I've got a '11 F250, RWD. Brakes worked fine. I was towing my 8000# car trailer on I-95 when steering felt weird, I pulled over, and left from brake was smoking. I got back on the road and made it to an exit and when I stopped, the hub cap had melted off and the "Service Advancetrac" was on the dash read out. I found a ford dealer 5 miles away. I drove there (and during the drive the service message about advancetrac went away.)

they said my caliper locked up and replaced both front calipers, rotors, hoses and pads. had to use parts from a supply house as they didn't stock the Ford parts.

The problem - If I apply anything more than 50% braking, the front tires leave two long black lines on the street. while not an issue in normal driving, when I tow the trailer, I need ALL the brakes. worse, when the road is wet, the fronts run the ABS pretty readily and overall stopping force is well below what it use to be. in the wet stopping distance goes up dramatically.

I re-bled the brakes - issue remains
I changed the front pads - issue remains
I swapped tires front to rear - issue got worse with tires that had less tread

It's almost like my brake bias is very front biased, but I don't know why?

are there more than one caliper that fits the front of an F250? did they fit a caliper that had a different piston bore? how does the F250 bias brakes front to rear? is that fixed? or is it sensor or inertia driven? is there a sensor by the rotor that could have been damaged by the heat of the locked caliper?

Grabbing at straws, maybe the front brakes work SO much better now that they are all new, that they are dwarfing the rears? I kind of doubt that since I replaced the rear rotors and pads in the spring.

Really looking for help.

 

You have a strange one.

Since TRW got the contract for the caliper design in 2005 on these trucks the brake balance has been targeted at 60/40, front to rear. You can alter that bias with aftermarket friction material that is higher or lower then the factory supplied parts, but it's usually never like you're describing, plus you've replaced the front pads again. Unless you used the same exact formula.

And if the rear material you replaced last spring is a low friction material, that would more the bias to the front. There's no rules for how effective any aftermarket material is sold, only for as the truck came off the assembly line. So when you did the rears did it feel like you lost braking effectiveness?

You should not leave two long black lines on the street, they should be broken up by the ABS actuating. Do you feel the ABS pulsing in the brake pedal? In the wet the distance can go up if the front wheels are skid prone and the ABS is fighting like hell to prevent the fronts from sliding. If the rears tires were doing it that bad then the ABS would proportion down the rear pressure, it doesn't and can't do that with the front, not programmed in.

 

second set of front pads appeared different than first set, but no way to measure friction coefficient. one set by wagner, second auto zone Gold.


when I replaced rears, all felt the same. so either they were never working or before and after they were fine

I leave 2 black tread stripes on the ground because the wheel is marginally sliding . if I slam my brakes, it probably pops ABS. have not tried in dry. in wet, ABS kicks and truck and trailer sail though intersections. UGH

 

 

What does the dealership that did the brake work say?? You paid them to fix your truck & they did not, make them fix it correctly.

 

have not been back to that dealer yet. they are about 2 hours away. It's possible that they would know the problem instantly. it's also possible they would go down the same trial and error path that I am and rack up a huge bill. so I was trying to pin point the issue before calling them. it's also possible the issue was created by the failure, but was not resolved by the parts they replaced (like a sensor that was damaged by the heat, etc.). I don't know enough about the F250 brake system to know the problem. certainly if they installed a caliper that had larger piston bores, that's a problem they should fix. but if the problem lies outside the hardware they installed, no reason for me to drive 2 hours and wait while they try and figure it out.

 

If I understand correctly, the F250 has a fixed front rear proportion based on piston size, etc. then the ABS can reduce force to the rear if rears slide. is that the only way braking force can be reduced in the rear? IF so, can anything about my initial failure (the overheated left front and subsequent Activetrac message) cause the ABS to keep the rears at lower force? for instance, a damaged sensor, or maybe when they bled the fronts, air got into the abs unit or rear system?

Cleary the fronts are more than capable of delivering clamping force. it seems like the rears are now underperforming.

 

I checked the pads the dealer installed. I can tell they are wagner SST's but there are no edge markings. the writing not the backing plate is worn from the caliper such that I can't make it out. I get there can be a mismatch in the front rear pad frictional coefficient, but I would think that the range of pads sold by aftermarket would have pretty similar coefficients?

It's funny, I went to the dealer with a front brake problem and now it appears my front brakes are too strong. Unless the front caliper pistons are bigger than before or there is an active reduction in rear brake force in the system, I'm now wondering if I have to start troubleshooting the rear system. seems crazy.

 

 

The Wagners are not going to be that much different since their OE side was the supplier of the OE pads. But there's no regulation in the USA for what aftermarket can be and you can get off brand or race only that can be higher. In Europe, EEC13 regulates the aftermarket pads to be within 10% COF of OE.

Has your pedal effort changed?

 

no pedal effort is the same.

not sure if you saw this question - If I understand correctly, the F250 has a fixed front rear proportion based on piston size, etc. then the ABS can reduce force to the rear if rears slide. is that the only way braking force can be reduced in the rear? IF so, can anything about my initial failure (the overheated left front and subsequent Activetrac message) cause the ABS to keep the rears at lower force? for instance, a damaged sensor, or maybe when they bled the fronts, air got into the abs unit or rear system?

