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Is it bad for your suspension?

Discussion in 'Commercial Snow Removal' started by digger242j, Sep 25, 2002.

  1. digger242j

    digger242j Senior Member
    Messages: 672

    It's something I've always heard, but never been sure of whether it's true or not....

    I mentioned today that it we might as well load one of our trucks with salt (bagged, not bulk) because it won't be doing anything else before the first time it snows anyway. It was suggested that to sit with all that weight on would be "bad for the suspension". Over the years I've even been told not to let a load of dirt sit in a 10 ton dumptruck overnight for the same reason. It seems to me that it would be even worse on your suspension to go bouncing down the road with all that weight on.

    It's not going to make a whole lot of difference because once the season begins the truck's going to have all that weight on all the time--sitting and plowing--until over the course of the night's work the salt gets used up, and then it'll get loaded all over again and wait for the next snow, but it did get me to wondering....

    Anybody have an expert opinion? :confused:
  2. sno-mover

    sno-mover Senior Member
    Messages: 274

    I dont think its the best thing for it. It would probly wear it out a lot faster. Also even though its baged just the fact of it being in the air will rot the truck a lot faster. salt is a real killer
  3. Pelican

    Pelican 2000 Club Member
    Messages: 2,075

    Putting a heavy stationary load on your vehicle will accelerate the weakening of your springs, causing them to take an ever so slight new "set" each time it is done. This "set" is the position of the spring at its unloaded state, and the spring's capacity will be slightly reduced at each new set. In other words, the spring will no longer return to its "as new" unloaded position.
  4. Sndun

    Sndun Member
    Messages: 56

    I would also imagine that it wouldn't be too kind on the tires either.
  5. digger242j

    digger242j Senior Member
    Messages: 672

    Pelican's explanation is what I expected to hear as the reasoning behind the theory about it being bad for your suspension. It is a reasonable explanation.

    My question is though, is it true?

    There's a certain amount of distance your springs will flex when you put a load on them. Just for the sake of arguement, let's say it's eight inches. Truck empty at the curb, the springs are not compressed and there's eight inches there. Truck loaded, driving down the road and hits a great big bump, and bottoms out--momentarily there are *no* inches of space. When you put a load in the truck as it sits still, the springs might compress three inches. And nothing moves any further than that until you begin driving. As you drive, the springs will work up and down as they're supposed to.

    I'm not necessarily convinced that sitting still with the springs somewhat compressed (be it for three minutes or three months), is harder on them than the constant flexing they get--sometimes to their limit--while driving.

    If sombody tells me that their brother's dentist's wife's cousin is a metallurgist in the spring department at GM and that *he* says it's true, I'll take their word for it.

    (Now watch, with my luck Pelican will tell us that his brother's dentist's wife's cousin *is* a metallurgist in the spring department at GM and how dare I question him....) :rolleyes:
  6. Pelican

    Pelican 2000 Club Member
    Messages: 2,075

    You know me better than that...

    I have no official titles, but a few years of physics and engineering education. If you leave a load on a spring (any spring) for an extended period of time, the spring will "learn" that this is its position at rest, and the reduced amount of travel results in reduced capacity.

    This is true of any spring, suspension or otherwise, one of my hobbies is guns. If you leave a magazine loaded with the spring compressed for an extended period, it learns this is its normal position and its ability to feed rounds is reduced. These springs need to be periodically replaced for this reason.

    Sndun is also correct about the tires. They will also take a set (this is especially true with old bias ply tires) and flat spot if left with a loads on for an extended period. We used to have a tanker at the fire house that would sit for a week or two between calls with a 1600 gallon load. Next time you took it out, it was thump, thump, thump for the first mile or so. The radials of today aren't as bad, but you can notice it if you pay attention.