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A couple months ago I replaced my rear calipers due to the passenger rear dragging. Before replacing the calipers I couldn’t smell anything like pads overheating, but the pads of that caliper were significantly more worn and when I took temps on the disc surface the front discs were both at 125F, the left rear was at 110F, and the passenger rear was at 175F. Outdoor temps were 50-60F at the time. So I replaced both rear calipers with rebuilt units from Advance Auto.
I’ve noticed my fuel economy hasn’t been so great the last couple tanks, so of course first thing I checked was brake temps. When I got home from a long drive (no real brake applications for about 1/2 mile) I measured brake temps. Both fronts were 110F, and both rears were 125F. This with outdoor temps being 25F. Although the temps were the same on both sides of each axle, it seems odd to me that the rears are at higher temps. While not much higher, I’d think the rears would be lower than the fronts, and that the calipers must be dragging slightly. Am I off base here?
Axle to axle brake temps vary depending on load and the character of the route. And with a low brake application per mile situation, the rears can be a little above the front as the front brake cooler at a faster rate then the rears (airflow under truck). And within the 6.0L brake designs, the earlier brakes (Akebono calipers) are more balanced front to rear than the later style (TRW calipers).
I'd have to hunt on my old computer to see if I had anything relavent to an Excursion, but they tended to run a little warmer on the rear due to the suspension height.
This example is from a TRW caliper equipped pickup at full GVW running an moderately aggressive test route. It's an accelerated wear and NVH test of 2000 miles. For the day the average brake application is 3.4 times per mile, almost 85 per hour. In the mid afternoon section the truck is in a low brake application section at 40 mph. There are stoplights, but the application rate is pretty low. Compared to the other sections of the day, where do you want to compare front to rear brake temps? So it can be really hard to determine what is the correct temp balance. Which also brings up the point of brakes being 70/30 bias is just so disconnected with reality.
Adding in ....
Hunting around on this computer I did find a graph from an Excursion. Loaded to 8,800? GVW, these are burnish stops, 40 to 0mph, every 1 mile at moderate deceleration. If you look carefully at the initiall 200 stop burnish to bed the brakes in, most of the time the rear brakes are running just slightly hotter then the front brakes. More at the last 10 applications. Then also look at the second reburnish, the third section of data. Again, one stop per mile is a lot of brake applications and at that speed and weight, a lot of energy dissipation. CONSISTENTLY!!! So there is a lot of heat soak to the components, not like what you would see in commuter driving.
So a way long way of saying the best thing a person can do is learn how their truck reads over time, maybe shoot the rotors (in the middle of the scrub width) every so ofter after the drive home from work. That way you establish your normal thermal pattern front to rear and side to side, and your'll have the baseline to know when things are going downhill.
Thanks for all that awesome info! I did some brake applications today on the way down the hill before my house and checked temps immediately after stopping at my house. Fronts were both between 140 and 145 and rears were both at 170. Will do my regular driving and see what temps are at so I can see any issues like you said. Thanks again!
Ha ha yep, the Motorcraft Severe Duty blue brake pads. At least I assume the friction material is the same compound front and rear for those pads. The rear pads are new, the front pads have been on quite a while, so...
The reason for the question is the brake system was implemented with the same exact friction front and rear. You can alter the temp balance with friction that has a different temp/friction curve.
The reason for the question is the brake system was implemented with the same exact friction front and rear. You can alter the temp balance with friction that has a different temp/friction curve.
Yep, understood completely. Think it’s possible that part of the temp difference is due to the difference in age and amount of use of the pads, even if the same compound?
The aged pads can have more foreign material embedded in the surface, which can alter the effectiveness slightly. Higher or lower depends on what's in there, rust from the rotors, road dust, this time of year de-icer. But it's a dynamic condition, changing due to the amount of brake wear. I wouldn't go out of my way to change pads just in case.
When you check brake temps you also have to realize there can be some temporary disparity that shows up now and then.
If you look at the F-350 data graph I posted around 7:30 in the morning there is a little differential in the front axle, which doesn't show up that much overall. Looking at the data distribution of temperatures, around 400-450F the left brake has a little more time at temperature. And at 550,650, 700F the right brake has more time. Suttle difference, and not something we would get hyper about. But if we shot the rotors right at that moment and only then, we'd be pulling the brakes down. But when viewing the entire day, it's fine.
When you first shot your brakes and found a problem on the right rear, the left rear may have been a little cooler than normal due to the right working harder. That's if you found something mechanically wrong with the right. For all intent, you can also have the left rear not working as well and the right rear kicking up. Brakes can get weird that way. Or not. It's why R&D was never boring.
Ha ha yep, the Motorcraft Severe Duty blue brake pads. At least I assume the friction material is the same compound front and rear for those pads. The rear pads are new, the front pads have been on quite a while, so...
Where did you manage to get your hands on the Ford Motorcraft Blue pads?
They aged that line out a few years ago.
just curious because i didnt see it mentioned... but when you changed the pads and caliper did you change the flex hoses too?? people tend to forget about the flex hoses aging and collapsing... sometimes they wont collapse all the way and just leave a narrower channel for the fluid to return to the mastercyl... it could result in a slight drag causing the higher temps... not all instances of brake dragging results in something you can feel going down the road... this is normally the more severe cases people complain of the feeling...
unfortunately fuel mpg is effected by many factors as well..
@TooManyToys Jack do you recall who it was that said the Ford blue pads are EOL?
Also I had asked Scott over at FICMrepair and he said he can't find them and that was after
one of the members here had posted the End Of Life on the pads. As far as Amazon goes
you can find a lot of counterfeit goods there.
