anyone got any ideas what the heck is going on

[Smeeagain]

before Christmas I reported a wheel wobble under braking (2004 E53 3.0 D). The collective diagnosis was warped discs so they were changed. Two or three weeks later same issue. it was suggested I change the pistons in the callipers. Problem went away and came back tree or four weeks later. I should add tyres are new, tracking and wheel balance ok. Front control arms were also worn and replaced.
So I bit the bullet and replaced pads, callipers and discs (3rd se tof discs in 3 months previous discs lasted 100k miles.

One month later the problem is back.

I will have the wheels rebalanced tomorrow but it points to warped discs again

Anyone got any ideas as to the root cause?

Smee

[TheHerd]

Hi Smee,

I heard that after some knocks and pavement jumping the hubs themselves could become misaligned, ie: even though you put on brand new discs and your wheel alignment, control arms, bushes are perfect; overtime your discs will shape to match the slightly misaligned hubs and then the wobble starts all over again!

Jason from BMW Chip Tuning told me of a 'on hub' disc skimmer, ie: you get your brake discs skimmed while still on the hub so that they can be shaped with the wobbling hub and run true. This could remove the wobble going forward with each new set of discs.

Hope this could be it.... let me know....

[Smeeagain]

Thanks for this. I'm not sure that I follow the logic that over time the discs will become shaped to the misaligned hubs, and in fact Id go so far as to say that if the hubs are 'out' then the disc wouldn't run true as soon as it was bolted on. And I'm only talking about this problem happening over tree or four weeks of motorway driving (so not a lot of braking time) so I'm not sure of that constitutes 'over time' or not.

That said ....... I tracked down one of the places that can skim the discs on the car and it wasn't that far away from me. £30 per corner, plus VAT, and took about an hour or so, if anyone is interested (skimmydiscs.co,uk). i would find it even harder to believe that both hubs were out and both discs were warped but for an extra £30 I got them both done this morning

The wobble has gone.

For now.

I say for now as the wobble had gone before and came back. But its cheaper to skim both discs for £60 all in that replace them both. Not sure how many times the discs can be skimmed so we shall see ......

[themoog]

It wont be discs it will be the front thrust bushes wearing out.

[Smeeagain]

Nope. Already done. and the problem came back. I did say in the original post that I replaced the front arms (bushes come fitted with them), so definitely definitely definitely not the front bushes! Both upper and lower arms have been done.

And even if it was that (which it isn't at the bushes have been replaced as I said), then why is it that I drive the car to the garage this morning with a braking wobble, get the discs skimmed, drive out and there is no wobble?

Smee

[X5Sport]

Are you a 'Demon Late Braker' by any chance?  The reason I ask is that warping can be caused by keeping the brakes hard on after a rapid stop.  Hot discs squeezed by the pads will warp.  I'm not suggesting this is the cause, just that it is something to consider - and dismiss if it does not apply.

I know I caused the discs on one of my previous cars to warp after braking late and hard, and then keeping the pedal where it was for about 30 secs at a roundabout.  That is all it took.

[Smeeagain]

[quote="X5Sport"]
Are you a 'Demon Late Braker' by any chance?  The reason I ask is that warping can be caused by keeping the brakes hard on after a rapid stop.  Hot discs squeezed by the pads will warp.  I'm not suggesting this is the cause, just that it is something to consider - and dismiss if it does not apply.

I know I caused the discs on one of my previous cars to warp after braking late and hard, and then keeping the pedal where it was for about 30 secs at a roundabout.  That is all it took.
[/quote]

No not at all. I got 100k out my discs before i had this problem and most folk cant achieve that. Im taking my Advanced Driving test this year and my instructor has repeatedly commented on my exceptionally smooth braking.
Smee

[X5Sport]

I remember that course.  That's the simplest option eliminated then. 

Is everything you are using in parts OEM (or the unbadged version)?  I'm wondering if the discs are actually too soft and even normal braking is causing the iron to ripple.

What state are the hub bearings and drive shaft couplings in?  Shaft CVJs would click I would have thought, but wheel bearings may be a source.  Just trying to think of anything that could have enough play to trigger an issue.

I don't know the correct wheel bearing procedure on the E53, but on other cars it is a case of jacking the wheel off the ground, holding it at 12 & 6 o'clock and see if it rocks vertically.  It should not move.

[Smeeagain]

[quote="X5Sport"]
I remember that course.  That's the simplest option eliminated then. 

Is everything you are using in parts OEM (or the unbadged version)?  I'm wondering if the discs are actually too soft and even normal braking is causing the iron to ripple.

What state are the hub bearings and drive shaft couplings in?  Shaft CVJs would click I would have thought, but wheel bearings may be a source.  Just trying to think of anything that could have enough play to trigger an issue.

I don't know the correct wheel bearing procedure on the E53, but on other cars it is a case of jacking the wheel off the ground, holding it at 12 & 6 o'clock and see if it rocks vertically.  It should not move.

[/quote]

The plan is to wait and see how I go with the skimmed disc but the local tyre place told me the same about OEM discs. They said that on heavy cars such as Range Rover or X5 they only fit OE discs as theyve found that non OE isnt hard enough. That said depending on how long the problem stays away I may just get them reskimmed if indeed that is possible. I also kept back the previous set that I replaced so they can be skimmed too. I will look at the bearings but zi think they eere done last year. Drive shaft couplings have not been looked at.
But ...... Per my post above, the discs must have been warped because skimming cured it so whilst bearings may need done that wouldnt in itself have warped the disc would it?

[martyp1001]

I have a similar problem with vibration/wobble at speed...  lower arm changed, wheels balanced (front passenger one slightly buckled), wheel straightened and still slight vibration..  bought new alloys as didn't trust the wheel was ok and found that with the spigot ring on new wheel (front passenger) doesn't fit hub as it should, all other wheels/hubs fine..  when the old wheel was buckled i reckon it has bent the hub out of shape and this is most likely causing the vibration on mine..  new hub on order

[x6edge]

Had very same problem on 2003 3.0 sport. Wobble started at 90,000 miles and after three sets of front discs, new pads and one skim the problem still kept coming back. Sold it in the end as I lost faith but the issue cannot be down to the discs themselves IMHO