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Hot Rods bias ply open fender last resort (drivers please)

Discussion in 'The Hokey Ass Message Board' started by scoottattoo, Aug 25, 2010.

  1. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member



    OK here it goes.
    Excess toe-in is better than excess toe-out [ for low performance drivers ]

    Toe-In is used to correct 2 things,
    1: Positive Camber thrust [ + cambered wheels travel in a cone direction outwards ]
    2: flexing of steering components [ resistance causes a slight tow-out ]
    Early cars had positive camber for the curvature of the roads with crossply tires ,so they needed toe-in

    Toe-Out is also used to correct the same 2 things,
    1: Negative Camber thrust [ - cambered wheels travel in a cone direction inwards ]
    2: flexing of steering components [ FWD cars try to toe-in under load ]
    Modern cars with IFS have negative camber to counter-act bodyroll [ this is a simple explanation ] Beam axles don't change camber during bodyroll.

    Excessive Toe-in causes the front to push [ understeer ] this is caused by weight transfering onto the tire with an already increased slip-angle

    Understeer can be controlled by slowing down [ all manufactured cars have built-in understeer ]

    Excessive Toe-out cause the car to be unstable [ like standing up in a dinghy ] ,
    When a car sways to the left side ,weight tranfers over to the right side ,the R/H front is steering towards the right [because of the toe-out] so the car darts in this direction transfering weight back to the left etc etc etc

    Toe-out is terrible in staight line ,but feels great when you "lean on it" through a corner.

    Circuit cars [ my background ] are terribly unstable when driven down pit lane at slow speeds, but great on high G corners
    We don't have straights on a circuit, just apex's and curves [ of varying lengths ]

    Quote; "Understeer scares the driver, Oversteer scares the passengers"
     
  2. sugarlou
    Joined: May 26, 2007
    Posts: 120

    sugarlou
    Member

    Have you ever seen a car (modern) driving down the road w/ a broken shock? The wheel pogo's up and down like a basketball, so in theory isn't a shock designed to reduce/eliminate oscillations? I'm not saying a shock will make up for a horribly out of adjustment front end or severely out of round wheel/tire but rather reduce slight inadequacies of the system.

    I put my truck up on a lift and one thing I noticed was how easily the axle rocked on the spring. One thing I haven't seen anyone addressing and am curious about is the spring it self. Seems to me if the spring was stiffer it would reduce the desire to pogo like this

    Has anyone added leafs or swapped the spring for a stiffer one w/ good results?????
     
  3. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    Ha!
    A very good theory but you want to do the dead opposite [ a softer spring can sometimes fix this ]

    firstly lets talk about springs

    Springs absorb shocks from the road [ shocks only dampen spring oscillations ]
    When you use a stiffer spring [ or a lighter weight vehicle above the spring ] the frequency goes up [ cycles per second ]
    A low frequency spring absorbs the bumps, whereas a high freqency spring will skip over them.
    Why is this? because the weight of the chassis is too light too absorb the energy [via the spring ] so the car bounces

    when you see a car with a broken shock bouncing on the highway, sometimes the driver is unaware of this because the spring is absorbing the energy instead of transfering it to the driver.

    Wrong choice of spring is the biggest mistake car builders make.

    Too much caster would be a problem here also
     
  4. BobbyD
    Joined: Jun 6, 2005
    Posts: 581

    BobbyD
    Member
    from Belmont NC

    I agree, a spring to soft combined with that shock angle could very well be your problem. I run into this once before where to many leafs had been removed to lower one and it did exactly what you desribe. Added leafs, problem solved. Just my 2 cents....
     
  5. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    Too stiff springs are the problem [ I probably didn't explain it properly ]

    Soft springs absorb energy ,whereas stiff springs transfer it to the driver
    [ imagine solid suspension on a rough road to get a better picture ]

    Shocks only dampen oscillations! An oscillation is the Yoyo effect after the bump.
    A Bump causes a shock which is absorbed by the springs, after the spring absorbs the shock it springs back [ hence the oscillations back and forth ]

    The correct terms are jounce and rebound
     
  6. mx6262
    Joined: Oct 2, 2008
    Posts: 375

    mx6262
    Member

    When I was a kid I worked at my dads service station "union 76" we had the big ball and all the latest equipment, the "tire Turner" was the work horse by far, it seamed like dad turned tires all day....Round is good..

    Dont let me get in the way..:D
     
  7. R Frederick
    Joined: Mar 30, 2009
    Posts: 2,660

    R Frederick
    Member
    from illinois

    Thanks for the breakdown. We would always put toe out on our oval track dirt cars. My brain is programmed from that, I needed to read the reasoning to reprogram. My car is set at 0 toe right now. I might try to tweak it in a hair, although the only problem I can notice is a "dead" feeling while driving straight down the highway. Everything else feels tight and tidy. Maybe if I put a little toe in it, the loss of steering feeling will go away when driving straight.
     
  8. sugarlou
    Joined: May 26, 2007
    Posts: 120

    sugarlou
    Member

    I understand a stiffer spring would bounce back harder than a soft one..but a soft one would continue to bounce where the stiff one would stop quicker..no?

    If my axle were rigid mounted to the frame there would n't be any pogo, so isn't a stiffer spring getting "closer" to a rigid mounted axle?

    I'm also curious if anyone here has had this problem and had it completely remedied by swapping to radials alone...no other modifications.
     
    Last edited: Aug 27, 2010
  9. 29nash
    Joined: Nov 6, 2008
    Posts: 4,544

    29nash
    BANNED
    from colorado

    Whatever the case, minor deviation on toe adjustment will not cure OPs problem; UNLESS the steering linkage is sloppy somewhere, the box is flexing at it's mounts, kingpins are worn, and/or etc. Of course we are presuming that OP has got all of that out of the way. If not, we're just pissing in the wind anyhow.

    All of the theory might sound good on paper, but setting the toe to ANY specification is a starting point. On my 'beam axles I always start at 0-toe. Then a test drive, if it tends to wander slightly, either direction, then I am assured that I actually got it right on 0-toe. I also want a couple of degrees of Positive camber. After that, if the car tends to drift off in either direction I will tweak with a little bit of toe out, just a half turn on the adjustment ususlly does it. I have tried it, but have never ended up with a car setup with toe-in, toe-out always works better for me.
     

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