how to figure out TIRE REVOLUTIONS per mile?????
Glenster
get for my car using 3.73 gears and the formula needed tire revolutions per
mile. my tire size is 275 35 18.
so would the formula be:
1. 275 x 35% = sidewall height(converted to inches of course)
2.a. (18" wheel+sidewall height) x pi = tire circumference
b. or is it (18"+sidewall height x2) x pi = tire circumfernce (for 2 side
walls??)
3. 5280ft / tire circumference = tire revolutions ?
please correct me if im wrong!!! i wanna go with 3.73 gears for my 94 mustang
gt. FMS makes no speedo correction gear for stock tires so im just wondering
if my combo will be correctable using the available speedo correction gears.
thanks
confused stanger,
glenn
Jared Rude
aspect ratio = 35%
rim diameter = 18 in
275/25.4 = 10.83 in (tread width)
10.83 in * .35 = 3.79 in (sidewall height)
3.79 * 2 = 7.58 in (two sidewalls)
18 in + 7.58 in = 25.58 in (tire height)
3.14 * 25.58 in = 80.36 in (tire circumference)
80.36 in/revolution
5280 ft * 12 = 63360 in (one mile)
63360 in/80.36 in/rev = 788.45 revolutions
--
Jared Rude
1990 LX 5.0
nospam...@bellsouth.net
remove "nospam_" to reply
Glenster wrote
vincent.dabrowski
tire revolutions/mile=5280/(pi*diameter in feet) or
tire revolutions/mile=63360/(pi*diameter in inches) or
tire revolutions/mile=1609344/(pi*diameter in mm) or
tire revolutions/mile=1609344/(pi*((rim size in inches*25.4)+(2*tire
width*ratio%/100)) or
788.47243 rev/mile (don't forget your significant figures) or
788.5 rev/mile
damn engineers!
VD
95 GT
Glenster wrote in message
<199807150557...@ladder03.news.aol.com>...
Erich Coiner
>
> tire revolutions/mile=5280/(circumference in feet) or
> tire revolutions/mile=5280/(pi*diameter in feet) or
> tire revolutions/mile=63360/(pi*diameter in inches) or
> tire revolutions/mile=1609344/(pi*diameter in mm) or
> tire revolutions/mile=1609344/(pi*((rim size in inches*25.4)+(2*tire
> width*ratio%/100)) or
> 788.47243 rev/mile (don't forget your significant figures) or
>
> 788.5 rev/mile
>
> damn engineers!
>
> VD
> 95 GT
Now take that number and multiply it by your rear axle ratio
788.5*3.73= 2957 rpm. This is your engine rpm at 60 mph in direct drive.
When you put it in overdrive the revs will drop.
If your overdrive ratio is 0.7 revs drop to 2070.
Erich
> >
Glenster
revolutions/mile in the equation the FMS book recomends a 23 tooth speedometer
gear to correct the MPH for my 94GT, which ford doesnt make. Are there any
other ways to correct my speedometer and odometer, without this speedo gear or
can I get a 23 tooth speedo gear somewhere else?
thanks again,
glenn
>From: "vincent.dabrowski" <vincent....@MCI2000.com>
>Date: 7/15/98 8:58 PM Pacific Daylight Time
>Message-id: <vTer1.163$dZ2.1...@news.mci2000.com>
>
>tire revolutions/mile=5280/(circumference in feet) or
>tire revolutions/mile=5280/(pi*diameter in feet) or
>tire revolutions/mile=63360/(pi*diameter in inches) or
>tire revolutions/mile=1609344/(pi*diameter in mm) or
>tire revolutions/mile=1609344/(pi*((rim size in inches*25.4)+(2*tire
>width*ratio%/100)) or
>788.47243 rev/mile (don't forget your significant figures) or
>
>788.5 rev/mile
>
>damn engineers!
>
>VD
>95 GT
>
>
>
Glenster
a...@wi.net
glen...@aol.com (Glenster) wrote:
> Thanks guys, now i have a bigger problem. Sorry!!! With the 788.5
> revolutions/mile in the equation the FMS book recomends a 23 tooth speedometer
> gear to correct the MPH for my 94GT, which ford doesnt make. Are there any
> other ways to correct my speedometer and odometer, without this speedo gear or
> can I get a 23 tooth speedo gear somewhere else?
> thanks again,
> glenn
>
I think you're in luck, pal. I checked my Mustangs Unlimited catalog and
they show a 23 tooth driven speedo gear for the T-5 (if that's what you
have?). The part number for the gear is DFM17271A and will run you about $25
with shipping. I don't know what's special about this gear, but there must
be something, since all the other gears cost about $10. If you want to call
them, their # is 800-243-7278. Good luck.
Andy Pluister
'90 LX 5.0 & '90 GT 5.0 Convertible
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Keith Lafever
says...
>
>
>please correct me if im wrong!!! i wanna go with 3.73 gears for my 94 mustang
>gt. FMS makes no speedo correction gear for stock tires so im just wondering
>if my combo will be correctable using the available speedo correction gears.
>
Just a question; do you have a 5-speed? It's the only way to get the speedo
correct with 3.73's. If you have an automatic, you're sunk. Just did mine and
I have to get a 6 tooth drive gear to put in the output shaft (replacing the 8
tooth for 2.73 gears) to match up the 18-tooth(yellow) speedo driven gear. The
FMS catalog bases their tire revolution on stock tire diameters, which are
about 24.5" - 24.7" overall, be it 15, 16, 17 or 18. Your tires are about
24.7" overall, so it is stock size.
You can also use a 7 tooth drive gear with a 21 tooth(red) driven (speedo)
gear. This is good if you have 3.27's in right now. That way you only replace
the drive gear in the output shaft. According to the FMS catalog, your car
comes with an 8 tooth drive gear. If you have anything other than an 18 or 21
tooth speedo gear, you need to replace both. Otherwise, match it in the
catalog and replace only the drive gear in the trans.
Keith Lafever
>
>In article <199807150557...@ladder03.news.aol.com>, glen...@aol.com
>says...
>>
>>
>>please correct me if im wrong!!! i wanna go with 3.73 gears for my 94 mustang
>>gt. FMS makes no speedo correction gear for stock tires so im just wondering
>>if my combo will be correctable using the available speedo correction gears.
>>
>
Just a question; do you have a 5-speed? It's the only way to get the speedo
correct with 3.73's. If you have an automatic, you're sunk. Just did mine and
I have to get a 6 tooth drive gear to put in the output shaft (replacing the 8
tooth for 2.73 gears) to match up the 18-tooth(yellow) speedo driven gear. The
FMS catalog bases their tire revolution on stock tire diameters, which are
about 25.5" - 25.7" overall, be it 15, 16, 17 or 18. Your tires are about
25.6" overall, so it is stock size.
Glenster
catalog and they sell the 23 tooth speedo gear for $14.99.
glenn
>Subject: Re: can i fix my SPEEDOMETER after getting GEARS installed ?????
>From: a...@wi.net
>Date: 7/18/98 9:00 AM Pacific Daylight Time
>Message-id: <6oqgq9$snr$1...@nnrp1.dejanews.com>