740iL steering judder

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I have a 1999 740il (63,000 miles and FSH) which has recently developed a steering judder when braking at speeds of between 50 and 60 mph approx.
There's no judder when simply driving at those speeds and there's no
judder when braking at speeds above or below those speeds but when I touch the brakes at around 50-60mph, the steering judders as if the wheels need balancing.
If I come off the brakes, the judder stops immediately.
I've had the wheel balances checked and they're perfect. The guys at the depot said the discs and pads looked fine too.
The car had an Inspection 1 Service a few hundred miles ago and no problems were noted then.
Any ideas?
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This isn't an unusual problem. The pads don't quite match the rotors, due to wear. It almost always happens if you replace the pads but not the rotors, but can happen with normal wear.
You can: 1) have the rotors turned/re-surfaced - this usually solves the problem (at lease for a while), 2) replace pads and rotors, 3) live with it.
FloydR
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I had same problem replaced front brake discs myself
VERY easy
cost $70 for both !
no more judder
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I have had exactly the same thing on a 2000 728i Sport on a couple of occasions in the past, after brakes have been replaced - even when both pads and discs were replaced. It *has* gone away by itself each time.
One thing though - it might be worth checking all the wheelnuts are tight, especially if the vibration begins to occur when driving along.
La Tercia Real
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thrust arm bushings... worth a check
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SharkmanBMW wrote:

That's what fixed the exact same problem on mine, 60k is about their life too...
A
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Disks slightly warped. Have you made a hard stop from high speed recently and then held the car with the foot brake?
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More on that: what can happen is if you lean on the brakes hard, say coming down a huge hill then stop, say at the bottom of the hill at a stop sign. Where the pads contact the disk has a different rate of cooling than the rest of the disc and they can be warped from that minute on. A friend of mine who lives at the top of a very big hill figured this out, the expensive way, over time.
If you use the brakes hard, that's ok, but keep MOVING to let them cool down evenly.
I'm no fan of engine braking (brakes are way cheaper than trannies) but for the aforementioned hill I will use the tranny as there is a stop sign and a busy highway at the end of the hill.
It could be some other suspension component too and the symptom may be the interaction of the two.
It's fairly easy to use a dial gauge and measure runout on the discs.
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No, I've never made a hard stop from high speed.
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pbmitchell wrote:

I takes a lot to warp OEM disks.
I drove my 740i hard and never warped a disk and in any case you'd get vibration at all speeds if it was disks...
99% chance it's the bush, nr. 6 on the diagram linked below:
06    SET RUBBER MOUNTING F TRACTION STRUT    1 31120006482
http://www.realoem.com/bmw/showparts.do?model=GH82&mospidG519&btnr1_0248&hg1&fg 
I'd be inclined to replace parts nr.5 too while it's apart since the ball-joints are probably near life's end too.
A
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ooooooook, next suggestion. tires? what happens if you swap back to fronts?
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Fronts and rears are different sizes: 235/50 and 255/45 so swapping them isn't really an option.
When I took the car in to have the wheel balances checked, the guys at the tyre depot checked the tyres, The fronts are fine but I'm having 2 new rears fitted next week.
Also, the judder only happens when I apply the brakes (even very lightly) at 50 - 60 mph approx. If it were a tyre problem, wouldn't the steering judder without applying the brakes?
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It's not that cut and dry. I've seen that both be true and not true.
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Fronts and rears are different sizes: 235/50 and 255/45 so swapping them isn't really an option.
When I took the car in to have the wheel balances checked, the guys at the tyre depot checked the tyres, The fronts are fine but I'm having 2 new rears fitted next week.
Also, the judder only happens when I apply the brakes (even very lightly) at 50 - 60 mph approx. If it were a tyre problem, wouldn't the steering judder without applying the brakes?
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Come to think of it, my earlier post was incorrect about the problem going away by itself...in fact, on both occasions, I took it to the dealer and they replaced the brake reaction arms and that solved it.
La Tercia Real
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Maybe I'm slow, but what's a "Brake Reaction Arm"? I'm not familiar with the term, but I'm getting the same problem on my 98 740iL. Control arms, Thrust arms, pads and rotors have all been replaced at different times with only temporary relief from the shake while braking.
Kyle. 98 740iL 01 525i
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I'm in the UK, some of the terms differ...think it is also called the upper control arm, but you say that has been replaced...
La Tercia Real
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Brake Reaction Arm is also known as Upper Control Arm or Thrust Arm.
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The BMW I have doesn't have these parts but an S clas Merced3s I have has a very equivalent part. Whaty happens is when the front wheel asembly is perfectly ba;lanced and round the problem does not manifest itself, but when a tire ir off (in my case separated treads) or an out of round rotos then an otherwise nonb-noticable problem exacibated by the brake rods causes the car to feel like it's tearing itself apart.
So, I woul dbet money on the fact your rotor is out of round or tire is uh, suboptimal and that fixing those would alleviate but not cure the problem. The brake rods are what's wiggling and almsot certainly need to be repaired.
I jsut went through this too.
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Almost certainly a worn centre tie rod (it links the outer tie rods). Common on large BMWs.
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