Home » Public Forums » GMCnet » Re: [GMCnet] Gary Bovee
| Re: [GMCnet] Gary Bovee [message #115533] |
Fri, 18 February 2011 14:13  |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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Maybe a bit of clarification is in order. The standard system can certainly be
called "automatic leveling", but to call it an "active" system would be a
stretch. The leveling capability is far too slow to respond to any normal road
inputs unless they are present for a long time, like a minute. Things like
gusts and normal curves, etc are not present for long enough to allow a
response. I suppose a continuous crosswind or road camber might be the
exception. Most coaches that I've seen, including mine, have a working leveling
system. With regard to other comments, the aerodynamic drag will generally be
lower if the rear is slightly higher than the front. This is because the air
velocity under the coach, a non-streamlined area will be reduced. A reduced
turning radius with a higher rear end?? I can't come up with a logical
explanation for that. As for "push" from other vehicles, the same comment as
above applies - for most vehicles, adverse response to a crosswind or gust is
reduced with a positive "rake." (front lower than the back). Sorry, but I just
can't make any of that make sense. Others have stated that lowering the rear
will increase the castor angle of the front wheels, but it would take a lot of
height change to make a difference. For a short-wheelbase coach a 1 inch change
in height will change the castor angle by only 0.4 degrees, Is that enough to
make a difference? I don't think so.
Gary Casey
'73 23'
However, I think it is important to expand on what JimK said. The GMC was
designed to have an ACTIVE rear air suspension. That means that as driving
conditions change, the system stays level without the driver having to adjust
the air system. I've never actually driven a GMC that had a working active
system, but that was the intent 30+ years ago. The wireless system is a STATIC
air system, meaning it will not automatically adust for shifts in weight,
crosswinds?, or sweeping turns to relevel the coach automatically.
I'd imagine that a working active system is a real treat to drive, but I wonder
how often it actually makes a difference. I find that I raise and lower my bags
depending on what kind of driving I'm doing. The bags go up when I'm doing local
or windy road driving to cantor the coach forward and improve the turning radius
(and yes it does help as I've proved in my driveway. I can't k-turn around at
the top with the bags at the "correct" height, but bags most of the way up and I
can make it around in a few k-turns), they go down when I'm on the highway and
tracking a straight line as a low back end relieves a large amount of steering
movement and push from other vehicles.
I've often thought the "correct" height was a happy medium GM engineers made up
because they were afraid people would not understand the advantages of raising
and lowering the rear end manually. Of course, if I'm right I always kind of
wondered why they just didn't add a "town" and "highway" setting to the
controls.
--
Thanks,
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| Re: [GMCnet] Gary Bovee [message #115539 is a reply to message #115533] |
Fri, 18 February 2011 15:09  |
jknezek
Messages: 1057
Registered: December 2007
Karma: 5
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Senior Member |
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| Gary Casey wrote on Fri, 18 February 2011 15:13 |
Maybe a bit of clarification is in order. The standard system can certainly be called "automatic leveling", but to call it an "active" system would be a stretch. The leveling capability is far too slow to respond to any normal road inputs unless they are present for a long time, like a minute. Things like
gusts and normal curves, etc are not present for long enough to allow a response.
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I agree with this completely. In fact, in my original response I had question marks after crosswind and used "sweeping curves" because you are right that it would take a bit of time in an imbalance to cause a successful reaction, but eventually it would react, making it active to a degree.
| Gary Casey wrote on Fri, 18 February 2011 15:13 |
A reduced turning radius with a higher rear end?? I can't come up with a logical explanation for that.
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I actually can't explain this either, except for the fact that it is true for my GMC. I've tested it a few times in my driveway, with my wife directing. I thought the first time it happened it was an optical illusion making me think I had less room front and back from the seat position. With her directing, it takes that out of the equation as she ensures I use all the space available. I have a limited amount of space to make a series of little K-turn movements to get the coach facing downhill. I simply cannot do it with the rear at what I call the normal ride height. Pump the bags up almost to the top, and sure enough I can get around. Perhaps "turning radius" is the wrong phrase, but for some reason I can make the tight turns with the rear up, but not in normal.
| Gary Casey wrote on Fri, 18 February 2011 15:13 |
As for "push" from other vehicles, the same comment as above applies - for most vehicles, adverse response to a crosswind or gust is reduced with a positive "rake." (front lower than the back).
Gary Casey
'73 23'
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Interesting. I'd say it's in my head but my wife agrees with me. Maybe great minds imagine things alike? (I'm sticking with great. Never know when my wife might read one of these comments) Either way, I don't feel as pushed by a passing 18 wheeler with my bags lower than higher. I also had a decent amount of play in my steering until working on it this winter. If the bags were high on the highway, I worked a lot harder at going straight than if the bags were lower. All my evidence is my own experience, but I'm pretty confident in what I've felt. Who knows, maybe something is wrong with my front and rear suspension, although I had a good long look at them this winter and can't see anything unusual now that I've replaced the intermediate steering shaft.
Thanks,
Jeremy Knezek
1976 Glenbrook
Birmingham, AL
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| Re: [GMCnet] Gary Bovee [message #115549 is a reply to message #115539] |
Fri, 18 February 2011 15:55 |
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All,
If you live within range of the GMCES Spring Rally you can come and learn a
little more up close and personal about this type of system. I've managed to
convince a member, who installed a similar system, to tell us a bit about
the whole thing.
One thing to keep in mind is that one must manually set the level. Of
course, if you're system is like mine, I do that anyway.
The only real reason, in my mind, for an active system is if a 200-pound
person decides to move from the front to the back such as the driver's seat
to the rear right on the gaucho. Then you'd want to see some change in the
system to compensate for the change of the person.
Still, I think this is a great "substitute" for the original if saving money
and having onboard leveling is a plus. Since the advertised claim is less
than the cost of a solenoid, sensor and pump I'd go for it. In fact, I just
might do that to make my $21,000 coach more attractive to the next buyer.
--
Byron Songer
1978 GMC Royale
Louisville, KY
http://www.gmceast.com
http://web.me.com/bnsonger
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Byron Songer
Full-timing to enjoy the USA
Former owner but still an admirer
GMC paint schemes at -
http://www.songerconsulting.net
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