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| [GMCnet] Disc brake conversion [message #278121] |
Thu, 21 May 2015 07:08  |
Neil Fonville
Messages: 68
Registered: May 2014
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I have installed the Manny 4 rear wheel disc brake kit. Did not change the master cylinder or port valve. Pretty sure it has been properly bled but the brakes are horrible. They are far worse than with the drums and not road worthy. The guy helping me thinks it's the master cylinder just too small. I think we still have air in the system somewhere for it to be this bad. I think the right move is to install the PV4 port valve and a larger master cylinder. I thought the only problem with the OEM MC was the reservoir was too small and would need to top off the fluid as the pads wore. Was hoping to use it this weekend but too unsafe now.
I need some input from the brain trust here.
Thanks
Neil Fonville
Allen, TX
75 GMC II
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| Re: [GMCnet] Disc brake conversion [message #278123 is a reply to message #278121] |
Thu, 21 May 2015 07:44  |
Dolph Santorine
Messages: 1236
Registered: April 2011
Location: Wheeling, WV
Karma: -41
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Neil:
Bleeding the brakes on a GMC motorhome can be a real mother dog.
If you "pedal bled" the brakes, it’s quite possible the master cylinder failed.
The seal on the piston establishes a wear zone where it usually works. When you pedal bleed, it goes beyond that zone, and that and often that causes it to fail.
I’ve seen more than one case where the job took a few days, and the fluid drained out of the master cylinder. It would not pressure up until the MC was "bench bled”
I use a pressure bleeder, and plan on having a lot of fluid move through the system.
Dolph
DE N8JPC
Wheeling, West Virginia
1977 26’ ex-PalmBeach
1-Ton, Sullybilt Bags, Reaction Arms, 3.70 LSD, Manny Transmission, EV-6010
“The Aluminum and Fiberglass Mistress"
> On May 21, 2015, at 8:08 AM, Neil Fonville wrote:
>
> I have installed the Manny 4 rear wheel disc brake kit. Did not change the master cylinder or port valve. Pretty sure it has been properly bled but the brakes are horrible. They are far worse than with the drums and not road worthy. The guy helping me thinks it's the master cylinder just too small. I think we still have air in the system somewhere for it to be this bad. I think the right move is to install the PV4 port valve and a larger master cylinder. I thought the only problem with the OEM MC was the reservoir was too small and would need to top off the fluid as the pads wore. Was hoping to use it this weekend but too unsafe now.
>
> I need some input from the brain trust here.
>
> Thanks
> Neil Fonville
> Allen, TX
> 75 GMC II
> _______________________________________________
> GMCnet mailing list
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| Re: [GMCnet] Disc brake conversion [message #278126 is a reply to message #278121] |
Thu, 21 May 2015 08:19 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Neil Fonville wrote on Thu, 21 May 2015 07:08I have installed the Manny 4 rear wheel disc brake kit. Did not change the master cylinder or port valve. Pretty sure it has been properly bled but the brakes are horrible. They are far worse than with the drums and not road worthy. The guy helping me thinks it's the master cylinder just too small. I think we still have air in the system somewhere for it to be this bad. I think the right move is to install the PV4 port valve and a larger master cylinder. I thought the only problem with the OEM MC was the reservoir was too small and would need to top off the fluid as the pads wore. Was hoping to use it this weekend but too unsafe now.
I need some input from the brain trust here.
Thanks
Neil Fonville
Allen, TX
75 GMC II
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Yup, Same thing happened to me when I went to the Harrison discs on the front bogie. After install, I had low or no pedal, so we spent the better part of a half day trying to bleed them with little improvement. What I came to realize after looking at the caliper while someone pressed hard on the brakes is that the new Harrison caliper brackets were not perfectly parallel to the discs, so when you stepped on the brakes, after the pad made nonparallel contact with the disc, the brackets...under immense hydraulic pressure... actually bent some until the rest of the pad made contact..this all taking up lots of pedal travel. In addition, the pads (Performance Friction) had not yet bedded into the discs. So, I took it out for a ride and smoked the brakes by making MANY repeated hard stops. A little at a time, the pedal started coming up and the braking got better as the pads wore parallel to the disc. Now, I had two new discs to deal with....you have four... multiplying the problem.
You have to keep in mind that the Manny system, the Harrison system, and others, are not factory systems that are designed and made to the exacting tolerances that the factory (GM) made. It is likely...IMO, that your pads need to be worn in. IMO, try taking it out on a deserted road and brake the hell out of it. Now that my brakes are bedded in, I have great braking. JMHO
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: [GMCnet] Disc brake conversion [message #278128 is a reply to message #278121] |
Thu, 21 May 2015 08:37 |
Jeff Marten
Messages: 199
Registered: August 2013
Karma: 1
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Senior Member |
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Bedding the brakes properly makes a huge difference. I do 7-8 hard braking iterations from ~60mph to ~10mph; getting back to 60mph quickly to keep as much heat in the pads as possible. Then drive a few miles to allow the brakes to cool; I do two more sets of 7-8 with cooling time in between. Don't come to a complete stop while bedding them because it can deposit an edge or lip of brake material on the rotor.
