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I know adjustable LCAs have been discussed before...


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I stand corrected (Thanks guys). The arms for a front rack do need to be angled away from the longitudinal centerline of the car for proper Ackerman effect. I had to simulate it and found I was reversed in my thinking. Anyway, this means that moving the rack toward the crossmember would increase the Ackerman effect. The previous drawing has been changed and an EDIT comment inserted.

 

In regards to increasing caster, I lengthened my TC rod by 1.25", which netted an increase (for the ride height that I was at) of just under 3º

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Jon, you are forgetting that ackermann steering can also be achieved by pointing the steer knuckles towards or away from the centerline of the car. I'm kinda new to the whole ackermann thing, but from what I understand, on a car that has the steering knuckles forward of the front axle, the steer knuckles must point outwards in order to achieve 100% ackermann effect, assuming the steering rack and tie rods are parallel. (in a top view)

I'm not forgetting that, but that isn't the ONLY way to do it. Go take a look at your steer knuckles. It would be great if we could bend the ends out in order to get more Ackerman, but the brake rotor is right there. 260DET had his cut and rewelded to maximize this, but I don't think you can get more than about 1/4" or so of bend. On a rear steer car (rack or box behind the crossmember, not rear wheel steer) this is easier because you're bending the steer knuckles away from the brakes. My friend bent the knuckles in his 510 for Ackerman years ago, which is what got me interested in it in the first place. His car turns in way better than mine used to... we'll see how I fare with all this crap I've done.

I honestly don't see how changing the inner position of the CA front to rear would significantly affect ackermann.

I agree, I don't think it does.

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Why could you not elongate the two holes either side of the balljoint hole to allow the ends of the steering rod to be rotated outboard. If nothing else, then weld a small glob on one end of the slot to prevent the arm from rotating inadvertently during normal use.

 

At the angle of the TC rod incident to the front CA centerline, a 1.25" increase results in about 1.08" movement of the spindle forward, which is close to 3º of caster increase. The OEM caster is 3º, so I now sit at about 6º caster. This is based upon a 20" length from balljoint to the top of the strut rod. This increase greatly increases the camber change as the wheel is turned. This is not a panacea for all the issues of camber increase, but it did help a LOT in allowing me to reduce the static camber, which allowed later braking.

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terry, jon & bj, now you've done it. just as i thougth i had a handle on the basics of car handling and suspension-i read this thread and, once again, realize that i really don't know much at all. yet another blow to my self-esteem:wink:

 

maybe if i read it a few times [and if you guys post some pics for us slower learners] it will start to make some sense...lol

 

never too old to learn!

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  • 4 years later...

Latest version of custom set of S30 LCA w/TC rods I just picked up from our local powder coater. Adjustable, clean looking and not a bad price in comparison to some other sets being sold. Now to see if they will stand up to some pounding!!??

post-311-050336800 1298763737_thumb.jpg

post-311-071917000 1298763745_thumb.jpg

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