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Speedo off... maybe?
Hello,
At 3000rpm in 5th gear my speedo runs at 75mph. Is it correct? It just seems as if the car runs slower then the indicated speed. I am running with 225x45 / 245x45-16. The rim width is 7 in front and 9 in the rear. Would there be a website to give this information just by entering in some numbers. Calspeed 1985 911 Carrera Cabriolet |
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01-30-2003, 03:03 PM
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Guest
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I've read magazine tests of SC's which give 22 or 23mph per 1000rpm in 5th gear. Carreras might have a slightly higher 5th gear ratio though- which would mean your indicated speed is pretty close. I think most speedos on any car run a few mph fast.
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01-30-2003, 03:13 PM
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Registered
Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,140
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BTDT.. try a portable GPS or follow someone on a level straight with a new car in cruse control.. I had to reset mine.. why not go to one of the speedo repair places that has a speed dyno.....Ron
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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01-30-2003, 03:17 PM
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Back in the saddle again
Join Date: Oct 2001
Location: Central TX west of Houston
Posts: 56,287
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a G50 Carrera will run about 70mph at 3000. The shorter tires 245 45 will spin faster for a given speed, so will cause a low reading not high, but the difference in height is so small that the difference is negligible at normal speeds. A 915 tranny may be different, but you could be running 5mph fast.
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Steve '08 Boxster RS60 Spyder #0099/1960 - never named a car before, but this is Charlotte. '88 targa  SOLD 2004 - gone but not forgotten
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01-30-2003, 05:48 PM
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There should be a chart in your owners manual that will give you speed vs rpm.
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Chuck 1987 911 Targa 1962 C182 "Dirt is permanent. You can move it around, but you can never destroy it." |
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01-30-2003, 05:58 PM
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FZR R4
