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    Results 1 to 11 of 11
    1. #1
      Join Date
      Dec 2006
      Location
      Ridgeland, Ms
      Posts
      59
      Country Flag: United States

      A-Body spindle question

      What is the King Pin Inclination (or SAI, Steering Angle Inclination) of a stock GM A-body front spindle. I am comparing to the ATS spindle for the A-body. Also trying to determine the best place to start with the caster settings for these to minimize understeer.
      Thanks,
      Jeff Peoples

    2. #2
      Join Date
      Apr 2014
      Location
      Cortes Island, BC
      Posts
      26
      Country Flag: Canada
      Quote Originally Posted by BuickGS View Post
      What is the King Pin Inclination (or SAI, Steering Angle Inclination) of a stock GM A-body front spindle. I am comparing to the ATS spindle for the A-body. Also trying to determine the best place to start with the caster settings for these to minimize understeer.
      Thanks,
      Jeff Peoples
      Hi Jeff, did you ever figure out what the stock 64-72 A-Body KPI/SAI is? I think that would be relevant when determining how much caster to put in with aftermarket control arms, from what I remember about track setup.

      Cheers,
      D

    3. #3
      Join Date
      May 2010
      Location
      kitchener,Ontario,Canada
      Posts
      2,336
      Country Flag: Canada
      you do know this dates back to 2013 ???
      Spinnin'my tires in life's fast lane

      Ryan Austin
      On twitter @raustinss
      On Instagram austinss70

    4. #4
      Join Date
      Apr 2014
      Location
      Cortes Island, BC
      Posts
      26
      Country Flag: Canada
      Quote Originally Posted by raustinss View Post
      you do know this dates back to 2013 ???
      I do, yes. Not much comes up from a google search, but this thread did. Was hoping someone on the forum might know the answer.

      Cheers,
      D

    5. #5
      Join Date
      Sep 2013
      Location
      Houston, TX
      Posts
      246
      Country Flag: United States
      I seem to recall from one of the chassis tuning books I read the stock KIA is 7-8 degrees. I can't find the chassis book at the moment to confirm this.
      Rodney Meyers
      72 Olds 442 Rest-mod clone

    6. #6
      Join Date
      Apr 2014
      Location
      Cortes Island, BC
      Posts
      26
      Country Flag: Canada
      Quote Originally Posted by cdrod View Post
      I seem to recall from one of the chassis tuning books I read the stock KIA is 7-8 degrees. I can't find the chassis book at the moment to confirm this.
      Quote Originally Posted by pitts64 View Post
      7 to 8 is what I've always been told and what I've read..
      Thanks for the feedback, much appreciated!

      Cheers,
      D

    7. #7
      Join Date
      Apr 2014
      Location
      Cortes Island, BC
      Posts
      26
      Country Flag: Canada
      Quote Originally Posted by pitts64 View Post
      My 69 el Camino has SPC upper and lowers with tall ball joints. My car rides best with 6.5 +caster drivers side, 7 +caster passenger side. If your across the pond, just reverse that cross caster. You want the wheel that rides next to the curb to have a little more +caster so the car doesn't keep drifting in that direction.. The streets have a crown built into them to aid rain drainage..
      Thanks for the input, and the rationale behind the cross-caster - I remember that from trade-school way back when.

      Your caster numbers are in line with what I'm planning. From what I've read elsewhere on this forum, a good rule of thumb (for competition at least) is to have 1-2 deg more caster than you have KIA/SAI. From my understanding (and there is a lot more going on than just this), that setting it up like this, as the steering moves you gain the difference as negative camber to the outside wheel and gain as positive camber on the inside wheel. Everything else being equal, assuming you had 8-9 deg of caster at full lock you'd gain (8-9 deg) - (7-8 deg) KIA => +1deg neg camber on the loaded outside wheel and -1deg neg camber on the unloaded inside wheel (making it more upright with better contact patch considering the body roll in the corner).

      This is how I set up my C5 race car (along with -1deg static camber), I may go with 7.5 driver & 8 passenger for the street when the time comes.

      I've been making inquiries about what the range of caster adjustment is, and how much negative camber gain you get with compression from some control arm vendors, but it's hard to get this level of detail.

    8. #8
      Join Date
      Apr 2014
      Location
      Cortes Island, BC
      Posts
      26
      Country Flag: Canada
      That is a sweet looking El Camino!

    9. #9
      Join Date
      Jan 2022
      Location
      Sacramento, CA.
      Posts
      2
      Country Flag: United States

      Caster Angle

      SAI should appear on the printout at the alignment shop. Add 1.5 degrees greater caster than your SAI angle.

    10. #10
      Join Date
      Dec 2006
      Location
      Ridgeland, Ms
      Posts
      59
      Country Flag: United States
      Wow, just happened to get on the forum after some years of inactivity, and saw this thread at the top. I have learned alot and done alot to the my car since 2013. Also spent alot of money and am building another car!
      I found an old alignment printout from high quality body shop here in Central MS, Capitol Body Shop. It shows an SAI 9.2 degrees on one side, and 9.5 degrees on the other side (stock spindles). I was running 5.6 degrees caster. I agree with the responses to this thread that state you should run a little more caster than your SAI. I could have never gotten 10 degrees of caster with my setup without the tire hitting the rear of the wheel wheel at full lock.
      Since installing the ATS spindles, my next printout showed 8.8 degrees and 8.7 degrees of SAI. I increased to 6.0 degrees of caster. The first few years of auto crossing my GS in the Goodguys (only two events a year), which started around 2010, I was competitive and could finish around eight or nineth place in Street Machine class. As more serious Corvettes and Camaros showed up, my finishes moved toward the bottom over time. I did not want to go crazy with more mods trying to compete with such a size and weight disadvantage, and because I was building a lighter car that was much more radical.
      In 2017, my last change to the GS was to enlarge the front fenders to allow a 315 front tire. I wanted fenders to look stock too. I had them widened 1.5" inches at the top of the wheel opening, and moved the lower front and lower back of the wheel opening 1" forward/backward. The fenderwell was also modified accordingly. I could only get 8 degrees of caster without the tire getting too close at the rear/lower portion of the fenderwell. I am running -2.0 degrees of camber, which is visible to the naked eye. If I park the car with the wheels turned to full lock, you can easily see the camber gain and the tire leaning inward. The factory chrome wheel opening trim fit right back into place, and the rocker trim fit after moving it back an inch, so the fenders do look stock. I get lots of questions at cars & coffee on how those tires fit.
      My next trip to a Goodguys event found me moved out of Street Machine and into the Pro-X class, since I had a 315 front tire (new rule that year). Last place finish of course, but I was having fun and enjoying the extra grip. I am now passed the limits of my modified oil pan, and have low oil pressure on extended turns.
      My suspension mods are now about 12 years old, and improvements have been made by parts vendors. I believe there are better A-rms now that move the ball joints around so the tire is more centered in the wheel opening when running extreme caster.

    11. #11
      Join Date
      Sep 2010
      Location
      corona,ca.
      Posts
      1,078
      Country Flag: United States
      BuickGS,which control arms did you use in the past?
      72 chevelle.



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