Handling/Ride improvements

[Don Bradner]

Some of you may recall that I asked if anyone here had ever had a Ride
Performance Assessment done on a Bird by Henderson's Lineup in Grant's Pass,
Oregon. Didn't hear from anyone who had, just one recommendation for another
place and Tom's very negative view of the idea.

Our first 2K miles or so were mostly freeway, and I would class the overall
handling/ride on freeways as good. I was therefore surprised on our recent trip
up the coast of Oregon and Washington at how poorly it rode the many
washout-dips on 101. Porpoise and sway was the order of the day!

I decided that it would be worth the $150 cost of the assessment to see what a
pro thought, and we took Blue Thunder into Grant's Pass this past Wednesday.
Their shop foreman did our assessment drive, and he did not feel that the ride
was exceptionally bad, but did agree that it could be better. He recommended, in
order of importance:

1. Adjust the existing front Konis (presumably a replacement by another owner)
to a stiffer ride.

2. Add their motion-control units to the air bags.

3. Replace the original shocks on the rear with Koni FSDs.

The first item turned out to be impossible - the shocks simply would not take an
adjustment. They tried both on (releasing the bottom end) and off the coach on
the bench. All they would do was spin. They were also very difficult to expand
and contract.

Replacing the shocks was not possible on the spot, because of the three
different part numbers needed (90-2490SP1 in the front, 9005-1025 on the
drivers, 8805-1010 on the tag) only the 8805 is a stock part for them, and the
various sources they use, including KoniRV, did not have the others in stock
either.

Item 2 is an interesting one, and a hard decision. The reason it is hard is that
you have to pay a lot for some very small parts. The MCUs are sold (exclusively
so far as I can tell) under Henderson's Steer Safe brand, but are made by
Donvel. They are about the size of a shotgun shell, and their purpose is to
allow normal fill-and-dump flows to each airbag, but resist sudden flow that
occurs when a bag is compressed or extended by going over a curb/bump or
dropping into a hole.

The most common installation is inline in typical plastic airlines, as near the
bag as possible. Fairly simple installation, and they run I think $185 a pair.
For hard-plumbed installations like the Bird, they have units that screw into
the top of the bag, then the airline is attached to the unit. Those are newer
designs and run $250 per pair.

I found a few postings on the internet that attested to them working well, and
none that said they didn't, although there were definite gripes about the price!

My tolerance for cost when it comes to ride/handling/safety may be higher than
most - I decided to go for it. They had 8 of them of the necessary size (there
are 7 units depending on pipe size and vehicle weight), so we did everything but
the tags.

We will likely go through there in September and get all of the shocks replaced.
With a glass-half-full perspective, we are able to evaluate the effect of the
MCUs with no other changes to the system.

Conclusion: significant reduction in sway. Flatter through corners. The most
obvious test is a speed bump taken at an angle. Before, when the drivers would
cross the bump, the coach would rock back and forth in a major way, now it just
tilts up as one side goes over, then the other way as the other side crosses,
then back to level.

The run home from Grant's Pass involves US 199 to Crescent City. That is about a
good a test run for cornering as you can find. I won't say the MCUs made the
drive fun, but I was a lot less worried about bouncing off things than in the
past. That will always be a bit of a paranoid run for me - I did bounce off a
guard-rail in the past on that highway in an SOB; I could swear I had enough
room, but I rocked outward just enough to hit. No scrape, just a linear crease
about 20 feet long.