By now you've heard all about the front brakes on our 2009 Ford Flex Limited. Amazingly, the front brake pads have lasted over 60,000 miles, and there's still a bit more meat left. But the rotors have developed too much "disc thickness variation" or DTV. It's not warping from overheating -- we wouldn't have surpassed 60k with such hard use. No, this moderately-driven family-mobile has a classic case of cold judder, high spots on the rotor built ever-higher by gradual pad material transfers.
One way this can happen begins with rotors that start off with imperceptible high spots, and then spend their lives in a driving pattern that's dominated by long freeway drives with infrequent brake use. You know -- road trips. Our Flex is the go-to road trip vehicle around here, so it's been on more than its fair share of them.
Anyway, over time the retracted pads can start to lightly brush the tops of those high spots, and a minute amount of pad material transfers to the disc. The high spots get a little higher and the deposition cycle repeats. Then, at some point, the driver lightly applies the brakes on a freeway off-ramp and gets a handful of steering wheel shake for his trouble. Some of the deposits wear off, so the shaking doesn't persist around town. But the high spots got a little higher in the process, so the same thing happens again -- easier this time -- over the next long-haul open-road stretch. The subsequent shaking while braking gets more noticeable over time. We've been living with this on-and-off for the last 10,000 miles or so.
But we've had enough. It's time for new pads and rotors. Yeah, rotors can be machine-turned on a lathe, but when you're done they're thinner and have less remaining thermal mass. If the price is right, I'd much rather install new ones. Doing it myself allows me to divert the labor savings into the cost of new parts. And I can't turn a rotor myself, but I can bolt-on a new one. Besides, 60,000 miles is a good run for a rotor.
On top of all that, changing front pads and rotors is deceptively easy on most mainstream cars -- easy enough to be enjoyable. Our Flex is no exception. Jump to the next page to see my Ford Flex brake pad and rotor change walkaround.
Sliding calipers like these have two pins on which the caliper slides. Usually, it's only necessary to remove the bolt that screws into the lower one.
NOTE 1: For reasons you'll see later, do one side from start to finish before doing the other side.
NOTE 2: Since you're doing one side at a time, do yourself a favor and turn the steering wheel so the caliper faces out.
With the bottom bolt out, the caliper pivots up on the upper one. The rubber hose gains even more slack while we do this, so there's no need to disconnect any hydraulic lines. The hose issue is THE reason why we're removing the lower bolt and pivoting the caliper on the upper one.
NOTE: If you get to a point where you think you have to disconnect a hydraulic line, you're probably doing it wrong. Seek professional help.
The sliding half of the caliper pivots so far up that we don't need to hold it up. In cars where it won't go quite this far over-center, a tie-wrap (or a friend) can be used to hold it out of the way.
At this point, the pads are just sitting there, nesting in the retaining clips. Pulling them out is easy work.
If we were only changing the pads, We'd put the new ones in right now. But we're changing rotors, too, so we're going to wait and do the pad part later. For now, close the padless caliper and make sure to keep anyone and everyone away from the brake pedal from this point until it's all done. Not even a little bit.
The slider bolt (yellow) is back in place, but it's only spun in a couple of turns. Now it's time to break out the big socket to remove the two bolts that secure the entire caliper assembly. These will be tight -- about the same as lug nuts. Here a 1/2-inch-drive breaking bar provides adequate leverage.
The first bolt is out. Now we have to remember to support the weight of the caliper with our free hand as we remove the other one.
We don't want to lay this thing on the ground, because that would make it necessary to disconnect a hydraulic brake line. Big no-no. Instead, hang the caliper from the spring using a chain of tie-wraps. An upper control arm works on cars that have those.
With the caliper out of the way, it's time to attack the rotor. Ford uses a Torx-head bolt to keep the rotor in place when the caliper is off. This isn't a critical part once the car is in service, but it keeps the assembly line workers safe when the car is on the line between the "rotor on" and "caliper on" assembly steps.
This bolt can be difficult because of the heat cycles and the rust that can build up after 60k miles of use.
In this case, my T40 Torx didn't fit at first, so I thought it was a T-35. I was wrong. The T-35 I bought was too loose. A solid rap with a mallet seated the T-40 in the bolt head and it came off easily.
Once that bolt is out of the way, the rotor comes off easily.
The new rotor simply slides over the studs. And look, there's no place for that retaining Torx bolt. Spin on one of the lug nuts instead, finger tight.
Time to cut the tie wrap, remembering first to support the caliper so it won't fall and ruin everything.
Then we re-seat the caliper, re-install the two large caliper retaining bolts and snug them down fairly tight. We'll torque them for good a bit later.
Now we can finally re-open the caliper and get back to installing our new pads.
New pads almost always come with new clips. These are the points where the pads slide back and forth during use, so it's important to replace them. There are no retaining screws -- they easily snap in place. It takes seconds.
