I was washing my 2004 MC40 yesterday and I decided to take a look at my discs because I have just over 80K and I figure I must be getting close to needing a brake job. What I have noticed is that on the outside of the disc is a slight lip or ridge.
Whenever we do a brake job on a Mini, is it the policy to replace the rotors when replacing the pads?

 

your supposed to measure the "lip" on the rotors. there is a spec, i think its on the door sill, of how deep you are "allowed" to go into the rotors.

 

my son had to use a grinder to get his rear calipers off due to lip , seems the rotors are as soft as the factory pads.

 

So is it normal to develop the lip? I am guessing that the lip is what the disc thickness was originally when new.

 

Some times its casted into the rotor hat, on OEM MINI rotors think its on the bevel need the wheel mount.


2004 MINI Cooper S

http://www.ecstuning.com/Mini-2004-Cooper-R53-S-Coupe-L4_1.6L_W11B16A/Braking/Rotors/



On outer is one the edge:




&&

2004 MINI Cooper S Rear:

http://www.ecstuning.com/Mini-2004-Cooper-R53-S-Coupe-L4_1.6L_W11B16A/Braking/Rotors/2




Think the spec are 20.4 fronts and 8.4mm rear for Non JCW. Stock.

Thanks

 

Yes it's normal! As the disc wear down, the part that doesn't contact the pads remain untouched and may expand a bit due to rust. Depending on the thickness of the disc, it might still be good enough to put on a disc lathe and machine it straight and clean. Depending where you get the job done, the labor cost may end up being close to what it would cost to simply replace the discs.

I'm a mechanic and I don't even bother machining them on my own car and I don't have to pay the labor

 

Moral of the story is measure the thickness of the rotor and if it is under spec then it needs to be replaced while you are in there doing the pads.

 

When I get home I will measure the thickness. This will be the first time I have ever done that as in the past on my other cars I just replaced the pads and not the rotors and some cars I would replace the rotors and pads automatically when I did a brake job.

 

Bet at your miles you have the OEM rotors...
Pretty soft...mine did the same thing...similar miles.
IMO just replace the rotors...when you need to do the pads....on gen1, the (OEM-very dusty)pads and rotors (very soft) were usually both about worn out at the same time....some folks that did pads early COULD get a second set of "rotor friendly pads"...aftermarket rotors can be 2 or more to one depending on the pads and use...
you can get decent ones for $30 each or so (centric premium, or even Centric 125 Series High Carbon Alloy Brake Rotors..not fancy, but seem to hold up well)...or various other brands...like Zimmerman, Brembro, or TSW.

 

I am a shadetree type, as much as that means with today's cars. Luckily I have an old car so I can still do most of my own work on it.
What are you using on your Mini, as far as pads and rotors? I am out of town for now but when I return I will check how much the rotors have worn down. Is it possible that I may not need rotors? I have always driven the car on the fwy to work for 10 yrs. Not a tracker, so its not been abused.
On my Infiniti I used Carbotech pads and they were great and had great customer service - I was able to talk to the owner.

 

I'm not the best person to give you advices on pads as I'm using Hawk HP+ pads, which are meant for the track (Used as a summer daily/track car). Dust level over 9000 and noisy even after trying multiple times to do the bed in procedure. I know from experience that the street version is better, but it's been a while since I've used them (previous car in 2009).

If you need new rotors, it's a matter of measuring them and checking if they can be machined. Just by looking at the surface and touching it (when the discs aren't hot of course), it can give you a good idea. If you see a tint of blue on them (overheating) or looks like old vinyl records, they would most likely be better of in the metal bin.

As for rotors, I usually go for the 1st quality aftermarket ones.

 

I touched them the other day and that's how I know about the lip. The surface of the rotor is not perfectly smooth but it is what one would expect after 80K of fwy and some street driving.
No blueing or colourization.

 

Okay, I finally got to remove the wheels and checked the rotor thickness.
Now, I am going to need someone who is familiar with reading micrometers.
I am just checking the front rotors and with this Starrett calipers. I have not used a caliper before. Here is a pic of the caliper. The one I have is the black half moon one of the two pictured.
Reading the number on the side of the caliper, it shows 8.4. I don't know what that means.

 

Okay, I finally got to remove the wheels and checked the rotor thickness.
Now, I am going to need someone who is familiar with reading micrometers.
I am just checking the front rotors with this Starrett calipers. I have not used a caliper before. Here is a pic of the caliper.
Reading the number on the side of the caliper, it shows 8 or I am guessing 800th of an inch. I don't know what that means.

 

I can't help you with reading those particular micrometers but like ECS said, it's stamped either on the edge or on the rotor hat. It will say "MIN TH. 20.4" or something like that for the front and probably 8.4 as well for the rears. When I checked my fronts, I did it the poor man way with a regular set of digital calipers (not the outside ones you're supposed to use with rotors) but I took 2 coins and stacked them putting one on each rotor face as to not measure the lip. I then measured them off the rotor and subtracted the difference and confirmed that mine will need replacing on my next brake job. Not perfect, but close. With yours make sure you measure in a few different spots if possible and on both the outside and inside edges.

 

Looks like I have plenty of rotor left and also plenty of pad thickness. With over 80K I thought I would be close to needing new pads and rotors. The difference between the lip and the face of the rotor is very small.
I don't see how people can miss the 'min. 20.4 thickness' stamping on this particular year rotors.

 

Remember...since you have a lip...get them cut on a lathe....
The important measurement is AFTER YOU HAVE THEN CUT....depending on the depth of the groves...and the amount cut off...could still be junk.

 

I am quite a ways away from having to do anything to the brakes. Looks like 90% of fwy driving had little affect on the brakes.
So I will button everything up once I restore the wheels.
Thanks

 

+1 Good point Zippy.