need a little help with some 31's

has anyone that has gone to 31 10.50 15 form the stock 235 75 15 recalibrated their Speedo? if so do you remember how many teeth the gear had of the part #. also will I get a lot of rubbing I have a 99 XLS two wheel drive with a 2" TT
Any help would be helpful Thanks.

 

[Redrig]

the tire will fit fine. not sure which gear to use but i wouldnt think your speedo would be off much. mines only off 8 mph with 33's

 

[jimbo74]

its one tooth higher than the gear you had...

but if its a new explorer... its computer controlled..... it isnt the old gear like the 91-94 X

rub should be ok, not a lot, but some.....

however, modification isnt really needed... with a 3.73 gear ratio, the math turns out to be something like, when the speedometer says you are going 85, you are really going 91, but the factory sets the speedos fast anyways, so when the speedo says 85, you will really be doing 85 with the 31s.....

 

[Okrazie1]

Jim is right in saying that you don't have a speedo gear. You would have to get the computer reprogrammed to correct the speedo. The margin of error is small enough that I wouldn't worry about it. I've been running my '99 with 31's for almost three years now and I never had the speedo recalibrated.

 

[jssong]

does the mileage go up slower or faster with bigger tires?