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A discussion of unsprung weight...

Colt SuperColt Super Member Posts: 31,007 ✭
edited June 2008 in General Discussion
OK, go ahead.

Edumacate me.

Doug
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Comments

  • catpealer111catpealer111 Member Posts: 10,695
    edited November -1
    I think its the weight of items that isn't supported by the suspension such as wheels, tires, brakes, suspension control arms, and axles. Correct me if I'm wrong.
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  • reloader44magreloader44mag Member Posts: 18,783 ✭✭✭
    edited November -1
    quote:Originally posted by catpealer111
    I think its the weight of items that isn't supported by the suspension such as wheels, tires, brakes, suspension control arms, and axles. Correct me if I'm wrong.
    thats it in a nutshell...Doug just GOOGLE it, it will make things alot easier[;)]
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  • Colt SuperColt Super Member Posts: 31,007 ✭
    edited November -1
    OK then.

    What are thye effects of increrasing or reducing it ??

    Doug
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  • reloader44magreloader44mag Member Posts: 18,783 ✭✭✭
    edited November -1
    quote:Originally posted by Doug Wilson
    OK then.

    What are thye effects of increrasing or reducing it ??

    Doug
    depends on application
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  • Colt SuperColt Super Member Posts: 31,007 ✭
    edited November -1
    Don't think so. I think it only depends on the laws of physics.

    Doug
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  • reloader44magreloader44mag Member Posts: 18,783 ✭✭✭
    edited November -1
    Ya know Doug, sometimes I wonder about you....why don't you educate me.
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  • kristovkristov Member Posts: 6,633
    edited November -1
    Every gram (in the case of Formula 1) or pound (if it is NASCAR) of unsrung weight you remove is equal to twice the amount of sprung weight. Alloy wheels, carbon fiber discs and rotors all add up to big weight savings.
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  • Colt SuperColt Super Member Posts: 31,007 ✭
    edited November -1
    So, could it be said that the less unsprung wait, the more effectively the suspension will function ??

    And, what is the best way to change unsprung weight??

    And, why would it matter ??

    Doug
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  • kristovkristov Member Posts: 6,633
    edited November -1
    Less unsprung weight means better handling and a more responsive drive. Take 100 pounds of weight off the suspension with light weight wheels, brakes and suspension components and you get the same results as taking 200 pounds off the frame. This also applies to bicycles and motorycles where you always alloy wheels and not steel.
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  • Colt SuperColt Super Member Posts: 31,007 ✭
    edited November -1
    Thanks everyone, especially K.

    I'm contemplating repalcing my steel wheels with alloys, but so far, the alloys weigh more.

    Also trying to figure out whether to go to stiffer or softer shocks if unsprung weight is reduced. Probably shocks with slower jounce and faster rebound ??

    Doug
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  • givettegivette Member Posts: 10,886 ✭
    edited November -1
    Best to go with adjustable shocks. Then you can dial-it-in. Joe
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  • beantownshootahbeantownshootah Member Posts: 12,776 ✭✭✭
    edited November -1
    quote:Originally posted by Doug Wilson
    OK, go ahead.

    Edumacate me.

    Doug


    http://en.wikipedia.org/wiki/Unsprung_weight
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  • iceracerxiceracerx Member Posts: 8,860 ✭✭✭
    edited November -1
    Unsprung weight has more to do with Momentum and or inertia. Bodies in motions and bodies at rest. Once you start a heavy wheel/tire moving (pot hole) you have to stop it before it affects the ride on the car. Then, as it rebounds, it wants to continue it's downward movement. In all cases lighter is better, all other things being equal (strength, width, diameter, etc)

    Shock springs deal with vehicle weight and damping deals with unsprung weight for the most part.
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  • HandLoadHandLoad Member Posts: 15,998 ✭
    edited November -1
    The less the unsprung weight, the more the suspension can keep the tire patch on the ground = better transient handling.

    Doug, the stock shocks will perform better when you lighten the unsprung weight. Unless you have a "Seven Post" chassis dynamometer, there is no real way to pick out which way to go on shock valving - your tire sidewalls have some spring constant, your control arms have some spring flex, your chassis has some flex, and they are all part of a resonant system - you would have better luck picking next week's lottery numbers than just picking the right shock valving. Just lightening the unsprung weight will allow your stock shocks to work better, and a really carefully engineered premium shock for your application will still be just a guess.

    Reducing rotating weight is also good - you find both benefits when you can find lighter wheels. That is another reason that racers shave tread off new tires, and why original "Mags" were made of Magnesium.

    Rotational inertia (in racing) is only good if it is in a flywheel, and then only if it is just enough to keep the fires lit. Anything else is a tax on acceleration, and added burden for the brakes.
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  • zipperzapzipperzap Member Posts: 25,057
    edited November -1
    quote:Doug Wilson:

    I'm contemplating repalcing my steel wheels with alloys, but so far, the alloys weigh more.

    ... Yugos have steel wheels, not iron?[:D]
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  • bobskibobski Member Posts: 17,866 ✭✭✭
    edited November -1
    alloy, right. good luck finding someone to change a tire when you get a flat. and if you crack an alloy rim, the unsprung weight of your wallet lessons by half.[:D]
    Retired Naval Aviation
    Former Member U.S. Navy Shooting Team
    Former NSSA All American
    Navy Distinguished Pistol Shot
    MO, CT, VA.
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  • Colt SuperColt Super Member Posts: 31,007 ✭
    edited November -1
    Thanks everyone for broadening my understanding of vehicle dynamics.

    I agree that steel wheels are best for off roading, and it looks like the only reason for alloys is to look pretty and to mount heavier tires (which would tend to detract from handling).

    Maybe Centerlines ??

    Doug
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  • HandLoadHandLoad Member Posts: 15,998 ✭
    edited November -1
    Centerlines have a stamped warning on them, not to use radials - if you plan to use Centerlines, you use radials at your own risk (I used them with Michelins and they never gave me a bit of trouble, and I gave 'em ha-double hockystix, for over hundred thousand miles)...your mileage might vary.

    Not all aluminium alloys are heavier - ya gotta look around. some are only for style, but some are for racing! Weld used to have some that were pretty light IIRC.
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  • mogley98mogley98 Member Posts: 18,291 ✭✭✭✭
    edited November -1
    Un-sprung weight: That is the parts of your lard * Aunt that don't fit into the back of your pick-up truck but slides over and onto the ground that is Un-sprung weight.
    Why don't we go to school and work on the weekends and take the week off!
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  • haroldchrismeyerharoldchrismeyer Member Posts: 2,213 ✭
    edited November -1
    Another effect of reducing the wheel and tire weight is acceleration. It takes horsepower to spin that tire and wheel combination too. It takes more of the brakes to slow down that heavy wheel and tire. A friend put a heavy set of wheels and tires on his hot rod Honda, and took them off in a couple of days because it slowed it down too much.
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  • iceracerxiceracerx Member Posts: 8,860 ✭✭✭
    edited November -1
    You need some old Hurst Wheels and Redline tires (or Tiger paws)
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  • IAMAHUSKERIAMAHUSKER Member Posts: 2,479 ✭✭✭✭✭
    edited November -1
    unsprung weight is just that, weight that is not sprung or "supported" by the suspension. Just that simple.
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