1985 Gulf Stream 34' Sun Stream
1964 Falcon 'Vert
1980 Bradley GTE
1999 Chevy Tahoe
2005 Saab 93 Aero
1987 Suzuki Intruder 1400
1978 Glastron/Carlson CV23
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| Re: [GMCnet] Disc brake conversion [message #278129 is a reply to message #278121] |
Thu, 21 May 2015 08:34 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Neil,
I've got 20,000+ miles on Manny Brakes + his One-Ton front end. I've never
been overjoyed with the braking forces, but considered them adequate. I
run the 1-1/4" OEM master cylinder with the combination valve modified to
disable the delay to the front brakes <
http://www.gmcmhphotos.com/photos/g3510-deciphering-the-combination-valve.html>
Over the past 15 years, I've run many different combinations of MC's,
drums, and discs with most available calipers. The Manny Brakes are the
best of the bunch.
With a group of other GMCers, I recently checked the front and rear brake
pressures, along with those on several other GMC's with similar setups. It
was very consistent that we're all using mostly the front brakes -- rear
line pressures are generally 1/2 those at the front. I and others are
pretty convinced that the MC's displacement is not adequate to support the
rear calipers' volume requirements. A larger MC, such as the P-30 will
supply more volume to the rear brakes -- but at the cost of lower pressure
to the front brakes.
Considering the difficulty of completely bleeding GMC brakes, there is a
strong possibility that you still have some air in them, but the MC
displacement is probably a part of the probem also.
Personally, I'm about to install a much larger MC and compensate for the
required higher pedal pressure with a Hydroboost. I'll publish the results
when that's installed -- probably a month from now due to schedule
conflicts.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc.
www.gmcwipersetc.com
On Thu, May 21, 2015 at 8:08 AM, Neil Fonville wrote:
> I have installed the Manny 4 rear wheel disc brake kit. Did not change the
> master cylinder or port valve. Pretty sure it has been properly bled but
> the brakes are horrible. They are far worse than with the drums and not
> road worthy. The guy helping me thinks it's the master cylinder just too
> small. I think we still have air in the system somewhere for it to be this
> bad. I think the right move is to install the PV4 port valve and a larger
> master cylinder. I thought the only problem with the OEM MC was the
> reservoir was too small and would need to top off the fluid as the pads
> wore. Was hoping to use it this weekend but too unsafe now.
>
> I need some input from the brain trust here.
>
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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] Disc brake conversion [message #278133 is a reply to message #278131] |
Thu, 21 May 2015 09:01 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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And
Read here
http://www.machinesoflovinggrace.net/gmc/brakes/ComboValves.html
On Thursday, May 21, 2015, gene Fisher wrote:
> Since you mentioned Mannys name, you should also say this is not his
> problem--IT IS YOUR PROBLEM-
>
> Did you read here?
> http://www.machinesoflovinggrace.net/gmc/brakes/
>
> Mannys kits are the best
>
>
> On Thursday, May 21, 2015, Neil Fonville > wrote:
>
>> I have installed the Manny 4 rear wheel disc brake kit. Did not change
>> the master cylinder or port valve. Pretty sure it has been properly bled
>> but the brakes are horrible. They are far worse than with the drums and
>> not road worthy. The guy helping me thinks it's the master cylinder just
>> too small. I think we still have air in the system somewhere for it to be
>> this bad. I think the right move is to install the PV4 port valve and a
>> larger master cylinder. I thought the only problem with the OEM MC was the
>> reservoir was too small and would need to top off the fluid as the pads
>> wore. Was hoping to use it this weekend but too unsafe now.
>>
>> I need some input from the brain trust here.
>>
>> Thanks
>> Neil Fonville
>> Allen, TX
>> 75 GMC II
>> _______________________________________________
>> 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
>
--
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] Disc brake conversion [message #278134 is a reply to message #278128] |
Thu, 21 May 2015 08:59 |
Neil Fonville
Messages: 68
Registered: May 2014
Karma: 0
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Rob: I have not spoke to Manny yet but will today. I just finished up last night and was really disappointed in the results so far.
I think I'm going to install the P30 MC and a new port valve anyway but wanted to drive it some this weekend. I know it was noted the braking would be bad initially but was expecting the pedal to drop so low. Since I'm on a private airport, I can test on the taxi way. I'm going to get a power bleeder today and try again.
Thanks for the input.
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1975 GMC II
Allen, TX
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| Re: [GMCnet] Disc brake conversion [message #278137 is a reply to message #278133] |
Thu, 21 May 2015 09:09 |
Neil Fonville
Messages: 68
Registered: May 2014
Karma: 0
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Yes, I have read the documentation numerous time before purchase and during installation. My combiner valve is not original. Most likely a PV2 replacement. I did discuss both the MC and valve with Manny. He indicated it would most likely be ok but with the disclaimer of your mileage may vary.
