Porpoising Bluebirds

[David Brady]

Hi Bruce,



Thanks for the input and a sincere thank you for bringing up my
favorite

topic.



I'm running Koni FSD's on the drive and on the tag, and Koni adjustables

on the steer. Yes, Brad and I have tried everything regarding the LXi's

porpoising and I appreciate your input too. I think that "porpoising"
is

the wrong term in this case. The LXi, in it's stock form, doesn't
porpoise.

Ninety percent of the time, it's very composed and very compliant, and

this is why 99.99% of the owners are quite happy and do nothing to

change it's behavior. What it does do is transfer weight violently from

the front to back, and then from the back to front when hitting

a fairly large perturbance in the highway (picture Hwy 10 thru
Louisiana).

As Brad will surely agree, most LXi owners will cringe a little upon

sighting an oil spot on the highway ahead, a sure sign that most
vehicles

experience some sort of suspension "event" upon traversal. Not so in

the LXi. If both front tires hit the dip simultaneously, then the event

is probably no more severe than any other 50K lb vehicle. However,

if the dip is asymmetrical, meaning one front tire hits it first, which
is usually

the case, well... you had better have your seatbelt on cause the bus's
front

tires will hit hard, barely registering any suspension travel, and
instead

toss the bus's weight rearward only to load the rear suspension just
when

the rear tires are hitting the bump. At this point, and thanks to the
SRI air

seat, the driver is catapulted toward the ceiling. The weight transfer,
to-and-

fro, can be so severe you'd think that a front tire or airbag is about
to

blow. I tried everything to compose the bus, tag axle air pressure, tire

air pressures, Koni FSD's, full stiff front Koni's, heavy cargo

weight distribution, finely tuning ride height, countless calls to the
"experts".

Everything improved the problem, but nothing solved it. Not until I

removed the front sway bar. Then nirvana. The anti-sway bar on slide

equipped LXi's is monstrous: 2.125" in diameter and possessing over

4000 lb/in in spring rate. It's capable of creating a 64000 ft-lb
moment, or

torque, at full deflection. It virtually eliminates independent wheel
motion

at the steer axle, and when it winds up - look out!  If your an LXi
owner,

it's gotta go: toss it in the garbage!



As I've learned, the LXi really is capable of a very good ride. It's got

good weight distribution, high tech hour glass shaped air bags,
315/80/22.5

tires, great Koni FSD shocks, and the Ridewell suspension typically
provides

very good independent wheel motion with good roll center and huge, long

life, rubber suspension bushing providing lots of compliance. All

the ingredients are there, but every LXi driver that you talk with will
tell

you that their buses ride rough. I've had one owner tell me that after

purchasing the bus brand new, he traded it 3 weeks later for an H series

prevost because the ride was so rough. I could have saved him some
money...



BTW, how's that Monaco?



David Brady

'02 LXi, NC





brad barton wrote:

Bruce, I think mine are big Koni's, but I can't tell you the model
or capacity.  Strangely enough, the problem seems to be the suspension
was overbuilt with the anti-sway bar rather than underbuilt. 



Brad Barton 00LXiDFW bbartonwx@hotmail.com

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To: WanderlodgeForum@yahoogroups.com

From: birdshill123@yahoo.com

Date: Wed, 4 Jun 2008 21:53:19 +0000

Subject: [WanderlodgeForum] Porpoising Bluebirds

David and Brad:



I have been following your posts on this subject and found your

results very interesting. I worked in a huge truck chassis/spring

shop in my youth. Of course in those days rauckers were macho and

never complained about anything ! Hear that Greg?? One thing I did

learn about pickup trucks was that good shocks ere very important. We

sreviced trucks that went to the oil fields and front suspensions

were always being repaired. he Monroe rep had special shocks built

for these units. My own experience is as follows: factory shocks on

just about any vehicle are usually cheap junk. In 2001 I had a new

Chev Duramax duallie crew cab. We had a 11.5 Alepnlite slide in on

the back. It handld horribly. I dropped the rear shocks and you could

compress them with one hand. Extension could be done by a child.

Naively I took it to the deAler thinking they were faulty. Shop

foreman brough out a new shock. We pumped it a bunch and it was the

same. Installed 4 Rancho 9000's and it became a new truck!! Last year

I took off he Sachs shocks that were factory on our 02 Bounder with a

Freightliner. The shocks looked small enough to be from a Nissan

pickup. Installed new Koni FSD's and I could drive without white

knuckle fever. My point of all this jibberish is: Have you considered

installing different shocks? I dont know what BB uses on the LXI's

but maybe they are not enough shock. I know that Henderson had some

real brutes at Q. Of cousre they were pricey. Once a vehicle starts

porpoising the dynamics just keep it going. Sems to me that som real

shocks would solve the problem. I now that BB uses Konis on some

units but the FSD's are fairly new to the market. Alternatively have

you tried going to Henderson,s? I find them overpriced but they are

experts.



my 2 pesos worth



Bruce



1988 FC35

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