Brake question

[Dave B]

Hi folks,

Showing my technical ignorance here. Probably an easy and simple question for you guys in the know, but........................

My 1975 3.0 CSi has recently developed a considerable judder felt through the steering wheel under braking. Normal driving is fine with no problem. Apply the brakes and the judder becomes apparent.

I am about to have this looked into. A friend suggested probable cause as cracked / worn front disc(s). Pads were replaced last year. I have not covered enough miles since for it to be them ( unless something is faulty!)

My question - are the discs the same as those fitted to any of the other BMW models of the same period? Seems to me that the E9 tag adds a bit on the price, compared to some of the other models. As soon as you mention that you need bits for a CS Coupe, the shop guys think you are made of money!

Were the same discs fitted to other models? Can anyone advise of a UK based seller, who is not wanting me to fund his next tour of the Caribbean? Any rough ideas of how much I should expect to pay?

Any advice would be much appreciated.

 

[Bill Riblett]

Front vented rotors

Sounds like either warped rotors or some bushing(s) in the front end are worn out.

As I recall, nothing else shares the front rotors. They are part number 34 11 1 152 090. I'd be impressed that dealer parts guys knew what a CS was enough to charge you more! Here in the US, prices are all computerized and differences are a question of whether you can get a discount. Do you belong to a BMW club? Here in the US, some dealers offer BMW CCA members a 'club' discount.

Only UK aftermarket seller I know of is Jaymic.

 

[tripower]

Hi folks,

Showing my technical ignorance here. Probably an easy and simple question for you guys in the know, but........................

My 1975 3.0 CSi has recently developed a considerable judder felt through the steering wheel under braking. Normal driving is fine with no problem. Apply the brakes and the judder becomes apparent.

I am about to have this looked into. A friend suggested probable cause as cracked / worn front disc(s). Pads were replaced last year. I have not covered enough miles since for it to be them ( unless something is faulty!)

My question - are the discs the same as those fitted to any of the other BMW models of the same period? Seems to me that the E9 tag adds a bit on the price, compared to some of the other models. As soon as you mention that you need bits for a CS Coupe, the shop guys think you are made of money!

Were the same discs fitted to other models? Can anyone advise of a UK based seller, who is not wanting me to fund his next tour of the Caribbean? Any rough ideas of how much I should expect to pay?

Any advice would be much appreciated.

Did you have the rotors turned or replaced when you replaced the pads? Excessive vibration during braking is a common occurrence when these are not done during a brake job. I am not familiar with the UK prices, I am assuming you wish to replace the rotors? Do you have discount autoparts stores where you can price out the rotors? There should be numerous models that match these rotors, I think your problem is the guy you are taking your car to not availability of rotors for this car.

 

[Malc]

Dave,
they are probably warped. However if they are pretty new or near maximum thickness you could try and find a good engineering firm or "old fashioned garage", they should be able to skim them true again
It used to be quite common practice until disks became pretty cheap, except of course for rare ones!

When fitting skimmed or new disks make sure that the hub surface to which they bolt is clean and free of rust. Use a thin, thin smear of anti-sieze compound on the mating surfaces.
Then use a dial gauge to check the run out (wobble) on them.

Good luck
Malc

 

[Honolulu]

not quite so fast to skim the rotors...

if you haven't run the car for a while there will be a rusty spot where the pads sat, and the uneven-ness of the disc surface will give you a shudder.

If the car sat for a bit, you don't know the discs are clean, I might pull the front wheels and calipers, clean the discs with 220 grit sandpaper, run the pads on that sandpaper, then reinstall pad where they were before and go for a drive.

 

[corsachili]

New rotors for E9s are neither hard to find nor expensive. I even found some nicely grooved and drilled and plated replacements off of eBay.