Steering/brake pedal judder upon braking - BMW F02

Ok, it's only been 151 miles since new brembo discs and pads and I've already today started feeling the 'pulsating' in the brake pedal and steering when braking. This is how it begins and then horrible judder after a few more hundred miles.

My observations so far: there is just a slight difference in temperature of both front discs. In the 151 miles covered I have always touched the discs after every journey and neither of them have been hot enough to burn my fingers and therefore certainly not hot enough for the solid metal to warp in the discs? I'm thinking it could be the Tyres? Even a warped hub couldn't warp the discs so quickly and such low temperature surely?

I phoned the previous seller and he said one of the front Tyres is a 2nd hand one and other has had a puncture repair in the past due to a screw....
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Its difficult to expect both discs to be at the same temperature really......indeed that would be ideal but in multi piston calipers its unlikely to happen. During an MOT the brake drag is tested and if a caliper is sticking its a fail.
Time to apply science - but you'll need a dial indicator and a stand for it. The dial indicator is set to touch the disc and the disc is slowly rotated by hand.....any run out is easily seen.
(I once had a vehicle in with 100 thou run out - that's a 10th of an inch! :eek:. That was due to a distorted hub.)
If the disc comes loose on the hub with the wheels off, there's a huge possibility of grit getting behind the disc.....I don't know if Beemers have a retaining screw on the disc or not.
A tyre fitter should have spun your wheels up to speed by now, and any ovality or dramatic balance issue would be seen. These days we balance at 10g steps, which is usually enough.
The fact of powder coating the wheels will have no effect on the balance or cooling - whoever said that!
So - I'm going to stick my neck out! I wouldn't fit second hand tyres to anything - especially a 7 series. You don't know if there's been damage or a kerbing or whatever. Puncture repairs are absolutely fine if done to standard.
Try swapping the wheels back to front as we have suggested.
Stay in touch!
John :)
Thanks John, only issue with swapping wheels is the fronts are 245/40/20 and rears are 275/35/20, now will this cause any problems? I don't ever put my foot down on the road so I don't think traction will be an issue.

I have put brand new Tyres on the rears. The fronts were also out of balance when I got the car, I took it to a tyre shop and got them balanced, they said they couldn't see any significant buckling of wheels either.

I don't ever purchase part worn Tyres either.

Only thing now is I'd have to jack the car up and get dirty taking wheels off etc to check run out on discs. Maybe I could buy the dti and get same garage to check warpage. My Mrs is getting annoyed now though, spending too much time on my beloved car!

Also, garage did say that they put the car on MOT brake tester and thoroughly checked calipers, all was good.
Swapping the wheels over for a test won't be an issue, but are those sizes designed that way?
One thing.....just swap near side to near side and offside to offside to keep the direction of rotation the same.
I would hope most garages would have a dial gauge.....they are only a few quid. I hold mine in a clamp and stand device errr acquired from a school :mrgreen:
Do let's know what you find!
John :)
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Yes, sizes are designed that way as its a rear wheel drive with 3 litre engine.

Will let you know... Thanks
I wouldn't expect the wheel diameters to differ but I must say I'm out of my depth here.....if the car doesn't like it, the ABS light will illuminate.
John :)
What about using calipers (is that the tool?) to check if there is any variation in disc thickness either due to defective manufacture or excessive run out?
Micrometer or vernier caliper Dave.....that'll measure the disc thickness but not the run out.
For sure this is a strange one, but changing the tyres will cost a bit!
John :)
Micrometer is what I was thinking of. 2 new tyres will cost but so will keep on throwing new calipers and pads at it and seems like it needs new tyres anyhow. I bet the previous owner was pleased to get shot of it
Ok thanks for replies, yes I agree, front Tyres need replacing regardless. My garage fortunately keeps changing the parts for me under warranty as they have good relations with ECP, just need to get down to the cause though...
Its highly unlikely the brembo discs are warping on their own easily, they are supposed to be one of the best in the world or certainly used to be years ago.
Are you sure a caliper isnt binding causing the heat to warp the disc/s after a certain time period?
Id echo what people are saying about the tyres, they can cause all manor of strange issues but this is a strange one.
I don't think that could be happening as yesterday was the longest journey I did and I touched the front discs straight after and they weren't hot enough to burn fingers, let alone warp solid steel.
Excessive play on the front wheel bearings? I'd have thought that would have shown up when the discs and calipers were changed. Strange your own mechanic thought it needed new discs pads etc when the seller claimed it had new genuine BMW parts fitted only months before. Was the seller lying? If so what else was he lying about? Is this car a rebuilt write off with all the geometry way out of spec?
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