Home » Public Forums » GMCnet » [GMCnet] Tid Bit. When making changes to your GMC. Does that change differ from proven automotive engineering practices.
| [GMCnet] Tid Bit. When making changes to your GMC. Does that change differ from proven automotive engineering practices. [message #332250] |
Thu, 17 May 2018 17:26 |
fbhtxak
Messages: 191
Registered: April 2006
Karma:
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Senior Member |
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Jerry,
'Comments on your remarks of 15May'18 -
Except for EFI/EBL, the drivetrain/suspension on my '78 Royale is also "bone
stock", with properly maintained/adjusted OEM front suspension, rear
suspension and brakes. I have never had cause for concern about its
safety/handling over 25 years of ownership and almost 150K miles (including
24K miles at time of purchase). I similarly drive it very conservatively in
that I, too, have avoided a "full lock brake situation, never flat spotted a
tire and never heated the brakes to fade". Its overall handling, while dated
by today's standards, has always been satisfactory, both in urban and
highway driving. I don't tow a car so I tend to drive it at posted highway
speeds. While not necessarily a compliment, its handling is not far removed
from the heavy Chrysler Town/Country and Mercury Colony Park station wagons
of the era that I owned.
Before buying the Royale in 1993, the original owner (A CPA in LaJolla, CA)
advised me to talk with Wes Caughlin, owner of Cinnabar Engineering, about
upgrades then available for GMCMhs. After I established my
professional/technical credentials with Wes, we had a productive
conversation. His view then (and still is) is that the difference between an
OEM coach with "proper ride height, proper alignment, and proper inflation
of the tires." and a coach with some/all available upgrades "will be at the
margins" . He noted, however, that owners should do "whatever appeals to
them" in applying upgrades vs. preserving the OEM
drivetrain/suspension/braking. While Cinnabar is an OEM parts proponent, Wes
was complimentary of entrepreneurs who develop alternatives to "OEM". He,
though, observed that few, if any, have the capability to do the level of
product development/testing done by GM on the parts used for the OEM coach.
Further to the OEM braking with front discs and rear drums, it compares
favorably to the 28' Airstream coach that I have in Alaska. The Airstream
has-all wheel disc braking (example:
http://www.viewrvs.com/motorhome/airstream/1981/1981-airstream-motorhome-28-
k.php) and is about the same weight as the Royale.
Fred
Fred Hudspeth
1978 Royale (TZE 368V101335) - Tyler, TX
1982 Airstream Excella (motorhome) - Cooper Landing, Alaska
Message: 7
Date: Tue, 15 May 2018 07:20:26 -0700
From: Gerald Work
To: GMC Motor Home Post
Subject: [GMCnet] Tid Bit. When making changes to your GMC. Does that
change differ from proven automotive engineering practices.
Message-ID:
Content-Type: text/plain; charset=utf-8
I can?t say I ever did a skid pad comparison, but I can share some direct
experience with stock and modified coaches. Our 1977/1994 Clasco was bone
stock with a good, tight front end, stock air bag rear and well adjusted
stock brakes. Our 1978 Royale had just about everything done one could do
to ?modernize? a GMC. That included the one ton front end, six wheel
reaction arm disk brakes, etc. But, it retained the stock one air bag system
as well. Both had the same wheels and tires aired to the correct pressures
for measured weight on each wheel. Both had the wireless air system with
the ride height set to factory specs. Both were aligned properly with as
much caster as they would allow and still be the same on both sides. The
offset bushing allowed a bit more caster in the Royale than in the Clasco -
one degree difference as I recall. The Royale was heavier by a few hundred
pounds than the Clasco due mainly to the fact that it had four 6v golf cart
batteries mounted in the rear PS compartment where the Clasco had one 4D 12v
AGM and one group 31 AGM house battery bank centered in the rear.
Bottom line, both drove equally as well and we put a lot of wonderful miles
on each of them. The only difference I could ever really tell from the
drivers seat was a tendency of the Royale to shimmy a bit on low speed hard
turns going up hill under acceleration. Other than that, they both were one
hand on the steering wheel rides. I never had either one in a full lock
brake situation, never flat spotted a tire and never heated the brakes to
fade. Probably more from placebo effect than anything objective, I always
thought I preferred the brakes in the Royale even though the pedal went
further towards the floor and the bogy mount location for the reaction arms
had a tendency to come loose from time to time.
My experience with these two coaches over a number of years is that proper
ride height, proper alignment, and proper inflation of the tires made more
difference in ride and handling than all the mods put together. I never did
understand why the Royale with the six wheel reaction arm disk brakes and
the larger front rotors from the one ton front end didn?t really stop any
better than the well adjusted stock brakes on the Clasco. That might have
been because I am a very conservative driver and never put myself in a
position where I had to rely on them in an extreme emergency.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple
building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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