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Could be worn bushes in the suspension. Either that or warped discs. Check the run-out on the discs with a DTI and compare that to manufacturer's specs. If it's not that, it's suspension bushes. If it's warped discs then it's not worth skimming the discs unless you have something very exotic with expensive discs.
If it was tyres you'd feel it all the time, not just under braking.
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What car and when did it start? Was it afterr you have had tyres changed. Part of me hopes that a bolt or nut would strip before damaging the hub in this situation.
Might be an idea to at the discs surface are like and see if the wheels spins freely. If the disc looks suspect try and find someone with an on car brake lathe such as https://brakelathe.co.uk/. Video on there to show the machine in action.
If the wheel is stiff to turn, you need to start taking tings apart to look at the problem.
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Run out between the hub and inner face of disc. Only takes a tiny amount (0.2mm) to cause epic problems, usually around 1000-2000 miles from install.
Disc unlikely to be warped, more common is disc thinning or just plain runout.
Runout you can maybe fix by taking it all apart and sorting the run out with a dial gauge, but usually by the time you have the symptoms is too late for that disc, as one area (high spot) will have been thinned down minutely by hundreds of thousands of passes across disc pad.I went through three sets of discs on one of mine until I sorted it.
First time, my bad, I had 10x the permissable runout at the hub (read the gauge wrong)
Second time run out was at limit of spec but couldn't make hub any cleaner, so bought new hubs (face was bent from either over tightened or road damage). Didn't get dial gauge our, just whacked my new £90 a corner disc on my new £170 a corner hub assuming both German companies who made them, made them right.
Third time. One hub was not straight from factory and caused thinning of a disc, again. Replace hub, again, replace did for third time, and finally no problems.During this time also.... Rebuilt brake calipers and master with all new internals to irraicate chance of a slow returning piston from causing disc thinning and checked every bush and joint in the car about 8 times.
Cars. Yeay.
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I had this - new discs on front warped after a year. Garage reckoned it was due to previous owner using cheap pattern parts and not BMW.
Current OEM set are 10k in and perfect.
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Brommers
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@kboy
Wobbly brakes. What’s the deal with this? Had brake discs and pads replaced in all corners about a year ago, and now there’s a fair bit of vibrations in the steering wheel when I brake.
What’s the reason for this? Haven’t used them excessively so it can’t be overheating. Someone told me it can happen when you change tyres and they do up the bolts too tight?
And finally, what can I do to fix it? Find someone with a lathe?