Ok, this is different than my usual instructables where I create a prop. There's one of them on the way, in the meantime I had to swap out the front brake rotors on our 1995 Volvo 850 due to a warped rotor which was giving us a pulse when coming to a stop.
This is a fairly easy job if you have the right tools. So lets start there:
19mm socket for lug nuts
15mm socket for Caliper Bracket
7mm allen for Caliper guide bolts
10mm socket for removing rotor holding pin
C-Clamp or equivalent for compressing caliper
Flat blade screwdriver for removing anti-rattle spring
Two new 15mm Caliper Bracket bolts, (they're one time use)
new pads while you're there.
Step 1: Loosen Lug Nuts
Depending upon your tool set, you can do this one of two ways.
If using a hand tool. Use the 19mm socket and the right sized ratchet to break the bolts loose. Hey, you could even use the lug wrench the car came with. We're not fancy here.
I have an impact wrench.
So if you're doing this by hand, break them loose, not too loose then we'll jack up the car.
Ok, all the safety things here: The car's in park, the parking break is on, you have not only a jack but a jack stand once it's in the air. Cars are heavy, they can swash things if you're not careful. Be careful.
The jack point for the Volvo is where the subframe attaches to the body. You'll find it. It's a good sturdy place to use.
Jack up the car to get the wheel off the ground. Then go a little higher and get the jack stand under the car near the jack. Lower the jack till the car is resting on the stand. Then I go and jack up a little again till the jack is tight against the car again. It's a belt and suspenders kind of thing. I don't want it to fall.
I use my impact wrench now to spin off all five lugs from the wheel. Then I slide the wheel under the car. Just one more way to keep me safe.
Step 2: Let's Get That Caliper Off.
The first thing we're going to do is remove the spring that keeps the assembly from rattling. I use a flat blade screwdriver and just pop it off.
Put it somewhere safe where the rest of the parts will go. Don't hide it. I like to keep all my stuff together, so once I'm done, I can look and see if I've forgotten something.
Step 3: Guide Pins
The guide pins on the back of the caliper are found under some plastic dust caps. You pry these out to get to the 7mm allen bolts that hold the caliper to the caliper bracket. They live in a bit of grease, so hopefully they won't give you too much hassle.
Once the guide pins are un-screwed, you'll have to pull them out just a bit further so they clear the bracket. I remove the pads and the caliper at once and hang it from the strut assembly with a bungie cord.
Use what ever you have to tie the caliper out of the way. Do not let it hang from the brake line, unless you like more work later. Replacing brake lines is a drag.
Step 4: Caliper Mounting Bracket Removal.
There are two 15mm bolts that hold the bracket on. You'll need to pull these and they need to be replaced. They are listed as one time use in the manual.
To help out, turn the steering wheel to the right, this gives you more room to swing a wrench on these bolts. They'r tight, as you can imagine, but they need to come out. Once they break free, you're in good shape.
Step 5: Rotor Pin
Here, there's a small retention pin bolt thingy that not only holds the rotor in place, but is a guide pin for your wheel. It's a 10mm socket to remove it.
Step 6: Time to Clean Things!
This hub was replaced not to long ago, so it's in good shape. Clean off any rust particle or dirt that may get in the way of re-assembly.
Can you tell this car has seen a few New England winters?
Step 7: Reverse Order! Put It Back Together!
So put on the new rotor. Give a light coat of anti-seize to the guide pin/bolt thing and tighten it down snug, not too tight just firm. The lugnuts will hold the thing together and you don't want to snap this little thing. Ask me how I know.
Step 8: Re-install the Caliper Mounting Bracket.
The manual insists on using new bolts here. That caliper is under a lot of stress to bring this beast to a stop, don't skimp. Get new bolts.
The bolts get tightened down to 77 foot pounds. Again, they're the 15mm bolts. The new bolts come with a small dab of loctite®t on them, no anti-seize here, you want these guys to be tight.
Having the wheel turned, gives you room to swing that torque wrench.
Step 9: New Pads, Since You're Here.
If you're in the neighborhood... you might as well. It will save you some hassle.
Fresh pads on the new rotor, everyone is new and happy.
Now of course, since the rotor is new, it's thicker. The pads are new, they're thicker. How do you get the caliper to fit again? You have to compress the piston back into the caliper body.
I use a 4" C-clamp and a small wrench to compress things. Go slow, don't rush, don't pinch the rubber around the piston. The excess fluid will get pushed back into the brake reservoir, so depending on how low that is, and how much you have to travel to get the piston all the way back, you may overflow the reservoir. Just keep an eye on it so you don't make a holy mess.
I have an old turkey baster handy to remove excess brake fluid if needed from the reservoir. Don't reuse it for turkey afterward.
Step 10: In With the Pads and Back on to the Bracket!
Drop in the new brake pads and the assembly should have plenty of room to fit right over the new brake disk.
The guide pins on my calipers were pretty greasy, so I didn't add anymore. If yours are dry, add just a thin coat of axle grease to the pin itself as you push it back into it's rubber dust cover. I add a drop of blue loctite to the threads of the guide pin and torque them down to the recommended 22 foot pounds.
We're almost done! Get the spring back on, believe me, I've forgotten it once.
Step 11: Reinstall the Wheel and Snug Up the Lugs.
With the car still on the jack and stand, put the wheel on, using the guide pin to help you center it. I finger tighten first all the lugs bolts, then while it's still in the air, use a wrench and the 19mm socket to go a little tighter. We want them snug but not torqued while it's in the air.
Remove the jack stand, and slowly lower the car onto the wheel.
Once you can remove the jack, use the torque wrench to tighten each lug to 81 foot pounds using a star pattern, which means tighten #1, then bolt #4, then bolt #2, then bolt #5 and finally lug bolt #3. A star shape, this helps make sure the wheel is on flush to the new rotor.
DO NOT USE AN AIR IMPACT WRENCH TO TIGHTEN LUG NUTS
Seriously, it warps things, cracks things and they are a BEAR to remove on the side of the road when it's dark and raining and you have a flat. Torque wrench, 81 foot pounds (This torque is specific for this car, you model may vary)
We're ALMOST done.
Step 12: Start the Car, Pump the Brakes, Go for a Test Ride.
Start it up, and press the brake pedal to the floor a couple of times. It will go all the way to the floor the first or second time as the caliper adjusts to the new rotor and shoes, but then things should tighen up.
If they do, YOU WIN!
And you're good to go. If they don't, you didn't hang the caliper properly, you broke a brake line and you're making a mess.
This is an easy job with the right tools handy. Once you've done one side, go do the other and make the whole front end match, new rotors, new pads. Car stops like new.
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