Home Forums General Karting Discussion Why do 125cc shifter karts always run 32 chassis?

This topic contains 5 replies, has 4 voices, and was last updated by  Chris Jennings 10 months, 1 week ago.

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  • #19547

    shaun s noll
    Participant

    I am looking at upgrading my chassis and shopping around for rollers.  I am going to be running a cr80 shifter and am looking at the CRG Road Rebel (32 chassis) vs. the Blackstar (30/32) chassis.  I am sure either can be made to work well but I am wondering from some of the more experienced guys on here what the difference in “feel” would be between the 30 vs 32 chassis and why the the TAG guys seems to typically run the 30 chassis while I think every 125 shifter I have seen has always been a 32 chassis?

     

    thanks!

    #19549

    Peter Zambos
    Participant

    They’re not always.  For instance, the default shifter model for OTK and Italkart are their 30mm versions.  There are so many other factors involved (seat position, seat stiffness, axle, hubs, etc.) that you could either one to work as long as you’re not either a very skinny driver or a very large driver.

    The 30mm will feel more lively.  All things equal, it’s more flexible, so you’ll feel the track more, the inside rear will pick up faster, and come down faster.  It also comes down to your style as well.  If you’re used to muscling the kart into the corners, a 32mm might be better for you.  Conversely, if you rely a little more on finesse, then the 30mm will be more appropriate.

    I would discuss your needs directly with the CRG importer.  As they get feedback both from their dealers and the factory, they should be the best candidate for accurate knowledge for their line.

    #19600

    shaun s noll
    Participant

    thanks Peter, am I accurate in assuming that the majority of guys in S1 or S4 etc are running 32 chassis though?  if so I am curious as to your thoughts on why they do?  it would seem to me that peak cornerning forces are likely as higher or higher in the rotax TAG classes so I am curious why the 125 shifter guys run the stiffer/thicker chassis.

    #19604

    Peter Zambos
    Participant

    I honestly can’t say what the majority of shifter pilots are using.  The overly-simplistic way to think of the difference between 30 and 32mm frames, apart from what I already said, is that a 32mm frame can offer more rear grip.  In higher BP applications, yes, a 32mm frame could very well work better for you.  I’m not talking about lateral grip at the apex, for, if the TAG kart and the shifter are on the same tire compound, that lateral grip is effectively the same.  Where the additional grip comes into play is accelerating out of the turn.

    But, as stated earlier, there are a lot of other factors in what makes a chassis work, and so you can’t always just go by the OD of the frame.  I’ve never run a CRG, so I can’t give you a definitive answer, sadly.

    #19616

    Brian Degulis
    Participant

    thanks Peter, am I accurate in assuming that the majority of guys in S1 or S4 etc are running 32 chassis though? if so I am curious as to your thoughts on why they do? it would seem to me that peak cornerning forces are likely as higher or higher in the rotax TAG classes so I am curious why the 125 shifter guys run the stiffer/thicker chassis.

     

    The answer may be Torque. Rotax is 28 HP lets say for the sake of discussion a CR80 is close to the same. When you add a gearbox to the equation the torque your putting to the axle rockets up. Torque not only requires more grip it also requires a stiffer frame to minimise deflection.

     

    Brian

    #19626

    Chris Jennings
    Participant

    In S4 I would say approximately 30-40% of the filed are on 30mm chassis.  S2 might actually be closer to 50/50.   I always ran a 32 until last year.  I switched to the DR 30mm chassis and it works better for me than any other chassis I have driven in (S4).  I’m also 6’4″.  Most people you ask would say I need a 32mm, but that isn’t the case.

     

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