Brakes Dragging/Pedal to Floor

[zekethegeek]

Hello everyone. This is my first post here. I bought a 2009 135i convertible recently and the brakes were shuddering. I bought new Bosch rotors and EBC pads. I have done probably a dozen brake jobs in my life but I have never experienced this issue.

Everything went well on the left, but while reassembling the right brake I found that the rotor was binding against the steering knuckle. I pulled the rotor and the caliper back off and put it back together. It was a close fit but it seemed to work. I closed up the brake fluid reservoir and pulled out of the garage.

The pedal went to the floor. I pumped them, they seemed to get strong again, but as soon as I moved they went back to the floor and there was effectively no braking at all. Also, the rotors are rubbing in rhythm with the motion of the car (so I would say "chuff", "chuff", "chuff" if I was on Car Talk).

I have never seen anything like this before. I used Dicor's excellent list but none of them seems to be an exact match. The "chuffing"--if the rotor is true (and it's brand new) how could it vary its clearance through the rotation of the wheel vs. just binding consistently? And why would brakes go to the floor and not build up their firmness again? There are no leaks visible, the reservoir cap is on tight.

Before I jack everything back up and look at it again I wanted to see if I could get some insight into what sort of mistake I made to cause this. Thank you all for your time.

[zekethegeek]

I couldn't believe it was even a possibility, but the Bosch rotor seems to be bad. Is this a thing? See the video--I have the new rotor (which I've now had on and off 4 times and I carefully cleaned before bolting it back on last time) in the first half of the video and the original in the second half. The collar in the middle of the new one does not appear to be square.

Using my (mostly woodworking) tools I can find no measurement that would indicate a wobble. The straight edge is square across the face of the rotor, the measurements from the hub's face to the rotor looks uniform around the perimeter of the hub.

Don't know if anyone's following me on this but it's driving me nuts. I find it difficult to believe that an anomaly like this even possible within the manufacturing process.

[tracer bullet]

Woah, that's insane. I would think they'd be genuinely interested in figuring out how that even got to you. Wow.

[Dackelone]

Quality parts there!! What brand were those rotors?

[zekethegeek]

Yeah, they are Bosch. The box even says that they are individually balanced. Weirdest thing. I hope Amazon gets me a new one quickly--supposed to be 70s and sunny!

[tracer bullet]

I'd consider contacting Bosch as well. Just to see what they have to say. I imagine they'd be appalled they let something like that go. I don't think they'd throw free parts your direction or anything but as an experiment it might be interesting to see their reaction.

[slonik]

it looks like rotor didn't fitted correctly on hub face.
are you sure that it sits correct and touches all surface of the hub?

try to watch thru the wheel bolt holes on rotor, that there are no clearance between rotor and hub.

[zekethegeek]

Originally Posted by slonik

it looks like rotor didn't fitted correctly on hub face.
are you sure that it sits correct and touches all surface of the hub?

try to watch thru the wheel bolt holes on rotor, that there are no clearance between rotor and hub.

That's what I was thinking Slonik. I thought that maybe it was dirty, so I took a wire brush to the hub and the rotor to make sure that it was clean. I put the wheel bolts in and carefully tightened them to center the rotor. I have had it off and on four times now. When I put the original back on it just went on with no drama. Is there a way I might have somehow damaged it putting it on? Could the rotor be close but the wrong size (the wheel bolts into the rotor directly seem to not all set evenly--some have gaps on one side).

BTW, how does the rotor itself center around the hub? The wheel bolts center the wheel with their cone shape, but the cones don't reach down through the wheel into the rotor, do they? It would seem like the rotor would never be perfectly centered over the hub and the little torx screw wouldn't be enough to hold it in place while the wheel goes on.

I have tweeted Bosch with this video. I have never had any problem with their products, and this seems impossible, so I still think I may be to blame. I just can't figure out how. Anyway, very curious. Even the Amazon return department seemed surprised. Like I was reporting the Loch Ness monster or Bigfoot or something.

[slonik]

BTW, how does the rotor itself center around the hub? The wheel bolts center the wheel with their cone shape, but the cones don't reach down through the wheel into the rotor, do they? It would seem like the rotor would never be perfectly centered over the hub and the little torx screw wouldn't be enough to hold it in place while the wheel goes on.

rotor must be centered on center bore (79mm). does it fits on it? you can see some lip which has larger diameter, than other length of the hub, where wheel located (72.6mm).
normally you can take new rotor and fits it easily on it's place on the hub.
may be this rotors have smaller center bore?

[zekethegeek]

Originally Posted by slonik

normally you can take new rotor and fits it easily on it's place on the hub. may be this rotors have smaller center bore?

It's centered, but it doesn't "press in" or feel like it would be perfectly aligned--in the example I posted I was using the wheel bolts to align it and pull it up into place. It's close, for sure, but at 85 mph (when I happen to have a vibration from the front end) is it aligned perfectly enough?

Just something about bimmer brakes and wheels I don't know.

Thanks!

[tracer bullet]

Seeing it again, the face wobbles along with the disc. That does indeed make it just not appear to be all the way on. If it's not an issue with the flat mating surfaces touching each other (i.e. chunk of debris in there), I agree it seems like an issue with the ID of it being small and not wanting to slide all the way up and on.

Originally Posted by slonik

are you sure that it sits correct and touches all surface of the hub?

I am thinking he's right.

[zekethegeek]

The diameter of the hole in the rotor is subtly smaller, causing it to not be able to seat and wobble.



You know why? It's a rear brake rotor. Somehow in my mad dash clicking around Amazon I didn't notice that Bosch doesn't offer a fitment for a front rotor, just rears.

[slonik]

i had some suspicion about this, cause bell's shape on your video were different and new one looks like rear ( wide bell like it has drum inside for handbrake).
but after that i thought that you can't fit rear rotor to the front - diameter, height and even thickness are different.
but, as we can see, you can!


different rotor diameter and thickness didn't gave you any ideas?


anyway, good news that your problem had solved now.

[tracer bullet]

Originally Posted by zekethegeek

You know why? It's a rear brake rotor. Somehow in my mad dash clicking around Amazon I didn't notice that Bosch doesn't offer a fitment for a front rotor, just rears.

LOL. Been there myself.