BMW X5 e53 Wheel Shake Under Hard Braking
 

So this issue just popped up a few months ago. Say I'm driving 35-60mph and I hit the brakes fairly hard, my front wheels will shake almost violently. But if I just brake normal, there is no shudder, nice and smooth. I've replaced the tension struts, ball joints, and LCA bushings, brake rotors and pads with FCP Euro parts not that long ago, within 20k miles I would say.

I have a random pop in the front every so often that I think comes from the top mount for the left front strut. It happens occasionally when I turn or hit a bump and I was thinking maybe that's what's causing the hard brake shudder. Thoughts on that as the cause?

The only thing I haven't replaced are the tie rods and I don't think that's the cause. Everything looks good underneath when I had it on the lift a couple weeks ago. All parts were tightened at K0 Lage.

The usual cause is the lower control arm. The test that usually determines if the control arm is worn out is riding on the center lane of three lanes and doing a very gentle curve staying in your lane where you drive over the crown of the road.

If that makes your steering wheel jiggle a little bit as you cross over the dead center every time I’ve done this test it was the rear arm of the front wheels.

The other test that usually confirms that problem is when you brake moderately from about 50 miles an hour to 40 miles an hour.

I had a similar issue solved, and then I got a wobble in my steering that turned out to be the steering gear.

have somebody steer the steering wheel left and right with the engine off and hold your hand on one of the tie rods feel for backlash in the gears to rule that out.

if it turns out to be the steering gear, I have a spare.

Alright so I was a little off on my mileage.
Control arm bushings at 172k
Lower ball joints at 175k
Lower control arms at 187k
Current mileage is 213k

I'll try those tests today and see how it does. Hope it's not the steering gear. But are you thinking that no way the top strut mount could cause that issue?

Guess I'm not the only one with a cost spreadsheet!

I have to keep a spreadsheet for all my cars, otherwise I forget what all I've done! Been doing it for 10+ years, works well.

I like the speed bump test...

Drive JUST fast enough to have the wheels drop off the far side (without slamming down) and if you heard the pop starting going up the speed bump it's the long control arm, but if you hear it as the weight gets "unsprung" then it's the short control arms.

DO NOT Dukes of Hazard it over the speed bump!! [emoji1787]


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Wobble usually only from the two things that directly affect toe: steering and lower (rear) control arm. Upper bearing is a regular cause of the clunks but I've not seen them make wobble but there's always a first time but eliminate the easy ones to test.

My last wobble that was the steering gear would wobble at certain curves in the road so see if you can find a magic curve where you get a wobble.

The more reliable way to check your lower control arm is to jack the car up and pry the control arm. "Speed bump test" or hard braking or whatever else was mentioned does not isolate the control arm and the behavior of the car in response to these "tests" does not tell you anything definitive.

A good quality LCA installed correctly will not fail at the mileage described. I would definitely rule out the upper strut mounts before doing anything. In bad enough condition those can allow the strut to wander, which in turn allows the hub to move along with it. This ends up with very similar symptoms to a bad LCA. Remove the wheel and pry at the strut, it should not have any discernible play.

Sticking slide pins on brake calipers can also cause brake shudder.

I'm not a master tech but I did fight this a good bit on the E36 and can give you my anecdote. The e53 has so far been very good in this regard, even before in a state of neglect, and still after I have messed with it extensively the wheel doesn't vibrate.

The E36 was initially vibration free, and then I went about replacing some blown shocks and control arms and the oil pan etc etc. Tore apart the whole front end. First drive the alignment was way out, and once I hit 55 mph the wheel was kicking back almost an inch.

I did the string alignment, and after three times to get that exactly right, it did help a lot but still on certain surfaces at a certain speed the wheel had a little shake.

I ended up cleaning and redoing the front brakes, not really replacing anything, just cut the rotors ( yeah I know ), clean the guide pins, lube where TIS says to (not the pins), and make sure everything was really clean and even. That helped with some clipping noises and some vibration that was appearing under braking, but the wheel shake remained. I don't think I torqued the calipers all that correctly at one point.

The issue was the sway bar and how I installed it. On that car it has to be torqued evenly on the ground and I just sent it with the wheels in the air, which I knew was wrong but didn't think would matter much. I redid that with some new end links, torqued it per TIS on the ground with some weight in the seats and the wheel is perfect again, the thing drives great.

So perhaps it's something with the sway bar end links or the stiffening plate which hasn't been mentioned yet. If you reuse those bolts a bunch they don't clamp and that could create some sloppiness. I initially came here to post guide pins as just suggested above.

I appreciate all the advice! I haven't had a good chance to check anything further yet but I will. I had it on the lift just a coupl weeks ago when I changed the oil and rotated my tires (no change before/after tire swap), and everything visually looks ok, meaning all the parts I've previously replaced. I did torque everything at K0 (on the ground weight of car). But I did remove the sway bar when I did the engine mounts a while back and I torqued those bolts in the air. I can't see how that would change things to be honest since the bar just rotates in the bushing. I put new links on in the air too if I recall. But I'll take a closer look.

I will grease the guide pins, I haven't done that. But no noticeable brake drag or pull to one side, ever. Just a dab of regular grease?

I still have that top mount in the back of my mind. It pops randomly backing out of a parking space, going over a speed bump, etc. I hate to pull the strut just for the mount but maybe I'll just do it. On one hand it's hard to see how it would cause this problem, but on the other, it can affect camber and caster if worn that bad I guess.

No grease on the brake caliper guide pins - they are supposed to be dry, in clean rubber boots. If the boots or pins are damaged, they are easy and cheap to replace.

https://i.ibb.co/42ggxXb/brake.jpg

where is the reasoning behind dry caliper guides? ive been curious for a long time :dunno:

The lube enables them to pick up dust and debris and make everything worse off after some period of time.

Alright.. I kind of feel like an idiot here. Truth is, I'm not 100% sure how it happened and how it went this long. And how I didn't notice it when I had it on the lift a few weeks ago changing the oil and rotating the tires. But the left front lower control arm bolt was loose at the subframe. :yikes:

I'm not sure if it loosened up over the last ~25k miles or if I just never final torqued it.. regardless it was about a turn loose!

https://youtu.be/8CZ0zHq4Y64?si=4YOIz9Ea9UhJK_Do

Embarrassing as it is to give this feedback, hope it helps someone else in the future. Maybe that fixes the random clank I hear that I thought was the strut top mount.

Tightened with the weight on the wheel? I'm happy to hear it was a relatively simple fix.

Yes always! (Except for maybe this one) 🤣
But I did torque it with the weight on the ground a few mins ago.

Easily done. After I replaced the engine mounts on mine I had really heavy clunk several weeks later when cornering. I hadn't tightened the subframe bolts..