Vented brake discs

[mrp]

Hi. I'm restoring a 3.0cs. The brake discs mounted in my car right now are non vented. Looking for new ones in the internet, I found these two part codes
34 11 1 152 090 front disc
34 21 1 152 095 rear disc
Both of these are vented and are thicker than the ones my coupe is using. I wasn't able to find other part codes than the ones I just mentioned, so vented brake discs are the only replacement option I have right now. The web site bmwmobiletradtion shows the drawings of both vented and non vented brake discs, but only shows the part code for the vented ones.
Wich one of the two options was a stock item for the 3.0cs???
If I get the vented brake discs, do I have to change calipers as well???
Thanks for your help.

 

[MMercury]

Hi. I'm restoring a 3.0cs. The brake discs mounted in my car right now are non vented. Looking for new ones

The web site bmwmobiletradtion shows the drawings of both vented and non vented brake discs, but only shows the part code for the vented ones.

I am unable to give you a definitive answer, but I will try for a semi-educated guess. It might be helpful for you to provide some details about your vehicle. Was it always a 3.0cs, or might it be a 2800cs converted with brakes from another model, for example an E3? The part numbers you quote appear to be correct for a 3.0cs.

See: http://www.realoem.com/bmw/showparts.do?model=7031&mospid=47808&btnr=34_0845&hg=34&fg=10

To the best of my knowledge, all 3.0cs/i models shared the same brake components (although there may have been some slight variations through model years and plumbing differences between left and right hand drives). The E3 (2.8 and 3.0 liter) sister models also have 4 wheel disk brakes, but not vented disk/rotors. There may be a few exceptions and for all I know, yours might be one of those exceptions. However, I would not bet on it.

Since you have solid rotors currently on your E9, without knowing more about the history of your car, it is likely someone merely transplanted the rotors and the corresponding calipers from an E3 or possibly another model. These parts would fit as I have seen the E9 brakes and calipers fitted to an E3. As you are aware, the solid front rotors are approximately 13mm thick versus 22mm for the vented versions. Solid rear rotors are approx. 10 mm versus 19mm for the vented rear rotors. The calipers are essentially the same except that the calipers for the vented rotors have two spacers per caliper adding additional width for the caliper to adequately fit the vented rotors.

Since the area of friction surface would be the same for solid and vented rotors, I would imagine each would perform the same when cold. The bigger difference is that the vented rotors theoretically shed heat better than the solid rotors. This would seem beneficial for higher speeds and/or mountain driving. Some may treat this as blasphemy, but if you are satisfied with the brakes you currently have, you might try replacement rotors parts from an E3 model. See attached link: http://www.realoem.com/bmw/showparts.do?model=4512&mospid=47247&btnr=34_0879&hg=34&fg=05

Notice that the diagram also depicts vented rotors but, does not provide a part number for them. This is the opposite of what you found when looking for at parts for the e9.

For slightly more on the subject:
http://www.e9coupe.com/forum/showthread.php?t=4380
http://www.e9coupe.com/forum/showthread.php?t=1648


Hope this helps. Good luck!

 

[Bill Riblett]

If you have both front and rear solid (non-vented) rotors, it really sounds like someone has switched to E3 sedan calipers and rotors on your car.

Switching to CS vented calipers is a straight-forward change and would return the car to its original specs.

Practically speaking, I seriously doubt you will be able to notice any difference between vented and non-vented brakes. I have had an E3 sedan (solid rotors front and rear), 2800CS (solid rotors front and drum brakes rear) and 3.0CS ( vented rotors front and rear) and really could not say I could tell a difference between them. I can see more difference between different brand brake pads.

If you do replace the calipers and you do not know when the brake hoses were last replaced, replace them with the calipers. They break down on the inside over time, to the point eventually where they can act like one-way valves and lock up a caliper.

 

[mrp]

OK. My car VIN has been erased, but thanks to this forum I was able to find out my coupe was manufactured in 1974. According to the spare parts catalog I own, no 3.0cs has non vented discs.
I already have four new vented rotors. Now I need to adapt the existing calipers or by new ones. Is it possible to addapt calipers for non vented rotors to vented rotors???
If I by new calipers, do they fit straight in??? Or some adaptation is needed.
Thanks again for your help.

 

[MMercury]

OK.Is it possible to adapt calipers for non vented rotors to vented rotors??? If I buy new calipers, do they fit straight in??? Or some adaptation is needed.

I tried to address you question. "The calipers are essentially the same except that the calipers for the vented rotors have two spacers per caliper adding additional width for the caliper to adequately fit the vented rotors."

If you compared the two different calipers, the difference would be obvious. The two halves of each caliper are the same, but there are spacers that widen the space between the two halves to accomodate the wider rotor.

A non-bmw caliper is depicted below. Look carefully at nos. 19 and 20. These are what a spacer looks like.

Here is a picture of a split caliper with the separated spacers:

Naturally, if you or a caliper rebuilder has the spacers, you could break the current calipers apart and insert the spacers. As easy as that seems, you should be aware that splitting calipers, even for rebuilding purposes, can prove problematic since they require special "o" rings and fasteners. I am not saying you can't rebuild calipers or that this proceedure isn't done all the time, but it is highly recommended that you used new fasteners, if you can find some. Safety should be paramount.


New calipers or even used calipers should mount exactly as your current calipers.


Good luck.

 

[bert35csi]

According to my orange CS parts book, the 2800 CS and the later 2.5 CS were both outfitted with the non-ventilated f/r rotors. There is good possiblility that your coupe is a 2.5 CS and not a 3.0.

You can get the non-vented discs @ http://www.wallothnesch.com/e/frameoffer.htm or uprgrade to the vented rotors and the corresponding calipers. The cost for a set of rebuilt calipers is not that great actually.

 

[Bill Riblett]

I already have four new vented rotors. Now I need to adapt the existing calipers or by new ones. Is it possible to addapt calipers for non vented rotors to vented rotors???

If I by new calipers, do they fit straight in??? Or some adaptation is needed.
Thanks again for your help.

You can convert your calipers if you can find these parts:
spacers
seals for the spacers
correct length longer bolts
These parts are not available from BMW and you must have all of them.
Try Walloth und Nesch in Germany

Personally, i think it is much safer to buy new calipers.
As I said in my original post, they are a bolt on replacement, or as you say, "fit straight in".

 

[jefrolison]

OK. My car VIN has been erased, but thanks to this forum I was able to find out my coupe was manufactured in 1974. According to the spare parts catalog I own, no 3.0cs has non vented discs.
I already have four new vented rotors. Now I need to adapt the existing calipers or by new ones. Is it possible to addapt calipers for non vented rotors to vented rotors???
If I by new calipers, do they fit straight in??? Or some adaptation is needed.
Thanks again for your help.

Today (or this month) is your lucky day! W&N has the conversion kit on sale right now...
http://www.wallothnesch.com/e/ws/ws1.htm this includes spacers, o-rings and new bolts to do all 4 calipers. Offer ends September 30.
Jef Rolison
2210088 71 3.0cs
3280253 74 3.0bav