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Not sure why theres an image of a proportioning value in this thread, the Superduty post MY2000 didn't have one.
One temp reading, one data point doesn't necessarily tell you everything. Brake temps, and the difference between the front and rear brakes vary depending on the driving environment. In normal driving all four can be close in temp, during times of different energy dissipation you can get more of a spread. It also varies from the early brake design to the later brake design, but all Excursions are built with only one.
An Excursion on Day 1 of a wear/durability/NVH test of aftermarket brake pads shows relatively normal spreads with the exception of a differential across the fronts after lunch break. The highest temps are inner city when speeds are low and air isn't pumped through the rotors, the balanced brake temps before the inner city are light highway into the city environment, as is the return home at the end of the day.
By Day 5 a temperature imbalance was routine, along with the reports from the driver of a left brake pull whenever the imbalance approached 100F. Test route on Day 5 is a different route, more surburban. Pulls are generally noted anytime brake differentials across an axle reach the 80-100F range on a Superduty. Inspection of these brakes showed the left front pads to have a slight hangup in the torque bracket, despite all new calipers and brackets. Aftermarket pads utilize steel backs that are cheaper then the OE pads and typically have a higher tolerance spec. Typically the only thing necessary to correct this problem (If it's the problem here) is to do a minor correction on the end tab of the steelback, wherever the resistance is. It's not a problem of brake application, it's a problem of the pads/rotor on that side not cooling since the brake pad doesn't fully retract off the rotor. This also in time leads to disc thickness variation, the cause of pulsation.
Semi-metallic brake pads which are typically used in this weight class have somewhat of a bell curve in friction vs temperature, so a 100F spread reflects that. The other thing that happens over time is the hotter running side develops a higher carbon content at the subbing surface, so even after correcting any pad hangup, the friction is higher on that side and will take some time to wear away to the normal friction level. The way around that is to exchange the outer pads side to side so now both brakes on that axle have one higher friction pad.
