I believe sobi6111 had the issue before he had the brakes done. Doing the front brakes reduced the issue 80% he mentioned.

I have another vehicle (not the X5) where the brake pulses and the wheel shimmies during braking. When I turn or replace the rotors and change the pads and correct the tire pressures, the issue goes away...but it comes back again after 15k or so until I do the brakes again. I've done the brakes 4 times so far. I thought it was the master cylinder, but everytime I do the brakes ... it goes away.

Then again it is not an X5 so this may not apply to your issue.

Have you bumped a curb or hit any pot holes recently? It was asked in the post before this, how many miles on the X?

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2003 X5 Steel Grey
3.0i e53