The ears of the pads nestle onto these runners. It's a sliding surface, so the places where the pads will make contact need to be coated with the supplied graphite-based grease. It can be applied to the clip or the mating ears of the pads. Either way works.
Here are the new and old pads. There's a little meat left, but not enough to keep them. Meanwhile, the new pads have two slots to the originals' single one. No biggee. These are still the correct pads. Ford engineers could have made this small running change for any number of reasons.
Thankfully, the new pad backing plates have riveted-on shims, so there's no need (in fact, no possible way) to smear the space between with more graphite lubricant. And the surface you're looking at even has a rubberized coating of some sort. Noise-wise, they've covered all the bases. For the DIYer, this is about as easy as it gets.
The new pads slot into place as quickly and easily as the old ones came out.
But the dual pistons shown here need to be pushed back in. They're sticking out because the old pads were thinned by use. The new pads are of course much thicker.
Don't laugh, this works. Sure, we could buy a piston retractor tool for a good piece of change, or we could pry the pistons back in like this.
The soft wood makes it easier to avoid nicking the rubber seals, and the width of this two-by-four allows both pistons to be pushed in at once. They have to go in together because, if one were pushed in singly, the other would pop out.
This is also why it is important to do one side of the car at a time. If both sides of the car were in this condition, the pistons on the other side of the car would pop out when the pistons on this side of the car were pushed back in.
The brake fluid in those pistons is being pushed back into the master cylinder reservoir through tiny passages, so the going is slow. It takes a couple of minutes. Steady pressure and patience are the key. In this example, a second plywood shim was added near the end to fill the ever-increasing gap.
While the pistons are being pushed back, the brake fluid level here will rise. Check often. This is more of a concern when the second brake is being done, because the combined fluid volume of two calipers is what will likely push this over the brink.
Overflowing will certainly be a bigger potential problem if the fluid level was ever topped off to the "MAX" mark during the course of those first 60k miles. This is why the brake fluid reservoir shouldn't be topped off like that. The fluid level naturally goes down as the pads wear. Let it be. It's not leaking out. As long as it doesn't go below "MIN", everything is cool.
Here, no fluid was added over the 60k miles these pads lasted. And so when both sides were done the fluid level came right back up to the "MAX" mark, but no farther.
If the level does push past the "MAX" mark, a turkey baster works best to remove some. Don't forget to permanently remove it from food preparation service -- buy a new one for the kitchen.
The pistons have been fully retracted and the seals are undamaged. Almost done.
The pistons have been retracted far enough, so the caliper slips over the pads with little drama and no effort.
Time to re-install and re-tighten the slider bolt.
Lastly, it's time to torque the caliper mounting bolts good and tight. Why do this now? It could have been done when the caliper was re-mounted, but there's something to be said for going through the torquing ritual at the end, to avoid second-guessing and make sure it gets done.
Done. Time to straighten those wheels, remove that lug nut and re-mount the tire.
And torque those lug nuts, of course.
Now it's time to move on to the other side of the car and do it all over again.
How much time did this take?
If I hadn't been stopping to take pictures, this entire job (both sides) would have taken just under 30 minutes. Few actual tools are involved. The T-40 Torx bit is the most exotic one here, but a torque wrench is a must for those caliper bolts. But any DIYer who so much as rotates their own tires should have one of those. If you don't have one, get one!
How much did this cost?
A set of Ford Genuine front brake pads cost $66.63, plus tax. As for the rotors, I had a choice at my Ford dealer: Ford Genuine rotors for $83.30 each or Ford Motorcraft factory-approved replacement rotors for $48.85 apiece. Since saving money is part of what DIY is all about, and since the Motorcraft ones still wear a Ford label, I went the cheaper route. Once I got them home, I noticed the Motorcraft rotor boxes wore the "Made in China" label. Not sure if the same is true of the "Ford Genuine" ones. I never saw the box.
Total parts cost: $164.03, plus tax. In this area that's 9.25%, so my total was $179.20.
Why go with Ford parts and not cheaper aftermarket stuff? Ford knows more about their vehicles than the replacement market does. They know their own brake system's noise, dust and wear susceptibilities better than any outsider could. And these factory parts lasted for over 60k miles -- well above average, in our hands, no less -- so that tells me that the Ford Flex brake engineers did their math right.
Dan Edmunds, Director of Vehicle Testing @ 61,180 miles (when I did the job)
bankerdanny says:
02:24 PM, 08/13/10
Nice, I just did the pads in my Forester a couple weeks ago (only 36k, but 80% city miles and my wife is hard on the brakes). The rotors were in good shape, no pulsing, so I left them alone.
