Brakes an the rotor

A

Aebous

Elite
 Okinawa
Ok, so I'll start by saying I had the tires replaced today. Anyways, the tech guy mentions to me that my left brake pad will need to be changed soon and the back side of the rotor was worn. So he shows me what he see's, and there is indeed a lip on the outer edge of the rotor. It's quite uniform around the rotor, probably about 0.30 inch deep. Not a grove in the middle of the rotor, just a lip along the outside edge. So I looked at the rotor on the passenger side and noticed it has the same lip at about the same depth. So are my rotors worn? Judging by the feel and look of the rotors , it feels/looks normal to me. I couldn't really get my fingers on the rear rotors as that fairing was in the way. Based on my jet engine maintenance experience I think it is likely it's normal, but I wanted to ask on here.

Now the easy question
Is there another way besides visually checking the brake pads to see when they need changing? Some kind of sensor perhaps? I didn't notice any kind of squeelers on the pads.
 
Depends an awful lot on the depth of the pad material. If you have lots of pad left bear in mind that your pad is shaped to the face of the rotor and isn't hitting the lip you see at all. If your pads are shot then you may find that new ones will not conform to the shape of the rotor that your tire tech was so happy to point out.

As long as your pads are fine you can ignore the shape of the rotor face because it is a match for the shape of the pad facing and will work just fine. You tire tech is "trained" to try to make you insecure about what might be needed for servicing on your car and oh by the way they just happen to have a special on the part he "noticed" for you.

If you did replace the rotor in this case you would likely have worse braking unless they changed the pads as well because the new rotor face will no longer be a match for the worn shape of your pad faces.

Easy check - get a flashlight out and examine the amount of pad material between the pad face and the metal backing plate. If you are less than 2.5mm then you might want to start making plans to replace both the pads and the rotors.
 
Aebous.

One step at a time:

Firstly you have pad wear sensors fitted on the Z4. You can see the wire going into the brake pad on the front LHS. They will flash a warning light up. Check they are in place. Front left and rer right I think.

Rotors - With the wheel off you can see a stamping on the curved face of the top hat that tells you the minimum rotor thickness. It simply needs a gauge putting on to see if its at or close to it. A lip of 0.3" sounds massive. It is however usual to have a small lip as the pad is narrower than the rotor so is of no concern. Thin rotors are though - thye don't cool propertly are prone to cracking and in extreme cases simply fold up under harsh braking

Always change both sides of pads even though the mech. points to the left.

Always put new pads with new rotors else you simply damage one to bed to the others shape.

Ideally replace all around at once for balanced braking
 
cj10jeeper said:
no fit state said:
0.3" = 7.62MM! Are you sure it's that much? Or have my calculations gone :dizzy:
Click to expand...

That's what I thought - way too big a lip
Click to expand...

I would of thought that much material being worn away would leave pretty much no disc left? 2-3MM is about the most I've ever seen.
 
no fit state said:
cj10jeeper said:
no fit state said:
0.3" = 7.62MM! Are you sure it's that much? Or have my calculations gone :dizzy:
Click to expand...

That's what I thought - way too big a lip
Click to expand...

I would of thought that much material being worn away would leave pretty much no disc left? 2-3MM is about the most I've ever seen.
Click to expand...

Yes I don't for one minute believe the figure but have just passed that by and focussed on what needs to be looked at, checked and measured.
 
Nice, thanks guys. Yeah the lip is there, but I didn't know the pads were smaller than the rotor. I agree with AlanL that the guy was trying to get more work out of me. Especially since he didn't mention the right side at all. Glad to know we have a sensor there, I'll check and make sure it's plugged in. Though when the wheels were off I didn't see any wires that weren't connected. No worries about the changing, if I change one I'd change em all.
 
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