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Suspension & Braking Forum by BimmerWorld
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Old 06-25-2010, 07:12 PM   #1
Motorglobin
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Replacing rotors and not pads legitimate? Also...

Sorry for the long post, please bear with me. My 2004 330xi was purchased mid-last year, and I want to start autocrossing in a few weeks. That said, I want to get it ready as soon as I can. I checked the brakes, and although I wasn't able to take terribly accurate measurements, it seems like my pads are find by rotors are starting to wear. I didn't have a micrometer, but i used a tape measure as best I could. I know the rear pads were replaced without the rotors being replaced, but I have no history on the front brakes. The measurements are below.

Rotors
Both front and rear rotors have a slight lip, with very, very light grooving in the rotor itself. I measured from the outer edge of the lips from the inner part of the rotor to the outer part of the rotor (if that makes sense) and got .9" for the rear and 1" for the front (which are 2.3 and 2.5 cm, respectively).

Pads
I measured the innermost part of the pads that would contact the rotor.
Rears = ~3/8" (approx. 1 cm)
Fronts = ~1/4" (approx .6 cm)


I'm not sure if I measured everything correctly, but any input is appreciated considering my uselessness when it comes to brakes. Given these specs and what I have read, it seems like the rotors are at the very minimum, but the pads are still in good shape. Is this correct? And if so, is it ok to replace rotors without replacing pads?

I have read up a bit, but the only information that seemed to go against replacing rotors without pads was the fact that the pads need to be somewhat transferred onto the rotors (from bedding) before they function properly. I'm not sure if the outer layer of the pads is important to this, or if any other layer would transfer in the same way.


Also...

Is it ok to mix rotors for front and back (like zimmerman in back and balos in front)? The cheapest place I could find rotors was pelican parts for the 330xi at $259 USD for the set of four rotors, but I would have to get the mixed setup. If anyone knows of any other cheap places for rotors, please let me know.


Whew, thanks for reading.
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Old 06-25-2010, 11:59 PM   #2
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Yeah you should be able to get away with just rotors, but why? I doubt you would have a braking problem at autox because of slightly worn rotors. You definitely need to change your brake fluid. Do that, and if your brakes feel good, just get new pads and rotors when the pads wear out.

Most brake pads are cheap anyway, although I highly recommend performance friction z-compound pads from bimmerworld.

Amazon has brembo front rotors for $50-60 shipped last i checked.
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Old 06-26-2010, 04:40 PM   #3
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I figure if I was measuring from lip to lip, that actually I was overestimating of the rotor thickness. So, it seems like my rotors are actually quite under the minimum requirements. I don't want to even leave the possibility of them cracking or something along those lines, so it would be more preventative than anything.

I'll check out those pads when its time to replace, I have heard some other good things on here about them. Thanks for the input Kubica.
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Old 06-28-2010, 11:09 PM   #4
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^ lip to lip? You measured thickness new then. You need a rotor caliper to reach over the lip.

As for your OP, replacing rotors and not pads, thats fine. Most people just op to do the pads everytime they are in there since its not worth their time to save a few bucks.
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Old 06-29-2010, 12:10 AM   #5
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after doing some more digging, it seems like there is a general consensus that if the lip is larger than 1 mm, the rotors should be replaced. i went ahead and ordered a set of brembo blanks from amazon (about 210 shipped if anyone else is looking) since the lips are definitely larger than that.

thanks for the input brilliant...i need to invest in a micrometer once i feel justified in spending that kind of money though, they are expensive!
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Old 06-29-2010, 01:17 AM   #6
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How did I mess this thread...

Depending on shape of the Pads you can reuse it but recommended to be replace as well. (I personally would replace the pads.)

If you decided to keep the Old Pads. Make sure the Brake Pads are Level and smooth. If they are grooved it will groove your rotor as well. (Bad Way to Ruin Brand New Rotors)

From your specs rotors are at min specs.

-Anthony@BimmerBrakes

Last edited by BimmerBrakes; 06-29-2010 at 11:49 AM.
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Old 06-29-2010, 10:46 AM   #7
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i haven't regularly been on E46F since Jan, and its nice to have a brake specialist around now! thanks for the response anthony, i will go ahead with the plan to do all four rotors only (assuming the pads aren't grooved).
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Old 06-29-2010, 01:06 PM   #8
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i went ahead and ordered a set of brembo blanks from amazon (about 210 shipped if anyone else is looking)


Sponsors need to step-up on brembo pricing. Amazon destroys everybody on brembo blanks.
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Old 06-29-2010, 01:43 PM   #9
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NEVER.

