Home » Public Forums » GMCnet » [GMCnet] Brake Residual Valves
| [GMCnet] Brake Residual Valves [message #284993] |
Sat, 15 August 2015 13:57  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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For vehicles with the Master Cylinder mounted below the calipers, it's
usual to install 1 psi residual valves in the brake lines to prevent fluid
from migrating back to the MC.
I'm thinking about installing some in the GMC's brake lines to try to raise
the brake pedal a little. There's certainly no drain back from our
calipers to the MC, but I suspect there's less than optimal, and equal,
hysteresis in the caliper seals. If so, that little bit of pressure might
help keep the pads lightly against the discs. It might even tend to
compensate for some of the run-out all of our discs have.
Has anyone here tried that? With what results?
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc.
www.gmcwipersetc.com
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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] Brake Residual Valves [message #284997 is a reply to message #284993] |
Sat, 15 August 2015 14:19  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Ken Henderson wrote on Sat, 15 August 2015 12:57For vehicles with the Master Cylinder mounted below the calipers, it's
usual to install 1 psi residual valves in the brake lines to prevent fluid
from migrating back to the MC.
I'm thinking about installing some in the GMC's brake lines to try to raise
the brake pedal a little. There's certainly no drain back from our
calipers to the MC, but I suspect there's less than optimal, and equal,
hysteresis in the caliper seals. If so, that little bit of pressure might
help keep the pads lightly against the discs. It might even tend to
compensate for some of the run-out all of our discs have.
Has anyone here tried that? With what results?
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc.
www.gmcwipersetc.com
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Those seals are designed to slightly retract the piston. However, I doubt a slight drag is going to hurt anything except that it will slow cooling of the rotors. I know a lot of work went into the design of those seals to retract the piston so there must have been some concern. I know modern cars will let the calipers drag a bit during rain, but only then--there must be a reason they don't let them drag a bit all the time.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Brake Residual Valves [message #285003 is a reply to message #284993] |
Sat, 15 August 2015 14:21 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Ken, don't know if residual valves would help pedal height or not. I have
found with the all disc systems that it is VERY CRITICAL to eliminate any
and all space between the caliper piston and the brake pad. This is
especially true on the calipers with the emergency brake mechanisms
incorporated into them. There is, on some pads, a center rivet in addition
to the positioning lug that protrudes out far enough to create space
between the caliper piston and the steel backing plate on the pads. That
center rivet should be ground away, being extremely careful not to grind
the positioning lug too. This will allow removal of that thin metal piece
under the rivet head. Double check for that lug to index with the hole in
the caliper piston. When this is correct, and the ebrake is properly
adjusted, all that space is eliminated. The pedal feel is firmer, and
engagement point is higher on the pedal as well. Disc brake pads are
supposed to ride against the rotors when relaxed.
Jim Hupy
Salem, Or.
68 GMC ROYALE 403
On Aug 15, 2015 11:58 AM, "Ken Henderson" wrote:
> For vehicles with the Master Cylinder mounted below the calipers, it's
> usual to install 1 psi residual valves in the brake lines to prevent fluid
> from migrating back to the MC.
>
> I'm thinking about installing some in the GMC's brake lines to try to raise
> the brake pedal a little. There's certainly no drain back from our
> calipers to the MC, but I suspect there's less than optimal, and equal,
> hysteresis in the caliper seals. If so, that little bit of pressure might
> help keep the pads lightly against the discs. It might even tend to
> compensate for some of the run-out all of our discs have.
>
> Has anyone here tried that? With what results?
>
> Ken H.
> Americus, GA
> '76 X-Birchaven w/Cad500/Howell EFI & EBL,
> Manny Brakes & 1-Ton, etc., etc.
> www.gmcwipersetc.com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] Brake Residual Valves [message #285004 is a reply to message #285003] |
Sat, 15 August 2015 14:27 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Ken, I should add to what I just posted, "but not drag on the rotors". The
caliper piston seals are specially designed to retract the piston a few
thousands of an inch to prevent drag. Like Bob said. I would be concerned
thar the residual valves might prevent that from happening.
