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Pitbull TRS twisting swingarms ?

Discussion in 'General' started by DBConz, Jan 4, 2021.

  1. DBConz

    DBConz Registered Idiot

    I've heard a theory that a few fellow swingarms have been tweaked from their Pitbull TRS system during transportation in the trailer. One blew a tire and the other had a suspension failure, both causing some unexpecting swerving from the trailer. neither person crashed, but had their bike geometry measured after noticing a turning issue after. they were both off by a decent amount (3 degrees or more). both bikes were measured straight previously and werent crashed between the two measurements.

    anyone else experience or hear of something happening to them?
  2. Phl218

    Phl218 .

    that could only be the case if the forces from transporting via PB TRS were higher than racing those said bikes. which i highly doubt to be.
  3. RRP

    RRP Kinda Superbikey

    My first question would be - did you contact Pitbull?
  4. Phl218

    Phl218 .


    re-read your post.

    the trailer blew the tire and swerved. !!! Not the bike from transportation.

    in that case, considering the center of gravity on the bike being quite distant from the trs attachment points on the swingarm, I can imagine this causing a problem when swerving at speed.

    but I’d also consider this an emergency situation, so not sure if PB is advertising holding up to a (near-) crash situation...
    Rising Sun likes this.
  5. Mongo

    Mongo Administrator

    Seems highly unlikely given the number of bikes I know of on the restraints in crashed trailers that are just fine.
  6. skidooboy

    skidooboy supermotojunkie

    highly doubtful unless, the swerve/impact was so violent, it bottomed the bikes suspension. I would think, it would have bent the pit bull pin, or restraint arm, before hurting the bike, in my opinion. Ski
    pjdoran and Gixxerguy855 like this.
  7. DBConz

    DBConz Registered Idiot

    explain how a swerving trailer would interact with the shock of a bike that much to bottom out? i'm talking about a trailer swerving side to side, and tweaking the swingarm from the motion.
    R/T Performance likes this.
  8. DBConz

    DBConz Registered Idiot

    i'm sure it's happened to all of us at least once every few years. it has made me curious if i need to remeasure my geometry since having a few close encounters during towing.
  9. pickled egg

    pickled egg Tell me more

    I’d want to know the axis of deflection to consider whether securing the wheel to a fixed point and the rest of the chassis being subjected to inertial forces could have caused the deflection.

    But I ain’t no enginenerd, so this is just one moron scratching his head over it.
  10. cav115

    cav115 Well-Known Member

    We use strapless, and always secure side to side with straps to prevent.

    There could be a lot of force there the swingarm never sees while riding.
  11. kenessex

    kenessex unregistered user

    I am not sure about that. Consider the length of the lever arm from the axle to the center of mass and with a severe enough side force it could well exceed what the swing arm is designed for and what force could be exerted during normal racing use. That wouldn't be the fault of the TRS, but would be the result of the axle being fixed. I suspect that it would be a very rare occurrence as noted by Mongo that there have been trailer crashes with no damage done to the bikes. Very dependent an the amount and vectors of the forces involved.
    tophyr, Phl218, cav115 and 1 other person like this.
  12. R Acree

    R Acree Banned

    I could see rapid oscillation generating enough lateral load to tweak the swingarm...think popping a towel. One way is not bad, but the change in direction might be.

    Being the paranoid idjit I am, I would secure the front even with the Pit Bull Restraint.
    lopitt85 and BigBird like this.
  13. fastfreddie

    fastfreddie Midnight Oil Garage

    Reminds me of earthquake-proof buildings...solid foundations break structures, floating foundations protect structures. TRS is a solid foundation and, given that PitBull stuff is damn near indestructible, it won't be the weak link.

    I've long hypothesized that extended trips with a TRS could do harm to axle/pivot bearings and, over the course of said trips, those precision components effectively get a continuous hammering, possibly resulting in peening. Wash/rinse/repeat for every trip and I think the probability for shortened bearing/bushing life is possible.

    Along the lines of this thread's topic, we can add that swingarms have their twist tuned as part of the bike's handling characteristics, not their ability to withstand levered moments incurred during emergency maneuvers of a transporting vehicle with the axle being locked in place while the rest of the bike is free to, as mentioned above, oscillate. I'm just gonna take a guess and say that those levels of extreme forces being applied as a result of emergency maneuvers by a transport vehicle were never considered in the swingarm's design so, yeah, why not swingarm damage, too? :D
    turbulence likes this.
  14. TurboBlew

    TurboBlew Registers Abusers

    the pins go in a hollow axle with a clearanced fit, correct? I would bet you could mount a trs on a centrifuge and not damage a chassis if you could launch & land it some how
  15. R Acree

    R Acree Banned

    On or off the treadmill?
    beac83 likes this.
  16. Phl218

    Phl218 .

    rectified that in my follow-up post
  17. baconologist

    baconologist Well-Known Member

    We talk’n a POS stamped steel swing arm like an R3 or something substantial with a bridge on it like an R6?
    Was it twisted around the axle centerline?
    R/T Performance likes this.
  18. Ducti89

    Ducti89 Ticketing Melka’s dirtbike.....

    Was the 3 degrees measured with a piece of wood?
    MachineR1 and TurboBlew like this.
  19. DBConz

    DBConz Registered Idiot

    GMD's chassis measuring tools with lasers.

    the bikes i know about are an 848 and a new gen R6
  20. turbulence

    turbulence Well-Known Member

    i agree.. i’ve never thought mounting a bike low with all the weight twisting above it around a lever arm seemed like a good idea.

    i was trying to think of a way to replicate this where you could feel the forces at work..

    best i could come up with was using barbell with removable plates.. put weight on one side and not the other.

    now hold the barbell outstretched at the end with no weight... your arm is the swingarm and your hand meeting the barbell is the TRS mounting point.. now gently move your arm side to side and try and keep the weight upright.

    change your grip to just under the plate replicating a higher bar mounted attachment point and do the same thing.

    the forces on your arm and subsequent joints will be much higher when you’re trying to stabilize the weight at it’s almost lowest point.
    Last edited: Jan 4, 2021
    beechkingd likes this.

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