I replaced my OEM B18B with a JDM B18B a couple years ago. I had 17"s on my car for a while so I expected a little difference in my speedo. Well I got some LS wheels and im pretty sure my speed is off even more now. I`ve been thinkin about it and I just realized that it had to be when I had the swap done. Because I have passed several cops while speeding(or thinking I was speeding) and not been pulled over since the swap.

Anyway, its the stock tranny and JDM motor, ecu, and sensors. Could that be whats causing the speedo to be off or is there another possiblity? Thanks guys!

 

Bump, 25 views and nothing.......?

 

bump,,wish i could help,,but i have the same problem,i bought my car with a obd2 to obd1 swap[gsr],,and i noticed my speedo is off,,it says im going alot faster than i really am,,at least 10mph faster,,and it not my wheels,,currently running oem size wheels 195 55 15,no cel or anything,,rpms seems to match the speedo too,,idk

 

There is no way to calibrate for speedometer error due to incorrect tire size. Tire size does not affect the indicated speed vs. RPM relation.