Violent shaking while braking

[E53 4.8is]

Ok, so i have a 2005 4.8is that recently has developed a pretty violent shaking while braking. No shaking while driving only while braking. If while the shaking is occurring I turn the steering wheel, the shaking stops. It doesn't alsways shake either, but it does get worse at higher speeds. I've done a lot of reading. I read a threat about one guy who somehow lost his spacers for his aftermarket wheels. I have the replica wheels from a 4.6is. I'm thinking lower thrust arm bushings. The boot on both from lower arms do have tears. Any help would be greatly appreciated it. I believe the shaking has also caused my dsc to malfunction do to the shaking and my ride height suspension to become inactive either from the shaking or from the sensors no being able to get an active read on the equipment.

[lhordmclain]

Wild guess

Some good readings (known symptoms for Control Arm Bushing) -> Beisan Systems - Procedures - Thrust Arm Bushings Procedure

Also, it might be your front rotor thickness (low side of the specs) together with low brake pads thickness.

+ Fix the existing : The boot on both from lower arms do have tears

Good Luck!

[Clockwork]

could be a couple of things:

faulty replica wheels or out of balance,

brake rotors (could be warped if heated up a lot)

control arm bushings. way to tell if its the control arms, is to drive slowly (ie 10-15mph) and at a medium speed (25mph) over a curb going into a parking lot say and feel if the steering wheel comes towards you physically. If it does, its the Control arm bushings.

tie rod knuckle (could give extra play in steering)

wheel hub bearings are worn/busted up (i say that because you said it goes away when you turn, but does it go away if you turn either way, or just one?)



Also, braking from what speeds produces this?

[E53 4.8is]

The shaking varies at lower speeds, but almost always occurs around 40+mph. As for turning the wheel, the shaking stops when turning the wheel either direction but requires less of a turn to the right. Is there a visual inspection I can make of the wheel bearings? Also it does seem that there is play in the steering wheel. My main problem is I'm in the middle of a cross country trip from florida to delaware. Currently I'm in NC. I have pretty much ruled out the rotors for the fact that braking efficiency isn't effected at all. The rear brakes have just been replaced, rotors and calipers. I will be replacing the lower control arm bushings and maybe the whole arm but I need to figure out if there is anything I can do to rectify this situation now. Could I use some kind of liquid poly euro thane as a temp fix until I get home to a garage and tools? The more I read the more I feel like this might be a wheel bearing problem. The X has 92k on the clock.

[LeiZ]

Make sure your caliper guiding bolt is not stuck. Otherwise the piston will push the pad one way and distort the rotor.

The way to check is, 1) see if there's any rust by visual. 2) take the wheel off and use a C-clamp to push it in, if no resistance, it's good. You might need to leave the brake reservoir cap open.

Originally Posted by E53 4.8is

The shaking varies at lower speeds, but almost always occurs around 40+mph. As for turning the wheel, the shaking stops when turning the wheel either direction but requires less of a turn to the right. Is there a visual inspection I can make of the wheel bearings? Also it does seem that there is play in the steering wheel. My main problem is I'm in the middle of a cross country trip from florida to delaware. Currently I'm in NC. I have pretty much ruled out the rotors for the fact that braking efficiency isn't effected at all. The rear brakes have just been replaced, rotors and calipers. I will be replacing the lower control arm bushings and maybe the whole arm but I need to figure out if there is anything I can do to rectify this situation now. Could I use some kind of liquid poly euro thane as a temp fix until I get home to a garage and tools? The more I read the more I feel like this might be a wheel bearing problem. The X has 92k on the clock.

[Big "J"]

I had the same shaking on my 4.8 and in my wifes X3. Bushings and ball joints were good as well as the wheel bearings. Had the rotors turned to smooth out any warping and bingo....all nice and smooth braking.
If the bearings are going bad...you'll hear a wha, wha, wha....sounds that gets worse the faster you go.

[E53 4.8is]

If the front rotors are warped, would the shaking stop while the wheel is turned.

[Clockwork]

No

[Big "J"]

For me oddly enough, the steering wheel shake lessened to near smooth when going into a turn.

To Clockwork's point.... agreed theoretically, no it shouldn't. But.....

In my case, I think possibly the control arm bushings were absorbing most of the vibration which smoothed out turning.
It may not be the case for you but, getting my rotors turned was the quickest and cheapest ($20/rotor) way to solve the steering wheel shake without throwing a lot of parts and money at it.

Good Luck!