A pad and rotor replacement at the dealer (or even Midas) is easily 2x what you just paid.
jdub53084 says:
02:30 PM, 08/13/10
good post, glad the Flex has some new stoppers!
yellowbal says:
02:38 PM, 08/13/10
Do you use the torque wrench for the slider bolts?
roadburner says:
02:38 PM, 08/13/10
Brakes are a dead easy DIY job. Especially on cars with fixed calipers such as Brembos.
felonious says:
02:58 PM, 08/13/10
Wow Dan, I think this could be the best IL tech article so far! But maybe I'm biased, being a Flex owner. I feel very inspired to do this myself someday! By the way, where did you get the torque specs? Would you mind posting them in a reply?
Thanks!
benson2175 says:
03:17 PM, 08/13/10
No professional mechanic I know uses a torque wrench. Are they all bad then? When I suggested on buying one I was told not to waste my money.
saxdogg says:
03:24 PM, 08/13/10
Great work. Do you have a car in the fleet with drum rears? I'd like to see that one too.
tjpark01 says:
03:51 PM, 08/13/10
Sweet write up. The only thing I may add is to use some brake cleaner on the rotor prior to installation. Rotors are usually shipped with a film of grease on them so they don't rust. It's not a big deal, cause the film will get burned off when you use the brakes. But the first stop or too, can be a little long, which could freak someone out, who's not expecting it.
actualsize says:
04:04 PM, 08/13/10
I won't deny that pro mechanics who do this every day can develop a good "feel" for this. Torque specs are generally proportional to the diameter of the bolt, so it is possible with practice. I am not here to say that a torque wrench must always be used. Note, however, that the casual DIY mechanic may not have that feel. One could argue that a rookie is a better candidate for a torque wrench than a trained pro.
But there are mechanics who overuse their precious air gun. Others simply over-tighten everything, thinking that more is always better. (It isn't - these guys often have lots of experience with stripped bolts and heli-coils, a thread repair method.) Any "pro" mechanic who will actually stand there and tell you that torque specs and a torque wrench are utterly useless is a mechanic I would not patronize, period. If they can spend $25,000 on a massive pro tool box full of Snap-On or Mac tools, they'd be silly to not have a least one 1/2-inch-drive click-type torque wrench in there. These guys usually fall into categories two and three, above.
For the caliper slider, I did it by feel. Lightly-torqued and lightly-loaded bolts like these are easy to handle this way. But the large main caliper bolts are another matter. I'll always tighten something this critical (and this large) with a torque wrench. Remember, these bolts don't have nuts on the other side: the receiving threads are cut into the knuckle itself. If you overdo it and strip them out, you just cost yourself hundreds of dollars. I don't have the torque spec in front of me, but if I remember correctly, it's north of 90 lb-ft.
jli585 says:
04:09 PM, 08/13/10
c clamps work well for pushing the pistons back
actualsize says:
04:14 PM, 08/13/10
@tjpark01: Yes, that is often true. But these rotors didn't have any such oily coating. They were bone dry. A lot of rotors now come instead with a hard, dry protective coating, something that's intended to be worn off in the first few stops without causing bad performance. Assembly line parts have this all the time. They don't have UAW guys and gals wiping down those rotors. But, to your point, I have seen this other times I've changed rotors.
actualsize says:
04:28 PM, 08/13/10
@jli585: Yep, that works too. If one was to do that here, I'd use one of the old pads as a bridge between the pistons so I could push both in at once with a single c-clamp. But I don't own a big-enough c-clamp, so I went this route.
kevm14 says:
04:30 PM, 08/13/10
On older or higher mileage cars, the slide pins should be taken out, inspected and possibly cleaned and re-lubricated. And wire wheeling is generally a no-no as the surface is usually galvanized or zinc coated or some other anti-corrosion coating. You'll wear right through that and it will be a lot more susceptible to corrosion after it goes back into service.
Also, for compressing caliper pistons on SLIDING calipers, I've had great luck with a giant C-clamp (the home centers have them, as does Sears). You put the fixed end on the back of the caliper and the other end through the caliper, onto the outer pad. Then simply compress. The outer pad pushes against the rotor and won't go anywhere, while the caliper will move toward you, compressing the pistons. But I've never tried this on a dual piston caliper. In fact, I've never had a car with dual piston calipers. And my new car has 4 piston fixed Brembo's at all 4 corners (CTS-V) so that will be completely different.
Drums are a pain, plain and simple. Lots of fighting. And I start by using the correct tools but always end up using vice grips on whatever I am trying to unhook.
I agree on the rotor turning. To me that is old school advice. I would never turn a modern rotor for the exact reason you mention. But I've also had bad luck with cheap Chinese rotors, at least in heavier use. My last set of rotors (for my 93 Caprice) was from Napa, from their Ultra Premium line. They were twice as much as Autozone cheapies, but made in the USA and are still going years later.
kevm14 says:
04:34 PM, 08/13/10
Also I forgot to comment on the torque wrench. I have one. I use it on lug nuts as those are extremely important to be evenly torqued but generally not on a job like this. The caliper bolts are set to "tight" by my own calibration system, and as Dan mentioned, torque is proportional to the fastener diameter. If it's a little fastener, and you have a 3/8" socket, with a 1/2" adapter, and a long pipe on the ratchet, and you are tightening it this way, you are doing something wrong. Common sense and thinking things through goes a long way.
