I have an AZE0 and a ZE1 and both of their speedo's read over by approx 10%. From investigating this I've found that it appears to be a "factory standard" inaccuracy. The speedos are actually very precise; just inaccurate.
Both are baseline trim models (JDM 'S spec') and consequently neither of them have the +/- 2.5% speedo correction feature exposed via their nav units. As a side note, I would be super interested to know of anyone has tried capturing the CAN packets from the nav ECU to the VCM when adjusting that setting and then replaying it in a low-spec Leaf without the feature. Would it work on the S-trim VCM? Could you maybe even set the value to MORE than +/- 2.5% and it still works? Who knows... I haven't explored that idea yet.
For now I decided to take the mechanical approach and change the rolling ratio of the wheels and tyres on one of them. I bought my model year 2018 JDM Leaf with factory 16" steel rims (with plastic hubcaps) and running 205/55/16s. I used the excellent online tyre size calculator here [1] to determine that changing to 215/55/18s would give the +10% rolling ratio necessary to correct the speedo. However I was unsure if the larger tyres and rims would physically fit inside the guards without rubbing on the sides at full lock in either direction (and at full load, eg perhaps while under braking on a corner).
Well the good news is that I did buy some 18" used rims from a Nissan Skyline and it turns out that they fit great; plenty of clearance. They actually came with some used 215/45/18s fitted, so the rolling ratio is only +5% for now, but I can see from the clearances that it will definitely fit the larger (215/55/18) tyres which will fully correct the speedo once these ones are worn down.
So this posting is primarily for anyone who is looking to achieve the same, ie to let them know that they should be able to fit a +10% circumference with no problems so go ahead and buy something if that's what you want to do
[1] Tyre Size Calculator
Both are baseline trim models (JDM 'S spec') and consequently neither of them have the +/- 2.5% speedo correction feature exposed via their nav units. As a side note, I would be super interested to know of anyone has tried capturing the CAN packets from the nav ECU to the VCM when adjusting that setting and then replaying it in a low-spec Leaf without the feature. Would it work on the S-trim VCM? Could you maybe even set the value to MORE than +/- 2.5% and it still works? Who knows... I haven't explored that idea yet.
For now I decided to take the mechanical approach and change the rolling ratio of the wheels and tyres on one of them. I bought my model year 2018 JDM Leaf with factory 16" steel rims (with plastic hubcaps) and running 205/55/16s. I used the excellent online tyre size calculator here [1] to determine that changing to 215/55/18s would give the +10% rolling ratio necessary to correct the speedo. However I was unsure if the larger tyres and rims would physically fit inside the guards without rubbing on the sides at full lock in either direction (and at full load, eg perhaps while under braking on a corner).
Well the good news is that I did buy some 18" used rims from a Nissan Skyline and it turns out that they fit great; plenty of clearance. They actually came with some used 215/45/18s fitted, so the rolling ratio is only +5% for now, but I can see from the clearances that it will definitely fit the larger (215/55/18) tyres which will fully correct the speedo once these ones are worn down.
So this posting is primarily for anyone who is looking to achieve the same, ie to let them know that they should be able to fit a +10% circumference with no problems so go ahead and buy something if that's what you want to do
[1] Tyre Size Calculator
