[JRANGER]

So My speedo was crazy jumpy so I replaced the cable and it works great! Now I have tires that are 2 big so the speedo reads about 3 -5 mph faster then I actually go but when I hit 70MPH it starts jumping between 70 - 100mph...

So what could cause this?

Is it the speedo gear? If so do I need a smaller or bigger tooth gear to get it closer to the right speed?

Currently have a 21 gear speedo gear

Thanks