245/70R16 vs 255/70R16

[exprunner11]

currently my 2001 2dr explorer is running the factory size 235/70r16 tires and in need to change them but I can get a 245/70 or a 255/70 for the same price, i know my speedo will be 1 or 2 mph off. but would running the 255/70 tires hurt my transmission at all with 150k on it without going to ford and pay to get it recalibrated for the bigger tires. also tire rack says that the 255/70/16 was a option for this vehicle

 

[boominXplorer]

255/70r16 is the factory size for that vehicle. Check your door sticker or gas cap to see what size originally came with your truck.

 

[exprunner11]

just doubled check the door sticker and it said 235/70R16

 

[swshawaii]

The ST used 235/70-16 with the 3:73 rear axle ratio, 255/70-16 with 4:10. On the 2001 Sport, cars.com shows BOTH the 2WD and 4WD have the 3:73 gearing. Long as the tires are all the same size you should be fine. As you mentioned, the speedo and ODO will be slightly off, and using larger diameter tires is essentially changing to a higher gear ratio. Less bottom end, more top and MPG.

http://www.cars.com/go/compare/trimCompare.jsp?acodes=USB10FOS111A0,USB10FOS112A0&compType=E

235/70-16 = 29.0"
245/70-16 = 29.5"
255/70-16 = 30.1"

 

[Flash]

I have 255/70/16 on my '97. I didn't worry about the speedo 'cause they're never accurate anyway.
I often use a GPS speedo.

I'll be fitting 265/70/16 next, if I don't get bigger wheels.

 

[exprunner11]

Thanks clearing things up I was a bit worried that the bigger tires without a retune would affect my transmission as for the speedo I'm not worried at all since it will only be about 1-2 mph off depending how fast I'm going