Pelican Parts Forums

Pelican Parts Forums (http://forums.pelicanparts.com/)
-   Porsche 911 Technical Forum (http://forums.pelicanparts.com/porsche-911-technical-forum/)
-   -   what is the stock tire diameter for accurate speedometer readings? (http://forums.pelicanparts.com/porsche-911-technical-forum/684513-what-stock-tire-diameter-accurate-speedometer-readings.html)

chatas17 06-19-2012 05:55 PM

what is the stock tire diameter for accurate speedometer readings?
 
My 84 911 has CS2 wheels (17").. The other day when I was driving 80 (according to my speedo) my friend had his cruise control set at 73 mph. So... I assume the tire diameter is creating the inaccurate reading. How do I correct this issue? Is there a plastic drive gear that "plugs" into the gear box? Any thoughts on what is the correct gear? Hey, at least I have fewer miles on the car than I thought! That's a plus!

Thanks!

Oh Haha 06-19-2012 06:46 PM

The standard tire diameter for 911s is about 25inches, give or take. From what I remember of your posting you have the correct sizes for tires to remain close to that. Different brands of tires will be closer, others not so much.

I think what most have found is that Porsche was a little optimistic in the speedo calibration.

Mine's in KPH so I use my GPS unit to know exactly how slow I am.

Neel 06-19-2012 08:45 PM

I've found that Porsche speedometers read about 5 mph faster than your actual speed.. When my odometer died, I sent it to North Hollywood, gave them my tire size and asked them to calibrate accordingly.. It 'seems' more accurate, but I have not verified it with my GPS..

RoninLB 06-20-2012 06:47 AM

ny 1977 has an internal adjustable pot

speedos changed over the years so a pot may not be in an SC or Carrera

chatas17 06-20-2012 07:02 PM

Thanks guys!


All times are GMT -8. The time now is 07:48 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website


DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.