Negitive Caster problem - Page 3 - Chevelle Tech
Brakes, Suspension & Steering Conversion questions & more.

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post #31 of 36 (permalink) Old Jul 16th, 19, 3:39 AM
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Joel
 
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Re: Negitive Caster problem

Quote:
Originally Posted by cheveslakr View Post
I believe these thing have been mentioned but in different posts so I'll try to clump them together as they all are very important.

The assembly manual addresses alignment specs and basic setup.
The assembly manual states that no more than 1ea 1/16" shim shall be used on the upper a arm shaft. That's just lazy to stack thin shims.
Rake front to rear, and overall frontend height can make positive caster unachievable.
Look at your front a-arms front to back. The upper is dramatically curved while the lower is somewhat straight. That relationship changes camber sharply with any compression of the front spring. You have to drive into the setup area so any adjustment is made while at operating height. Your setup area needs to be on a level plane front to back and side to side.
Torqueing your lower a-arm bushing bolts while at bushing lockup is necessary to achieve operating height and load. If your spring rates vary greatly from factory, than I recommend adjusting the factory specs slightly, meaning if the spring sets the car 1 inch higher than stock, adjust lockup procedure 1 inch higher than factory specs. Factory lockup specs should be adjusted in the rear also, as this will affect the "rake" which in turn affects caster.

This is my understanding but I hope an expert will comment if I'm incorrect.
Toe should be 1/8"-1/4" per factory specs. Factory specs are with bias ply tires and rubber bushings.
Radial tires require less toe, and I'm assuming poly bushings will probably require less toe also since deflection has been limited.

I spent the entire day setting up my frontend but it's new and all the procedures had to be addressed as above. Your alignment guy will assume all is right and just put the frontend to spec. This can be chasing your tail if you want it done right. Techs won't spend that kind of time for obvious reasons.


Thanks Trying to understand all that you said. the last place I took it to was Les schwab where an older man that had " cut his teeth" aligning older cars worked. they had a very nice alignment rack I drove it onto. but let me back up.
you said
"Torqueing your lower a-arm bushing bolts while at bushing lockup is necessary to achieve operating height and load"
does this mean with the weight on the wheels? we assembled on a 2 post lift. working on understanding this may have to go borrow my buddy's assembly manual.
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post #32 of 36 (permalink) Old Jul 16th, 19, 3:47 AM
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Joel
 
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Re: Negitive Caster problem

I think the car is stock height ( front and rear, no more air shocks)but the car is new to me so I have no knowledge of springs being changed.

I just located a good front end guy / older man - Chevelle owner has his own shop now. but I am interested if we torqued things incorrect.
Thanks Joel
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post #33 of 36 (permalink) Old Jul 16th, 19, 8:31 AM
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Re: Negitive Caster problem

If you torqued the control arm bushings in full droop, you did torque them incorrectly. It should be done with the wheels on the ground with the springs in their normal compression.

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post #34 of 36 (permalink) Old Jul 16th, 19, 12:48 PM
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Eric
 
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Re: Negitive Caster problem

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Originally Posted by Alan F View Post
If you torqued the control arm bushings in full droop, you did torque them incorrectly. It should be done with the wheels on the ground with the springs in their normal compression.
Or you can support the car with jack stands under the lower control arm.
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post #35 of 36 (permalink) Old Aug 13th, 19, 9:08 PM
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Re: Negitive Caster problem

...or install Polyurethane or other non-bonded bushings instead of rubber bushings, and then it doesn't matter what position the control arms are in when you torque the through-bolts.

Yet another in a series of reasons to not use rubber bushings.

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post #36 of 36 (permalink) Old Aug 13th, 19, 9:47 PM
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Re: Negitive Caster problem

Quote:
Originally Posted by joelbert62 View Post
Thanks Trying to understand all that you said. the last place I took it to was Les schwab where an older man that had " cut his teeth" aligning older cars worked. they had a very nice alignment rack I drove it onto. but let me back up.
you said
"Torqueing your lower a-arm bushing bolts while at bushing lockup is necessary to achieve operating height and load"
does this mean with the weight on the wheels? we assembled on a 2 post lift. working on understanding this may have to go borrow my buddy's assembly manual.
A 2 post lift with the lifts arms under the frame lifts the car and then puts the suspension at full droop.The cars weight is now supported by the lift.If so that is not the correct way to torque the control arm bolts.
A couple of drive on ramps will give you access to the control arms and the underbody too.There are other ways to do this and I hope some others will let you know their favorite way too.

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