After i put on my new tires (still 15's but bigger tread pattern) my speedo has been off. ive had my buddies drive with me on the phone and it doesnt seem to be off till around 50mph or so and at that point my actual speed jumps 5 - 10 mph with my speedo reading that much less. anyone have an idea on how to figure this out? or if anyone knows where to get a new speedo gear that will fix the offset. thanks for the help.

 

I'm confused a little so I appoligize...You put new tires on (15" rims still) but the tread pattern is different?....is the tire bigger or is it the same size?

to change your speedometer 10 mph at 60 mph you would have to increase the diameter of your tire by 4 inches!...which is alot that would be like going from a 30/x/x to a 34/x/x! To change it 10mph at 50mph you would have to probably do about 5" diameter increase....

 

I went from 265/70/16 and 265/75/16 and noticed that at 60 mph on my speedo my GPS reads about 63 mph.

Dunno if that'll help. As CynicX mentioned 5-10 is a HUGE discrepancy.

 

i just put some 33's on my runner and i had my brother in law, who is a statie, follow me on the highway. He said that at 70 in my runner, he was getting 73 mph if that helps any. The factory size for my tires were about 30 inches overall.