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Author
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Topic: Rack and Pinion placement and Ackerman angles??
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SundanceKid
Gearhead Posts: 1260
From: UT
Registered: Feb 2001
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posted 01-04-2004 03:04 PM
   
Can anyone explain or provide links to more infomation on how the placement fore and aft of a rack and pinion will change Ackeman angles? What is the proper placement of the rack? Inline, Fore, or aft of the outer balljoints? TIA
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indyphil
Gearhead Posts: 2398
From: Senoia, G.A. USA
Registered: Jul 2002
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posted 01-04-2004 05:26 PM
Interesting thinking. You want the inside wheel to turn a little sharper. I would guess rearward placement of the rack would help but I would need to draw some pictures to prove it. ------------------
'68 coupe 289 C code
66 heads, edel 600cfm carb, performer intake, dual exhaust http://www.geocities.com/ottouk_77/68mustang.htm
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TomP
Gearhead Posts: 5761
From: Delta BC Canada
Registered: Dec 99
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posted 01-04-2004 07:05 PM
If you have the right rack it should be slightly forward of the tie rod ends for a rear steer or slightly behind if the rack sits in front and the steering arms go forward. Swapping the spindles side to side to put the steering arms forward will affect Ackerman too. What you want is the tire on the inside of the curve to turn sharper than the outside... but not too much. You have to watch modifying this stuff if it's a street car...i've seen some very scary looking stuff like using a Mustang II/Pinto front suspension and moving the rack forward a bunch to clear the oil pan... the car was steered all the way to one side while parked with the hood off... the tie rod was directly inline with the angle of the steering arm, a good recipe for going over center and jamming the steering.
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SundanceKid
Gearhead Posts: 1260
From: UT
Registered: Feb 2001
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posted 01-04-2004 08:33 PM
Well, this all comes from me trying to "improve upon" The R&C rack and pinion kit I have installed on my Mustang. The way R&C made the kit the rack bolts directly to the crossmember and mounts the rack aft of the outer rod ends. I made rack mounts that brought the rack forward an 1 1/4" ala Heidt's.
The idea was to fix the steering design, allow the input shaft on the rack to better align with the steering column, and give clearence to be able to use my headers. My thought at the time was that like bumpsteer the rack needed to be parallel. I also had it in my mind that if the rack wasn't inline with the outer rod ends the steering movement would be wasted by the changeing ark of the spindles..aka Ackerman angle..LOL Since I originaly posted the thread I've done several hours of reading on the net. Most people feel that Ackerman angle isn't necessary for racecars. To the point many reference Yunick and Coleman as trying to design ackerman out of their cars?? So, what I think I'm going to do is return it back to the way it was, aft of the outer ends. LOL this sucks!
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