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Suspension & Braking
Have some questions about suspension or brake setups for your E46 BMW? Get all your answers here!

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Old 11-08-2012, 09:09 PM   #1
Mesa3077Boogie
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Rotor Resurfacing and Pads Question

When braking I am experiencing a "fast/slow fast/slow" type of deceleration when applying the brakes. The best way I can describe it is that during braking there is lots of friction then less friction then lots of friction then less friction, over and over with an al together jerky feeling stopping.

I just put on new drilled rotors in April 2012 along with some EBC Yellow Stuff 4000 high friction pads.

I have put 20K on them since April.

I am well aware of what ABS feels like and this is totally different.

The pedal does not "pump" as it has on other warped rotors like it has in the past on other cars so I am hesitant to think the rotors are warped. There are no large visible grooves or a lip on the rotor. The pads are at 80-90%.

The calipers were rebuilt at the time and new SS lines were added.

The parts store said that a new rotor thickness should read .806 on a micrometer and anything less than .803 they would not touch as far as resurfacing. I was getting a solid .807 reading all over on various pars of the rotor which measures thicker than "spec". ??

The parts store kid also said that I would need to replace the pads IF I resurfaced the rotors. I have never heard this before but I am aware that the rotors and pad make a bond together and match each others micro grooves which helps braking.

Question: Do you think what I am feeling is just buildup? These are the most dusty pads I have ever had even more so that OE semi metallics. I have used wax on my rims, tire shine and go to spray down style washes at least twice a month.

Question: If I resurfaced the rotors would I ruin my old pads or newly resurfaced rotors by not changing my pads?

Question: I realize that bad bushings and ball joints effect braking performance but would that cause what I am experiencing?

Question: what do you recommend?

Thanks in advance!
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Old 11-08-2012, 09:16 PM   #2
Zell
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Mine does that too, it's most likely buildup. I personally think I have something else going on, when I spin my rotor with the wheel off I can actually feel it having more friction in certain places and less in others as I spin it, and I see no buildup anywhere. If you have cementite that has gotten on there, you'll need to resurface them, but you need to be doing some really hard braking.

You can resurface the rotors and use old pads, you just need to bed them in again. The rotor is harder than the pads. It may take more than a few bed-ins, but it'll all settle out.

I don't know about balljoints, but bushings can affect braking performance as well.
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Old 11-08-2012, 10:01 PM   #3
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Quote:
Originally Posted by Zell View Post
Mine does that too, it's most likely buildup. I personally think I have something else going on, when I spin my rotor with the wheel off I can actually feel it having more friction in certain places and less in others as I spin it, and I see no buildup anywhere. If you have cementite that has gotten on there, you'll need to resurface them, but you need to be doing some really hard braking.

You can resurface the rotors and use old pads, you just need to bed them in again. The rotor is harder than the pads. It may take more than a few bed-ins, but it'll all settle out.

I don't know about balljoints, but bushings can affect braking performance as well.
You hear the brake rotor rubbing more in some places than others with the wheel off because there's only 1 rotor hold down bolt. It doesn't fasten the rotor evenly to the hub. That hold down bolt is there more or less to keep the rotor in place while bolting the wheel on...which does evenly apply pressure. A lot of cars with studs (like my brother's Lexus) don't even have anything to hold the rotor down.
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Old 11-09-2012, 02:35 AM   #4
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When my 540 used to feel like that I'd find a long straightish road and brake heavily from 60 mph to about 5 mph. I'd do this about 6 or 7 times. You'll smell the brakes at the end of it :-) Then let the brakes cool down to normal temperatures. It is important that after this cleaning process you don't sit at a stop with your foot on the brake pedal (at traffic lights for instance) when the brakes are hot as this can leave a pad imprint on the rotor, beginning the whole build-up problem again.
Check out zeckhausen site for further details.
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Old 11-09-2012, 02:57 AM   #5
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Likely pad deposits.
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Old 11-09-2012, 04:50 AM   #6
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Yes, I'd start with bedding the brakes first, OP. Just find the directions from your pad manufacturer's site, as I hear protocols vary slightly from one pad to the other...but basically what was said above. Use them hard on the highway...slowing from 60-10 or so a few times with a minute in between...and then after they're hot, don't use the brakes until rotors cool down.

You can collect materials, I hear, from holding the pad onto rotors when they're hot...so I try not to do that. I'll creep up at a stop to ensure the rotor moves under pads.
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Old 11-09-2012, 08:35 AM   #7
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Thanks for the information guys. Im thinking its deposits too. I did paint hubs on the rotors come to think about it. So it could be paint buildup. I am familiar with the bed in process and will also try that.

I am doing a new front end in the next week or two and will give it all a good cleaning. Hopefully all the new parts will help the braking feel.

How bout my other question? If I resurfaced the rotors would I ruin my old pads or newly resurfaced rotors by not changing my pads? I realize that the pads are softer than the rotors and they may conform to re surfaced rotors, but I am wondering why the guy at the parts store who seems to have experience in re surfacing rotors would suggest that I would ruin my used pads and need new ones.. ? Was he just trying to sell me on his lifetime replacement $19.99 brake pads?
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Old 11-12-2012, 04:22 PM   #8
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I did a good cleaning to the rotors and brakes and it seems to have helped a little. I am going to better clean them when I do my front end work either this weekend or next.

Question: Is there anything that I can soak my rotors in to clean them? They are cross drilled and the drill holes are filled on most holes with debris. Can I soak them in gas or a mixure of purple power and water, so long as I rinse them well when I am done?
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Old 11-13-2012, 11:14 PM   #9
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You could soak them in washer solvent, the same stuff you use in the parts wash tank.
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