Shopping Cart syndrome?

Discussion in 'PSI Superchargers Tech Questions' started by alt 6153, Dec 23, 2011.

  1. alt 6153

    alt 6153 Member

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    What causes the front wheels to "Shopping Cart" after the burn out? I have a 125" blowen altered and sometimes the front wheels will go into the shakes, I call it the "shopping cart" after the burn out. I have never had any weird stuff happen on the run or shut down, but it is a little unnerving when it does it on the shut down of the burn out.
    Thanks,
    Chuck
     
    #1
    alt 6153, Dec 23, 2011
  2. Woodchip

    Woodchip Top Alcohol Dragster

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    #2
    Woodchip, Dec 23, 2011
  3. secondwindracing

    secondwindracing top alcohol

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    its all in the castor..Dave
     
    #3
    secondwindracing, Dec 23, 2011
  4. Comax Racing

    Comax Racing Member

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    12 degrees is what we use and its perfect. You can damn near take your hands off the wheel at 190MPH
     
    #4
    Comax Racing, Dec 24, 2011
  5. Woodchip

    Woodchip Top Alcohol Dragster

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    A little more angle on the bean!!

    castor are beans, caster is spindle angle.
     
    #5
    Woodchip, Dec 24, 2011
  6. Mike Canter

    Mike Canter Top Dragster
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    It is caster AND toe in. Real positive caster causes that shimmy and it is worse if the toe in is not set correctly. Make sure you check your front wheel bearings by shaking the wheels and make sure they are tight and make sure nothing else in the steering is worn or loose. We just had a front wheel bearing failure on the promod in the finals that caused the front wheels to think they where on a shopping cart. Adam had to shut the car down. At least it didn't happen at 240 mph.
     
    #6
    Mike Canter, Dec 24, 2011
  7. Chi Town Brown

    Chi Town Brown Member

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    Ceramic Bearings?
     
    #7
    Chi Town Brown, Dec 24, 2011
  8. Mike Canter

    Mike Canter Top Dragster
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    I don't know. Will have to ask Adam. Why do you ask?
     
    #8
    Mike Canter, Dec 24, 2011
  9. Chi Town Brown

    Chi Town Brown Member

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    Just inquiring to see if the "Trick" bearing didn't do the job it was designed to or if it was a standard bearing and failed from lack of maintenance?
     
    #9
    Chi Town Brown, Dec 24, 2011
  10. Bob Meyer

    Bob Meyer Comp Eliminator

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    air psi and rod ends

    Everytime this is brought up, I'm surprised that many relate their front tires to car tires.
    Most daily drivers use 32-35 Lbs.
    Front race tires are not car tires, generally it's moulded into the sidewall what psi to use, if not, call your race tire distributor. Most call for 45-50 psi (or more).
    Nature of the run forces toe in, deceleration (weight slung forward) forces toe OUT, the sidewalls must be stiff.

    Also, tired out rod ends can cause it. Pull the bolt out of any rod end to check it. If the ball wiggles and spins, it's next to dead. Of course, brand new gippo cheap rod ends off the shelf will do this too, so feel'em before use, hint: more expensive means nothing if they are loose !!!!!!!!!!
     
    #10
    Bob Meyer, Dec 26, 2011
  11. alt 6153

    alt 6153 Member

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    Toe in?

    Thanks everyone for your input. I will do some checking on loose rod ends etc. What is everyone running for toe in?
    Thank,
    Chuck
     
    #11
    alt 6153, Dec 26, 2011
  12. backmotor

    backmotor Owner/Crewchief/Test Pilot

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    We run 3/16th toe in and 30 psi in front tires, 125" wheelbase, rack and pinion steering, tried it with less toe-in, and it wanted to skate at speed :cool:
     
    #12
    backmotor, Dec 26, 2011
  13. john348

    john348 Top Alcohol

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    I run about 1/8" toe and 40-45 psi in front tires
     
    #13
    john348, Dec 26, 2011

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