Front calipers dragging on 135i with the 6 piston Brembos

[JPuehl]

I seem to have always had an issue with front brakes dragging, the drivers side a little more than the passenger side. With the front jacked up after the car has been sitting for a while, if I try to spin the front wheels I can only get maybe 1/4 free turn before the wheels stop. maybe 1/3 on the passenger side. Over the weekend I rebuilt the front calipers with a kit from StopTech and they still drag. I replaced the pistons and the seals & boots.

Is this normal?

It seems to be wearing down my brake pads and rotors quicker than they should. The OEM pistons seemed to have wear you'd expect from normal usage and the seals and boots were fine. In fact I probably didn't need to rebuild them. The piston bores seemed un damaged. The front wheels on my wifes E93 335i spin very freely however the car stops really good.

[NorthernDancer]

Not normal.
Drive car 10 minutes or so without touching brakes too much and then coast to a stop without touching the brakes. Get out of car and carefully touch wheel nuts. If they are really hot, you surely got a problem.

[JPuehl]

Thinking about this, I wonder if it's my DSC. in the winter when the temps are below about 40* I hear a noise from the front when I let off the throttle and the stops when I apply brakes. I think it might be the system pretensioning the brakes, which I need to turn off when I can. I checked with a friend and they don't have this issue when they had the OEM brake calipers on his 135.

[juld0zer]

I've heard of false ABS intervention but false DSC intervention would surely cause the vehicle to change direction too. Try with DSC off if the conditions are suitable?
Do you drive on very bumpy roads often?

[JPuehl]

So this weekend I re-bled my brakes and while bleeding the left front something made me look at the spring that is in the middle of the caliper and I noticed that the part of the spring that is supposed to put some tension on the inside brake pad (tension to push it away from the rotor) didn't have the same shape as the part on the outside pad. It turned out that the spring was bent in a way that it was catching on the back side of the metal part of the pad pushing it into the rotor. I popped off the spring, corrected the shape, and after putting it back on my wheel spins much freer, not as free as my Wife's 335i but much better than before. I made sure the spring was correct on both sides. I think rebuilding the calipers helped free up the pistons also.

[JPuehl]

Originally Posted by juld0zer

I've heard of false ABS intervention but false DSC intervention would surely cause the vehicle to change direction too. Try with DSC off if the conditions are suitable?
Do you drive on very bumpy roads often?

Thanks for the response but I seemed to have figured out the problem, and it's operator error since I put new pads on a couple years ago and missed the cause.

[Vorsprung_CJB]

Having a similar issue so interested. Are you referring to the square anti-rattle spring? I looked at mine, some pics online, and pics of the part up close. It looks like the side of it that points toward inside of the car is supposed to sit a little differently, a little lower maybe. I didn't realize this helps push the pads apart? Is that true? Maybe it flattens out over time and has less force? Thanks

For reference (they call it 'expansion spring' as well):
https://www.ecstuning.com/b-genuine-...g/34106786062/

[JPuehl]

Originally Posted by Vorsprung_CJB

Having a similar issue so interested. Are you referring to the square anti-rattle spring? I looked at mine, some pics online, and pics of the part up close. It looks like the side of it that points toward inside of the car is supposed to sit a little differently, a little lower maybe. I didn't realize this helps push the pads apart? Is that true? Maybe it flattens out over time and has less force? Thanks

For reference (they call it 'expansion spring' as well):
https://www.ecstuning.com/b-genuine-...g/34106786062/

Yes, that's the spring and the reason they call it the expansion spring. I'll try drawing a pic of how mine was vs. how it should be, that might help you.

[juld0zer]

It's hard to lose the spring though. You'd have to be quite deliberate to remove it. It's not like the 4 pot Brembos with the big spring and two long pins where the spring can fly

You don't even have to touch the Torx pins or the spring when changing pads. Just push the pads in on an angle to overcome the spring and engage the ears into the pins

[Vorsprung_CJB]

It's not a matter of losing the spring. But given the age and mileage of a lot of these cars and the fact they are usually not replaced with the rest of the brakes, I wonder if they may change shape or properties over time due to heat cycle, exposure, etc. It is certainly easy to check/replace them if it is an issue.

