>I going to ask this worn out question again because I think that someone
>must have a similar set up and has found an answer before me. Or maybe Tom
>still has his Excel Spreadsheet gearing mock up and can just hit his famous
>"Graph" button and Voila! an answer.
>
>I would really like to get my speedometer to read correctly. It seems when
>I'm on the freeway, I'm always doing 90+
>
>70 SRL
>Stock 5 speed
>Stock 3.70 rear (may go to a 1600's 3.90 someday)
>P195/60R14 Eagle HP's
Victor,
I don't think there is a magic formula. Too much variation in tire
diameter, even for a given size, across different brands. As far as I'm
concerned, the best way to approach this would be to use mile markers. If
I remember correctly, CalTrans in their wisdom(?) doesn't use the
standard interstate style mile posts, but I know there are
speedometer/odometer test sections marked off in the area that you could
use to calculate the difference between measured distance and your
roadster's odo/speedo.
I'd suggest using at least a 10 mile section and see what your odometer
measures over that know (reasonably) accurate distance. If your odo says
you went 13 miles then it (and the speedometer, too, I'd think) is
reading 30% too far/too fast.
Next you need to know how many teeth are in your driven speedo gear and
see if you can't get one with 30% fewer teeth so your speedo/odo reading
are reduced by that amount. I may have the math backwards but I think
you'll understand the idea. One of roadster suppliers (or Courtesy
Nissan) might be able to help with a replacement gear with the right
number of teeth or you might even find a speedometer repair shop in the
area that would have a substitute that'll fit.
Heck, now that I think of it, a well equipped shop might even be able to
check the accuracy, too. If you're a AAA (Cal Auto Club) member, they
have test rigs that they move from office to office, too.
FWIW, Ron
________________
Ronnie Day
rday@home.com
Dallas/Ft. Worth
'71 510 2-dr (Prepared class autocrosser)
'73 510 2-dr (Street Toy)
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