Home » Public Forums » GMCnet » Drum brake cylinder volumes
| Drum brake cylinder volumes [message #165634] |
Sat, 07 April 2012 09:59  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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I have the one ton front end which uses a 75mm front caliper.
I also have a rear-disk kit which I'd like to install.
I've also been reading about possibly needing the 1.25 P30 master cylinder due to the extra volume required when going to 80mm fronts and 80/70mm on the rears. I would be going to 75mm fronts and 80/70 on the rear, so I'm not going to need quite that much volume.
I've been looking at the GMC Brake calculator spreadsheet to see what the difference is going to be, but I can't find what volume the OEM drum cylinders required.
I'm wondering if I can get away with the 1.125 OEM MC for a while. I'm a working stiff and will need to do this in my driveway so I don't want to make this a long involved project if I can help it.
Thanks all.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: [GMCnet] Drum brake cylinder volumes [message #165638 is a reply to message #165634] |
Sat, 07 April 2012 10:21  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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You can drill a hole through the separator half way down so that the
fluid will bleed over to the lower side.
I would not do that on a customer's unit, but if your going to do it
to your own, it is a good trick.
On Sat, Apr 7, 2012 at 7:59 AM, Bruce Hislop <bruce@perthcomm.com> wrote:
>
>
> I have the one ton front end which uses a 75mm front caliper.
>
> I also have a rear-disk kit which I'd like to install.
>
> I've also been reading about possibly needing the 1.25 P30 master cylinder due to the extra volume required when going to 80mm fronts and 80/70mm on the rears. Â I would be going to 75mm fronts and 80/70 on the rear, so I'm not going to need quite that much volume.
>
> I've been looking at the GMC Brake calculator spreadsheet to see what the difference is going to be, but I can't find what volume the OEM drum cylinders required.
>
> I'm wondering if I can get away with the 1.125 OEM MC for a while. I'm a working stiff and will need to do this in my driveway so I don't want to make this a long involved project if I can help it.
>
> Thanks all.
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
> Hubler 1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
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jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Drum brake cylinder volumes [message #165639 is a reply to message #165634] |
Sat, 07 April 2012 10:25 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Bruce,
With very true (low run-out) discs, and tight wheel bearings, you should be
OK with your 1.125" MC for a while, but I'd really recommend going to the
1.25" OEM-style MC -- NOT the P30 34 mm (1.34"). You may want the P-30
later, but it's a lot cheaper and easier to install the 1.25". If you
bench bleed the MC, you should be able to change it in the driveway with no
further bleeding.
Unfortunately, someone else will have to give you an application for the
1.25" MC -- I can't find it.
Ken H.
On Sat, Apr 7, 2012 at 10:59 AM, Bruce Hislop wrote:
>
>
> I have the one ton front end which uses a 75mm front caliper.
>
> I also have a rear-disk kit which I'd like to install.
>
> I've also been reading about possibly needing the 1.25 P30 master cylinder
> due to the extra volume required when going to 80mm fronts and 80/70mm on
> the rears. I would be going to 75mm fronts and 80/70 on the rear, so I'm
> not going to need quite that much volume.
>
> I've been looking at the GMC Brake calculator spreadsheet to see what the
> difference is going to be, but I can't find what volume the OEM drum
> cylinders required.
>
> I'm wondering if I can get away with the 1.125 OEM MC for a while. I'm a
> working stiff and will need to do this in my driveway so I don't want to
> make this a long involved project if I can help it.
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Drum brake cylinder volumes [message #165647 is a reply to message #165646] |
Sat, 07 April 2012 11:19 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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did you read this excellent research by your brother (Cnadan)
http://www.bdub.net/branscombe/Disc_Park_Brake_Improvements.pdf
you might want to put on the booster and keep the OEM master cyl. ;>)
gene
On Sat, Apr 7, 2012 at 9:07 AM, Bruce Hislop <bruce@perthcomm.com> wrote:
>
>
> Ken,
> Yes, you are right, I meant the 34mm MC which is what I have that I can
> put on.
>
> I think what I'll do is put on the new 34mm master cylinder at the same
> time since I have to do a major brake bleeding anyway (have to replace the
> proportioning valve for the rear disks)
>
> I have the sensitized booster as well, but I'll put that off till another
> time.
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
> Hubler 1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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