Same thing happened with my 04 with only about 30K miles. I didn't know there was a TSB on it and I just replaced them with Goodyear Fortera Silent Armors, which have broken in well and am enjoying them.
edit: Sorry, images didn't carry over.
Here's the TSB info:
TSB 05-11-11
06/13/05
IRREGULAR TIRE WEAR
FORD:
2003-2005 Explorer Sport Trac
ISSUE
Some 2003-2005 Explorer Sport Trac vehicles equipped with the Goodyear Wrangler RT/S, P255/70R16 109S AT OWL tire, may exhibit signs of feathering heel-toe wear on the inside or outside edges of the front tires. Tire noise may also be present during regular highway drive or when braking.
ACTION
Inspect the tires for feathering heel-toe wear. It may be necessary to rotate or replace tires and reset toe. Refer to the following Service Procedure.
SERVICE PROCEDURE
1. Visually inspect the front tire's inside and outside shoulder ribs (Figure 1).
2. Measure the difference in tread depth of the leading edge compared to trailing edge, of the most-worn lug (figure 2). If the average difference in tread depth between leading and trailing edge is less than 2 mm, rotate the tires. If the average difference is more than 2 mm, replace the front tires. Also inspect the rear tires and replace if necessary.
3. Ensure that the camber and caster readings are within specification.
4. Set the total front toe (TFT) to 0.12 +/- 0.05 degrees (nominal).
NOTE IT IS VERY IMPORTANT THAT THE TOE BE SET POSITIVE TO 0.12 +/- 0.05 DEGREES (NOMINAL).
NOTE REFER TO WORKSHOP MANUAL SECTION 204-00 FOR ALIGNMENT PROCEDURES. REFER TO THE WARRANTY AND POLICY MANUAL FOR TIRE AND ALIGNMENT REIMBURSEMENT COVERAGE.
WARRANTY STATUS: Eligible Under Provisions Of New Vehicle Limited Warranty Coverage
OPERATION DESCRIPTION TIME
051111A 2003-2005 Explorer Sport 2.0 Hrs.
Trac: Inspect Tires, Check
And Adjust Front End
Alignment
051111B 2003-2005 Explorer Sport 2.1 Hrs.
Trac: Inspect Tires, Rotate
Tires, Check And Adjust
Front End Alignment
051111C 2003-2005 Explorer Sport 2.3 Hrs.
Trac: Inspect Tires,
Replace And Balance 2
Tires, Check And Adjust
Front End Alignment
051111D 2003-2005 Explorer Sport 2.7 Hrs.
Trac: Inspect Tires,
Replace And Balance 4
Tires, Check And Adjust
Front End Alignment (Do
Not Use Any Of The Labor
Operations With 1007AT,
1007AF, 1007AFT,
1007AB, 1007ABT, 1007D,
1007D3T 1007D3F,
1007D3FT, 1007D3B,
1007D3BT)
DEALER CODING
CONDITION
BASIC PART NO. CODE
FRONT (ALIGNMENT) USE WITH
OPERATION W OR "B" W6
TIRE (TIRE REPLACEMENT) USE
WITH OPERATION "C" OR "D" 30