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milemarker/speedo calibration [windbag edition]


NAXJA Forum User
just got my 33's [up from 30's] on the ol stock height xj [the fenders went anorexic] and today was trying to get a rough idea of how far out the speedo is now... so i went 20 miles down the highway and marked the odo with each milemarker and it came out like this
164 8.4
163 9.2
162 10.1
161 11.0
160 11.9
159 12.7
158 13.6
157.... not there, but who's counting :laugh3:
156 15.3
155 16.25
154 17.1
153 17.95
152 18.7
151.... another missing
150 20.5
149 21.4
148 22.2
147 23.1
146 24.0
145......not there again... oh well, it's alaska
144 25.6

20 mile posts, 17.4 odo revolutions so the speedo is 'about' 87 percent of what it should be.... does that mean that all speeds are 13 percent slow or is it just like 7mph off consistently for all speeds :confused:
i would LIKE to think for the sake of easy calculation that it's just a fixed number, but my brain says otherwise; ie 5mph is 5.75 but 65mph is 74.75.... IE a PITa to figure while driving
BTW don't give me crap about just getting the proper gear....
some recent 'special order' parts from napa have been 4.0L head gasket [oem, nothing fancy], timing chain, ball joints, brake parts, standard shocks.... let alone a gear to recalibrate my speedo :exclamati and they make you prepay for ordering most parts not in stock :gag: