Dalej suggested a thread to help define some of the terms that are used to describe a truck’s stability/handling characteristics when hauling a truck camper. Here are some ideas we came up with, feel free to add any observations that you may have.
Sway - generally a slow side to side rolling/rocking motion, also seen as a general lack of upright stability Caused by: many things, including overloading, high CG, inadequate swaybars, inadequate springs, inadequate shocks, undersized tires, low tire pressure, etc Controlled/reduced by: DRW, stiffer springs, airbags, Timbrens, Supersprings, swaybars, stiffer shocks, etc
Bounce – excessive vertical up and down motion Caused by: inadequate suspension dampening, weak springs, etc Controlled/reduced by: stiffer shocks, stiffer springs, etc
Porpoising - front to back pitching motion Caused by: truck suspension not tuned to road conditions, excessive truck frame flexing, etc Controlled/reduced by: cabover struts, adjustments to suspension
Sag – truck suspension compression from normal/empty; measured at the bumpers and most pronounced at the rear. Caused by: overloading, inadequate factory springs, lack of aftermarket overload springs such as Supersprings, airbags, Timbrens, etc Controlled/reduced by: DRW, stiffer springs, airbags, Timbrens, Supersprings, etc
Lean - camper/truck leans to the driver's side or passenger's side even while at rest. Caused by: camper much heavier on one side than the other, or truck springs weaker on one side, etc Controlled/reduced by: airbags, replace defective spring, etc
What else???
Brad
* This post was
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edited 08/13/06 01:04pm by BradW *
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On edit: After reading DandE's post, I spent some time looking at anti-sway bars. DandE was right. So I have edited this post to remove misleading data. My experiences lead me to my earlier post, but they apparently lead me to an erroneous conclusion. So, I stand corrected and better informed. For fishtailing, one apparently wants traction bars. At least, according to the Roadmaster site.
* This post was
edited 08/10/06 03:43pm by Hey there *
2001 Silverado 3500 DRW CC LB 6.0
1993 Lance Squire Lite 150 (8'6")
2001 Fleetwood Caribou 11J (11'6")
Hi again,
I would like to comment on porpoising. I have found, that my rig can porpoise if the front Ranchos are set too low. So, when I start to get some porpoising, I stop and rachet the Ranchos up a couple notches. Has worked so far.
On edit: Porpoising is when the front end goes down as the back end goes up and vice versa. Both ends of the truck are bouncing at the same time; but each end is bouncing in the opposite direction of the other. So what one has to do is to stop/control bounce at both ends of the truck.
One could add "Bump Steer" and in the case of 2G Dodge's.... "Death Wobble."
ON EDIT:
BUMP STEEER: Definition: The tendency of a vehicle to suddenly veer or swerve to one side when hitting a bump or dip in the road. The condition is caused by uneven toe changes that occur as a result of the steering linkage or rack not being parallel with the road surface. This causes the wheels to change toe unevenly as the suspension undergoes jounce and rebound.
DEATH WOBBLE: (parahrased as applicable to second generation Dodge trucks) The tendency for the uncontrolable (at high speeds) out of phase cyclical vibrations in the steering system after hitting a hole, bump, item etc...in the road. NOTE to reader: I never experienced it, but from reading from those who have, it is a very heart pounding, unpleasant experience. Refer to TURBO DIESEL REGISTER searching keyword "death wobble" for more complete understanding.
* This post was
edited 08/10/06 07:01pm by d3500ram *
2005 Dodge 3500 SRW, Qcab long bed, NV-6500, diesel, 4WD, Helwig, 9000XL,
Nitto 285/70/17 Terra Grapplers, Honda eu3000Is, custom overload spring perch spacers.
2008 NorthStar Arrow short bed.
We might mention that sway is referring to a different issue in the tow vehicle forum, for new folks that are doing a search on this term. On that forum they are talking about an inability to drive straight due to the trailer forces acting on the tow vehicle.
Also I have talked to some folks that had wandering problems with brand new 19.5 inch tires due to them following grooves in the road. This seems to go away after the tires have broken in.
I think Sway should be redefined. Side to side roll (The top of the camper moving side to side) is controlled by the "sway bar" but is better defined as roll. However sway in handling terms is the side to side motion of the back of the vehicle. it might be caused by a trailer or a large overhanging camper or the center of gravity behind the rear axle. This type of motion will not be cured with a sway bar. You need to look at tires, hitch set up (if applicable) and/or moving the center of gravity forward. The "Death Wobble " is caused by the shocks inability to control the spring. People beef up there suspensions with air bags and stiffer springs, even the Timbrens act as just a real stiff spring. If you don't have the shock to control the extra spring rate you get all kinds of unwanted suspension motion. I'm coming at this from many years of racing many different types of cars. I have also hauled around a couple of different TC's for 11 years as well as trailers of all shapes and sizes. I will not profess to be the "Know it all" just presenting my experience.
I think dicussions like this are valuable so that more people understand what is happening to their suspension when things are loaded up.
Drive safe out there.
2008 PSD F350 CC DRW 6X6
2001 Lance 961, solar, Polar cub, EU2000.
20' Pace enclosed car trailer
Miata race car, Porta Boat, Traxter Max
CTSDIESEL wrote: I think Sway should be redefined. Side to side roll (The top of the camper moving side to side) is controlled by the "sway bar" but is better defined as roll. However sway in handling terms is the side to side motion of the back of the vehicle. it might be caused by a trailer or a large overhanging camper or the center of gravity behind the rear axle. This type of motion will not be cured with a sway bar. You need to look at tires, hitch set up (if applicable) and/or moving the center of gravity forward. The "Death Wobble " is caused by the shocks inability to control the spring. People beef up there suspensions with air bags and stiffer springs, even the Timbrens act as just a real stiff spring. If you don't have the shock to control the extra spring rate you get all kinds of unwanted suspension motion. I'm coming at this from many years of racing many different types of cars. I have also hauled around a couple of different TC's for 11 years as well as trailers of all shapes and sizes. I will not profess to be the "Know it all" just presenting my experience.
I think discussions like this are valuable so that more people understand what is happening to their suspension when things are loaded up.
Could not have been better described. Dampen vs spring action, a reminder of engineering days.
Bob
Bob & Jan
25C106 BIGFOOT Loaded Followed by a Regal LX 1750
2006 Dodge Ram 3500 4X4 DRWRhino Liner & Rubber Bed Mat
Tork Lifts Front and Back Fastguns Superhitch Super Truss 32"
And a Pumpkin Orange Rubi in tow
Another stability term that is important for us new guys to be aware of is CENTER OF GRAVITY. This has a tremendous importance in the stability equation. Most camper dealers tell us how far horizontally the center of gravity is from the front of the bed or the back. Most of the posts ive found seem to indicate an increase in wandering with a cog behind the rear wheels and of course is not recommended by any truck manufacturer.
None of the manufacturers give a basic vertical center of gravity which would be just as important to take into account when you are loading. I guess the rule of thumb would be to keep all weight as low as possible(as many have said). The higher the vertical cog gets the worse the sway/roll. It would really be interesting to see a comparison of similar size campers by different manufacturers that were actually tipped to check the vertical center of gravity differences.
* This post was
edited 08/11/06 04:52pm by dalej *
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