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Old 12-07-2009, 06:30 PM   #12 (permalink)
Mr Ed
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Join Date: Aug 2009
Location: Brisbane, Australia
Posts: 162
Drives: 09 Nissan 370Z M6
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Quote:
Originally Posted by GTRFAN View Post
I'm starting to think Nissan got the tyre specs wrong and the overall rolling diameter is whats causing the innacuracy.

The thing is, if the indicated speed is higher than the actual speed, then the rolling diameter (circumference) is slightly too small (and not rolling the car the distance the speedo thinks it's going).

To fix this we can either get taller side % profiles, but I'm not exactly going to do this as the side wall profile already looks too fat for an 18" rim compared to other cars.

Hopefully Nissan can adjust the speedo calibration at a service? I'll look into this when I get 19" and new tyres in the profile I want.

Just my 2c worth of daily rambling
nope that doesnt fix it.

remember with the 18" and 19" rims - they have the same overall height.

I got 19" rims and ran tyres as per Jap/US spec.

ie front 245/40/19 and rear 275/35/19 as opposed to Aussie front 225/50/18 and rear of 245/45/18.

if you do the calculations - the overall heights of the rims are negligible

my speedo is off too! Nissan will not adjust unless it is 10% out. I raised this issue on the forum this year.

So I do about 10km higher and I am fine - ie keeping up with traffic.
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