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Changing brake pads on WRX

229K views 152 replies 72 participants last post by  15WREX 
#1 ·
Changing brake pads

My front brake pads finally gave up the ghost this last week at ~18,000 miles. While I was changing them, I noticed that the pads are retained a little differently than all the other vehicles I have worked on. Henceforth, it seemed like it might be worthwhile for me to document the procedure...
 
#29 ·
It does. Totally separate so not really involved in this discussion.

Pace's last bit about making the pistons easier to press by opening the bleed valve is something that should be done every time rather than just if it's tough. Otherwise you run the risk of overflowing the fluid reservoir on the top side, assuming you've kept it topped up to compensate for pad wear. I've also heard that forcing the fluid up stream can cause issues with the ABS system too. I don't remember what that issue is though! Plus it's a good opportunity to bleed any air out of the caliper while making the job easier on yourself.

Oh, just looked at the instructions again and have a correction - If you use a tube over the bleed valve and make sure you have pressure on the pistons before you crack open the valve, you won't have to bleed the system - just be careful to close the valve before releasing pressure on the pistons so you don't suck any air back into the caliper. Doing it this way gives no opportunity for air to enter the system, so no further bleeding is necessary (unless, of course, it's necessary for other reasons!). If you mess up and see even the tiniest air bubble get sucked in, do the full bleed procedure to be on the safe side.

C
 
#30 ·
I hate to step into this so late, but there is actually an even easier/faster way to do this job. If you just remove the bottom slide bolt, the caliper will pivot up and you can do the rest of the job as instructed.
I also like to use a little anti-seize between the ends of the pads and the clips. It cuts down on noise sometimes.

Personally, Ive never heard of there being a problem with pushing fluid back up into the system. I dont see how it coudl be harmful, seeing as its a pressurized hydrolic system, and youre not generating NEAR the pressure with your hand that you do when you activate the master cylinder with the pedal.

If youre problem is that youre going to overflow the master cylinder - just get yourself a regular old turkey baster - and suck some of the fluid out as you go...

If youre problem is that you cant generate the pressure to push the piston back in, and you dont have a C-clamp or a large adjustable wrench to push with, then I would go for cracking the bleeder screw. However, I would then definitely bleed the system - youd have to be pretty slick to crack that screw and not get air in there with just your hand on the caliper....

Speed safely,

Joe
merlin916@aol.com
 
#31 ·
Another reason to open the bleeder screw would be that you would get rid of some of the old fluid that is at the caliper end of the brake system. It seems that this fluid gets the hottest and the dirtiest. If you don't crack the bleeder screw, you push this fluid back up into the system.

Just an observation, Very nice write up and pics!
 
#32 ·
call me crazy... but when I had to change front brake pads on my WRX, I didn't need a C-clamp to push the pistons in. I'd been in the habit of doing that with my Integra, but with the WRX, I just pushed the pistons in by hand. It did take a fair bit of effort, but it was quicker that strapping a c-clamp and old brake pad on to clamp it the pistons in. :)
 
#38 ·
Its true that subaru reccoments bleeding the brakes in this order. I dont know exactly why - but before asking why Id have to ask - Why not? Since I cant come up with a good answer for that second question - I just do it Subaru's way.

Joe
 
#39 ·
It has to do with the order that the wheel cylinders are connected the master cylinder. If there is any air in the master cylinder, and you bleed say, the RR first, then when you bleed the RF it might push air back into the RR.
 
#40 ·
Youre logic is good, but the fact of the matter is, bleeding air out of the master through the lines is almost impossible. Thats why, when you change a master cylinder, you essentially bleed it back into itself until its clear.

Rather than air - they are more concerned about the old fluid getting back into the lines (same logic applies though).

Brake fluid is hydroscopic, meaning it will absorb water. Water has a boiling temp muuuch lower than that of brake fluid, and as such, will boil earlier, and form steam - which can be compressed. This gives your brakes a spongy feeling, and thats why the fluid neesd to be replaced. Thus, you want to make sure you get all the old garbage out before you put the new in.

Joe
 
#43 ·
Prince Ali said:
What are the torque value for the caliper bolts and how do I "bed in" the pads?
If you mean the bolts that mount the caliper to the knuckle (the 17s) they are 59 ft-lbs. If you mean the slide bolts (the 14s) they are 19.5 ft-lbs.

Im also not sure what you mean by "bedding the pads." If youre just asking how you get them in there - I usually bring them in at a right angle and press one side of the clip, then push down and pivot them in.

If you mean braking them in on the car - I do this:

Get up to about 40 mph - apply very light brake pressure until you come to a complete stop.

Go to 50 mph - reapeat with a little more pressure.

Go to 50 again and apply heavier pressure - try to stop in about 100 ft.

Go to 60 and apply as much pressure as you can without locking up the wheels or activating ABS, stopping as quickly as possible.

Joe
 
#44 ·
Lots of great info and tutorial here!!! Thanks very mcuh to everyone's contributions. Keep all the good stuff coming!

Quick note on bleeding the system, speed bleeders works well and they aren't all that expensive to buy.
 
#46 ·
NJSubieTech said:
If you mean the bolts that mount the caliper to the knuckle (the 17s) they are 59 ft-lbs. If you mean the slide bolts (the 14s) they are 19.5 ft-lbs.

Im also not sure what you mean by "bedding the pads." If youre just asking how you get them in there - I usually bring them in at a right angle and press one side of the clip, then push down and pivot them in.

If you mean braking them in on the car - I do this:

Get up to about 40 mph - apply very light brake pressure until you come to a complete stop.

Go to 50 mph - reapeat with a little more pressure.

Go to 50 again and apply heavier pressure - try to stop in about 100 ft.

Go to 60 and apply as much pressure as you can without locking up the wheels or activating ABS, stopping as quickly as possible.

Joe
Thanks Joe. I wanted the value for the two bolts that hold the caliper in place. What is the slide bolt? I was reading about different brake kits and I read about "bedding the pads" on Stoptech's web site. I guess they call breaking in "bedding the pads and rotors..
 
#48 ·
Identical, except there is only one piston to depress when putting the caliper back on the rotor.

BTW, there's really no reason to remove both caliper bolts. If the remove the bottom one and loosen the top, you can rotate the caliper out of the way and work on the pads.
 
#49 ·
Bask Oner said:
BTW, there's really no reason to remove both caliper bolts. If the remove the bottom one and loosen the top, you can rotate the caliper out of the way and work on the pads.
That sounds like a better idea because you don't have to worry about dropping the caliper and having it yank on the brake line and swing around.
 
#51 ·
Well I got Axxis pads and they only came with the 4 pads and 2 clips.


Now am I suppose to re-use the clip and plates that are already on the stock pads? The Axxis pads didn't come with new clips and plates like on page one of pace's post. What are these 2 new clips I got from Axxis and where do they go? Any pics?
 
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