Home Forums Chassis & Handling Inside rear wheel hop

This topic contains 7 replies, has 4 voices, and was last updated by  FREDDY SANDOVAL 6 months ago.

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  • #28083

    I seem to have this inside rear wheel hop and I really noticed on a short track I just practiced at the last two weekends. In turns 3 and 8 it seems that when the kart get up on 3 wheels it will repeatedly slam the rear inside tire up and down until in a straight line again. I tried lowering and raising the tire pressure on sets of MG Yellows and Dunlop hard compounds. I have the rear track set to 1″ out each standard Tony Kart Krypton hubs. It is also a standard Tony Kart Krypton N axle. Should I shorten the inside width to keep it tight and rid the “spring” or widen the rear width to give it more flex?

    Thanks in advance.

    #28097

    FREDDY SANDOVAL
    Participant

    How wide is the rear track? From outside wheel lip to outside wheel lip?

    What engine are you running?

    Are you running seat struts?

    Are you running front and rear torsion bars?

    I can give you some advise, but I need those answers first. Fast Freddy.

    #28100

    TJ Koyen
    Participant

    You need to measure rear track width as a whole.

    First thing I do to correct a hop is widen the rear. But I’m not sure how wide you are already. A good baseline rear track width is 1390mm or 54.75″.

    But it must be said, a kart will never really work or flex properly if you aren’t driving it at the limit and from this video, you aren’t even close. The best advice I could give to a newbie would be to set the kart up neutral and just pound laps before adjusting the setup. It’s good that you are picking up on these things you’re noticing in the handling already, but a lot of handling woes will go away themselves once your driving is on-point.

    #28102

    Gary Lawson
    Participant

    Tj is spot on. You need a lot of seat time so you can drive the kart harder throughout the corner to help keep the onside rear up. From experience after a race is over my kart will sometimes hop on the cool down lap when im not driving it very hard.

    #28104

    That post was rushed without details since I was at work and just looking for a basic answer on wider track = more flex or contribute to bouncing. I guess that video was a bad example also since it was a second run on an engine break-in and that was my 10th lap around that track. I wasn’t driving hard, but towards the end as I was pushing a bit more is when the hopping started to arise. I’m mainly on road courses in the past years, so short tracks are a bit different for me.

    Measurements:
    -Track with wheels = 56.5″
    -Tony Kart Type N = 40.5″ or 1030mm
    -Tony Kart Mag Hunbs = 3.5″
    -Hubs are 1″ out from bottom on each side

    Equipment:
    -06/07 Tony Kart Krypton 30mm
    -MY07 Parilla Leopard
    -1 set of seat struts
    -Full caster
    -Scrub radius: All spacers inside of spindle (wide width) except for 1 small
    spacer on the outside behind the wheel nut.
    -Was running front torsion bar and was removed last weekend.
    It free up the kart and feels nice, but hopping still persists

    #28106

    FREDDY SANDOVAL
    Participant

    Fix your rear track to 54.5

    If you have a rear torsion bar, remove it and throw it in the trash can

    Remove front torsion bar and save for other time

    Remove another small spacer from front inside spindle, and put it outside

    Try that and let us know what happened

    This should be a good start. My 2 cents.

    Fast Freddy.

    #28113

    TJ Koyen
    Participant

    I would start with taking caster out. Too much weight jacking = hopping.

    #28124

    FREDDY SANDOVAL
    Participant

    Yeah, I agree, Remove some caster too

    And that would be a good starting point to start tuning the chassis

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