Rear brake pressure regulator variations.

[thai-wronghorse]

Can anyone tell me what the difference is between the disc & drum specific rear brake pressure regulators?  (apart from the part numbers)

Drum - pt no.1H0612151

Disc - pt no.1H0612151C

[boneybradley]

ATE on tec-doc say

drum brakes
Brake Booster
Braking / Drive Dynamics: for vehicles without ABS, Parameter: T52, Ø: 9 Inch, Operating Mode: Pneumatic, Brake System: ATE
o.e 1H2 612 107 - 1H2 612 107 B - 1H2 612 107 D

disc
Brake Booster to Ch.No.: 1H-S-088704
Braking / Drive Dynamics: for vehicles with ABS, Parameter: T52, Ø: 10 Inch, Operating Mode: Pneumatic, Brake System: ATE
o.e 1H1 698 107 - 1H1 698 107 A

So it's the diameter (or size) that's different (what ever this refers to Ø)

[thai-wronghorse]

I kinda assumed it was probably down to internal biasing variations and it appears one has a larger diameter valve in it. Im confused at the info you've posted in relation to one having ABS though as I thought it was only the non-ABS equipped vehicles that used rear brake pressure regulators regardless of whether they had drums or discs as the biasing would otherwise be done inside the ABS pump/ ECU?

[boneybradley]

early gti's also had a load valve (due to pre-historic abs and they make changing axle bushes so much harder as they are next to the bolts on 1 side), when they changed in 95 to 288's the load sensor was part of the abs

[thai-wronghorse]

Ah right so early ABS equipped cars still had them, im wondering whether I should swap the one on my wagon to the other type once I fit rear discs that all?

[boneybradley]

Ah right so early ABS equipped cars still had them, im wondering whether I should swap the one on my wagon to the other type once I fit rear discs that all?

I know people don't bother to change them when fitting discs (and t.b.h never adjust them when lowering, they are not as bad as corsa's if lowered and the spring not shortened it makes the brakes tail happy! Golf's don't suffer that way)

[thai-wronghorse]

Yeah i know some people don't bother I just want to make sure I do it properly and the safest i can. When lowering a car equipped with a rear brake pressure regulator am I correct in saying you want all the spring tension relieved off the valve before tightening the nut with the boot completely unloaded or does it need any kind of pretension?