Rack and pinion conversion advice.

[linkstar69]

Hey guys I'm looking to convert my PT truck to R&P and want some advice in regard to positioning the rack to not introduce bump steer and more importantly improve steering over stock.
Should the rack more or less follow the stock steering location, or is lower/higher better?

Any comments welcome.

[Bryce]

it all depends, you really need to lay it out in a program and crunch the numbers.

If you start with parrallel to the LCA at about the same height you will have a decent starting point, but that is not alwasy true. then you need to be concered with ackermann.

Good luck! I have a suspension program if you measure everything out I can input it. shoot me a PM.

[linkstar69]

Thanks for your input Bryce. I don't have a program for it but I can certainly have a look at how it all looks with the rack positioned correctly against the lca's at ride height and then cycle the suspension.
In regards to Ackerman I'm hoping my starting point isn't to bad given I'm running stock front steer spindles and a stock (from a different vehicle) front steer rack.

[linkstar69]

Thanks for your input Bryce. I don't have a program for it but I can certainly have a look at how it all looks with the rack positioned correctly against the lca's at ride height and then cycle the suspension.
In regards to Ackerman I'm hoping my starting point isn't to bad given I'm running stock front steer spindles and a stock (from a different vehicle) front steer rack.

[exwestracer]

One way to get it very close is to measure the locations of the UCA and LCA pivots relative to chassis centerline and ground. This will give you a trapezoid shape \ /

Set your rack height and length so the rack ends fall along the 2 end lines, and the tie rods match the angle of the LCAs.
Sorry if that's a little sketchy...I'm in a rush.

[19,69camaro]

If you don't know the exact length of the inner pivots for the rack you are using, make sure you pull off the boots and get a good measurement. It can make a huge difference if there isn't a huge variation in the widths between the inner pivots of the ucl and lca.
BTW fox body racks are about 24.5"ish from what I remember.

[linkstar69]

Thanks for the input gents. I now have the rack and the car together so I'm in a position to start measuring what has been mentioned above. Given I'm building on a full frame car I'm thinking of making the rack cradle mount to the frame rails. My previous rack conversion was on a mopar so the rack was attached to the K member. (the mopar was a commercially available conversion so the number crunching was already done for me)