and it will give you the actual speed you're traveling. If the larger tire is being substituted, you'll be going faster than your speedometer reads.
For example, take NITTO's smallest diameter 17" tire... NT-450 205/40ZR17. It turns 886 revolutions per mile. 943/886=1.064334 or 6.4334%. If your speedometer says 80mph, you're really going 85.14673 mph.
So there you go. Tire tech that everyone can use. Thanks for putting up with my babble.
Jafro
The tires that came on my civic were 22.1" 943 Revolutions per mile Michelins with 9/32" tread depth. Michelin is a FRENCH company that doesn't like putting any of their product specifications on-line. I had to go to a tire store to find out their specs. :angry:
If you can't get the tire's rev's per mile, but you can get the diameter...
Take the overall tire diameter and SUBTRACT twice the tread depth. Multipy the adjusted diameter by pi (3.14). Divide the number of inches per mile by the circumference. The answer is the number of rev's per mile.
(D - 2(tread depth))3.14 ÷ 63360 = revolutions per mile.
That size is difficult to match outside of low-end econo-radials. You're supposed to stay within 3% of the OEM diameter or you'll throw off your speedo and cause the geometry of your suspension to change, hurting its performance.
Here's how you find out how far off your speedo/odo will be per mile...
Take the larger tires' rev's per mile, divide it by the smaller tire's rev's per mile. The answer is a percentage that you can multiply by what your speedomoeter reads and it will give you the actual speed you're traveling. If the larger tire is being substituted, you'll be going faster than your speedometer reads.
For example, take NITTO's smallest diameter 17" tire... NT-450 205/40ZR17. It turns 886 revolutions per mile. 943/886=1.064334 or 6.4334%. If your speedometer says 80mph, you're really going 85.14673 mph.
So there you go. Tire tech that everyone can use. Thanks for putting up with my babble.
Jafro