Charles,
Here's the formulae:
mph = (rpm * tire_diam) / (gear_ratio * 336)
rpm = (mph * gear_ratio * 336) / tire_diam
gear_ratio = (rpm * tire_diam) / (mph * 336)
tire_diam = (mph * gear_ratio * 336) / rpm
And if you don't know your tire diameter:
tire_diam = 2 * ((section_width * aspect_ratio) / 2540) + rim_diam
And the gear ratio is overall gear ratio, which would be transmission gear
ratio times the final drive ratio.
Ron
Dalton, GA
62 Triumph Vitesse Sports 6 77 Triumph Spitfire 1500
84 Nissan 300ZX Turbo 92 Ford Tempo GLS
-----Original Message-----
From: Charles Ackerman <C2H60_@email.msn.com>
To: triumphs_list <triumphs@autox.team.net>
Date: Tuesday, September 22, 1998 12:40 AM
Subject: Wacko Speedo/Tach?
>
>Hi everybody,
>
>Recent posts about incorrect speedo/tachs got me wonder'in.
>So I got the TR on the road with a pen and paper. (Tire size 195/65R15)
>MPH RPM RPM (OD)
>30 1500 1300
>40 2000 1600
>50 2400 2000
>60 2800 2400
>70 3300 2700
>Is there a formula to determine if the speedo/tach. is wacko?
>
>Charles Ackerman '70 TR6 CC51493LO North Bend WA
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