Posted by David on February 20, 1998 at 06:21:42:
In Reply to: '98 Explorer Tires posted by Jeff on February 18, 1998 at 21:20:07:
Your question is to wide open! The model/year of your Explorer may impact the answer to
your question. There are three possible tire sizes that come as OE fitments on the
Explorer. Depending on options and model, Eddie Bauer, Limited, XL, XLS, Sport.
1. 255/70R16 - OD=30.1
2. 235/75R15 - OD=28.9
3. 225/70R15 - OD=27.5
These are the overall diameters (tire hieght)in inches. The OD of the is used for
speedometer calculations. The speedometer data is used for many things besides speed
information - Engine computer- cruise control - trnsmission shifting - antilock brakes
as examples. When changing tire sizes you must maintian the same tire OD as the OE size
OD. Exceptable variations are limited to 3% +/- as a general rule. Because the variations
from the OE options range from 30.1 to 27.5 = 2.6 inches, you first need to determine which
you have. Then base you search from there, maintaining as close to the OD of the size your
Explorer came with. You should check with FORD to see if the are differences in programing
for the three different sizes on this vehicle as well and that may allow you to widen your search.
Some Vehicle manufactuers allow for re-calibration of computers to allow for a change in tire
size to a different OD, FORD can provide you that information also.
You do have some choices in tire size, possibly going to floatation type size format-i.e.
30X9.50R15 = 29.5 OD, you may also want/need to consider a wheel change in order to accomodate
a different tire size. This would be dependant on the width of the tire in relation to proper
fitment on the wheel, wheel width needs accomdate tire width for proper fitment. Wheel diameter
would also be a consideration (15,16,17 ect.) you may want/need to factor or consider if
you want to chage tire size. You can increase the wheel/tire diameter and maintian a similar
OD for the assembly. i.e. -
225/70R15 = OD 27.5
255/55R17 = OD 28.0
A half inch variation would be within the 3% tolerance.
Hope this helps and doesn't confuse you. There are definetly benifits to a change
in tire size - ride quality, traction, handling, mileage, tire/tread type options,
load capcity and cosmetics to name a few.
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