JPuehl - let me know what you saw I'll be interested to check mine as well.

[JPuehl]

Originally Posted by Vorsprung_CJB

It's not a matter of losing the spring. But given the age and mileage of a lot of these cars and the fact they are usually not replaced with the rest of the brakes, I wonder if they may change shape or properties over time due to heat cycle, exposure, etc. It is certainly easy to check/replace them if it is an issue.

JPuehl - let me know what you saw I'll be interested to check mine as well.

I hope the drawing helps. It's basically a side/cutaway view of how the spring should be resting on TOP of the brake pad backing plates. As shown in the drawing of the "incorrect" spring positioning which was my issue, one of the tabs of the spring was bent down slightly and the edge was pushing on the back of the backing plate pushing the pad into the rotor causing constant drag.

The pad backing plates are slightly angled as shown in the drawing allowing for the spring the contact the top edge of the backing plate applying pressure to push, or "expand", the pads away from the rotor. I was able to correct the bend in the spring which resolved my issue.

[Vorsprung_CJB]

Interesting, thank you. Yes that makes perfect sense. I will inspect mine tonight.

Are the springs keyed to a certain orientation? On mine and pictures I've seen, it looked like the inside arm was shaped differently than the outside arm when installed on the caliper. Maybe a thickness/distance difference between inner and outer?

[JPuehl]

Originally Posted by Vorsprung_CJB

Interesting, thank you. Yes that makes perfect sense. I will inspect mine tonight.

Are the springs keyed to a certain orientation? On mine and pictures I've seen, it looked like the inside arm was shaped differently than the outside arm when installed on the caliper. Maybe a thickness/distance difference between inner and outer?

Yes the spring definitely has a specific orientation. If you held the spring you'd see that the tabs that rest against the top of the brake backing pads looks completely different than the 2 other tabs coming out from the middle of the spring. The 2 other tabs should have a "V" shaped bend/notch in the end that secures it into the caliper. I'll either try to find a pic online and take a pic of my car, most likely over the weekend, if needed?

[Vorsprung_CJB]

Oh, no I didn't mean which 90 degree orientation, its obvious which way it goes. I mean if one end is meant to go towards in inside or outside, or if it can be turned 180 without making any difference.

Looking at some pics again, I think it is just an illusion because of the way the caliper is cast.

I'll check tonight and report back.

[JPuehl]

Originally Posted by Vorsprung_CJB

Interesting, thank you. Yes that makes perfect sense. I will inspect mine tonight.

Are the springs keyed to a certain orientation? On mine and pictures I've seen, it looked like the inside arm was shaped differently than the outside arm when installed on the caliper. Maybe a thickness/distance difference between inner and outer?

I found a pic of the spring on the ECS website. The spring looks slightly different than mine but is close enough. The spring is upside down in the pic. The 2 arms/tabs of the spring that are smooth go inside to outside and rest on top of the pad backing plates. The tabs that look wrinkled go top to bottom and fit against the opening in the caliper and secure the spring in place.

[JPuehl]

Originally Posted by Vorsprung_CJB

Oh, no I didn't mean which 90 degree orientation, its obvious which way it goes. I mean if one end is meant to go towards in inside or outside, or if it can be turned 180 without making any difference.

Looking at some pics again, I think it is just an illusion because of the way the caliper is cast.

I'll check tonight and report back.

Sorry, didn't know exactly what you meant. No I didn't notice a difference between either side so it shouldn't matter which way the spring is installed.

[Vorsprung_CJB]

I didn't have time to remove the wheels but I stuck my boroscope in there and it appeared they were sitting correctly for all 4 pads. Unfortunately looks like my issue won't be so simple. Thanks for your help and suggestion.

[AndyW]

Glad you got it sorted!