Home » Public Forums » GMCnet » [GMCnet] Rear Wheel Cyl. ?
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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120378 is a reply to message #120377] |
Wed, 30 March 2011 17:33   |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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I believe all 4 rear wheels were originally 15/16" but since the leading bogie has more braking ability, some people use the larger wheel cylinders on the front set.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120379 is a reply to message #120377] |
Wed, 30 March 2011 17:34 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
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| larry erd wrote on Wed, 30 March 2011 17:08 |
The parts interchange book shows 3 different sizes of
cyl. 15/16" std., 1 1/16, and 1 1/8". what is recommended??
Larry Erd
77 Kingsley
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bigger is better. i installed the 80mm calipers and 1 1/16" rear cylinders. i couldn't find the 1 1/8" or i would have used them. big improvement in the brakes.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120387 is a reply to message #120379] |
Wed, 30 March 2011 21:11 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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I would leave the rear most wheel 15/16". In the middle wheel I would use 1-1/16" or 1-1/8". I used 1-1/16" on mine.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120439 is a reply to message #120435] |
Thu, 31 March 2011 13:25 |
James Hupy
Messages: 6806
Registered: May 2010
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The difference in wheel cylinder diameters was an attempt, work around,
temporary expedient, call it what you want. Chuck figured out the real
problem of the rearmost wheels lifting during hard braking, and the reaction
arm was the result. That one change has opened the door to further
refinements in the braking system, and led to a rather large decrease in the
stopping distance of the GMC so equipped. Now all we have to be worried
about is the dog sleeping in the back of the coach that becomes a live
projectile during panic stops.<Grin>
Jim Hupy
Salem, OR
78 GMC Royale 403
On Thu, Mar 31, 2011 at 10:59 AM, Emery Stora <emerystora@mac.com> wrote:
>
> On Mar 30, 2011, at 4:34 PM, fred veenschoten wrote:
>
> >
> >
> > larry erd wrote on Wed, 30 March 2011 17:08
> >> The parts interchange book shows 3 different sizes of
> >> cyl. 15/16" std., 1 1/16, and 1 1/8". what is recommended??
> >> Larry Erd
> >> 77 Kingsley
> >> _______________________________________________
> >> GMCnet mailing list
> >> Unsubscribe or Change List Options:
> >> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> > bigger is better. i installed the 80mm calipers and 1 1/16" rear
> cylinders. i couldn't find the 1 1/8" or i would have used them. big
> improvement in the brakes.
> >
> > --
> > Fred V
>
> To a degree. However, bear in mind that as you go to a larger diameter
> wheel cyllinder you have less pressure on the piston so going to 1-1/8" on
> all wheel cylinders might not give you the improvement that you expect.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
>
>
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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120440 is a reply to message #120435] |
Thu, 31 March 2011 13:42 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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| emerystora wrote on Thu, 31 March 2011 11:59 |
On Mar 30, 2011, at 4:34 PM, fred veenschoten wrote:
>
>
> larry erd wrote on Wed, 30 March 2011 17:08
>> The parts interchange book shows 3 different sizes of
>> cyl. 15/16" std., 1 1/16, and 1 1/8". what is recommended??
>> Larry Erd
>> 77 Kingsley
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> bigger is better. i installed the 80mm calipers and 1 1/16" rear cylinders. i couldn't find the 1 1/8" or i would have used them. big improvement in the brakes.
>
> --
> Fred V
To a degree. However, bear in mind that as you go to a larger diameter wheel cyllinder you have less pressure on the piston so going to 1-1/8" on all wheel cylinders might not give you the improvement that you expect.
Emery Stora
77 Kingsley
Santa Fe, NM
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Emery, I may be misunderstanding what you are saying so bear with me. The pressure is generated by the master cylinder so assuming there's enough volume, a larger wheel cylinder diameter will increase the force on the brake shoes. On the otherhand a larger master cylinder diameter will decrease the system pressure for a given input. Other than using more volume, it seems to me that larger wheel cylinders will always exert more braking force.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120446 is a reply to message #120440] |
Thu, 31 March 2011 14:58 |
emerystora
Messages: 4442
Registered: January 2004
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On Mar 31, 2011, at 12:42 PM, Bob de Kruyff wrote:
>
>
> emerystora wrote on Thu, 31 March 2011 11:59
>> On Mar 30, 2011, at 4:34 PM, fred veenschoten wrote:
>>
>>>>
>>>
>>> bigger is better. i installed the 80mm calipers and 1 1/16" rear cylinders. i couldn't find the 1 1/8" or i would have used them. big improvement in the brakes.
>>>
>>> --
>>> Fred V
>>
>> To a degree. However, bear in mind that as you go to a larger diameter wheel cyllinder you have less pressure on the piston so going to 1-1/8" on all wheel cylinders might not give you the improvement that you expect.
>>
>> Emery Stora
>> 77 Kingsley
>> Santa Fe, NM
>>
>>
>
> Emery, I may be misunderstanding what you are saying so bear with me. The pressure is generated by the master cylinder so assuming there's enough volume, a larger wheel cylinder diameter will increase the force on the brake shoes. On the otherhand a larger master cylinder diameter will decrease the system pressure for a given input. Other than using more volume, it seems to me that larger wheel cylinders will always exert more braking force.
