88 13b and stock 5 speed in a datsun 510 with 390 rear and 13 inch wheels. I seem to be off about 10+ mph faster.



Is it the rear end gearing that's throwing the speedo or the smaller wheels? Or both?



I'm sure the RX7 never came with 13inch wheels but the Miata did right? Don't they share similar trannies? Can you order speedo cable gears from Mazda?



thanks guys,



Craig