Jim Hupy
On Aug 15, 2015 12:21 PM, "James Hupy" wrote:
> Ken, don't know if residual valves would help pedal height or not. I have
> found with the all disc systems that it is VERY CRITICAL to eliminate any
> and all space between the caliper piston and the brake pad. This is
> especially true on the calipers with the emergency brake mechanisms
> incorporated into them. There is, on some pads, a center rivet in addition
> to the positioning lug that protrudes out far enough to create space
> between the caliper piston and the steel backing plate on the pads. That
> center rivet should be ground away, being extremely careful not to grind
> the positioning lug too. This will allow removal of that thin metal piece
> under the rivet head. Double check for that lug to index with the hole in
> the caliper piston. When this is correct, and the ebrake is properly
> adjusted, all that space is eliminated. The pedal feel is firmer, and
> engagement point is higher on the pedal as well. Disc brake pads are
> supposed to ride against the rotors when relaxed.
> Jim Hupy
> Salem, Or.
> 68 GMC ROYALE 403
> On Aug 15, 2015 11:58 AM, "Ken Henderson" wrote:
>
>> For vehicles with the Master Cylinder mounted below the calipers, it's
>> usual to install 1 psi residual valves in the brake lines to prevent fluid
>> from migrating back to the MC.
>>
>> I'm thinking about installing some in the GMC's brake lines to try to
>> raise
>> the brake pedal a little. There's certainly no drain back from our
>> calipers to the MC, but I suspect there's less than optimal, and equal,
>> hysteresis in the caliper seals. If so, that little bit of pressure might
>> help keep the pads lightly against the discs. It might even tend to
>> compensate for some of the run-out all of our discs have.
>>
>> Has anyone here tried that? With what results?
>>
>> Ken H.
>> Americus, GA
>> '76 X-Birchaven w/Cad500/Howell EFI & EBL,
>> Manny Brakes & 1-Ton, etc., etc.
>> www.gmcwipersetc.com
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
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| Re: [GMCnet] Brake Residual Valves [message #285009 is a reply to message #285004] |
Sat, 15 August 2015 14:47 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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I used a 2lb valve on the rear brakes when I went with all discs. Couldn't have been happier with the results. I always check the heat with my IR gun whenever I stop and have found NO heat issues at all. It sure brought the pedal up for sure. I think there is enough run out on the rear discs that it plays havoc with pedal height. I only used the vale on the rear brakes BTW.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: [GMCnet] Brake Residual Valves [message #285018 is a reply to message #285017] |
Sat, 15 August 2015 15:43 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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Bob de Kruyff wrote on Sat, 15 August 2015 14:41""Disc brake pads are
supposed to ride against the rotors when relaxed.""
Absolutely not!
OOPS--I posted before I read your second post Jim--sorry !
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Brake Residual Valves [message #285049 is a reply to message #285004] |
Sat, 15 August 2015 18:33 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Jim, et al,
I don't know why I referred to 1 psi residual valves -- I meant 2 psi, of
course.
Yes, I understand that the caliper seals are SUPPOSED to retract the
pistons minutely. What I'm not confident of is that the performance of
what we get these days come anywhere close to the original specs; it seems
logical to me that the residual valves might be more precise.
Since I don't use parking brake calipers, I didn't have to make the mod
you're talking about. And I checked all the drums for run out, winding up
with about 0.005" max.
I like Hal's experience, so I think I'll go ahead and try it -- 'tho not
right away since we're leaving Tuesday for the Rhine River cruise with the
W. Coast GMCers.
Ken H.
On Sat, Aug 15, 2015 at 3:27 PM, James Hupy wrote:
> Ken, I should add to what I just posted, "but not drag on the rotors". The
> caliper piston seals are specially designed to retract the piston a few
> thousands of an inch to prevent drag. Like Bob said. I would be concerned
> thar the residual valves might prevent that from happening.
> Jim Hupy
> ...
>
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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] Brake Residual Valves [message #285053 is a reply to message #285049] |
Sat, 15 August 2015 18:43 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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O.k. Ken we will see you in Switzerland on Wednesday. Looking forward to
this trip.
Jim Hupy
On Aug 15, 2015 4:34 PM, "Ken Henderson" wrote:
> Jim, et al,
>
> I don't know why I referred to 1 psi residual valves -- I meant 2 psi, of
> course.
>
> Yes, I understand that the caliper seals are SUPPOSED to retract the
> pistons minutely. What I'm not confident of is that the performance of
> what we get these days come anywhere close to the original specs; it seems
> logical to me that the residual valves might be more precise.
>
> Since I don't use parking brake calipers, I didn't have to make the mod
> you're talking about. And I checked all the drums for run out, winding up
> with about 0.005" max.
