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Rear Brake Questions

2K views 12 replies 6 participants last post by  NSXBill 
#1 · (Edited)
Hi. I'm planning on replacing rear rotors and pads on my 2001 325i this weekend and I have a few questions:

What is the one bolt that looks like it holds the rotor on? Does it hold the rotor on? Do I need to remove it to change rotors (see #3 in picture)?

Also, the rotors look like they are rusted to the hub (not a clean line of clearance between the centering-hub and the center hole in the rotor). Do they usually come off easily?

What areas do you grease? The two guide bolts and rub points between caliper and bracket?

My sensor looks like toast. I am getting a new one. Does the clip come with the sensor or the pads, or either?

What service should I do to the parking brakes while in there?

Anything else?

Thanks,

Bill
 

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#2 ·
NSXBill said:
Hi. I'm planning on replacing rear rotors and pads on my 2001 325i this weekend and I have a few questions:

What is the one bolt that looks like it holds the rotor on? Does it hold the rotor on? Do I need to remove it to change rotors (see #3 in picture)?
yes

Also, the rotors look like they are rusted to the hub (not a clean line of clearance between the centering-hub and the center hole in the rotor). Do they usually come off easily?
may not be easy. Heard a 5lb dead mallet striking it inward is the best method(for safety, wear glasses )

What areas do you grease? The two guide bolts and rub points between caliper and bracket?
correct, but use the hi-temp grease made for guide pins.

My sensor looks like toast. I am getting a new one. Does the clip come with the sensor or the pads, or either?
do not believe it come in either

What service should I do to the parking brakes while in there?
None, unless you want to grease the cable and hinges

Anything else?
Nope, sounds like you know what you are doing..
 
#4 ·
The light never came on. I don't know why.

I heard the squeel of the RR pad plate rubbing the ridge formed on the outer diameter of the rotor.

I checked, the noise and saw .030 pad/sensor remaining thickness.

Hey, I don't recall what I need to remove that one bolt. Allen wrench? Size?

Also, what is the reinstallation torque for the guide pins?

Thanks
 
#5 ·
7mm allen wrench

NSXBill said:
The light never came on. I don't know why.

I heard the squeel of the RR pad plate rubbing the ridge formed on the outer diameter of the rotor.

I checked, the noise and saw .030 pad/sensor remaining thickness.

Hey, I don't recall what I need to remove that one bolt. Allen wrench? Size?

Also, what is the reinstallation torque for the guide pins?



Thanks
 
#7 ·
OK, after reviewing the two different DYI's...

One says to remove the 17mm hex bolts that hold the BRACKET AND CALIPER on and the other says to remove the 7mm allen guide bolts to remove the CALIPER ONLY. Which is it to replace pads AND rotors.

Seems like removing the guide bolts is what I've done to GM's and Acura's...
 
#8 ·
NSXBill said:
What is the one bolt that looks like it holds the rotor on? Does it hold the rotor on? Do I need to remove it to change rotors (see #3 in picture)?
It is called a rotor retaining screw and must be removed. It is not a 7mm Allen screw. It is 6mm.
Also, the rotors look like they are rusted to the hub (not a clean line of clearance between the centering-hub and the center hole in the rotor). Do they usually come off easily?
If you use the right tools and technique, they are easy to remove. Spray a small amount of penetrating oil (not WD40) around the hub lip that protrudes through the center of the rotor. Let it sit for a minute and work its way in. Install one wheel bolt through the rotor and screw it in about two turns. This keeps the rotor from falling off and landing on your foot when it breaks free from the hub rust. Make sure you have RELEASED the parking brake. Next, use a dead-blow hammer (the type with sand inside the head) with a rubber (non-marring) face to strike the outboard face of the rotor until it breaks free from the hub. You do not have to swing from inside. It's every bit as effective to hit the outboard face. You are merely trying to apply twisting force to break the rust bonds. I find that it works well to turn your back on the rotor and swing the dead-blow hammer downward and backward in order to get the most power. After a few strikes, the rotor will suddenly make a hollow sound just prior to letting go. Then you can remove the wheel bolt and pull it off.
What areas do you grease? The two guide bolts and rub points between caliper and bracket?
You do NOT grease the two guide bolts! They should be cleaned with brake cleaning spray but do NOT put grease on them. This is because the caliper slides back and forth on these guide bolts with a pair of rubber bushings. The bushings will swell in reaction to grease and the caliper will not float freely causing rapid outboard pad wear. Also, the grease will attract dirt, which will chew up the rubber bushings. This is not an Audi or VW rear brake caliper! The BMW caliper is different. The guide bolts are not sealed and protected by rubber dust boots. They are exposed to the elements.

