Speedo calibration
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From: Fort St John B.C
Speedo calibration
My speedo (cluster and HUD) are a bit off since Ive put on new tires with a smaller profile.
I also have a pioneer Z2 and it has setting under maps that shows you your direction of travel and your speed.
It looks to me like the speed being shown by the Z2 is correct, but its hooked up to the vehicles VSS. Unless its the gps antenna unit that is deciding the speed.
At about 120 km/h shown by the hud, the Z2 will read ~114 km/h.
I take it you need a programmer to fix the speedo?
Thanks
I also have a pioneer Z2 and it has setting under maps that shows you your direction of travel and your speed.
It looks to me like the speed being shown by the Z2 is correct, but its hooked up to the vehicles VSS. Unless its the gps antenna unit that is deciding the speed.
At about 120 km/h shown by the hud, the Z2 will read ~114 km/h.
I take it you need a programmer to fix the speedo?
Thanks
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From: Fremont CA
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20
NCM Sinkhole Donor
The GPS is probably correct, but the car's speedo is off due to the new tire height. You can go into the computer with many tuner software systems and tell the computer what the new REAR tire height is. It will them adjust your speedo based on calculated distance travelled per tire revoltion. 
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From: Charlotte, NC (formerly Endicott, NY)
You are off about 5%. That puts you in the 25.3 inch tire diameter range. Did you switch to 315/35/17s or 275/35/18s (that is their diameter) by any chance?
Bill
Bill
Last edited by Bill Dearborn; May 30, 2008 at 01:25 PM.
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From: Fort St John B.C
I went from stock front and rear sizes- 245/45/17 and 275/40/18 to......245/40/17 and 275/35/18.
So the car is showing me faster than what Im really doing, not a huge number but still off.
According to my calculations my front diameter is 24.716" or 24.7" and the rear is
25.578 or 25.6".
So the car is showing me faster than what Im really doing, not a huge number but still off.
According to my calculations my front diameter is 24.716" or 24.7" and the rear is
25.578 or 25.6".
Last edited by clayton1; May 30, 2008 at 01:45 PM.
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From: Not on either liberal coast.
Plug your oem tire sizes and new tire sizes into this tool, scroll down a bit and it'll tell you % of speedometer error, indicated and actual speeds...adjust you speeds accordingly.
http://www.miata.net/garage/tirecalc.html
http://www.miata.net/garage/tirecalc.html
Race Director
Joined: Apr 2005
Posts: 11,138
Likes: 11
From: Fremont CA
St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20
NCM Sinkhole Donor
I went from stock front and rear sizes- 245/45/17 and 275/40/18 to......245/40/17 and 275/35/18.
So the car is showing me faster than what Im really doing, not a huge number but still off.
According to my calculations my front diameter is 24.716" or 24.7" and the rear is
25.578 or 25.6".
So the car is showing me faster than what Im really doing, not a huge number but still off.
According to my calculations my front diameter is 24.716" or 24.7" and the rear is
25.578 or 25.6".
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Thread Starter
Banned Scam/Spammer
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From: Fort St John B.C