Recently my brakes were feeling a little spongy so I took my X to a local shop who installed new front and rear brake pads and flushed the brake fluid.
The brakes seemed to operate properly.
But, then while driving on the interstate in Tampa, I had to SLAM on the brakes but it seemed like it took forever to slow down.
It's hard to describe, but it's like when you are moving at interstate speeds and then you have to SLAM on the brakes, the X just slows down and comes to an eventual stop. It does not stop quickly.
I do not feel any pulsing from the antilock braking system so I don't think it is being activated for some reason.

This seems to only happen at faster speeds. I have no problem when driving around town and slowing down for stop signs or red lights. It slows and stops just fine.

So I took the X back to the shop and they replaced the Booster w Ford booster.
I thought I checked it out as soon as I picked it up around town AND on the interstate.
But, today I had to SLAM on the brakes while on the interstate again and it is acting just like before - just slowing down, but not fast and without the antilock brakes activating (apparently).

Does anyone have any ideas?

 

Sounds like a poor grade of brake pad or if the rotors were turned it was too coarse.

If they were turned and rough it will take a long time for both the friction material and the rotor to bed into each other and develop the highest friction.

If it's a poor grade of material you got a situation of fade, which may improve with some more heat conditioning, or may never will.

Other then that it's hard to comment without knowing what the brand and grade of brake pads were used, without seeing the rotor surface firsthand, and not knowing if you have larger then stock tires on the vehicle.

 

fmtrvt - Thanks for the response!
My X is 4X2 and the tires are 265 75 R16

I requested original Ford parts when I took it in for the brakes and I assume that's what was installed. Same with booster. But I have no way to verify that.
He charged me $88.23 for the front pads (parts only) and $76.12 for the rear (parts only) and $307 for the booster (parts only).

The rotors feel relatively smooth to the touch (IMO) but I don't really have anything to compare to. There aren't any big ruts, etc.

 

Your tires are not causing over leverage of the brakes so that's not the reason.

The rotor finish is a hard one to determine. Even experienced mechanics are often surprised when a profilometer is used to measure the surface finish compared to what they believe, In the field some like to use a ball point pen and if you can write on the surface it's deemed OK.

Those prices are in line with the Motorcraft pads, not production line. But I'm not sure the production "Genuine' parts are still available through Ford.

Boosters fail catastrophically, so IMO that wasn't needed. You would have to take the brake apart and look at the pad's edge code to know if the pads were Motorcraft, or get to look at his invoice from the dealer.

The reason the brakes are OK at slow speed is that energy is squared with the doubling of speed, so 60mph is a lot more energy then at 30mph. Often we would call this situation (if friction material related) as "green" fade.

One thing you could try is to go out on a lonely road and complete 4 or 5 slowdowns from 50 to 10mph with about 1/2 mile in-between. You don't have to make a panic style stop as the energy (temperature) will be the same at any deceleration rate. After the series of stops drive for a while to let the brakes cool. Hopefully that will carbonized more of the friction material at the rubbing surface and get you normal friction. do not do more then that amount of stops as you are not trying to burn up your caliper piston boots, which can happen with excessive heat.

The problem with a too rough rotor surface finish is the rubbing surface of the brake pads that carbonize keeps getting worn away by abrasion, so until the surfaces smooth out you never establish optimum braking. Which actually beings up another point, if the brake pads were ground too roughly in manufacturing. This does the same as a too rough rotor, taking a long time before there is good, full contact between the rotor and pads.

BTW, the worst situation of this type of issue is when all four brakes are serviced. When only one axle is serviced the other axle takes more of the load and the braking is not that abnormal.

 

Honestly I was never really that impressed with the brakes on my X. They didn't inspire a lot of confidence if you had to make a panic stop like you experienced.
(Time to stir up a hornets nest) I upgraded to slotted and drilled rotors with pads on all 4 corners and the difference is amazing. I can hear the abs howl and the tires squaking if I brake hard now. More than a few deer are glad I put them on too.

During the break in you accelerate to 40 then moderately brake to 5 and do it a few times to bed them in. It almost made me sick because they provided so much grab.
Almost 10k miles later I still think they're great and would do it again in a heartbeat.

 

Yes, STOP texting and driving!!!

 

I don't think anything is going to slow a vehicle of that weight at that speed unless you go to expensive high friction pads and rotors with a bunch of holes in them which costs even more because they won't last as long. You don't want to lock it up at that speed anyway.

 

The holes and slots in the rotors are not doing anything, and in some case hurt the performance. It's all about the pads.

People end up paying hundreds of dollars for a "package" when in fact for 1/3 of that they could have just bought the pads, or if rotors are needed, just good quality solid, non-special treated rotors.

 

Yep. I'll bet that's why you see them Ferraris. Because they aren't doing anything.

For the price I payed for my slotted/drilled rotors and pads ($230 for all) I would have been hard pressed to replace the stock hardware. The rotors and pads that I took off both had plenty of life left in them, they just sucked. And for that price I questioned the longevity but mine are still great and I'd buy another set in a heartbeat.