BMW cross post - vibration under braking.

[bkreigsr]

Cross post from the 5 series pbbs technical forum;
I appreciate any feedback offered - I know there's a bunch of members here familiar with the 535.

We took our 2013, 535 on a 1,100 mile (round trip) this month and the front end started to vibrate under braking.

Kinda felt like wheel bearings, but the dealership checked them last month....
Kinda felt like one of the front rotors was warped...
Kinda felt like the anti-lock brakes were acting up...

Some of the braking from highway speed (75-80) was particularly violent - like the ball joints were loose. (they are not - I checked that today in the driveway)
Around town the car is very well-behaved.

Is there a common area of concern in these models that would generate this symptom?

(The car only has 43,000 miles - always dealer maintained.)

Thanks in advance
Bill K

[911 Rod]

I had the same problem with my 96 M3.
A couple of places couldn't figure it out.
The caliper was sticking periodically. When on the highway some pad residue would build up on one spot on the rotor. As it built up it would shake real bad, but then the build up would come off with driving using the brakes and it was fine again.
Rebuilt caliper and all was good.

[Bob Kontak]

Originally Posted by 911 Rod

The caliper was sticking periodically.

Daughter's Hyundai front caliper stuck. Zero pulse when cold as the rotor cooled back to "straight". Heat it up, it pulsed violently.

I used a laser thermometer and it was 215F but a brief touch of the alloy wheel told the story just as well.

New caliper.

[bkreigsr]

Thanks guys
Makes sense - car has exhibited these symptoms since I bought it at 22,000 miles- except now it is a lot more pronounced.
Will the dealer replace just the one caliper?
Otherwise I’m looking at the big bucks for calipers, rotors, and pads probably at all 4 corners- ouch.
Might be time to hit up an independent.
Bill K

[Shifter]

Front control arm bushings.
When they wear out, you get a horrible front end vibration when you are braking. Braking on the freeway is where it really shines.

At least this is the case with the E36 and E46 platforms.

[bkreigsr]

Thanks Shifter
Definitely sounds cheaper than 4 corners of Genuine BMW brake parts.
BillK

[asphaltgambler]

If it only vibrates while braking, it's very likely the rotors are warped. As said above, worn thrust arm bushings will exacerbate that. Also any rotor that is not OE / OEM will warp, just ask me how I know. The OEM rotors are 'soft' and designed to wear with the pads, effective with absorbing/ dissipating heat. Any other brand rotors are a 'harder' metal.

[bleucamaro]

Had a similar issue on a Mazda 3 rear (single piston) caliper. Symptom was a warped rotor. Cause was a bind in the caliper causing unequal pressure.

[cstreit]

Rotors VERY RARELY warp. However they do commonly get uneven pad deposition, particularly the performance variety that will lead to measurable runout due to uneven wear.

https://alconkits.com/technical-info/brake-tech/56-the-myth-of-warped-brake-discs

https://alconkits.com/support/brake-pad-info/110-the-real-truth-about-warped-brake-rotors

Disclaimer - this is my site. Yes I've monetized the solution because its the #1 piece of content for us by a factor of 10. You can buy the same bits anywhere though. Just read the articles.

[Jeff Alton]

Check the Lower "front" control arms. The ones that arc back to the main arm. Common to see these bushing fail at low mileage. Crappy design, on pretty much every BMW....

Cheers

[Shifter]

Digging this one up, curious minds want to know the answer.

[bkreigsr]

The dealer fitted new rotors and pads at each corner.
He showed me the old rotors, and even after our 1,100-mile weekend in Mass. they were still not bright and shiny. They seemed to be coated with a mixture of pad material and rust.

They don't re-bush the lower A arms, so they installed new on both sides.
(Cheaper to replace than remove and replace the old ones.)

Of course with the new lower control arms, we got an alignment done.

Testing this week - round trip to Corollo Island NC. - 850 miles RT.

Thanks for your interest/guidance.

Bill K

[brp914]

Something I've had on 914 and 911 is that someone in the past used an air wrench rather than a torque wrench and torqued the lug nuts way beyond spec. The rotors soon warp and you get vibration. The problem is that the hub is also distorted. If the rotors are replaced, initially the vibration is gone, but the warped hub will warp the new rotors and the vibration returns.