>
> I like Hal's experience, so I think I'll go ahead and try it -- 'tho not
> right away since we're leaving Tuesday for the Rhine River cruise with the
> W. Coast GMCers.
>
> Ken H.
>
>
> On Sat, Aug 15, 2015 at 3:27 PM, James Hupy wrote:
>
>> Ken, I should add to what I just posted, "but not drag on the rotors".
> The
>> caliper piston seals are specially designed to retract the piston a few
>> thousands of an inch to prevent drag. Like Bob said. I would be concerned
>> thar the residual valves might prevent that from happening.
>> Jim Hupy
>> ...
>>
> _______________________________________________
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| Re: [GMCnet] Brake Residual Valves [message #285057 is a reply to message #285053] |
Sat, 15 August 2015 19:01 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Right! Me too -- except the flights (I like to see where I'm going). :-)
Ken H.
On Sat, Aug 15, 2015 at 7:43 PM, James Hupy wrote:
> O.k. Ken we will see you in Switzerland on Wednesday. Looking forward to
> this trip.
> Jim Hupy
> On Aug 15, 2015 4:34 PM, "Ken Henderson" wrote:
>
>> Jim, et al,
>>
>> I don't know why I referred to 1 psi residual valves -- I meant 2 psi, of
>> course.
>>
>> Yes, I understand that the caliper seals are SUPPOSED to retract the
>> pistons minutely. What I'm not confident of is that the performance of
>> what we get these days come anywhere close to the original specs; it
> seems
>> logical to me that the residual valves might be more precise.
>>
>> Since I don't use parking brake calipers, I didn't have to make the mod
>> you're talking about. And I checked all the drums for run out, winding
> up
>> with about 0.005" max.
>>
>> I like Hal's experience, so I think I'll go ahead and try it -- 'tho not
>> right away since we're leaving Tuesday for the Rhine River cruise with
> the
>> W. Coast GMCers.
>>
>> Ken H.
>>
>>
>> On Sat, Aug 15, 2015 at 3:27 PM, James Hupy
> wrote:
>>
>>> Ken, I should add to what I just posted, "but not drag on the rotors".
>> The
>>> caliper piston seals are specially designed to retract the piston a few
>>> thousands of an inch to prevent drag. Like Bob said. I would be
> concerned
>>> thar the residual valves might prevent that from happening.
>>> Jim Hupy
>>> ...
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
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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] Brake Residual Valves [message #285058 is a reply to message #285057] |
Sat, 15 August 2015 19:06 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Hands on the yoke kind of guy, I bet. They might give you a cockpit tour,
heck, the autopilot probably is flying most of the time anyway.
Jim Hupy
On Aug 15, 2015 5:02 PM, "Ken Henderson" wrote:
> Right! Me too -- except the flights (I like to see where I'm going). :-)
>
> Ken H.
>
>
> On Sat, Aug 15, 2015 at 7:43 PM, James Hupy wrote:
>
>> O.k. Ken we will see you in Switzerland on Wednesday. Looking forward to
>> this trip.
>> Jim Hupy
>> On Aug 15, 2015 4:34 PM, "Ken Henderson" wrote:
>>
>>> Jim, et al,
>>>
>>> I don't know why I referred to 1 psi residual valves -- I meant 2 psi,
> of
>>> course.
>>>
>>> Yes, I understand that the caliper seals are SUPPOSED to retract the
>>> pistons minutely. What I'm not confident of is that the performance of
>>> what we get these days come anywhere close to the original specs; it
>> seems
>>> logical to me that the residual valves might be more precise.
>>>
>>> Since I don't use parking brake calipers, I didn't have to make the mod
>>> you're talking about. And I checked all the drums for run out, winding
>> up
>>> with about 0.005" max.
>>>
>>> I like Hal's experience, so I think I'll go ahead and try it -- 'tho
> not
>>> right away since we're leaving Tuesday for the Rhine River cruise with
>> the
>>> W. Coast GMCers.
>>>
>>> Ken H.
>>>
>>>
>>> On Sat, Aug 15, 2015 at 3:27 PM, James Hupy
>> wrote:
>>>
>>>> Ken, I should add to what I just posted, "but not drag on the
> rotors".
>>> The
>>>> caliper piston seals are specially designed to retract the piston a
> few
>>>> thousands of an inch to prevent drag. Like Bob said. I would be
>> concerned
>>>> thar the residual valves might prevent that from happening.
>>>> Jim Hupy
>>>> ...
>>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
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