 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:
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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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