About the pro mechanics: yes some still just over torque with their air impact. However, years ago I discovered something called a "torque stick" which looks like a long extension with a set hex size at the end. They have a calibrated twisting yield to a given torque spec. I understand that it is actually ok to use a "100lb-ft" torque stick and install a lug nut with it. Though the best guys will walk around and check each lug nut with a torque wrench afterward anyway.
fuhteng says:
04:54 PM, 08/13/10
I've never done this before (or even seen it done) and my best source of advice (my Dad) passed away 8 years ago so I'll ask: Is this is the same procedure for any disc-brake equipped car? For example, would it be the exact same procedure for my bone-stock G8 GT?
Thanks.
actualsize says:
05:26 PM, 08/13/10
@fuhteng: If the front calipers are of the sliding type (and I am 99% sure they are on that car), then the procedure is more or less the same. I've done about the same thing on a Miata, GTI, CRX, Civic Si, my wife's Odyssey minivan (last week!) and a couple of others. It only gets weird on some of the newer German ones, where the slider mechanism is buried, involves clips and is less obvious.
I think your G8 GT is similar enough that these principles apply. It has a single piston instead of the dual pistons shown here, but all that does is simplify the retraction process.
The pad slider clips differ from car to car, but the principle is always the same. Many times the shim stack is not riveted on - they snap on to the back of the pad. In these cases I like to smear more graphite between the shim and the pad's steel backing plate. Sometimes there's a little pad-wear indicator that clips on in a specific corner of one of the two pads. Simply lay the old pads on the ground, keeping them on their original "sides" of the rotor, and simply copy what you see when configuring the new pads and new shims.
The riveted nature of the Flex's pad shims made these steps unnecessary, but it also robbed me of the chance to show this part.
vvk says:
07:06 PM, 08/13/10
fuhteng,
Your best bet is to buy a repair manual for your car. It will have step by step instructions on what to do.
mark19 says:
07:11 PM, 08/13/10
Dan (actualsize, i think that's you) - Why didn't you use a run-out dial gauge to measure the runout of the rotor/disc? That's what I always do, because the runout can sometimes be too much in one spot. So you take it off and move it one lug, re-measure until you get it perfect or within specs.
I agree with everything else you did in this, except for that one step I've found to be crucial to ensure a vibration free ride, and braking as well.
cello_one says:
06:56 PM, 08/14/10
That really was a great post. I have only done pads once but it wasn't nearly as hard or scary as I thought it would be. I had enough advice to do one wheel at a time but that was about it.
I since I have a Flex that gets 4-5 1,500 mile trips a year, I will expect to have the cold shimmy. Perhaps I will try it on the shaking 2005 Elantra before tackling the the larger car. Easier on the jack and stands and all.
s197gt says:
11:13 PM, 08/14/10
you might want to mention that after replacing pads or pads/rotors you should start the car up and pump the brakes to push the pistons (which have been retracted) back up against the pads. after replacing all the pads on my car i pumped the brakes and it took two to three pumps to get back to a normal feel.
someone who doesn't do this might back out of their garage and down the driveway and be taken by surprise when they push their brake pedal to the floor and roll right out into the street!
mrjost55 says:
09:28 PM, 08/15/10
You should have used some Brake Klean on the new rotors to get all the storage prolonging substance off of them. Also it got a little dirty from your hands.
Another thing, some mechanics suggest to clip off the brake line and open the bleeder screw while pushing back the piston so that you don't damage the Master Cylinder.
sodaguy says:
03:55 AM, 08/16/10
The slide pins should have been cleaned and regreased. Why was this crucial step omitted?
actualsize says:
04:33 PM, 08/16/10
Well @sodaguy, I checked theses sliders and they were fine. The two or three dozen of these I've done on my own street and race cars have been the same. But I think it's a good idea to mention this inspection and, if necessary, re-greasing step. Other parts of the country use road salt, a driver may drive frequently on unpaved roads, or a car that has more than 100,00 miles on the clock can certainly get "dry". But fairly new cars driven in mild climates with intact rubber slider seals oftentimes don't need to be re-greased. Doesn't hurt to do it, but it's not an automatic step. Still, it's worth pointing out next time.
fuhteng says:
12:08 PM, 08/17/10
vvk - I would love to, but there isn't a Haynes/Chilton manual out (not enough sold) so my only option is the $150 Helm set. Yikes.
Thanks Dan. I appreciate it.