Insted of buying tubular A arms for an f-body

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by 1320feet, Apr 18, 2020.

  1. 1320feet

    1320feet Member

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    As I understand it, tubular a arms main advantage it to gain some caster. I was thinking of machining the stock shaft back 3/8 to 1/2 (from blue line to red line in photo)and adding a spacer to the other end. Why will this not work?
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  2. badazz81z28

    badazz81z28 Veteran Member

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    I understand the aftermarket arms geometry is built into the arm, not the cross shaft. I’m not a engineer, but I can’t grasp how that mod gives you caster.
     
  3. McCune

    McCune Veteran Member

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    It would move the upper a arm towards the rear of the car,tilting the spindle back giving you more caster.
     
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  4. ULTM8Z

    ULTM8Z Veteran Member

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    They have offset cross shafts that give you another degree or so. But frankly it's not worth the effort, as you won't notice any difference from stock. I ran those prior to my tubular arms and got ~2 to 2.5 deg.

    When you go to tubular arms and get your caster up to 6-7 degrees, that's when you really notice the improvement.
     
  5. 79T/Aman

    79T/Aman Veteran Member NastyZ28 Sponsor NastyZ28 Sponsor Lifetime Gold Member

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    the gains would not be worth the effort and there is not enough room to move it because of the frame mount
     
  6. 1320feet

    1320feet Member

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    The offset cross shafts I've seen only affected camber. Are there others that affect caster that I've missed?
     
  7. ULTM8Z

    ULTM8Z Veteran Member

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    It rotates the A arm toward the rear by a little bit relative to the lower arm, so it gives you a little bit of caster.
     
  8. 79T/Aman

    79T/Aman Veteran Member NastyZ28 Sponsor NastyZ28 Sponsor Lifetime Gold Member

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    correct, offset cross shafts affect camber, there are none that change caster, offset cross shafts can help add more caster to some degree because it allows for more shims to be used but it will not come near what an aftermarket arm can do
     
  9. 1320feet

    1320feet Member

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    I've not been able to find info on how far back the ball joint is moved on aftermarket arms. I just made some calculations and 3/8" would only add 1.9° and 1/2" would be 2.6°. Therefore 5° would have the joint back almost an inch.
     
  10. flht99b

    flht99b Veteran Member Gold Member

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    Just my opinion like all the rest here. Getting caster to +6 is best accomplished with custom fabricated and engineered upper control arms. The 1/2" to 1" longer upper ball joint is well worth it too especially when installing custom control arms. Stock lower control arms are fine with new bushings and ball joints, pick your bushings material, all have pluses and minuses. Couple the control arms with a newer style steering box (many threads here in that subject). While the steering box is out either rebuild the steering intermediate shaft, replace the rag joint or better yet go with a universal joint assembly, again many threads here on this. Make sure all your tie rod ends, idler arm and center link are good or replace them. Get a GOOD front end alignment and you'll find your 40+ year old car steers very much like a modern pony car. Dramatic improvement. I use PTFB products on customers and my own car and I'm 100% satisfied. Sway bars,shocks, wheels and tires are whole other subjects and there is much info on this site about them. Which ever vendor you decide to use, talk to them and be very honest about the REAL driving you will do. Don't buy a full on race suspension package if all the car will ever see is street driving or cruise nights, you will not be happy. I drive my 71 Z28 including the 2019 long haul HRPT, 1983 miles door to door and have a real world experience what of works well for driving real street miles.
     
    Last edited: Apr 19, 2020

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