> --
> Bob de Kruyff
>> To a degree. However, bear in mind that as you go to a larger diameter wheel cyllinder you have less pressure on the piston so going to 1-1/8" on all wheel cylinders might not give you the improvement that you expect.
>>
>> Emery Stora
>> 77 Kingsley
>> Santa Fe, NM
>>
>
> Emery, I may be misunderstanding what you are saying so bear with me. The pressure is generated by the master cylinder so assuming there's enough volume, a larger wheel cylinder diameter will increase the force on the brake shoes. On the otherhand a larger master cylinder diameter will decrease the system pressure for a given input. Other than using more volume, it seems to me that larger wheel cylinders will always exert more braking force.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
We must all be careful with the logic behind sizes of master and sizes of slave cylinders (I refer to slave here as any wheel cylinder or caliper -- the driven cylinder that is). Increasing the size (that is to say, area or diameter) of the master cylinder will reduce line pressure for a given input force. If you push with 100 lbs on the pedal, a 1"master cylinder will give LESS pressure to the line than a 3/4"master.
However, in this case we are only talking about increasing the area of the wheel cylinder. I was not good in my choice of words. I see that I said pressure ON the cylinder. I really should have pointed out that a larger diameter wheel cylinder would give more travel of the brake pedal and/or less travel of the wheel cylinder against the brake shoes. This can impact the friction generated at the surface of the brake drum. At some point that might not give the anticipated results.
The larger wheel cylinders will translate to more force on the brake shoes. But it won't FEEL right. Why? Because the stock master cylinder is now trying to fill bigger wheel cylinders and that translates to more pedal travel. It doesn't FEEL like the brakes are doing their job. To get the added braking force AND maintain decent pedal travel and feel, then you must increase the master cylinder bore a like amount as the wheel cylinders.
Prior to my installing six wheel disk brakes I had increased the piston sizes to 1-1/6". I then changed the center ones to 1-1/8" but I felt that I did not have as good braking so I changed them back to 1-1/16"
In my email to Fred I was basically saying that one might not get the braking one anticipates with the change.
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120450 is a reply to message #120446] |
Thu, 31 March 2011 15:35 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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Yup--we're on the same page. As it turns out I'm running 15/16 on the rear bogie and 1 1/16 on the front bogie and stock on the front calipers. I've always said I'm running a stock system, but not quite.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120464 is a reply to message #120463] |
Thu, 31 March 2011 18:23 |
emerystora
Messages: 4442
Registered: January 2004
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I looked at that section and see that you have something by me called
What Master Cylinder to use for Disk Brakes
HOWEVER, that information is outdated it is from 2004.
I did a new write up in 2008 and sent it to you but I don't know if you ever posted my newer information from October 2008 regarding the use of a 34mm piston bore master cylinder.
I had sent you that information a couple of times but I don't know if it ever got posted to your site anywhere.
A note should be put on the 2004 information that it is now obsolete.
If you don't have that information I can send it to you again.
Emery Stora
On Mar 31, 2011, at 5:00 PM, Mr.erf ERFisher wrote:
> easy to see the trade-offs, just read DaveM's calculations
>
> http://www.gmcmotorhome.info/brakes.html#calc
>
> gene
>
>
>
> On Thu, Mar 31, 2011 at 12:35 PM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
>>
>>
>> Yup--we're on the same page. As it turns out I'm running 15/16 on the rear
>> bogie and 1 1/16 on the front bogie and stock on the front calipers. I've
>> always said I'm running a stock system, but not quite.
>> --
>> Bob de Kruyff
>> 78 Eleganza
>> Chandler, AZ
>> _______________________________________________
>> 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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| Re: [GMCnet] Rear Wheel Cyl. ? [message #120471 is a reply to message #120464] |
Thu, 31 March 2011 21:29 |
Mr ERFisher
Messages: 7117
Registered: August 2005
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>
> If you don't have that information I can send it to you again.
>
> good idea, and also think you should send me
in-tank fuel pump
and
zerk drill guide
I cannot find them anywhere I can down load them or point to them from my
web page.
what a waste to not have them in the public domain
gene
> Emery Stora
>
> On Mar 31, 2011, at 5:00 PM, Mr.erf ERFisher wrote:
>
> > easy to see the trade-offs, just read DaveM's calculations
> >
> > http://www.gmcmotorhome.info/brakes.html#calc
> >
> > gene
> >
> >
> >
> > On Thu, Mar 31, 2011 at 12:35 PM, Bob de Kruyff <NEXT2POOL@aol.com>
> wrote:
> >
> >>
> >>
> >> Yup--we're on the same page. As it turns out I'm running 15/16 on the
> rear
> >> bogie and 1 1/16 on the front bogie and stock on the front calipers.
> I've
> >> always said I'm running a stock system, but not quite.
> >> --
> >> Bob de Kruyff
> >> 78 Eleganza
> >> Chandler, AZ
> >> _______________________________________________
> >> 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
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
>
> _______________________________________________
> GMCnet mailing list
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--
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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