740iL steering judder

"pbmitchell" wrote

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

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

thrust arm bushings... worth a check

That's what fixed the exact same problem on mine, 60k is about their life too...

Disks slightly warped. Have you made a hard stop from high speed recently and then held the car with the foot brake?

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.

Almost certainly a worn centre tie rod (it links the outer tie rods). Common on large BMWs.

So common that I have never heard it of less still experienced it, and I have had four.

On my 3 the brake shudder was control arm bushes and on my 7 the thrust arm thing.

No, I've never made a hard stop from high speed.

The centre tie rod was replaced 4000 miles ago at 59,000 miles.

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...

Had this on my 635, my fiance's E34 Alpina B10, my mate's 525i, my 525e, my other mate's 525iX and his E32 730i :-)

ooooooook, next suggestion. tires? what happens if you swap back to fronts?

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?

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?

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

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.

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