Home » Public Forums » GMCnet » A Suggested Modification for GMC coaches
A Suggested Modification for GMC coaches [message #209122] |
Wed, 29 May 2013 09:09 |
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Matt Colie
Messages: 8547 Registered: March 2007 Location: S.E. Michigan
Karma: 7
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As some of you may know, I got what are called reaction arms in this group installed at the most recent Bean Station rally. This system is different than most offered as it uses the original rear drum brakes with parking brake and requires no other changes be made.
Please be aware that I have only 600 miles on this modification and it was not fully functional part of that.
I had hoped to have hard numbers to put in this discussion, but the pavement has been wet every time I had time to conduct such a set of experiments. It is on my list, but that will just have to wait for another day. But, I can tell you the stopping is now very car-like. On a very hard stop, one or more of the rear wheels will lock and it is usually one of the intermediate. I have already dropped the driving habit of increasing the braking until I hear the rear scream and then let up so as not to flat spot another tire.
My evaluation at this time is that this is a very worthwhile mod to add to any GMC motorhome. This is particularly true as it is a single mod only. It will not require anything other than the basic modification to achieve the desired result. The total extent of the modification of your coach is the counter-sinking of the holes that the brake backing plates are currently bolted through.
While admittedly, my coach is lighter than most that should make the braking performance less critical. It might be, and it was adequate, but it did leave a lot to be desired. No longer will I say that. (This a fact that I am very pleased by.) My coach now has brake performance that (as near as I can judge by the accelerometer reading that my smart phone provides) is very car-like. Yes, I can lock some of the rear wheels, but now it is most often an intermediate in skidding on dry pavement. Which wheel will lock up has not been predictable and seems to have more to do with pavement conditions than anything else I can identify.
It is also interesting that the modification is completely reversible. (I can’t imagine why one might choose to do this, but the thought is somewhat comforting.) It would also be possible to complete only half of the installation (I don’t think it would matter which half) and still have the coach road worthy in short order.
Next thing you will probably want to know is what will it cost. The kit as delivered to me at Bean Station was priced at under nine hundred dollars. I can't even guess what shipping might cost, so you will have to get that from JimK. Add in some money for a 7/32 square drive (Snap-On is worth it, CC will probably break at the torque required), brake fluid that you probably need anyway and maybe buy a real bottle of Loctite (the small size). That should be it. You don’t need to up-size the master cylinder or get a sensitized booster (unless you want one).
Is it cost effective?
When I first saw this system and the data Tom and Jim had collected at Amana, I was ready to take one home right then. At that time, the target price was somewhat higher but there were no kits ready to ship. Well, there are now. And, yours will be even better than mine.
Why haven’t I written about it before this?
Because, I had some difficulties on the way home. I did not believe that I could provide an honest assessment of the this modification until I had all the surrounding issues cleared up. Those issues are now cleared. Some of the issues were the direct result of the location and conditions where the installation occurred (the result working on grass and gravel). Some were manufacturing problems that were largely the result of mis-interpretations by a parts supplier and others were caused by the variations between coaches and model years, but they have all been identified and corrected.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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Re: A Suggested Modification for GMC coaches [message #209124 is a reply to message #209122] |
Wed, 29 May 2013 09:35 |
JohnL455
Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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Thanks for the update Matt. At that price point it really is attractive especially if you subtract the cost of 2 flat spotted tires and a front bumper, it's virtually free.
John Lebetski
Woodstock, IL
77 Eleganza II
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Re: [GMCnet] A Suggested Modification for GMC coaches [message #209228 is a reply to message #209173] |
Thu, 30 May 2013 01:22 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
Karma: 9
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Our tests on a 26 foot coach was slightly different than Matt's 23 ft cosch.
The rear wheel lock up was short and at the end when the speed fell down to
around 25mph from 45mph.
Funny why our original disc rear reaction units did not wxibit this
skidding issue.
Tom Prior has been gathering some har data from pros at brake suppliers and
there is an indication that the drum brakes can exibit a stromger friction
than our larger clipers wiyh a larger master cylinder.
On Wed, May 29, 2013 at 2:24 PM, Matt Colie <matt7323tze@gmail.com> wrote:
>
>
> A Hamilto wrote on Wed, 29 May 2013 12:48
> > Matt Colie wrote on Wed, 29 May 2013 09:09
> > > ...On a very hard stop, one or more of the rear wheels will lock and
> it is usually one of the intermediate. ...
> > Are your wheel cylinders the same size on both intermediates and rears,
> or have they been replaced with mismatched ones (15/16 on the rear and
> 1-1/16 on intermediate)?
>
> My coach is Box-Stock.
> It also varies sometime port will lock first and sometimes starboard....
> The better joke is that the temperature surveys always have the rear drum
> Hotter that the intermediate - Go Figure??
>
> Matt - I may like it, but I don't have it all figured out.
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumière (say show-me-air)
> Now with 4 working Rear Brakes
> SE Michigan - Twixt A2 and Detroit
> _______________________________________________
> 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
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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Re: A Suggested Modification for GMC coaches [message #209242 is a reply to message #209122] |
Thu, 30 May 2013 08:16 |
Keith V
Messages: 2337 Registered: March 2008 Location: Mounds View,MN
Karma: 0
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Senior Member |
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remember that drum brakes are self engaging. you apply a little pressure and they wedge them selves in tighter effectively applying more force than you would predict based on pedal pressure.
