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Old 09-24-2018, 07:03 PM   #61
rumatt
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Interesting... The plot thickens. The opinions (comments) are highly opinionated.
I'll let you know what I find. I won't have a chance to look at the car again until next week.

But this was the part of the article that piqued my interest. I'm not driving on these rotors until they are damn-near perfectly true.

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The “Proper” Brake Job


Properly tightening the lug nuts prevents one major cause of premature rotor wear. The other major cause is “improper” installation of the rotor. And here is where you may get some resistance from your veteran techs who have been doing brake jobs for 10 years. You cannot do a proper brake job without a dial indicator to measure rotor runout.

Those who have turned a wrench before may think they already know how to properly change brake pads and rotors. This may be. However, if the brake job is performed on a modern two-piece hub and rotor the same way it was on the old one-piece hub and rotor, the job is probably not being done properly. That means the brake job is not being done per OE factory spec and how the OE dealers do it.

This habit of “continuing to do it the old way” may explain why rotors produce a pedal pulsation, i.e., “warped” rotors in just a few thousand miles. That alone may explain premature pad wear and premature rotor wear, even in premature for police operations.

“A brake repair shop without a dial indicator is like an engine rebuild shop without a torque wrench,” said Dann Ingebritson, technical instructor, Affinia Under Vehicle Group.

The rotor lateral runout is a slight wobble or slight wave in the surface of the rotor as it is being rotated. This out-of-true condition can be caused by an out-of-parallel condition of the rotor—even a brand new one or one that just came off the bench lathe. This can also be caused by an out-of-parallel hub mounting surface or by a stack up of out-of-true conditions on both the rotor and hub.

This runout or wobble will cause exactly the same intermittent contact between the rotor and the pad as the improperly torqued lug nuts. Again, material will be removed from the rotor by semi-met pads, or added to the rotor by ceramic pads in just the high spots. Again, the result is rotor thickness variation which causes brake pedal pulsation and steering wheel vibration. Again, the rotors need replacement in less than 5,000 miles. Again, the officer driving the car does nothing to cause the problem.

This was not a problem 10 years ago when the runout spec was 0.010 inch or so and the brake pads used softer friction materials. Today, this is a major problem, when the runout is 0.002 inch max and the pads are rock hard.

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Old 09-24-2018, 08:35 PM   #62
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Time for someone to invent a braking system that doesn't require rotors, pads, calipers, and hydraulic fluid.
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Old 09-24-2018, 09:23 PM   #63
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Time for someone to invent a braking system that doesn't require rotors, pads, calipers, and hydraulic fluid.
I hear the Tesla Autopilot is so magical it will automagically add/reduce brake pressure to match the out of true condition so passengers, i mean drivers, won't be bothered by the peas under their mattresses.
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Old 09-24-2018, 09:53 PM   #64
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Time for someone to invent a braking system that doesn't require rotors, pads, calipers, and hydraulic fluid.
Welcome to 2018?

Interestingly I find regen braking one of my favorite things

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I hear the Tesla Autopilot is so magical it will automagically add/reduce brake pressure to match the out of true condition
It's not autopilot. But see above.

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so passengers, i mean drivers, won't be bothered by the peas under their mattresses.
The steering wheel and brake pedal shaking violently when you brake hard is not a pea.
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Old 09-24-2018, 10:01 PM   #65
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Welcome to 2018?

Interestingly I find regen braking one of my favorite things



It's not autopilot. But see above.


The steering wheel and brake pedal shaking violently when you brake hard is not a pea.
You know me well enough to know when I;'m being an asshole just for fun.
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Old 09-24-2018, 10:27 PM   #66
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You know me well enough to know when I;'m being an asshole just for fun.
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Old 09-27-2018, 04:40 PM   #67
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0.09" of runout.

That's the max of what they say you can shim.


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Old 09-27-2018, 07:06 PM   #68
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0.09" of runout.

That's the max of what they say you can shim.

Shim it to win it!
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Old 09-27-2018, 07:10 PM   #69
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Now the only problem is that I can't find anyone who makes shims for bmw. Summit racing has some that might work but I have to call back when the supplier is open to confirm. Oh and they don't make 0.009 shims. Stacking a 0.003 and a 0.006 sounds like an excellent idea to me.

How am I the only person in the world with this problem?

I think I might just buy new wheel bearings/hubs and see if that fixes it.

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Old 09-27-2018, 10:16 PM   #70
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I think I might just buy new car and see if that fixes it.
I jumped ahead for you.
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