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Thread: Rear axle lift?

  1. #1
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    Rear axle lift?

    When setting up a Champion Turbo Flex chassis (or any chassis for that matter), how much height do you want under the rear tyres when downwards pressure is applied to the guide flag?

    None, a little, 1/8"???

    Is there an ideal lift?
    Last edited by Zippity; 05-26-2016 at 05:18 PM.
    Zippity

    "Rules are written by FEAR; and that Racers are motivated by the Fear that somebody may have something that gives others an Edge." - Rocky Russo



  2. #2
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    Independence, MO
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    Good question Ron. I assumed that it would be best to have little to no lift but we are just getting into Sprint cars with rolling front wheels so I have no idea what is best.
    Mrk

  3. #3
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    Zip it all depends on what your using to check for the lift and what the braid depth is on the track. On a flat tech block I use about .050 since most of the tracks I race on have about .015-.030 braid depth. If your using a block with braid depths already cut into it and you set up for the track you race on then .025 is a good starting place. You have to take in consideration the braid depth because the deeper the braid is the shallower the up angle of the guide. You can change this angle by using braid of different thickness (which also changes the front end ride height). Thinner braid will reduce the angle and thicker will increase it. More angle is better then not enough. Try to shoot for wear on the last 3/4 of the braid and that should be real close.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  4. #4
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    St Charles, Illinois, USA
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    Surely you gest.... NEVER should a rear tire lift on a slot car. The retro and hardbody cars that I race always have the flag 'ride height' shim adjusted to keep the car level and the fronts lightly rolling... and I always have to fix those plastic cars that are made like tricycles.
    l.d. kelley, M.A. Ramcatlarry@aol.com

    60 year pin 1959-2019
    Racing slot cars in America
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    IRRA, ISRA/USA, Hardbodies 1/24 &
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    retired raceway owner 1992-2007
    Omni/Cidex service center

  5. #5
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    Norcross, GA
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    891
    Quote Originally Posted by Fast Freddie View Post
    Try to shoot for wear on the last 3/4 of the braid and that should be real close.
    Yep, read what the braid wear is telling you.

    Zip, as the other posters said, the 'lift' to shoot for changes with braid depth and track design (banked or flat). Freddie's approach doesn't change with track conditions.

  6. #6
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    I jest you not

    I am ashamed to admit, that after all these years of racing, rear axle lift is NOT something that I had regularly checked for - stoopid me!!

    Maybe I have just been lucky with my chassis. Last week, my Saloon car handles like a pig and it wasn't until Gill pointed out that my guide flag was too high, that I learned the reason for adding spacers. Previously, I only added spacers after "eye balling" that the front of the chassis wasn't rubbing on the track/

    So Fredie, do I want any lift or not?
    (Oh, I see Larry says NO!!)

    I am now using a milled aluminium Ultimate Racing products chassis block, with braid recesses, to set up my cars.

    Our track braid averages around 10/12 thou
    Last edited by Zippity; 05-27-2016 at 03:00 PM.
    Zippity

    "Rules are written by FEAR; and that Racers are motivated by the Fear that somebody may have something that gives others an Edge." - Rocky Russo



  7. #7
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    Zip, if your using a traditional scale car (no front wheels just sticker fronts) where the out riggers on the chassis make contact with the track then yes you want rear tire lift so as to wear the last 3/4 of the braid. Like I said braid depth will dictate how much angle is needed. What I neglected to include was so will rear tire diameter. As the rear tires wear the angle increases. The preferred angle of the guide is 2-5 degrees. This angle causes the rear tires to lift when you push down on the guide flag but not during the race. In fact this angle actually has the effect of growing the guide blade in the slot, not only in depth but also in length.

    On the other hand if your using a car that sets all four tires on the track the guide angle isn't really necessary unless the chassis sits higher in the rear. If that's the case you still need the angle to cause the braid to sit flat on the track braid, but a slight up angle doesn't hurt even in this case.

    Using the correct recess, for your track, in the block you have I would set the guide up angle to 2 degrees this should give you minimal rear tire lift which will increase as the tires wear. Braid wear is the best indicator for correct guide angle.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  8. #8
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    Thanks Freddie

  9. #9
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    How would you apply this theory on a laser chassis where you cant change the guide tongue angle ?

  10. #10
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    Sep 2014
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    Auckland, New Zealand
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    shim it during assembly?
    listen, study, spy, try, research, invent

  11. #11
    Join Date
    Sep 2014
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    Quote Originally Posted by Zippity View Post
    When setting up a Champion Turbo Flex chassis (or any chassis for that matter), how much height do you want under the rear tyres when downwards pressure is applied to the guide flag?

    None, a little, 1/8"???

    Is there an ideal lift?
    I thought the answers were in the Tome you have put up on your own site...



    Just sayin'
    listen, study, spy, try, research, invent

  12. #12
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    Feb 2005
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    Chesapeake, Va.
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    809
    This guide tilt has been normal practice for me since 1987. As for laser cut chassis you could shim the guide piece like Swodem says or you could just bend it before you solder it on the chassis. The current GP12 chassis have integral guide tongues that can be bent the requisite 2 degrees without damage to the chassis, I've done it. The problem here is the current USRA rules state that "the bottom of the guide mount must be level with the bottom of the chassis with no offset" negating even the 2 degree up angle for the guide. I got around that problem buy purchasing several RED FOX guide flags that had a 2 degree angle incorporated into the guide flag and they work fine. I'm not sure if they still make the guide flags or not.

    Zip, just to warn you the coined guide tongues are the hardest to get right. I made a simple tool using a 4 inch long fully threaded screw the same diameter as the guide flag post and nuts and washer on top and bottom of the guide tongue. The washers follow the radius of the coined bend and use the weakened bend to create the angle when I push the top of the screw against my work bench. Mossetti chassis are the toughest.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  13. #13
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    I do have a Toolman guide tongue tweaker
    Last edited by Zippity; 05-29-2016 at 11:23 AM.
    Zippity

    "Rules are written by FEAR; and that Racers are motivated by the Fear that somebody may have something that gives others an Edge." - Rocky Russo



  14. #14
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    Zip, the Toolman Tweaker should work fine just make sure you use washers that match the radius of the coined tongue that way you bend the whole tongue. I made the mistake of using washers smaller than the radius and suffice to say it doesn't do a good job. The easiest tongue to adjust is the JK C11, you can tweak it with a set of pliers and it's fine.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  15. #15
    Join Date
    Jun 2004
    Location
    Australia
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    If the chassis is perfectly flat and true then how could the rear " lift " ???

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