rear disc brakes

[nick sparrow]

Hello there I have just aquired a rear disc brake set-up from a friend that fits directly on the rear of my 1974 412 LS. Now that’s great apart from the fact the discs are looking worn and I would really need two new discs…. here in lies the question, I have no idea what they are from. The previous owner told me that they were VW and they sure fit like they were VW. The dimensions are as follows.

PCD 130mm
Hat height 45mm (including disc thickness)
Rotor thickness approx 10mm
Rotor diameter 270mm
Spigot (centre hole) 86mm


So I have been told they were VW but what VW, or what else, any help would be really appreciated on this one.


nick

[ray greenwood]

That would be interesting to find out. What can you tell me about the caliper? Twin piston? E-brakes or not? What was the mount fabricated from? A set of CB performance castings will bolt right up with some very minor turning to the edge of the stub axle to fit the 914 rear rotors. There are several stock calipers that will fit the casting. Ray

[farmer]

Allright Ray!
I have had more than one look at the CB rear disc brake setup for usae on my 412S Variant.
My question is . How much more brake power do you relly get, compared to stock T4 rear drums???
As I do not want to throw my dize into this option unless I get a real improovement.
- OK the rumble from braking from high speeds will disappear, but how much more ?
Any guess ?

[ray greenwood]

Thats an interesting question. Some of the brake experts I know tell me that its rare that you will get any more power from swapping to rear discs. But...you will get quicker response, less fade and no adjustments. The type 4 rear drums were sizable. If you go to a rear rotor with as much swept area as the front ...or more...you can get quite a bit better power. But remember this...you have to have the hydraulic power to run that baby. If you go to calipers with much larger volume than the original wheel cyls. had, you may have to use a larger mastercylinder. The rumbleing you are getting should not be there. It is usually from either warped drums...or worn rear trailing arm bushings. Ray

[farmer]

Forgive me for not explaining myself right.
I was referring to fading when I wrote brake power.
As for the rumble. Well, try a couple of "emergency" brakings from 100 - 0 mph. You´ll get rumble, even from brand new drums, and on brand new cars!

Back to the discs. - Here CSP/Tafel a.o. has a rear kit that is constructed a little different than CB´s kit, with a different disc. (And therefore cannot be used on 412´s)This disc can be bought crossdrilled and heat treated! - Now, if the 914 disc received the same treatement, I´m sure it would be attractive. Even in the rear of my 412 Variant.
And yes I am aware of maybe having to switch to a different mastewr cylinder.
But it might be woth looking into once more after all.

[ray greenwood]

Farmer, I have just recently changed to a different master cylinder from stock. It took a small amount of welding to make a mount, but allows the use of a different master cyl.It is much more available (superbeetle). As for the emergency brake...it is simply applying pressure with the same shoes...but with less force. What you are feeling in the rumble is the same thing you would get if only slightly applying the hydralic brake. This is from warpage. It is a common problem as you note, with all drums. It is also a serious problem with the aftermarket type 3/4 one piece drums. Not as straight as the original two piece because the one piece construction causes the warpage to increase as they get hot. If your rear control arm bushings are not new...this multiplies the rumble. One of the best ways to get to a larger master cylinder, would be to drill out the stamping bosses that are already in the sheetmetal that were there to install power brake units in the trunk. Putting a larger master cylinder under the dash will leave you with a space issue..unless it is the diameter that increases and not the stroke. The power brake unit location in the trunk, with or without the power unit would be a pretty fair way to go, except that you will have to fabricate a pivot arm and linkage rod with a fulcrum bracket in the correct ratio for pedal stroke. Unless of course you can find the proper power brake linkage, or perhaps adjustable linkage? It will be interesting to see where this leads you. Ray

[farmer]

Yearh, you got me thinking again. I have a couple of other projects to attend before I can consentrate on my 412 again. But I will keep you posted when/if I work something out that is worth sharing.
Torben.

[Guest]

Hello there I have just aquired a rear disc brake set-up from a friend that fits directly on the rear of my 1974 412 LS. Now that’s great apart from the fact the discs are looking worn and I would really need two new discs…. here in lies the question, I have no idea what they are from. The previous owner told me that they were VW and they sure fit like they were VW. The dimensions are as follows.

PCD 130mm
Hat height 45mm (including disc thickness)
Rotor thickness approx 10mm
Rotor diameter 270mm
Spigot (centre hole) 86mm

nick

www.brembo.com ->

Citroen C 32/35 YEAR 74-92

PCD ? mm
Hat height 45mm (including disc thickness)
Rotor thickness 9 mm
Rotor diameter 279 mm
Spigot (centre hole) ? mm

OR

NISSAN Maxima 3.0i (HJ30) 12.88-91
NISSAN Primera 2.0i 16V (P10E/P11E) 90-9.99
NISSAN Primera 2.0i 16V (P10E/P11E) 90-9.99
NISSAN Primera GT 2.0i 16V (P10E) 90-9.96
NISSAN Primera GT 2.0i 16V (P10E) 90-9.96
NISSAN-USA application Maxima Sedan 8.88-90
NISSAN-USA application Stanza GXE (+ ABS)

PCD ? mm
Hat height 45mm (including disc thickness)
Rotor thickness 10 mm
Rotor diameter 258 mm
Spigot (centre hole) ? mm

[raygreenwood]

So...they bolt right up to teh stub axle? The next thing is teh caliper mount. The ones from a type 3 set should fit fine. The bolt pattern on the bearing cover is identicalto type `1 and 3. The measurement of the rotor thickness also sounds identical to the rotor from a rabbit. Ray