Paul,
I really do respect opinions of those who have tested GMC mods and are
willing to spread their findings. I have to say though in regard to the 4
air bag system that if there are doubts about the attributes of the system
that one really needs to try it! I have only talked to one person who took
the system off and found after the fact that his unfavorable driving
characteristics were found to be caused by something else. He was too
embarrassed to call Leigh to get the system back!
Look, it really makes sense that the driving characteristics would be
improved. With regard to a 23' with the system, ask Chuck Botts. I put
the set up on his and after his trip back to CA., he said it was a night to
day transformation.
With regard to shocks: I want a shock that will not break even under
extreme conditions, the eyelets, pistons or whatever. Chuck Stoddard
certainly has the credentials and first hand experience to make definitive
statements as to the GMC motorhome suspension. If I were you, I would
listen to what he has to say. I must say though, I have installed KYB and
Delco shocks with favorable results. To Bilsteens credit, they do replace
every shock that have broken eyelets! If I had a Bilsteen that had
catastrophic failure of the piston, you better believe Bilsteen would have
the opportunity to replace it as well!
Although I have talked with many people who use the risers, I do not have
first hand knowledge of them. I am going to get a set for my dumpster to
experience them before I install the 4 air bag system. Make no mistake
though, I will install the 4 air bag system on mine!
I have also been told of the future of the OEM bag being in question.
Personally, I do not have the bucks to fork out needed to repair the air
bag mold, besides the 4 air bag system uses current off the shelf Firestone
air bags that are easily found.
Firestone has looked at the 4 air bag system and is evaluating it for the
future. You may be surprised what the future will bring on this question!
I guess that's why I take the position I do, I recommend products I find
work well. I do not have to worry about offending General Motors or anyone
else for that matter.
There are many great things out there I do not sell- I'm happy to recommend
any of them that prove worthwhile. I purchase parts for my restorations
from many suppliers to get the best performance and value.
>The Cinnabar article isn't from a December issue. It's from their September
>1998/Issue 17, p. 1. The article, titled an Engineer's Perspective, was
>authered by Chuck Aulgur.
>
>The article is referring to Leigh Harrison's four-air bag suspension system,
>and does not include any supporting data, only opinions. You know what they
>say about opinions, they're like r___ ends, everybody's got one. It does
>not address air bag lifters.
>
>I also suspect Al's opinion about the author is correct.
>
>I installed the four-air bag system during the GMCMI Myrtle Beach Rally in
>March 1995 at the same time as I installed Leigh's six-wheel disc brake
>system. As I said the other day in response to an e-mail message asking
>about the wear of carbon metallic brake pads, I have over 40,000 miles
>experience with the system. Compared to the original, I notice a definate
>increase in the fore-to-aft dampening of the ride, and much greater
>stability in truck-rutted asphalt paving. I can't even feel the difference
>when the coach drifts over the joint between the roadway and paved
>shoulders, and have demonstrated such with folded arms not even holding onto
>the steering wheel at the time. When I drift onto an unpaved shoulder,
>there is no problem recovering. I haven't met anyone yet, without Leigh's
>system, who feels very comfortable in running off the edge of the road.
>
>Leigh also claims that the rear-rear axel spring rate is doubled to around
>815 psi, compared to the original. This in turn, makes the brakes on the
>axel able to exert more stopping ability prior to lock-up (which I've never
>experienced thus far).
>
>If you already haven't heard it in a few previous e-mail messages, the
>original air bags are rumered soon to be in short supply, as the molds used
>to make them are supposedly near the end of their life. Then what are you
>going to do??????
>
>I would encourge any doubting Thomas's to go with Leigh during the GMCMI
>rallie's, when he routinely takes people for a demonstration ride. You
>can't believe the stability his coach demonstrates.
>
> Paul Bartz
>
>From: The Hamiltons
>Sent: 12/25/98 8:16 PM
>Subject: GMC: Air Bags
>
> I haven't read the Dec article in the Cinnibar Newsletter and I
>suspect it is excellent based on the quality of other newsletters and
>articles. I am going out on a limb and assume the author never used air
>bag
>risers/lifters and therefore is only making theoretical comments.
>
> I asked a lot of questions before putting a set on in early 1996
>or
>about 13,000 miles ago. Non-users were against them having not used
>them.
>Those that had substantial experience with them on either didn't notice
>any
>difference or some difference.
>
> The air bag pressure is reduced from around 95 psi to about 72 -
>75
>psi. Somewhat less dangerous and damaging if and when a bag explodes.
>The
>air pressure regulator can be reset from a maximum of 120 psi to 100 psi
>-
>that took 30 to 40 seconds off total pump up time. The air pump doesn't
>have
>to labour that last difficult 20 psi.
>
> I contend there is only one suspension change and it's an
>improvement
>with risers/lifters installed. The lower air pressure is off set by the
>increased control arm length and mechanical advantage - no change in
>ride.
>There is no change when lowering the coach. I think it may not go as
>high
>but has not been a noticeable problem in campground levelling. I
>believed I
>detected less sway since installing the risers and asked others for
>their
>opinion. Some noticed no change. Some felt there was less sway, and like
>I,
>could not explain it. Here is a possible reason there is less sway in my
>opinion. The air bag cones cause progressive dampening as the two ends
>of
>the bag are forced further and further to the wider parts of the cones.
>With
>risers on, the bag is on a narrower part of the cone at the same ride
>height
>as before - more force is required to move the air bag from a narrower
>part
>to the wider part, producing more dampening or less sway.
>
> I would be interested in other opinions and experiences.
>
>
> Al Hamilton
> 76
>Eleganza II
>
>Kingston, Ont
>
>