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of gene Fisher
Sent: Thursday, May 21, 2015 9:02 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Disc brake conversion
And
Read here
http://www.machinesoflovinggrace.net/gmc/brakes/ComboValves.html
On Thursday, May 21, 2015, gene Fisher wrote:
> Since you mentioned Mannys name, you should also say this is not his
> problem--IT IS YOUR PROBLEM-
>
> Did you read here?
> http://www.machinesoflovinggrace.net/gmc/brakes/
>
> Mannys kits are the best
>
>
> On Thursday, May 21, 2015, Neil Fonville > wrote:
>
>> I have installed the Manny 4 rear wheel disc brake kit. Did not
>> change the master cylinder or port valve. Pretty sure it has been
>> properly bled but the brakes are horrible. They are far worse than
>> with the drums and not road worthy. The guy helping me thinks it's
>> the master cylinder just too small. I think we still have air in the
>> system somewhere for it to be this bad. I think the right move is to
>> install the PV4 port valve and a larger master cylinder. I thought
>> the only problem with the OEM MC was the reservoir was too small and
>> would need to top off the fluid as the pads wore. Was hoping to use it this weekend but too unsafe now.
>>
>> I need some input from the brain trust here.
>>
>> Thanks
>> Neil Fonville
>> Allen, TX
>> 75 GMC II
>> _______________________________________________
>> 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
>
--
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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1975 GMC II
Allen, TX
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| Re: [GMCnet] Disc brake conversion [message #278138 is a reply to message #278126] |
Thu, 21 May 2015 09:53 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Senior Member |
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Larry wrote on Thu, 21 May 2015 08:19
Yup, Same thing happened to me when I went to the Harrison discs on the front bogie. After install, I had low or no pedal, so we spent the better part of a half day trying to bleed them with little improvement. What I came to realize after looking at the caliper while someone pressed hard on the brakes is that the new Harrison caliper brackets were not perfectly parallel to the discs,
Stop. That is a manufacturing defect, it is not right. The bracket needs to be perfectly square to the rotor. No discussion. If it's not get one that is, Or make it so it is. Brackets should not be 'warp to fit' no way, no how.
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] Disc brake conversion [message #278144 is a reply to message #278129] |
Thu, 21 May 2015 10:37 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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Ken has it right, disc brake caliper pistons are larger than drum brake wheel cylinders and require more displacement to develop the necessary pressure from the same pedal travel. The master cylinder needs a larger bore for the rear brake section.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] Disc brake conversion [message #278146 is a reply to message #278121] |
Thu, 21 May 2015 11:14 |
captjack
Messages: 271
Registered: February 2010
Location: Sebastopol, California
Karma: 1
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Senior Member |
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My brakes have never been better since I installed Manny's kit. I replaced the MC and proportioning valve and used Jim Hupy's brake bleeder. I'm really pleased with my brakes now.
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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| Re: [GMCnet] Disc brake conversion [message #278152 is a reply to message #278151] |
Thu, 21 May 2015 11:35 |
Dolph Santorine
Messages: 1236
Registered: April 2011
Location: Wheeling, WV
Karma: -41
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Senior Member |
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When you change, there is an updated bracket, too.
Dolph Santorine
DE N8JPC
Wheeling, West Virginia
1977 ex-Palm Beach TZE167V100820
1-ton, Sullybuilt Bags, Reaction Arms, 3.70 LSD, Manny Transmission, EV-6010,
> On May 21, 2015, at 12:22 PM, Neil Fonville wrote:
>
> Lots of good info here. Sounds like I may have killed the MC while
> pumping the brakes. Sounds like no harm since I need a larger MC anyway.
> I will pick up the 34mm MC and new valve anyway. Thanks everyone and I¹ll
> report back after I get them changed outŠ
> Neil
>
> _______________________________________________
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> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Disc brake conversion [message #278153 is a reply to message #278151] |
Thu, 21 May 2015 11:39 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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The OEM distribution valve will work with an all discuss system. You need
to disable the hold off spool. Ken Henderson published a detailed process
for this. Unless you are a masochist and just thrive on frustrating
yourself, and your hard brake lines are in good shape, leave the valve in
place and do the modification. Ten minute job. If you Insist upon messing
with all six of those brake line fittings, use lots of penetrating oil and
wire brush where the lines and fittings join. Wait a day, spray some more
stuff, check your vocabulary skills and proceed with stripping, rounding
off, breaking or twisting off brake lines. Your choice. I work on these
things every day. Nearly always twist off one or two. The brass valves most
often will leak brake fluid after you are done. The threads and seats where
the lines sit are poorly formed on most of those offshore produced valves.
But hey, it's your money. Spend it how you see fit.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On May 21, 2015 9:22 AM, "Neil Fonville" wrote:
> Lots of good info here. Sounds like I may have killed the MC while
> pumping the brakes. Sounds like no harm since I need a larger MC anyway.
> I will pick up the 34mm MC and new valve anyway. Thanks everyone and I¹ll
> report back after I get them changed outŠ
> Neil
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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