Cleary the fronts are more than capable of delivering clamping force. it seems like the rears are now underperforming.

 

Front to rear balance or bias is primarily based on the rotor swept diameter, the caliper piston area (clamping force) and the friction material coefficient of friction. Typically you design around the first two and keep the friction material the same front to back. Disc/drum brakes were at a severe disadvantage to due the different efficiencies of the two designs, so hydraulic proportioning valves were utilize to attempt to do that over the entire hydraulic pressure range.

But with a disc/disc you still get into situation where weight transfer alters tire traction so you may need to proportion hydraulic pressures to the rear. That's done by algorithms based on the speed, deceleration rate and pressure applied, when needed. Weight transfer does not alter how much a brake generates torque, a misconception. If you apply 1000psi to a caliper, it's going to generate a specific brake torque. If a tire is going to skid with that force, that's due to the tires weight load at the time. A front brake with load transfer to the axle doesn't work more, the unloaded rear tire is generating less overall brake contribution due to the skid.

With standard ABS I'll show some stop data. The graphs are different because of coming from different tests, but they are good examples. All of these are best effort stopping distance GVW 60mph with a target of not to exceed 150lbs pedal effort.

In this first one the vehicle senses a rear brake condition where it should proportion down the rear pressure to avoid an impending rear wheel skid. It does that from 0.5 to 2.1 seconds. At that point a rear skid happens anyway, the ABS closes the rear valve and dumps to the accumulator. It releases, the ABS pump re-pressurizes to get close to the driver applied pressure without proportioning. Skid happens so it repeats going deeper and then having learned slowly brings the rear pressure back up.




Next stop. Not as an aggressive rear skid trait, but still happen later in the stop. Rear brake proportioning was applied at 0.5 seconds. Neither of the two stops had any front activity.





The third stop has both front and rear wheel skid tendencies. You can see the proportioning to the rear channel, but not to the front. the front is working off ABS activity, no proportioning.





I uploaded all that since that was your questioning. But I guess I missed that your truck has AdvanceTrac. That's a whole other ballgame which takes into account other aspects of vehicle control. I was out of the game before that was in production but what you're seeing could be a fault within that system. Typically when AdvanceTrac goes off there are other aspects to look into, and for that you need dealer instrumentation. It's not just simple foundation brake issues.

.

• A faulty wheel-speed sensor
• A faulty steering-angle sensor
• A faulty rotational-speed sensor
• An issue with the steering rack

 

jack - very much appreciated.

I did not even know the vehicle had Advancetrac. when I pulled to the side of the road, I had a "service Advancetrac" message, but then when I restarted and continued to the dealer, no message. so I thought it was gone. I've driven over 1000 miles since and never seen the message again, but I just can't explain what the heck is causing the current condition. I understand brake physics, but it seems there's something I don't even know exists in this trucks brake system. that's why I'm asking if there's any active proportioning that could have been affected by the overheated wheel or clues as to what I'm missing. Maybe the dealer fixed the physical issue (rotors, calipers, etc), but did not check the electronics?

maybe from what you said, there's an advancetrac fault that's not been cleared? who knows. I suppose I can try a local dealer. just did not want them doing trial and error unless it was necessary.

 

The other thing you could do is pull any fuses related to the ABS/AdvanceTrac circuits. You will lose the signal for the speed/mileage as ABS takes in the signal, calculates it, and then sends it out to everything else including PCM. You would be back to base hydraulics and not a situation I'd recommend driving with traffic in for safety sake, but a few miles on a light traffic road may provide a clue with electronics out of the equasion.

To run the FMVSS section of ABS Failure mode the guys would just pull one of the fuses. We had to hunt which one worked proper for shutting done the controller and not the ABS computer to get speed function, but I'd do an "everything" just to see. You'll get an ABS yellow light and a set code, but re-fused and everything comes back. But a code will remain.

Also, do you have an infrared thermal gun? Mine from years ago was in the $200-300 range, but today you can get an inexpensive reasonable one from Harbor Freight for just a few dollars. After normal driving you could shoot the rotors and see the temp balance front to rear. It changes with driving conditions so go with the flow. It's with me everytime I tow because when I take a break I shoot the trailer tires and brakes to make sure things are going proper. Over time you learn the traits.

We used to do fleet assistance for bus fleets, Waste Management, OTR, whatever. One of the things I showed fleet maintenance was to have a guy when the fleet came home to be a the fuel pumps and shoot the wheels. Just about every other day in a large operation they would find a tire or brake issue. For a trailer it can be as much of a warning as tire inflation sensors. so having one wouldn't be a waste of money in my view.

 

Ok if I've understood correctly, you had ONE brake overheating BEFORE it was worked on. AFTER it was worked you now have TWO wheels with brake issues.... they installed wrong parts. Most likely calipers. I've installed every brake pad under the sun and no brake pad will be so extreme from oe that causes a brake issue such as this. Your inclination is correct. They installed wrong parts