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Is there a difference in drum n disk master cylinders,some,in one book there is one part no.then in another book shows two part no.spoke to brake specialists some say there the same,some say there different, thanks.
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Yes there is. Drum brake master cylinders have a residual line pressure valve to hold the brake shoes near the drum whereas disc brake master cylinders don't have the valve.
If you put a drum brake master cylinder onto a disc braked car you will hit the brakes once and they will stay on (I have deliberately tried this and it does happen).
The one exception to this rule is front disc brake equipped HR Holdens which only had single circuit braking so they used a disc brake master cylinder to feed the front discs and the rear drums. FWIW the HR disc brake master cylinder is the same thing as an HR clutch master cylinder. |
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PBR list them as being the same
the only difference is between the body styles
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What Jim has noted is the same for Commodores from the era too (which also ran the PBR master cylinders).
Many people have been caught doing disk brake conversions without changing the master, then wondering why the rear pads wore out in 5000km.
There is a difference in the masters, even if it's no longer listed correctly. |
Cheers,
Mick
_______________________________________________________________
Judge a successful man not on how he treats his peers, but on how he treats those less fortunate. |
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Ok,I have a xd fairmont ghia it had a borgy disc rear end,I put a 9 inch drum brake in,so should I change the master cyl,? Does anyone have the part no.as big cav said there is only one no. Listed. Thanks.
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I would advise the change but you might get away without it although you might end up with a slightly spongy brake pedal especially if the drums are not adjusted up constantly.
Technically if you have converted an XD V8 to a drum brake rear your car is no longer road legal as 4 wheel disc brakes were mandatory with the XD V8 models.
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Thanks Jim,the 9inch has been in the car for 15 years have not had brake problems with it,have only heard about different cyls recently,didn't know about drum brakes are illegal with a v8 in n xd.I have been put through department of transport before for no. Plate light not working,wide types n to low,they went all over the car,tested the brakes on there machine,there stopped to there spec.didn't say anything about the diff or the drum brakes.but yer I know where there is a disc brake 9inch,I will get it n fit it.
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That is why I said technically illegal. No one will ping you for it because earlier Falcon V8's had rear drums and stopped perfectly well.
I think that it came under "downgrading of safety equipment" but anyone that would remember what it should be like have probably long since retired. Not that rear drums are that much of a downgrade really. I would not worry too much.
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