I wonder if the movement of the backing plate during braking changes the servo rate?
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] A Suggested Modification for GMC coaches [message #209377 is a reply to message #209228] |
Fri, 31 May 2013 00:37 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
Karma: 9
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There are people that believe that the rear back brakes does not do much.
All the GMC shops know that it is almost impossible to guess which
shoes came of which wheel as they all do lot of work.
The one thing the Reaction Arm does is to apply all the force into
braking and non to lifting up he rear of the coach.
Chuck Aulgur can be credited for doing the preliminary work to bring
this to life and working with us.
That is one of the reason we call our disc system, Aulgur Reaction Arm System.
On Wed, May 29, 2013 at 11:22 PM, Jim Kanomata <jimkanomata@gmail.com> wrote:
> Our tests on a 26 foot coach was slightly different than Matt's 23 ft cosch.
> The rear wheel lock up was short and at the end when the speed fell down to
> around 25mph from 45mph.
> Funny why our original disc rear reaction units did not wxibit this skidding
> issue.
> Tom Prior has been gathering some har data from pros at brake suppliers and
> there is an indication that the drum brakes can exibit a stromger friction
> than our larger clipers wiyh a larger master cylinder.
>
> On Wed, May 29, 2013 at 2:24 PM, Matt Colie <matt7323tze@gmail.com> wrote:
>>
>>
>>
>> A Hamilto wrote on Wed, 29 May 2013 12:48
>> > Matt Colie wrote on Wed, 29 May 2013 09:09
>> > > ...On a very hard stop, one or more of the rear wheels will lock and
>> > > it is usually one of the intermediate. ...
>> > Are your wheel cylinders the same size on both intermediates and rears,
>> > or have they been replaced with mismatched ones (15/16 on the rear and
>> > 1-1/16 on intermediate)?
>>
>> My coach is Box-Stock.
>> It also varies sometime port will lock first and sometimes starboard....
>> The better joke is that the temperature surveys always have the rear drum
>> Hotter that the intermediate - Go Figure??
>>
>> Matt - I may like it, but I don't have it all figured out.
>> --
>> Matt & Mary Colie
>> '73 Glacier 23 Chaumière (say show-me-air)
>> Now with 4 working Rear Brakes
>> SE Michigan - Twixt A2 and Detroit
>> _______________________________________________
>> 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
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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Re: [GMCnet] A Suggested Modification for GMC coaches [message #209429 is a reply to message #209427] |
Fri, 31 May 2013 13:34 |
jhbridges
Messages: 8412 Registered: May 2011 Location: Braselton ga
Karma: -74
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Senior Member |
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We call that 'Normal Atlanta driving". Nick is researching shipping for me at the moment. Gonna be the next upgrade on the 23'
--johnny
'76 23' transmode norris
'76 palm beach
________________________________
From: Matt Colie <matt7323tze@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Friday, May 31, 2013 2:27 PM
Subject: Re: [GMCnet] A Suggested Modification for GMC coaches
We had an occasion to demonstrate the braking capability today. It was kind of an "OH 5H1T" test. I will not go into any particulars of the other driver's heritage.....
I will, however, revise my description of braking from "Car Like" to "Throwing out a Heavy Anchor on a short piece of Chain".
Matt - At the MIller's a little later than expected.
--
Matt & Mary Colie
'73 Glacier 23 Chaumière (say show-me-air)
Now with 4 working Rear Brakes
SE Michigan - Twixt A2 and Detroit
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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Re: [GMCnet] A Suggested Modification for GMC coaches [message #209450 is a reply to message #209429] |
Fri, 31 May 2013 16:02 |
LarryInSanDiego
Messages: 336 Registered: September 2006
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Senior Member |
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Having not seen either drum or disc version of the reaction arm system, let alone side by side, I am wondering: if I buy the drum version, and then convert to disc later, what (how much really in $$$) would need to be purchased besides the disc system to convert the reaction arm system from drum to disc?
Being on a budget, I'd like to install the reaction arm system with my existing brakes, and convert to disc as finances allow at a later time.
Any estimate of what is involved? Thanks.
Larry Engelbrecht
San Diego, CA
'73 26' ex-Glacier
TZE063V100319 03/07/73
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Re: [GMCnet] A Suggested Modification for GMC coaches [message #209452 is a reply to message #209450] |
Fri, 31 May 2013 16:16 |
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Matt Colie
Messages: 8547 Registered: March 2007 Location: S.E. Michigan
Karma: 7
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Senior Member |
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LarryInSanDiego wrote on Fri, 31 May 2013 17:02 | Having not seen either drum or disc version of the reaction arm system, let alone side by side, I am wondering: if I buy the drum version, and then convert to disc later, what (how much really in $$$) would need to be purchased besides the disc system to convert the reaction arm system from drum to disc?
Being on a budget, I'd like to install the reaction arm system with my existing brakes, and convert to disc as finances allow at a later time.
Any estimate of what is involved? Thanks.
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Larry,
You want to talk to Tom Pryor Directly. He has addressed this and has many optional ways that he can make his kit work.
He is on the net here, so hopefully you can PM him.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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