technical F90 Brake shudder @ hi speeds

[Ash_Jhb]

Hello guys.

I have this problem so I’m looking for some suggestions to fix...

I have this brake shudder (feel it on the brakes, not the steering and no it not the ABS) braking from above 180km/h downwards.

I have been to BMW ABM twice, complaining about this, and they keep telling me that nothing is wrong with the discs and pads....cleaned and within specs. They say I must do something called a brake force distribution test ( think that’s what’s it called) in the region of 3k not covered by MP. And they won’t test my car above 120km/h themselves.

It’s has become quite frustrating now breaking from hi speed.

Anyone had similar experiences.
Looking for suggestions.


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[lebofa]

If you only feel it on the break pedal, you need to skim the rear disks but I would skim all four just to save time on troubleshooting.

 

[tman]

If you only feel it on the break pedal, you need to skim the rear disks but I would skim all four just to save time on troubleshooting.

Don't skim disks, ever

 

[lebofa]

Don't skim disks, ever

why?

 

[lebofa]

would really like to hear why you must not skim the disk. When the disk is warped or has wear lip and there is still enough thickness to skim and straighten the disk or to remove the wear lip, then I do not see why you shouldn't. Performance disks or normal disks, same applies. If you have enough thickness you can skim. Just find out at which thickness, should you replace the disks. Then make sure when they skim, they do not get to that minimum thickness. That will also tell you if you can skim or if you should replace

 

[VinceM]

Hi Ash,

See if you can force them (dealership) to change the discs nevertheless.




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[akash]

Also check if your rims are not perhaps buckled

 

[Ash_Jhb]

Hi Ash,

See if you can force them (dealership) to change the discs nevertheless.




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Hi V, I tried. They are refusing....they say it’s within specs.


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[Ash_Jhb]

Also check if your rims are not perhaps buckled

Would bucked rims cause a vibration when braking only, at high speed?
If I brake normally under 140 kph, then it’s smooth.
As soon as I brake (recently) from say 170-210... I feel the vibration.


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[Ash_Jhb]

If you only feel it on the break pedal, you need to skim the rear disks but I would skim all four just to save time on troubleshooting.

Is this allowed by MP or does MP need not know?


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[lebofa]

Is this allowed by MP or does MP need not know?


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if your car is still under plan then you have to replace them. Tell the dealership to replace all four disks. They know that when the breaks shudder because of heat, which is what is happening in your case, then the disks should be replaced. If they refuse, try a different dealership

 

[Ash_Jhb]

if your car is still under plan then you have to replace them. Tell the dealership to replace all four disks. They know that when the breaks shudder because of heat, which is what is happening in your case, then the disks should be replaced. If they refuse, try a different dealership

Thank. 18 months old. Will try another dealership. Any suggestions?


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[S1NGH 911]

Thank. 18 months old. Will try another dealership. Any suggestions?


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BMW Sandton


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[Peter@AEW]

It could well be that the disc and hat connection (pindrive) is not 100% and the disc "flutters or does a rocking horse action" when under severe stress as would be the case when brakes are applied at 200Ks.
The disc face may be straight but the rotor can still move on the hat so I fail to see what the brake bias non MP covered R3k expense will ascertain.
The agents as per normal are talking through ignorance which is their normal default
My advice would be for you to get a proper disc set up from someone such as Powerbrake Alcon AP Racing and keep your calipers.
The standard BMW disc brakes if not carbon are average (the brake calipers are much improved)

 

[TurboLlew]

Skimming the M disc makes it more susceptible to cracking.

I am curious as to how the dealer measured the disc as 'within spec' (was this a few points across the disc in terms of thickness? How did they check the flatness or consistency of the surface?) The sensitivity to imperfections in the surface, balancing etc increases dramatically at higher speeds. This was most evident (especially on cars like this) before road force balancing became more common and the car would be perfect at 120/140 but then have funny balancing issues at 180+ (just using this as an example)

A brake force distribution test is NOT what you need. Your car is vibrating - not pulling under braking or abnormally heating specific discs/wearing specific pads. This is also not a R3000 test and can be done at a roadworthy place.

This is frankly a crap response from the dealer and I would definitely get another opinion. JSN/Bryanston will also not take you car to those speeds from a policy perspective, BUT they will drive with you as you break the law in replicating the issue LOL. If they can't fix it they will bring out the area representative to check your car out. I had this done when I did my clutches. Curious as to why they don't want to at least escalate it to the area rep for an opinion.

 

[TurboLlew]

would really like to hear why you must not skim the disk. When the disk is warped or has wear lip and there is still enough thickness to skim and straighten the disk or to remove the wear lip, then I do not see why you shouldn't. Performance disks or normal disks, same applies. If you have enough thickness you can skim. Just find out at which thickness, should you replace the disks. Then make sure when they skim, they do not get to that minimum thickness. That will also tell you if you can skim or if you should replace

Apart from the issue skimming the disc and causing cracks between the perforations etc. why should he resort to this when BMW should be fixing the R40K issue on his R2.4M car under motorplan? What is the point buying that car and having plan if he has to get some dodge guy to skim his discs outside his house?

 

[lebofa]

Apart from the issue skimming the disc and causing cracks between the perforations etc. why should he resort to this when BMW should be fixing the R40K issue on his R2.4M car under motorplan? What is the point buying that car and having plan if he has to get some dodge guy to skim his discs outside his house?

Please check my response after being made aware that the car is still under plan. BTW, I have personally seen performance/slotted disks being skimmed at safety brake and clutch in Randburg, No cracks. If you use some dodge guy to skim your breaks then they will crack 😁

 

[Nick]

cool.
Let us know how it goes.

 

[RAArmstrong]

Go ahead and skim disks. Then come crying here when after a month they shuddering again

In the grand scheme of things, disks are not expensive. Why cheap out on a premium car? These are components that are there to keep you save when you need it the most. Cheaping out on stuff like brakes and tyres frankly blows my mind.

 

[Nikhil]

Please check my response after being made aware that the car is still under plan. BTW, I have personally seen performance/slotted disks being skimmed at safety brake and clutch in Randburg, No cracks. If you use some dodge guy to skim your breaks then they will crack 😁

I've also seen a workshop use Castrol GTX in an M car... that doesnt make it ok. These cracks on skimmed discs dont occur immediately and happen after a few heat cycles. I'm sure that car at safety brake also had Wanli tyres and pops and bangs.