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Going to 285x70x17 .. do i need to reprogram right away?

J_One17

J_One17

Full Member
Joined
Feb 1, 2011
Messages
124
Location
Sun Valley Ca
Im going to be getting new tires in a few weeks (bfg at ko2) after i rebuild my front steering and suspension on my avalanche. I want to go to 285/70/17 and had planned on getting a programmer to re cal for the tire size change.. But funds are running a bit low from all the parts i have been buying so i want to know if i can get away without using the programmer for the time being. I figured i can buy the programmer after everything.
 
I would not bother with the re cal the change to the 285 is not that much different.
What size tires are on it now.
 
268/70-17        7.4in  15.9in    31.8in        99.8in        635        0.0%
285/70-17        7.9in  16.4in    32.7in        102.8in        617        2.9%

http://www.miata.net/cgi-bin/tirescgi
 
I moved up from 265/70R17 to 285/70R18, which was a considerable difference in diameter, and never bothered reprogramming. According to my GPS, the speedo is off by about 10 km/hr (6 MPH) at 120 km/hr (~70 MPH) (speedo shows 110, GPS shows 120). The speed limit on the highway around here is 110, so if I set my cruise at that speed I figure I'm safe.
 
Thank for the input from eveyone. I was going try and hold out for a month so i can buy a programmer before i got new tires but they are in such bad shape that i am going to have to get them next week. I guess 285/70/17 it is. I'll track my speed via gps so i can get a ideal how fast i'm really going.
 
For mine, I went from 265 to 285, then to 295 and there really wasnt much of a difference. In fact I reprogrammed it for the 295 and it over corrected enough so that it is now spot on with my 35s. So you should be fine man
 
Well i able to take a moment today and download a app on my phone to track my speed on the freeway on the way to work. I was suprised to see that at 65 mph on the app was 66 mph on my truck. I'm only getting about 1 to 1.5 mph difference with the 285.
 
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