... Speedometer accuracy - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

/etc/shadow · 08-18-2002, 12:45 AM

How inaccurate would getting new wheels (say 17" SSR competitions) and tires typically make the speedometer? Is there any way to correct the stock one? I'm looking for clean solutions... no ghetto Apexi Rev/Speed meters all over the car to tell me my "true" speed.

AKADriver · 08-18-2002, 02:36 AM

Get tires in the correct overall diameter, and your speedometer output will be fine.

Stock 240SX tire sizes are 195/60R15 (S13, S14 base), 205/60R15 (S13 w/handling pkg), and 205/55R16 (S14 SE/LE).  All came with the same speedometer gear as far as I know.

These tires have diameters:
195/60R15: 24.21"
205/60R15: 24.69"
205/55R16: 24.88"

So, for a 17" wheel, the following tire sizes would be in the right ballpark:

205/45R17: 24.26"
215/45R17: 24.61"
225/40R17: 24.09" (a little too small)
225/45R17: 24.97" (a little too big)
235/40R17: 24.40"
245/40R17: 24.72"

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08-18-2002, 12:45 AM	#1
/etc/shadow Zilvia Member Join Date: Jun 2002 Posts: 167 Trader Rating: (0) Feedback Score: 0 reviews	How inaccurate would getting new wheels (say 17" SSR competitions) and tires typically make the speedometer? Is there any way to correct the stock one? I'm looking for clean solutions... no ghetto Apexi Rev/Speed meters all over the car to tell me my "true" speed.

08-18-2002, 02:36 AM	#2
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 39 Posts: 3,112 Trader Rating: (0) Feedback Score: 0 reviews	Get tires in the correct overall diameter, and your speedometer output will be fine. Stock 240SX tire sizes are 195/60R15 (S13, S14 base), 205/60R15 (S13 w/handling pkg), and 205/55R16 (S14 SE/LE).  All came with the same speedometer gear as far as I know. These tires have diameters: 195/60R15: 24.21" 205/60R15: 24.69" 205/55R16: 24.88" So, for a 17" wheel, the following tire sizes would be in the right ballpark: 205/45R17: 24.26" 215/45R17: 24.61" 225/40R17: 24.09" (a little too small) 225/45R17: 24.97" (a little too big) 235/40R17: 24.40" 245/40R17: 24.72"