Changing Speed ratio after changing tyre size

[InfamousDuckMan]

So I went from this:

 

 

...To this...

 

 

So now, my Speedometer is wrong, because I have fatty tyres.

 

Any ideas on how to adjust that so its correct?

 

--DuckMan.

[GrimGreg]

Best to get a GPS and measure via that. On my 93 when I traded up to 31s my speedo was pretty good up to 45 then it started to go off, at 65 my speedo reads 61. However on my 88 when I swapped to 31s I found out that my speedo was dead on and had actually been off with the factory wheels/tires.

[glenn]

MY 1990 has gear driven speedo; so when I changed to 32s it was off quite a bit. The gears need to be swapped out. I went to a shop and they did this; IIRC it wasn't too expensive.

[bitemedoughboy.com]

MY 1990 has gear driven speedo; so when I changed to 32s it was off quite a bit. The gears need to be swapped out. I went to a shop and they did this; IIRC it wasn't too expensive.

there are different tooth speedo drive gears for the different gear ratio/tire combinations from the factory. ask member "nissannut" or look on his website nissannut.com he has some info on the different speedo drive gears.

[94extreme]

Best to get a GPS and measure via that. On my 93 when I traded up to 31s my speedo was pretty good up to 45 then it started to go off, at 65 my speedo reads 61. However on my 88 when I swapped to 31s I found out that my speedo was dead on and had actually been off with the factory wheels/tires.

 

i bet the real factory tires were 31 you just didn't know it.. you know the info is on the door jamb, right.

[5523Pathfinder]

There used to be a whole list of speedo gears in the Nismo catalog. I lowered a Frontier at my old dealer and we swapped out the speedo gear to compensate for different wheels and tires.

[GrimGreg]

i bet the real factory tires were 31 you just didn't know it.. you know the info is on the door jamb, right.

 

You lost, pay up sucka!

 

It had the 15 275s stock.

[CrazzyMax]

When i had 31", it was the only time the speedo was correct

[94extreme]

You lost, pay up sucka!

 

It had the 15 275s stock.

 

 

fair enough.. i'll buy you a brew when/if i see you next time.

[GrimGreg]

fair enough.. i'll buy you a brew when/if i see you next time.

 

 

Your political view is for crap, but you have always been a good guy in person!

[MY1PATH]

i bet the real factory tires were 31 you just didn't know it.. you know the info is on the door jamb, right.

yeh my door jamb has info for 29" tires but I know for a fact my dad bought it new with 31" the tire size is listed wrong but they put a "disreguard prevous label" sticker in there with appropriate PSI ratings.