The pads can have grooves and ridges, etc., that result in hot spots on the new rotor. Not to mention reduced contact.
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Old 06-29-2010, 02:23 PM   #10
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Quote:
Originally Posted by Kubica View Post


Sponsors need to step-up on brembo pricing. Amazon destroys everybody on brembo blanks.
Those are for Bare Rotors and will Rust!

-TrippinBimmer
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Old 06-29-2010, 05:46 PM   #11
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hmmm, anyone have any experience with the performance friction z rated v. the cool carbon for autocross/light track us as well as daily driving? the cool carbon are about half the price, and they seem too good to be true.

i might get a set of pads JIC the original pads are grooved (if they aren't ill just keep the new ones until its time to replace).
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Old 07-04-2010, 11:49 AM   #12
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i'd suggest taking a sander or grinder to the old pads to resurface them and you'll be fine but if they are more than half gone I'd go ahead and replace and not be bothered for a couple of years.
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Old 07-05-2010, 12:52 PM   #13
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Quote:
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Sponsors need to step-up on brembo pricing. Amazon destroys everybody on brembo blanks.
We're an authorized vendor for Brembo. I love their BBK setups, but there are some other companies out there that have better OE replacement rotors.

Quote:
Originally Posted by kejriwalv View Post
hmmm, anyone have any experience with the performance friction z rated v. the cool carbon for autocross/light track us as well as daily driving? the cool carbon are about half the price, and they seem too good to be true.

i might get a set of pads JIC the original pads are grooved (if they aren't ill just keep the new ones until its time to replace).
A lot of our customers have stated that some of those brake pads squeal and can get a bit obnoxious for daily driving.

We have had great success campaigning the Stoptech rotors with Stoptech Street Peformance Brake Pads! They offer race pad like heat temperature ranges, but dust way less and are very quiet for daily driving.
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Old 07-05-2010, 11:50 PM   #14
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i misread the prices for the cool carbon pads, they are actually about the same price unfortunately.

modbargains, are you talking about this: http://www.modbargains.com/StopTech-...de-Kit-E46.htm ?
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Old 07-06-2010, 11:18 AM   #15
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Quote:
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i misread the prices for the cool carbon pads, they are actually about the same price unfortunately.

modbargains, are you talking about this: http://www.modbargains.com/StopTech-...de-Kit-E46.htm ?

You got it!

That's a great upgrade to increase your stopping power and make your entire braking system more fade resistant!

It even comes with upgrade Motul brake fluid so everything that you need for a brake job is included!
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Old 10-14-2010, 12:35 PM   #16
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bumping this thread for a similar question. opinion seems split between a) NEVER reuse pads and b) it's ok as long as the pads are smooth and still thick.

i did front brakes this morning, but the first rotor wouldn't budge and i was running out of time before work.... so i just put the new pads on and figured i'd give the rotors another shot later tonight or this weekend. one of my buddies is in the "never reuse pads" camp, and he is warning me not to do this, even if the pads have only been used a day or two. he argues that if i've driven at all, the new pads are already bedded in to the old rotors, and shouldn't be reused.

i'm thinking this is silly, but for my own peace of mind, i need the internet to agree with me
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Old 10-15-2010, 08:17 PM   #17
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bumping this thread for a similar question. opinion seems split between a) NEVER reuse pads and b) it's ok as long as the pads are smooth and still thick.

i did front brakes this morning, but the first rotor wouldn't budge and i was running out of time before work.... so i just put the new pads on and figured i'd give the rotors another shot later tonight or this weekend. one of my buddies is in the "never reuse pads" camp, and he is warning me not to do this, even if the pads have only been used a day or two. he argues that if i've driven at all, the new pads are already bedded in to the old rotors, and shouldn't be reused.

i'm thinking this is silly, but for my own peace of mind, i need the internet to agree with me
For racing pads, used pads are preferred when bedding in new rotors. After they are bedded, new pads are then introduced. This is due to the nature of the resin binders and their chemistry.

With street pads, things are a little bit less critical. However, if the new pad has picked up any grooving from the old rotors, hit them quickly on a belt sander to bring them back to flat. It will make bedding in the new rotor more effective. There are no problems associated with using slightly used pads as long as they've been cleaned up.

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