| master cylinders in general [message #70168] |
Sat, 09 January 2010 09:55  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
|
Senior Member |
|
|
Time to perk things up a bit.
I've been doing some googling on master cylinders and note that there are units which have "stepped" bores with different size pistons for front and rear. I haven't gotten past that very much, but it seems someone here may have tried one on their GMC, although I don't know what's out there that may fit. Also, I started realizing that about 90% of tandem units have the rear piston (the primary piston) actuating the front brakes. It seems so universal that it got me wondering why. I usually think these things through when I'm camped on a mountain with a few brewsky's but haven't had that luxury lately. I also think that even with same size pistons, there appears to be a fair amount of tuning available with spring rates and individual piston travels. The reason this is interesting goes back to the notion that some people can't get any significant pressure to the fronts while others seem to have no issue at all with "stock" brakes.
Bob de Kruyff
78 Eleganza
Chandler, AZ
|
|
|
|
| Re: [GMCnet] master cylinders in general [message #70169 is a reply to message #70168] |
Sat, 09 January 2010 10:10  |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
|
Senior Member |
|
|
while you are at it
1 some years ago, folks said the OEM master cyl. had more volulme output
that just a standard 1.25 MC. something about a modified chamber..
2 there is a different push rod required for different MC. This just
might be because of the mounting bracket, however might also be a function
of the MC
I would like to know for this list
http://gmcmotorhome.info/master%20cyl.html
if you look here at Harison's MC, he includes the pin (taped to the top)
and I would sure like to know the length.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=15886&cat=3928
gene
On Sat, Jan 9, 2010 at 7:55 AM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
>
> Time to perk things up a bit.
>
> I've been doing some googling on master cylinders and note that there are
> units which have "stepped" bores with different size pistons for front and
> rear. I haven't gotten past that very much, but it seems someone here may
> have tried one on their GMC, although I don't know what's out there that may
> fit. Also, I started realizing that about 90% of tandem units have the rear
> piston (the primary piston) actuating the front brakes. It seems so
> universal that it got me wondering why. I usually think these things through
> when I'm camped on a mountain with a few brewsky's but haven't had that
> luxury lately. I also think that even with same size pistons, there appears
> to be a fair amount of tuning available with spring rates and individual
> piston travels. The reason this is interesting goes back to the notion that
> some people can't get any significant pressure to the fronts while others
> seem to have no issue at all with "stock" brakes.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription 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
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] master cylinders in general [message #70171 is a reply to message #70169] |
Sat, 09 January 2010 11:06 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
|
Senior Member |
|
|
""while you are at it
1 some years ago, folks said the OEM master cyl. had more volulme output
that just a standard 1.25 MC. something about a modified chamber..
2 there is a different push rod required for different MC. This just
might be because of the mounting bracket, however might also be a function
of the MC
I would like to know for this list""
Agree--maybe time to step back a bit and have another look at the basics
Bob de Kruyff
78 Eleganza
Chandler, AZ
|
|
|
|
|
|
|
|
| Re: [GMCnet] master cylinders in general [message #70187 is a reply to message #70179] |
Sat, 09 January 2010 13:10 |
Ron
Messages: 250
Registered: February 2004
Location: Conifer, Colorado
Karma: 0
|
Senior Member |
|
|
Bob D..
I have been watching this conversation about master cylinders with interest starting with Dan Gregg's problem ti this conversation..
I have been battling very poor brakes for a few years.. Actually since I had the coach.. And, am contemplating going with a power master to try to overcome my issues.. I too am a believer that simpler is better but am almost at the end of my rope.. To recap I have
Replaced the booster twice (Sensitized from Jim K)
Replaced the master 3 times with new (from Jim K Because of leaks)
Replaced all flex lines
Replaced front calipers and Pads Used various kinds (80 MM)
Replaced rear cylinders (with recommended staggered sizes)
Replaced rear shoes with new (Jim K)
Replaced Combo Valve (new brass from Jim K)
Installed Vacuum pump with adjustable vacuum switch to deal with low pressures at my altitude 9300 feet. (also new from Jim K)
My question is.. What master cylinder would you install? I may do it for the hell of it just to be sure that Jim's supply wasn't the problem all along. The $16 price for the one used on Dan Gregg's coach made this a no brainier!
Thanks in advance for your help..
Ron
now a P.O.
Conifer, CO
|
|
|
|
| Re: [GMCnet] master cylinders in general [message #70191 is a reply to message #70187] |
Sat, 09 January 2010 13:29 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
|
Senior Member |
|
|
Hi Ron--a few thoughts. The unit we installed in Dan's coach was a Fenco M1730 from Autozone. Although his brakes seem to work great, they also worked great (before failure) with whatever was on there before. Dan may want to pipe in whether they are as good now as originally. One issue with recommending this for you is that you have 80mm front calipers which could result in a volume problem for this M/C. But as you say for $16 (including tax) it may be worth a try. Another thing to watch is the bleeding of the unit. Dan, Jeff and I were surprised how much you have to bleed the M/C itself. We had to do it on the coach which was fine, but it took a lot of recirculating pushes of the pedal before we hooked up the lines. I have a suspicion that some folks may have issues just because of inadequate bleeding of the M/C itself.
Bob de Kruyff
78 Eleganza
Chandler, AZ
|
|
|
|
|
|
|
|
|
|
| Re: [GMCnet] master cylinders in general [message #70279 is a reply to message #70168] |
Sat, 09 January 2010 20:53 |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
|
Senior Member |
|
|
Bob,
In Mark Donahue's autobiography, when discussing the problem they
had when they were developing the Camaro for Trans Am, he said
they solved
the problem of running out of brakes by switching the lines at
the master cylinder. At the time, I couldn't see how that could
make a difference, but
the results spoke for themselves. Of course, I still don't
understand the "why".
Gary Kosier
----- Original Message -----
From: "Bob de Kruyff" <NEXT2POOL@AOL.COM>
To: <gmclist@temp.gmcnet.org>
Sent: Saturday, January 09, 2010 10:55 AM
Subject: [GMCnet] master cylinders in general
>
>
> Time to perk things up a bit.
>
> I've been doing some googling on master cylinders and note that
> there are units which have "stepped" bores with different size
> pistons for front and rear. I haven't gotten past that very
> much, but it seems someone here may have tried one on their
> GMC, although I don't know what's out there that may fit. Also,
> I started realizing that about 90% of tandem units have the
> rear piston (the primary piston) actuating the front brakes. It
> seems so universal that it got me wondering why. I usually
> think these things through when I'm camped on a mountain with a
> few brewsky's but haven't had that luxury lately. I also think
> that even with same size pistons, there appears to be a fair
> amount of tuning available with spring rates and individual
> piston travels. The reason this is interesting goes back to the
> notion that some people can't get any significant pressure to
> the fronts while others seem to have no issue at all with
> "stock" brakes.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
