How is the speedometer calibrated?? Mine seems to be strangely off...
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AudiWorld Super User
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How is the speedometer calibrated?? Mine seems to be strangely off...
<center><img src="http://pictureposter.audiworld.com/19014/calibrated.jpg"></center><p>Now I do have 18' rims w/ 235/40's and I'm not sure how far off that is from the stock 17' set-up but I'm assuming it threw off my speedo long ago. That is not my question....
My question IS...If I get on a very straight, flat piece of highway and I put the cruise control on 78MPH, then if I reset my avg MPH on the trip display it will read as a constant 76mph (as seen in the supplied pic)
So regardless of what size tires I have on...shouldn't the trip display be going of the speedo reading or is it just taking the speed off the wheels; and if that's the case, shouldn't it be reading a speed above what my speedometer is saying.
And don't tell me it's a bad cluster.
My question IS...If I get on a very straight, flat piece of highway and I put the cruise control on 78MPH, then if I reset my avg MPH on the trip display it will read as a constant 76mph (as seen in the supplied pic)
So regardless of what size tires I have on...shouldn't the trip display be going of the speedo reading or is it just taking the speed off the wheels; and if that's the case, shouldn't it be reading a speed above what my speedometer is saying.
And don't tell me it's a bad cluster.
AudiWorld Senior Member
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pointer may have been installed slightly off alignment
I don't know how they install the pointers during manufacture of the cluster but when I removed and replaced them for my white face gauges it would be very easy to install them in a position that doesn't agree with the digital display
relationship between tach and speedometer appears reasonable assuming in 5th gear
relationship between tach and speedometer appears reasonable assuming in 5th gear
AudiWorld Super User
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your speedo is 1.7% too slow...
when your speedo indicates 60mph, you're actually traveling 61.0mph.
calculator at the link below...<ul><li><a href="http://www.miata.net/garage/tirecalc.html">Tire size calculator</a></li></ul>
calculator at the link below...<ul><li><a href="http://www.miata.net/garage/tirecalc.html">Tire size calculator</a></li></ul>
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GPS's are very accurate for speed. Speedo said 136 when I was going 135.
<center><img src="http://email.net/~scott/TT-Scott/TT120.jpg"></center><p>I had a similar experience (no photos) of speedo saying 143 and GPS said 141. So, less than 1% error but consistently high as other posts say here. 17" wheels.
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