Since at least one person responded that you should grease them, I suppose I'll have to provide evidence to back up my claim. Here's an excerpt from the BMW TIS:




My sensor looks like toast. I am getting a new one. Does the clip come with the sensor or the pads, or either?
If you are asking about the tiny spring clip located at the end of the sensor (see photo below) then the answer is it comes with the sensor.



If you're asking about the metal spring clip that keeps the pads from rattling in the caliper, you can usually reuse the old one, but new ones can be purchased at your local BMW parts counter.

What service should I do to the parking brakes while in there?
Just inspect the shoes to make sure there is material on them and there are no big chunks missing. There is an adjustment wheel that can be turned with the tip of a screwdriver to adjust the tightness of your parking brake lever. It's similar to the one at the bottom of the next photo. This is a shot of the parking brake on my 2001 540i/6.

 
#9 ·
NSXBill said:
One says to remove the 17mm hex bolts that hold the BRACKET AND CALIPER on and the other says to remove the 7mm allen guide bolts to remove the CALIPER ONLY. Which is it to replace pads AND rotors.
You need to do both.

Removing the 7mm guide bolts will alllow the caliper to lift off the caliper frame so you can remove the pads. Removing the two 16mm bolts that hold the caliper frame to the back of the rear knuckle is necessary before you can remove the rotor. The caliper frame (BMW calls it a "carrier") straddles the rotor and is in the way when you try to remove the rotor.
 
#10 ·
DZeckhausen said:
You need to do both.

Removing the 7mm guide bolts will alllow the caliper to lift off the caliper frame so you can remove the pads. Removing the two 16mm bolts that hold the caliper frame to the back of the rear knuckle is necessary before you can remove the rotor. The caliper frame (BMW calls it a "carrier") straddles the rotor and is in the way when you try to remove the rotor.
Thanks to all for all the good info.

Dave, Great info. Are you sure I have to remove the bracket/carrier? It seems like I could just angle the rotor in.

You have access to the TIS, can you post it for that part of the E-46 procedure?

Thanks,

Bill
 
#11 ·
that bolt doesn't hold on the rotor at all it is simple to keep the rotor from moving from side to side to keep the holes alligned the rotor is held on fromt preassure from the wheel hub and if u notice the rotor hub its self is liek a conacil shape it widens up to hold the rotor securely its simple u will need to remove the caliper seat to get the rotor off though
 
#12 ·
NSXBill said:
Dave, Great info. Are you sure I have to remove the bracket/carrier? It seems like I could just angle the rotor in.
The carrier will have to come off. You'll see when you get the caliper off. There's no way to remove the rotor without first removing the carrier. You have to pull the rotor straight out toward you in order to clear the parking brake and the center hub lip. If the carrier remained in place, it would only allow the rotor to come out about 3mm. You need far more movement than this before the rotor can be removed.

Here's a photo of a 5-Series rear carrier:

 
#13 ·
Roger that

Does anyone have the torque values for the hex bolts on the carrier (81 lb-ft, I think I saw somewhere else).

Also need torque values for the guide pins...

When I pull the rear rotors off, is the entire parking brake assy exposed? Does the PB use the inside of the rotor hat for its "drum?" Do I adjust so that the new rotor hat just barely fits over the shoes, or how much clearance do I leave?

Sorry for all the dumb-a$$ questions. Most will probably be self-evident when I tackle the job, but I like to know ahead of time what's in store.

thanks

Bill
 
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