265 to 285 tires

[birddog]

could anyone tell me what my speedometer difference is from 265 tires to 285's, I was supposed to have it calibrated but it isn't happening. I calculated percantage wise myself but I am not sure if I have it right. I went from stock michelins to 285 wrangler silent armors with 617 revs per mile.

 

[NavyDood]

Speedo will read around 2mph faster than you are really going. This is at 70mph on the speedo.

 

[KSears]

I recently changed my tires from 265-70-17 to 285-75-17, the speed will read different depending on how fast you are driving , ex. say at 25 it will be maybe 2 mph off, at 50-60 it will be say 4-5 mph off, at say 70 -75 , it will be say 6-7 mph off, I asked a couple of dealers about adjusting the computer to read the speed properly and got the run around from them all.

 

[SWithrow]

Try the links below

Performance Probe

Tire Size Calculator - tire & wheel plus sizing

 

[RLHannink]

My careful calculations yeilded:



265's: 3% faster/more mileage than odometer



285's: 6%



using both a GPS, and doing the 100 mile mile marker check on the interstate. I have 16" rims, but I don't think it makes a diff